Mechanical Engineering

What is Mechanical Engineering?

Mechanical engineering is one of the most interesting disciplines in the engineering field. In essence, it is the study of the motion of objects and systems as they relate to the broad spectrum of modern life. At its center, mechanical engineering studies force, motion, stress, and other factors that influence how objects react under real world conditions.

Using a knowledge of physics and mathematical principles, mechanical engineering combines elements from the sciences of design, analysis, manufacturing, and mechanical systems. It requires knowledge of a wide range of areas such as mechanics, dynamic, thermodynamics, materials science, structural analysis, and electricity. Additionally, students need to know the software capable of fabricating, designing, and developing products. Every aspect of modern industry relies on mechanical engineers to develop innovations to improve production methods as well as increase efficiency and machine design.

The study of how things work began when the first mechanisms were produced in China, Greece, Egypt, and Rome. When Hero of Alexandria developed the first steam engine in Ancient Greece, he used the knowledge and skills of a mechanical engineer.

Ancient Grecian Steam Engine

What we know as modern mechanical engineering had its beginnings during the first industrial revolution in the 18th Century with the development of the steam engine. Built on the foundation of the steam engine, other mechanical devices developed leading to the founding of the Institution of Mechanical Engineers in Birmingham, England in 1847.

As technology changed and innovations were introduced, mechanical engineering changed from the practice of the art of mechanics, that used trial and error to solve a problem, to a more scientific approach of research, design, and production. The real impetus to the advancement of science was the need for the designing of more efficient methods of production. As manufacturing became more complex, mechanical engineers needed to learn a variety of academic methods and approaches to be able to resolve large scare issues. This led to the development of educational programs designed to guide potential engineers to an understanding of the many factors of how things work.


What Do Mechanical Engineers Do?

The nature of mechanical engineering makes it difficult to pin down to a simple list of duties and jobs though there are commonalities between its different facets. Much of the work of a mechanical engineer centers on analyzing and examining issues related to systems and how they operate. In many instances, they develop an experimental model to try a concept to see if it will solve a problem.

To better understand a problem, a mechanical engineer will study dynamic issues that concern the relationship between forces and the motions that are involved. A complete study of these factors requires a knowledge of how things work and the mechanical nature of things, which is part of the science of physics. Much of an engineer’s approach to a problem is the interrelationship that is found in the normal natural actions of objects.

Newton’s Laws of Motion in Physics

A difficult part of a mechanical engineer’s job is the constant need to research a problem to find its origins. This can be accomplished empirically but normally necessitates a study of all of the pertinent data related to the present problem and other methods devised to solve it. The dialogue between engineers, whether through writings or in person, plays a critical part in an engineer’s success.

The third aspect of a mechanical engineer’s job relates to their business sense because it encompasses a knowledge of production and management methods that will require the least amount of investment but produce the greatest amount of profit. Included in this is a systems analysis of how things are done, much like what lean manufacturing does. In many ways, this part of the job is a study of the production of a product from its inception to its completion carefully measuring every process along the continuum.

The 8 Wastes of Lean Manufacturing

In conjunction with the business functions are managerial skills and the ability to market an idea and gain support. From a certain perspective, this function is multifaceted and includes parts of counseling, psychology, marketing, and salesmanship. Though an engineer may have a revolutionary and innovative method of approaching a problem, they have to be able to relate their vision to others. Typically, engineers place little emphasis on interpersonal relations and a study of people. Much of the concentration of their studies is on technical and scientific information. The most successful mechanical engineers are able to work as a member of a team and envision their performance in relation to their place on the team. Being individually motivated is essential but must be balanced with the need for interaction with others.

As the field of mechanical engineering progresses, a great emphasis is being placed on scientific and technical analysis of problems with solutions predicated on data and empiricism. A popular and widely used format for resolving problems and understanding the underlying parameters of a problem is PABLA (problem analysis by logical approach), which has a step by step method of analyzing and resolving issues to produce clearly defined results. PABLA thinking has become the foundation of several mechanical engineering curriculums with a greater focus on the process and development of clear objectives. What tends to be ignored in this method is creative thinking that may not have a rational foundation, another difficult factor for mechanical engineers to balance.

For a mechanical engineer to be successful, it is necessary for them to develop a balance between scientific analysis and dreaming. Not all solutions can be substantiated by an examination of the numbers. Stepping outside the problem and looking at the many human factors can be as beneficial as spending hours pouring over a data sheet.

Example of an Engineer’s Data Sheet

The Best Places to Study Mechanical Engineering

The challenges of our technically advanced world makes it necessary for future leaders to develop problem solving skills to deal with the complex issues that will arise in the future. For many educators, these mental disciplines are developed by having an understanding of STEM (science, technology, engineering, and math), a concept that is gaining a great deal of popularity in the academic community. According to STEM, the workforce of the future has to be prepared for the unique dynamics that are associated with change, necessitating an understanding of change theory and its implications.

It is very likely that the knowledge of today may not be applicable to issues of the future. Having and understanding of mathematical operations and how they work will not be sufficient. What is necessary is to know why a certain function works and how it relates to the larger picture. In essence, STEM is an attempt to help people focus on the dynamics outside a neighborhood, school, or city and look at cultural effects that will shape the thinking of groups and the direction of society.

What is STEM?

In October of 2019, the government published a report on the progress of STEM educational goals. Several federal agencies are implementing and developing STEM strategies as corporations are working toward the same goals with their own initiatives. The center of the STEM program is organizing educational curricula that will prepare students to face future issues. As of the moment, the program has a five year plan to measure progress and determine the achievement of STEM objectives.

The list of universities providing the highest quality mechanical engineering programs begins with Georgia Institute of Technology in Atlanta, Georgia. It is one of the highest ranked colleges in the United States and provides both undergraduate and graduate programs in mechanical engineering.

Rose-Hulman Institute of Technology in Terra Haute, Indiana is a private college with a small student enrollment. Regardless of its size, it is very popular and has an exceptional mechanical engineering program with very reasonable tuition. It also has an undergraduate and graduate mechanical engineering degree program. Graduates are guaranteed employment after graduation.

One of the best mechanical engineering institutions in the world is Cal Tech, or California Institute of Technology, in Pasadena, California. It is in the top fifty technical universities in the nation and has produced some of the most dynamic minds who have had a tremendous impact on the world. It offers three different degrees in mechanical engineering including a Master’s degree. Qualifications for acceptance are very rigid and require an impressive academic record to be considered.

The three institutions listed above have been recognized as world leaders in educating future engineers. When making a choice of institution, it is important to consider both ends of the spectrum whether the institution fits a person’s style of learning and whether a degree from the institution will provide sufficient acceptance by the mechanical engineering profession. Careful consideration is necessary when determining where to advance your education. Though the credentials of a college or university may be impressive, they may not fit an individual’s specific needs.


Why Mechanical Engineers Need to Know Programming Language “C”

Programming language C is a machine independent language that is simple and flexible. A knowledge of C provides an understanding of other programming languages that are based on C concepts. The C programming language combines all of the features of ALGOL, BCPL, and B programming languages and was developed at Bell Laboratories by Dennis Ritchie in 1972.

Features of C Programming Language

When C was first introduced, it was restricted to the UNIX operating system. As it became better known, it was adapted for other systems. Today, it is used in several operating systems as well as different hardware platforms. At one point, C changed so rapidly that many developers were operating using outdated versions. In answer to the confusion, the American National Standards Institute (ANSI) created a clear concise definition for the C language, which was later accepted by the International Standards Organization (ISO). The present version of the C programming language is ANSI C.

C is a compiled language that is a special tool for compiling a program and converting it into an object file that can be read by a machine. At the completion of the compiling operation, a linker combines other object files to create an executable file to run a program. There are several compilers available that have the same functions necessary to execute C and C++.

Much of the work of a modern mechanical engineer is involved with the creation and rendering of designs on a computer. Having a knowledge of the essential computer programming language can put an engineer in a better position to understand the inner workings of a program and how it functions as well as knowing its capabilities.

Every mechanical engineering university curriculum requires students to take at least one programming class. During the development of an educational plan, most of them choose the C programming language, because it is internationally accepted and approved. More than 90% of computer programs, from operating systems to word processing, are written using C or C++. Most of the other programming languages can be translated into C. Though FORTRAN and Matlab have been generally taught over the years, they have fallen in popularity or completely vanished.

C is the language used for hardware interfaces, data acquisition, and robotic control as well as many other software functions. Though it is difficult for mechanical engineering students to grasp the principles of the C programming language, as they work at it, they gain an understanding of compiling, different data types, and linking, which improves their programming skills and develops an appreciation of how a program is written.

Structure of C Program

A mechanical engineer has to be able to wear many hats to do their job and perform to the highest expectations. Their duties can range from common repairman to a leader and guide. Adding the knowledge of the most foundational computer language enhances their skills giving them the ability to understand every aspect of a project and how to successfully complete it.


Mechanical Engineering Certification and Exams

There has been some controversy regarding the licensing of engineers since some engineers get a license while others don’t. The purpose of licensing in any field is for the protection of the public. A licensed engineer is held accountable for the safety and well-being of the public and has demonstrated sufficient knowledge and skill to be able to perform their duties according to established standards. The qualifications for the engineering license varies from country to country with all versions built on humanitarian concepts. When a licensed engineer contracts for a project, they take legal responsibility for all of the engineering work of a project.

The National Society of Professional Engineers (NSPE) strongly supports the licensing and approval of an engineer’s qualifications. Before taking the PE exam, which is administered by the National Council of Examiners for Engineering and Surveying (NCEES), there are necessary steps that need to be completed. First, an applicant must complete a four year accredited university or college engineering program. Upon graduation, they must pass the FE (Fundamentals of Engineering) exam. After completing four years of practical experience, a candidate is eligible to take the Practice of Engineering (PE) exam.

As with any other profession, a PE has to continue to improve their skills and be enrolled in continuing educational programs. This is necessary due to the constant growth and technological advancements of the modern era. Unlike unlicensed engineers, only a PE may submit engineering plans for approval by local authorities. According to the NSPE, being a licensed engineer is a legal requirement since they must take full responsibility for the lives and practices during the completion of a project.

The Fundamentals of Engineering exam is designed for recent college graduates or students completing an engineering program. It is computer based and offered year round in several locations. It consists of 110 questions and takes six hours to administer. As with all +standardized testing, the testing session begins with the completion of a nondisclosure agreement and tutorial. Registration can be conveniently completed online at the NCEES website. An exam fee of $175 is payable during registration though that may vary depending on the requirements of the local licensing board. Special accommodations are available. There are seven types of FE exams ranging from chemical engineering to more specialized disciplines.

The Principles and Practice of Engineering open book exam is a test of competencies and is designed for engineers who have had four years of practical experience. It is administered year round and is computer based. The exam takes nine hours and includes a nondisclosure agreement, tutorial, and the exam. The NCEES provides an easy online application with a charge of $375 for the exam. The licensing boards may vary in terms of pre-exam requirements.

As with all standardized tests, there are accommodations available for people with special circumstances.

Experienced engineers recommend studying every day for three months prior to taking either of the exams. Also, there are several PE reference books on the market with sample test questions and test prep suggestions. Since the exams permit the use of reference materials, it is a good idea to make a collection of books that are familiar and can be easily referenced. The PE or FE have handbooks to serve as a guide to taking the exams and can be useful during the administration of the test.

The HVAC and refrigeration portion of the PE requires special preparation. Though references may have been prepared for other portions of the PE, it is important to be knowledgeable about the principles behind HVAC and refrigeration concepts since they require a special understanding. Suggested references include ASHRAE Fundamentals, ASHRAE HVAC Strategies AND Gear, ASHRAE HVAC Functions and ASHRAE Refrigeration, a Mechanical Reference Handbook, relevant ASHRAE codes (62, 90.1, 15, and lots of others.) and NFPA 90A. NCEES provides a PDF that has an overview of the contents of this portion of the exam.

Another significant part of the PE is the section on thermal and fluids strategies. Since the study of these concepts is very wide ranging and inclusive, it is important to take time to make special preparations prior to the exam date. Much of the information regarding thermal and fluids is from the study of physics, a central discipline in the mechanical engineering curriculum. Information regarding thermal engineering may not require much review since it is a major portion of mechanical engineering programs. As with the HVAC and refrigeration portion, the thermal and fluids strategies portion of the PE has an outline provided by the NCEES.

Much of the PE exam covers general knowledge of engineering. NCEES does offer exams specifically designed for certain specialized types of engineering. When applying to take the PE, the selection of the applicable engineering type will be available on the application form.


Satellite Design and Engineering

The United States Space Surveillance Network (SSN) tracks every object in orbit around the Earth. According to their calculations, there are approximately 3,000 satellites operating out of a possible 8,000. During the history of SSN, which was founded in 1957, there have been over 24,000 different types of objects that have been placed in orbit, most of which had decaying orbits and burned up in the atmosphere.

What was once considered an exclusively government project has blossomed into a commercial enterprise involving hundreds of companies from every continent on Earth, according to the World Teleport Association. These highly technical devices relay television images, telephone calls, radio transmissions, and internet data keeping our technically advanced society continually in contact and informed.

The creation of satellites is a field of engineering much like that of a mechanical engineer since it requires a group of seemingly unrelated skills. As with any aspect of engineering, a satellite engineer has to have a substantial grasp of computer technology and programming. Much of their job is dealing with equipment that cannot be touched after it is put into operation and must be adjusted and controlled by electronic signals.

Satellite engineers design software that guide satellites and keep them operating. This is accomplished by creating a command system designed to maneuver the position and function of a satellite from a stationary ground site. The initial part of a satellite engineer’s job is to program the satellite prior to its launching. This is just the beginning of the process though it does require precise and accurate calculations. Once a satellite is in orbit, the engineer has to constantly monitor it and make adjustments to ensure proper performance. Also, since orbiting equipment can be damaged or have orbit decay, data regarding the path of the satellite has to be collected, and reports developed predicting the satellite’s life span. Unlike other engineering projects, the work of a satellite engineer never ends.

A bachelor’s degree for a satellite engineer includes the study of several engineering disciplines. Computer science and a complete understanding of computer programming is a necessity. Unlike a typical engineer who is required to take one course in programming, satellite engineers have to take several classes and have comparable knowledge to that of a degreed computer programmer. The essence of satellite maintenance, control, and operation is based on sending signals using computer language where one machine is speaking to another.

Satellite Orbiting Earth

Everything in society operates by using electrical energy and power. This is very evident when there are power outages and rolling blackouts. For an engineer, a knowledge of electricity is essential since the discipline is a study of how objects react to each other. Satellite engineers need to have to understand electrical circuitry, electrical implementation, and equipment. Satellites operate on battery power, which is usually produced by solar energy, another form of required knowledge.

The obvious next element of a satellite engineer’s education is aeronautics and aerospace engineering. All of a satellite engineer’s work takes place in space, which is a complex and complicated subject since the normal rules of physics don’t always apply. Though aeronautics and aerospace may piggyback on the other disciplines, its unique and specialized features require a broader understanding of each of the other fields.

Only a select number of people have personalities that can endure the years of education and training necessary to be a satellite engineer. To be successful in the profession requires an understanding of spacecraft systems, different forms of electronic communications, space exploration operations and procedures, and the function of ground based controls. All engineers have to be detail oriented, mathematically minded, and analytical, which are general and common characteristics. For a satellite engineer, logically focused analytical thinking is a necessity with the added ability to calculate every minute aspect of a project down to the finest detail.

Though having a bachelor’s degree is sufficient to be employable as a satellite engineer, it is not enough for the varied qualifications that many employers demand. In order to be fully skilled and marketable, the best educational path is a masters or doctorate degree. The growing and expanding satellite engineering field is rapidly gaining new innovations and developments. Having minimal knowledge of the many changes is a disadvantage that can only be over some with further education.

Satellite Components

The wide range of knowledge required to be a satellite engineer places graduates in the unusual position of being able to name whatever profession they wish to follow, if they decide to forgo working with space craft. Aerospace design and development would be the next obvious choice since it closely relates to a satellite engineer’s education. The fields of electronics, mechanical engineering, and research and development, though not as closely related to satellite engineering, are jobs that could easily be filled by a satellite engineer. In reality, satellite engineers are a good fit for any type of engineering job. The strenuous training and wide range of knowledge gained during their education gives them a set of skills that are superior to any of their competitors.


Five World Changing Engineering Feats

Over the centuries, there have been significant engineering accomplishments some of which have been listed as wonders of the world. To list all of them would require the publication of a coffee table book. In recent years, there have been some engineering feats that were thought to be impossible when they were first conceived but have become a reality. Listed below are few significant engineering projects that have made an impact on the world and society.

The Palm Islands of Dubai Land reclamation has been around for hundreds of years and has been the focus of several famous engineering developments. The Palms of Dubai are another implementation of this ancient process. Using the sand from the sea, engineers designed a series of islands off the coast that are in the shape of palm trees. Palm Jumeirah and Palm Jebel Ali are surrounded by a seven mile crescent where several luxury resorts have been built. The regulations for the construction were determined by the government specifying guidelines to avoid environmental contamination or impact.

The Taj Mahal of India The architecture of the Taj Mahal is a mixture of several far eastern cultures. It was built in honor of the memory of the wife of Shah Jahan, Mumtaz Mahal. The marble for its construction was brought from China, Afghanistan, and Arabia and was cut on site. It has several passages from the Quran and a welcoming message for visitors carved into the marble. A reflecting pool stretches in front of the building and has adjacent gardens and assorted other buildings, including a gateway, mosque, and mausoleum, that dot the property. Approximately 28 kinds of precious and semi-precious stones decorate the structure. To many, it is the ultimate act of love.

The Trans-Siberian Railway of the Russian Federation The Transsibirskaya Zheleznodorozhnaya Magistral is a 5,778 mile railroad that runs from Moscow to Vladivostok on the Sea of Japan. The concept for the railway was conceived by Tsar Alexander III, the father of the last Tsar of Russia. Construction began in 1891 and progressed in sections. To pass through Manchuria, builders had to get the permission of the Chinese government to construct the trans-Manchurian section, which was completed in 1901. A second route, around Manchuria, was completed in 1916. All sections of the railway were connected in 1904. For many years, Siberia was isolated from the rest of Russia. The completion of the railway opened up Siberia for commerce and industrialization.

Skytree of Tokyo, Japan Skytree, also Sky Tree, is 2080 feet high and is the world’s second tallest structure after the Burj Khalifa of Dubai. It is also the tallest freestanding tower in the world. The design of the tower was created by Nikken Sekkei architectural firm of Chiyoda, Tokyo. A core of reinforced concrete, enclosing elevator shafts and stairways, is supported by a framework of steel tubing. The base of the structure is in the shape of a triangle. As the tower rises, the triangle is transformed into a circular pattern. The central core goes halfway up the structure. The remainder of the tower is supported by a steel framework with oil dampers to act as shock absorbers. As with many buildings built in seismic active areas, the tower is designed to sway during an earthquake.

Grand Canyon Skywalk of Eagle Point, Arizona The Skywalk is a U shaped walkway on the edge of a side canyon of the Grand Canyon. It is owned by the Hualapai Indian Tribe and opened on March 20, 2007. The idea for Skywalk came from David Jin who commissioned architect Mark Ross Johnson to design it. The structure is 65 feet long and extends 70 feet out over the canyon. Posts extend out to support the walkway and are anchored by four large concrete footings placed along the bedrock. The concrete footings are held in place by rod anchors. Part of the specifications for Skywalk was that it should be able to withstand significant seismic activity. The overall structure is said to be able to survive an 8.0 seismic event.

These few examples demonstrate the significance associated with high quality mechanical engineering practices. Though the ancient builders of the Taj Mahal and the Trans-Siberian railway did not have the advantages of modern computers, they still applied the principles of mechanical engineering to complete massive and spectacular projects. Skywalk, Skytree, and The Palms have taken the example of those earlier builders and applied them to their modern day structures to produce present day wonders.


Electrical Waves and Solenoid Valves

Before having a discussion of electrical waves and solenoid valves, it is important to understand the function of a valve, which, through the operation of an actuator, opens and shuts a valve or turns a device on or off. A solenoid valve is a mechanical device designed to control the flow of grease, water, air, and gases by the movement of a plunger. A solenoid is a set of wires that becomes magnetized when charged with an electric current. There are three types of solenoid valves: direct, internally piloted, and externally piloted.

Solenoid Valve

A direct acting solenoid valve has a seal connected to the solenoid core. Known as zero rated valves, they are electro-mechanical and used to control liquids and gases. They convert the signals from an electrical impulse into mechanical movement by signaling a coil to create movement in the valve. They come in a variety of configurations, including two-way and three-way, each of which breaks into other types of normally closed and normally open.

Internally piloted solenoid valves work by using system pressure for control. They can control air flow with less power by putting pressure on the line. The solenoid gate is a smaller passage between the line and cavity behind the spool. When it is opened, pressure pushes the spool to open the valve. Since it controls smaller openings, internally piloted solenoids require less power to operate.

Externally piloted solenoid valves use air to create valve movement. As with internally piloted solenoid valves, externally piloted ones use less energy since the valve is engaged by an intake of air. When the solenoid is electrically charged and magnetized, the pole piece shifts allowing air to flow through the internal of a direct acting solenoid valve and moving the valve spool. Once air flow dimensions, the spool shifts back. Externally piloted solenoids can shift massive valves with less electrical energy.

Beyond single port solenoids are multiple port ones of two, three, and four way valves. With a two-way solenoid valve, two ports permit flow and close the valve. Three way valve solenoids have two ports to permit flow and close the valve while a third port allows pressure to escape. A four way solenoid valve has two ports for flow and two to release pressure and are normally used with a dual acting actuator.

Another distinction of solenoids is “normally closed” and “normally open”. “Normally closed” valves remain closed until activated and are the most common type while “normally open” valves remain open until activated. Each type can be manufactured from several different kinds of metals and materials.

Solenoid Valve Working

One of the differences between direct acting and piloted solenoids is the amount of energy required to operate them. Direct acting solenoids have low pressure. When the valve is open, it has no pressure and starts up faster making it perfect for conditions requiring immediate connect and disconnect. It uses large amounts of electrical energy, which may cause early burnout but can work in conditions with a vacuum. Direct acting valves use more electrical power making them expensive to operate.

Piloted operated solenoids can operate with larger diameter valves and under high pressure, a requirement for operating the valve. Pure air is needed for optimum performance. Electromagnetic heads on piloted operated solenoids are small making power consumption low and energy efficient. Impurities in liquids can block the valve making it unreliable for controlling them.

Solenoids are a basic part of multiple pieces of equipment from cars, planes, and trucks to the operation of production machines. As simple as their construction and operation may be, they are a critical part of controlling and managing gases, liquids, and air flow. They can vary in size depending on the work to be done.


Gears and the Science Behind Them

The first gears are believed to be invented by the famous Greek mathematician and engineer, Hero of Alexandria, who created the first steam engine. He based his concepts on the Archimedes screw used to transfer water from one level to another. Hero created gears to lift balls. It is possible that gears preceded Hero’s work since the history of gears is not completely clear.

Gears are a fundamental part of most devices, equipment, and motors providing gear reduction, change of direction, and increased torque. A common use of gears is in small motors that have sufficient power to activate a device and help it operate but not enough torque. Electric screwdrivers, for example, require a great deal of torque to work. With gear reduction, the speed of the electric motor is reduced producing the necessary torque.

Another function of gears is to change the direction of a motor’s rotation, which is evident in the operation of a car. The drive shaft runs in a straight line down the middle of the underside of a car rotating circularly in relation to the chassis. The differential changes the direction of the rotation at 90 degrees to turn the wheels.

The determination of gear ratio is essential to understanding the function of gears. When a two inch gear interlocks with a four inch gear, which is twice as large, the ratio is said to be 2:1. Understanding gear ratio is necessary for calculating the speed the gears will produce where one gear is the driven gear and receiving power to turn the other gear.

Calculating Gear Ratio

An important part of understanding gears is the number of teeth they have. Gear teeth are in an involute shape, so they can firmly mesh. When two gears interlock, each has a different number of teeth, which must equal a prime number. The involute shape allows contact to be even to avoid vibrations. The ratio of rotation is determined by the number of teeth while the angle of contact controls torsional load and amount of friction.

The production and manufacturing of gears is completed using several different methods that include casting, forging, and extrusion. Regardless of the process, meticulous finishing is required for each method to ensure correct dimensions and shape. Flaws, burrs, deformities, and other imperfections have to be eliminated for a gear to smoothly mesh with other gears.

Gears are produced using a variety of materials that include plastic, copper, different types of steel, aluminum, and other types of metals. The first step in the process is designing to create a rendering that determines the gear ratio and serves as a map for its production. Casting of gears involves a mold of proper dimensions allowing for potential shrinkage. Molten metal is poured into the mold. Once the hot metal cools, the formed gear is sent on to be finished and checked for proper dimensions. Gears can also be produced by grinding, cutting, or a combination of each using fully hardened metals. Depending on the tensile strength of the gear material and its purpose, various production methods are used.

It is difficult to say what is the best type of gear since its selection depends on how it will be used. Steel, iron, and stainless steel gears are the sturdiest and have the ability to withstand wear and have long life. Gears made from different forms of steel are used in machines that endure high torque and continuous use. Plastic gears can be seen in toys, some tools, copiers, and other items that do not endure severe or stressful conditions. As technology has progressed, lighter materials are being perfected to take the place of steel gears for some applications.

Gears are divided in several ways aside from the type of material used to produce them. Common types are spur, helical, spiral, bevel, worm, and rack and pinion. The most common of the group is spur, which has straight teeth and is normally mounted on a shaft and comes in cylinder or disk form. The teeth on helical gears are not parallel to the shaft and are cut on an angle, which reduces noise and stress. Bevel gears are cone shaped and are used in pairs to create rotary motion. They can send power between axles that intersect at an angle. Rack and pinion gears change rotational motion to linear motion where a circle gear is connected to gear teeth on a flat bar. As with bevel and rack and pinion gears, worm gears have two parts the worm and worm wheel where the worm wheel has one continuous tooth and the worm wheel has the shape of a traditional or spur gear.

Bevel Gear Types

When gears are mounted together, they form a gear train or set. There are several types of gear trains. The variety and types change according to the ingenuity of engineers and designers. As with any type of machinery, gear trains vary from very simple where two gears meet to complex and complicated with multiple types of gears meshing at different speeds and ratios.

Regardless of the many advances of technology, there are basic elements of equipment and devices that remain the same through each new evolution. Gears have been a part of machines for thousands of years and will, most likely, continue to be essential for new inventions. They are at the core of the conveniences and machines we use.


Timing Machines

Timing machines, or timergraphers, are devices designed to show how accurate watches or timepieces are by checking their beat rate, amplitude, and errors of beats. Under normal circumstances, when purchasing a watch, the first thing that is noticed is its appearance, condition, and whether it works. Little consideration is given to its accuracy unless it is drastically incorrect. A timegrapher can check the performance of a timepiece far beyond its external appearance and provides a quick, easy to read snapshot of how well a watch is running. This is important for watch collectors.

Timing Machine

When measuring the functioning of a watch, the key statistic is the bph or vph, beats per hour or vibrations per hour, the top line statistics for determining the watch’s mechanical movement. The present standard for bph is 28,800 bph indicating a good mix of accuracy and durability.

One of the most important settings on a watch is its lift angle, what the balance wheel goes through in relation to the pallet fork. An understanding of the lift angle helps to calculate the amplitude, the amount of rotation in the swing of the balance wheel. When listening to a watch, the normal sound is tick tock. In reality, that sound has three parts. The first part is when the balance wheel’s pulse pin comes in contact with the pallet fork while the second sound is when the pallet leaves the wheel. The last and loudest sound is when the wheel and pallet meet. The angle at which the wheel moves between the first and last sound is known as the lift angle.

The balance wheel of a watch swings in two ways, clockwise and counterclockwise. Each swing is a beat. The number of degrees of rotation found in one beat is the watch’s amplitude, which varies depending on its position. Lying flat, the amplitude is higher, and lower when the watch is held at an angle.

The data produced from the timegrapher can give an indication of the health of a watch. The bph and amplitude are data produced by the timegrapher and are indicators to assist in calibrating a watch. There are two types of timegraphers on the market that are used by collectors - WeiShi 1000 and the Ace 1000. Neither of them is any more efficient than the other, and their operation and data are identical.

At the top of a timegrapher is a small flat surface to place the watch, which is also a microphone. It is adjustable for different sized watches. The longer a watch is on the timegrapher the more data will be displayed. Prior to testing, it is necessary to go to the main menu to set readings for beat rate (bph), lift angle, test period, and language. Once these are set, they will not need to be changed each time the machine is activated. Timegraphers have a small blue display screen similar to the blue screens of early PC’s. The labels for the data are printed on the device above the blue screen and include bph, amplitude, and beat error. The beat rate should be between a plus or minus seven seconds per day with an amplitude between 270 and 310. Beat error should be at zero or close to it. Small variances will occur the longer a watch is on the timegrapher.

A timegrapher is a valuable device for watch collectors or people who have timepieces left by relatives. It has the function of determining the accuracy of a watch and the watch’s value. Most watch repair places and jewelers have timegraphers to take initial readings. Also, a timegrapher can tell the difference between a finely tuned expensive watch and one of lesser value. For obvious reasons, timegraphers cannot read quartz or battery operated timepieces.


Transforming Mechanical Energy into Electrical Energy Using a Mill (possibly OOB)

Electric windmills, or wind turbines, produce electricity by using the force created by the wind. They are able to withstand wind speeds of up to 10 mph to produce a steady stream of electricity and usually operate at wind speeds of six to nine miles per hour. The principle behind wind turbines is rather simple. The wind turns the propeller blades of a turbine around a rotor that spins a generator. The blades have to be aerodynamically designed to work like an airplane wing or helicopter blades. Air pressure varies on each side of the blade creating lift and drag. The force of the lift is stronger and causes the rotor to spin.

Wind Turbine Components

Electricity from a wind turbine is created by a generator that is directly connected to the turbine. As the magnetic rotor spins, electromagnetic induction occurs producing electric current to be stored or placed on the electrical grid. The wind turbine process for producing energy is attractive since it is abundant, renewable, and inexpensive as well as a way to revitalize rural communities. Several areas of the United States have benefited from wind turbine electricity generating up to 14% of their electrical needs. A wind powered electricity plant near Lake Benton, Minnesota produces 107 Mega Watts.

Wind turbines have five major parts: tower, rotor, nacelle, generator, and base. The base is underground and covered with soil and is a large block of concrete capable of supporting the weight of the turbine. The tower can be a few feet up to 250 to 400 feet. Towers have to be at a height comparable to the diameter of the blades when they are rotating. The rotor is the part of the turbine that rotates and has three blades or more attached to the hub. The nacelle, or housing, is on top of the tower and has all of the operating components for the turbine including the generator and turbine shaft. Power is transferred from the nacelle by a gearbox to the generator.

Wind turbines need to be located in areas where the wind is strong and constant. Coastal areas, tops of hills or mountains, or on the ocean are typical. The European Union has placed several turbines in the Irish and Baltic Seas. California has wind farms along the coastline and in the desert. Wind farms come in several sizes and are in open areas where they won’t interfere with the populous. Five states have the majority of wind farms with Texas leading the nation with turbines producing over 20,000 MW. The largest single wind farm is in Oregon, which produces 845 MW. The largest farm in the world is in China.

Wind Energy Process

Wind turbine power can be used in two possible ways: stored for future use or sent immediately to the power grid. The storing of the generated power can be accomplished by using batteries, compressed air, or hydrogen fuel cells. The types of batteries are the same as those used for solar panel power storage, which consist of lead acid suited for trickle charging and high output efficiency. The compressed air method uses above ground tanks. When the power is needed, the air is released to a compressed air motor. With hydrogen fuel cells, a hydrogen generator creates electrolyzed water using the power from the wind turbine.

The stored power from wind turbines can be used to supplement the grid or serve as a reserve for times when the grid goes down. Activation of this back up system depends on an automatic mains failure panel (AMF), which monitors the grid with sensors and switches power from the grid to an alternate source such as the stored wind turbine power. In most cases, an uninterruptible power supply (UPS) sits between the grid and the wind turbine power and activates immediately to preclude any interruption in service. AMF’s have different sensors that determine their sophistication and ability to react. Systems with highly advanced and technical AMF’s will react to any loss in the normal power flow and are commonly used by large utility companies.

A simple form of an AMF is a load switch that connects or disconnects a power source and is controlled by an external signal. They monitor a system’s current flow or voltage. The heart of a load switch is a metal oxide silicon transistor (MOSFET) that requires no input current to control load currents. The MOSFET turns the load on or off depending on a control signal. Most load switches have a MOSFET pass transistor and a gate-drive circuit containing a gate drive transistor.


DC Motors

A DC motor, direct current motor, changes electrical energy into mechanical energy and contains a stator, armature, rotor, and commutator with brushes. The basic concept of a DC motor is based on Lorentz Force, when a current carrying a conductor is placed in a magnetic field, it will experience mechanical force. In a DC motor, opposing polarities between two magnetic fields in the motor cause it to turn. This type of motor is found in several common conveniences such as electric windows on a car or a razor.

The heart of a DC motor is a set of magnets that can be permanent or electromagnetic that are used to produce a magnetic field. When an electrical current activates the armature. or wire coiled iron core, located between the two poles of the magnet, the field from it interacts with the magnet to create torque. The magnet, in this case, is the stator. The commutator, a cylinder with multiple contact points on the armature, reverses current direction, which creates a steady rotating force, or torque.

DC Motor Components

Three common types of DC motors are stepper, brushed, and brushless. Each is designed to operate on a set of specific conditions for greatest efficiency. The basic principles of each type follow the general design of DC motors but vary in how they apply the concepts. The main difference is how the electromagnetic field is generated in either the rotor or stator.


Stepper Motors

A stepper motor does not rotate continuously. Full rotations are divided into steps with phases that are organized into groups. Each phase receives energy causing the motor to rotate in steps. The magnet serves as the rotor and is surrounded by electromagnetic stators. When voltage is applied, the rotor aligns with the stators forming a small gap. Each stator is energized in order to produce a full rotation in small steps. Stepper motors are used when there are requirements of precise positioning and speed control and are found in 3D printers, cameras, plotters, and scanners. Since it provides maximum torque at low speeds, it is applicable to devices that have a low speed requirement.


Brushed Motor

The magnet on a brushed motor is inside the outer body with a rotating armature inside it. In this case, the magnet, or stator, remains stationary while the armature has an electromagnet, or rotor. The rotor spins 180° when a current is applied. To have the rotor turn 360°, the electromagnetic fields have to be switched. This is achieved with a set of brushes that are in contact with the stator as the rotor is spinning. The brushes flip the direction of the magnetic field enabling it to make a complete rotation. The advantages of a brushed motor include its ability to react quickly and supply high torque as well as being easier to control.

Brushed motors are found in consumer goods, small appliances, car power seats, and windshield wipers. Though they have components that can wear out, their inexpensive design balances that disadvantage.


Brushless Motors

A brushless motor, or BLDC/BL motor, has two parts: a rotor and stator. The rotor has rotating magnets while the stator is stationary with stator windings. A permanent magnet on the rotor moves the electromagnets to the stator. High powered transistors activate the electromagnets to turn the shaft. BLDC motors come in two designs: outer and inner rotor motors. With the inner rotor design, the rotor is at the center of the motor with the stator wound around it. In the outer rotor design, the rotor is around the winding at the core of the motor. Brushless motors are more efficient and produce less friction. They operate at high speeds and can be designed with more magnets on the stator to increase control. Unlike brushed motors, brushless motors have to have an electronic speed controller (ESC) for current for the electromagnet. Much of the expense of a BLDC is due to the controller.

Alternating-current (AC) motors have decreased the use of DC motors. Though this has become true in many cases, DC motors can be an advantage for certain applications. In many cases, DC motors and controllers are a low cost option compared to inverter duty AC motors, which is especially true for fractional hp jobs.

AC Motor Components

Since DC motors have been in use for over 125 years, there is a great deal of information and experience that comes with their use. Their simple design and accessibility makes them easy to service and maintain since brush replacement and motor design are understood by electricians. Though the variable frequency drive motors (VFD) have been popular for over 25 years for their speed control, DC motors can compete with VFD’s and are a viable option.

DC motors easily and quickly develop torque at low speeds, which makes them a perfect choice for torque loads like conveyor belts, elevators, cranes, extruders, and mixers. Though these pieces of equipment may stop when they reach capacity, a DC motor can instantly set them in operation when the load balances. In applications like these and similar ones, DC motors greatly outperform AC motors.

There are any number of applications that can be improved and enhanced by a DC motor. With their adjustable speed control and constant torque, they are the perfect choice for a variety of industries. In the final analysis, if a machine requires quick acceleration with immediate stopping and reversing capabilities, a DC motor is the perfect choice for the job.



Autodesk, Inc., the developers of AutoCAD, is a software developing corporation that makes software for the design industries such as architectural companies, engineering design, construction, variance forms of manufacturing, education, and the entertainment industry. The first software developed by Autodesk was computer aided design (CAD) and is their best known product. From the success of CAD, Autodesk has rapidly expanded into other fields developing software for a variety of industries and purposes.

AutoCAD Features

Since its introduction 35 years ago, AutoCAD has grown producing 31 one variations during its time on the market. Interestingly enough, AutoCAD has been available longer than Adobe Photoshop and Microsoft Windows. Prior to its introduction, designers worked with mainframes on their individual terminals without any interaction. In many cases, they reverted to drawing their designs, which took hours to perfect and days to complete. Necessary mathematical calculations were completed using a handheld calculator, which was time consuming and led to errors and miscalculations.

The introduction of AutoCAD revolutionized the production of engineering, architectural, and manufacturing designs. Instead of producing inaccurate and flawed products that had to be adjusted and corrected during production, AutoCAD gave engineers and designers the ability to create renderings of designs and test them on a computer without the bother of a physical prototype. Efficiency improved and losses from production errors significantly dropped.

AutoCAD software assists in the rendering, creation, and visualizing of engineering designs in 2D or 3D. Construction and manufacturing industries create ideas and test them in a computer environment where the designs can be adjusted and manipulated for various applications. Unlike hand drawings and calculator figures, AutoCAD can precisely determine the dimensions, materials, and spacing needed for a design and customize it. Once a design has been perfected, it can be printed in blueprint form, transferred to other programs, or shared electronically with other users. With computer numerical controlled (CNC) manufacturing systems, commands for machines can be easily moved from AutoCAD to a machine to give directions and procedures for producing parts, materials, and products. This particular feature speeds up production and eliminates possible human errors.

Since AutoCAD is used across a wide range of industries, it has had to be adjusted for the specific needs of each industry. In architecture, the program has building parts and construction data to support the development of a building design. A key benefit of AutoCAD is enabling designers who may not have drawing skills to still work as creative artists and engineers. Every university program in the country relies on AutoCAD to assist students in producing their ideas. Certification in the use of the software is required for most positions.

Though AutoCAD has a vise grip on the designer market, other products are being developed that may, someday, make it obsolete. It is unlikely that this will happen very soon since AutoCAD is constantly adapting its products to fit new industries and applications. There are knock offs and free alternatives available that do not have all of the functions of AutoCAD. Also, an AutoCAD replacement cannot be dropped into a system or modified to AutoCAD specifications. The technological generation has shown us that no software product or design will last forever as seen in the evolution of Microsoft. Whether AutoCAD will be replaced in the next ten years is hard to say. As of the moment, it is a vital part of producing today’s conveniences.


Mechanical Seal

A mechanical seal uses two flat surfaces to form a perfect seal and prevent leakage where one of the faces is stationary and the other rotates. As the two surfaces rub together, a fluid film forms for cooling and lubricating. When a centrifugal pump is sealed, a rotating shaft has to be able to enter a wet area with fluids being kept from escaping. A seal needs to be formed between the shaft and the pump housing where the housing has to be able to withstand the pressure from the liquid. In general, mechanical seals are used whenever a rotating shaft has to move a fluid. The seal protects against contaminants as well as preventing leaks.

Mechanical Seal Components

There are several different types of mechanical seals. The type being used depends on the industry, kind of housing, and the nature of the liquid or fluid. Since mechanical seals are found in so many different applications, it is impossible to list every type. Below is a description of a few of the common seals.

Inside seals: With the inside seal design, the rotary portion of the seal is inside the pump chamber where the fluid pressure is against the outside diameter. They are ideal in situations where there is high pressure.

Outside seals: Conversely, with an outside seal, the rotary part is outside the pump chamber where the pumped fluid does not come in contact with any of the parts of the seal. They are perfect for pumps that have non-metallic parts.

Unbalanced seals: Unbalanced refers to when the box pressure times the exposed area is greater than the average pressure between the seal faces. This type of seal creates hydraulic forces which are caused by the actual pressure to be sealed. Unlike balanced seals, unbalanced ones are more adaptable for low pressure conditions.

Balanced seals: Balanced seals have a load balance. Pressure is equal in all directions and forces the primary ring against the mating ring acting like a closing force on the seal face. The balance is achieved in the construction of the pump where the correct ratio is achieved between the two faces reducing the hydraulic forces acting against the closed seal face. This allows the seal to withstand higher pressure limits and create less heat.

Double seals: This type of mechanical seal is positioned face to face and back to back to create a buffer between the seal faces. The primary seal keeps the fluid in the pump housing while the secondary one controls the possible flushing of the liquid by leakage. Double seals are ideal to control hazardous substances and work well with polymerizing media.

Mechanical seals are a reliable and dependable part that can last for many years as long as they are the right fit for their application. There are several factors to consider when making a mechanical seal selection. The most obvious first step is the type of liquid to be moved and the pressure it creates as well as the liquid’s temperature. The viscosity of a liquid is another factor and can have an effect on the pressure. The final consideration are the regulations and requirements of local government and company rules regarding emissions since environmental issues are a great concern and vary from region to region.

Regardless of any other factors, mechanical seals are the first choice of pump manufacturers and are applicable for a variety of functions. They have several benefits from reduced friction and zero leakage to reduced maintenance and long term durability. Making the right selection can prove to be highly efficient and cost saving.


Mechanical Merchandising Machines (Automatic Retailing)

As amazing as it may sound, the concept of mechanical merchandising or automated retailing goes back thousands of years to the ancient Greeks. A Greek mathematician and inventor, Hero of Alexandria, inventor of the steam engine, created a device that would disburse holy water to the Egyptians. A few thousand years later, an English inventor designed a machine that dispensed tobacco in taverns, which was followed in 1822 by publisher Richard Carlisle with a machine to sell newspapers. A little over forty years later, right after the Civil War, the modern version of the vending machine was introduced for selling stamps. Coin machines were widely used in London in the 1880’s usually located in railway stations and post offices for the convenience of selling envelopes, stamps, and notepaper.

The first vending machines in the United States were distributed by the Thomas Adams Gum Co. installed on subway platforms in New York. The popular gumball machine entered the picture in 1907. As people became attracted to vending devices, they became the rage for selling candy to dispensing cigars. In Philadelphia, the Horn and Hardart Co. opened a coin operated restaurant or automat. Their idea was inspired by Max Sielaff’s AUTOMAT in Berlin, who manufactured the machines and sold them in the United States.

Vending Machine Technology

As technology has improved and perfected the process, vending machines have become more sophisticated and capable of completing a wider variety of sales. When money is put in the machine, a digital scanner identifies the amount before sending it on to the cash box. Quarters are identified by their diameter, thickness, and number of ridges while a dime is determined by diameter and thickness. These classifications are used for other coins as well.

Once the amount of money entered has been approved, the customer can make their selection. In older machines, a lever was turned or pulled to release the product. More modern devices have a keypad for entering numbers or letters to make a selection. The machine compares the sum of money entered to the purchase price of the item. If it is less than required, it will refuse the purchase and send a message to the customer.

When all of the programmed conditions of the machine are made, the product is released. Older machines use mechanical functions for dispensing while modern ones use a wire coil that spins to dispense its merchandise. As the motor on the coil spins, the rotation pushes the product forward much like an auger pulls dirt out of the ground to make a hole. The coils are a little longer than the length of the shelf allowing the product to fall from the end of the shelf to the receiving and excess bin. A door to the bin keeps the product from bouncing out of the machine and opens inward for ease of access for the customer.

Automated retailing is one of the fastest growing businesses in the United States. On average, $79,000 is spent every minute in the United States in vending machines. Company owners can make as much as $5 million dollars a year. This may seem to be an easy business where you install a group of machines and wait for the profits to roll in. As with any form of business, managing a collection of vending machines requires hard work and planning.

It has been said several times regarding retail that location is the key. For a retail operation to flourish, it has to be located where there are customers. This is especially true of automated retailing. The proper placement of 10 to 15 machines can earn a daily income of $2000, provided that the machines are regularly stocked and maintained. Once the machines are purchased, which is a one time fixed cost, the other expenses are personnel to service the machines and the purchase of merchandise.

Research indicates that automated retailing is the wave of the future. Online companies will continue to grow and be profitable. There will always be people who want to shop and visit a store. Automated retailing will be able to streamline the point of purchase process by totaling sales rapidly. For example, several years ago, it was proposed to place a scanner at the exit of a store. As the customer exited, a scanner would scan the customer and the barcodes of all of the items the customer has. The device would total the amount and automatically charge it to a credit account or bank that the customer had set up with the retailer. Shopping would be a simple process of choosing the items and walking out the door. A version of this process can be seen today with the security detection devices at the doors of retailers.

Automated Retail Machines

As brick and mortar operations fail, go bankrupt, and close, there is a great likelihood that there will be a revolution in the retail industry where it can increase profits by installing electronic equipment. Watching the progression and growth of this form of business could be the investment opportunity of the future.


The Significance of Welding

There are several processes used to create products that are named welding, which gives the impression that a significant number of products are made using the process. Thirty different methods of connecting metals are termed welding since they involve some form of connecting of metals or metallic material. Though welding began with forge welding where two pieces of metal were heated and hammered together, it has advanced into several different forms beginning with arc and oxy-fuel welding. Those two methods gave birth to processes we use today, which include shield metal arc, gas metal arc, flux-core arc, laser beam, and robotic welding.

A popular welding process available to do it yourselfers (DIY) is metal inert gas (MIG) where a solid wire electrode is fed through a welding gun to create a weld pool to join two metals. The process includes sending a gas through the gun to protect the weld pool from contamination. The technical name for MIB is gas metal arc welding (GMAW), which is also known as wire welding. Though safety can be a concern with MIG, it is available to a variety of users from farmers and ranchers to hobbyists and artists. It is designed to weld light weight non-ferrous metals.

Stick welding, or arc welding, is an old fashion process and difficult to master but inexpensive. An electrode connected to a welding device creates an electric arc between the electrode and the metals to be connected. While the weld is laid, the flux coating on the electrode disappears producing vapors that provide a shield of gas and a layer of slag that protects the weld pool. It is used in industrial fabrication, repairs, and steel construction.

Electroslag welding is a fast welding method used to connect large pieces of metal such as heavy steel and is a combination of arc and resistant welding. As with arc welding, heat is generated when an electrode connects with the work pieces, which melts the flux to create the molten pool. The electric current flows between the pool and heat, which creates electrical resistance. The filler wire goes into the joint area and solidifies to join the two pieces.

Electro-slag Welding

Flux core welding is another form of stick welding and involves an electrode that is continuously fed. The wire has a flux core, which is a tubular wire that has a flux filled inner center. The electrode melts the flux core wire and the base metal to be welded forming a small pool of molten metal. The flux core produces a protective gas to protect the molten metal. Flux core welding is used to weld various types of low alloy steel such as stainless steel.

When the first laser was invented in 1960, it was unclear how it could be used for practical purposes. Since then, lasers have become a vital part of several scientific and medical procedures. Laser welding, also known as laser beam welding, fuses two metal pieces by focusing a laser beam in the cavity between the metals. When the beam contacts the two pieces, it produces enough heat to melt the metals. The melted material fills the cavity connecting the two pieces. Laser welding is used in production processes that produce a large volume of products.

Most common welding processes are done by hand requiring manual labor. In production, some welding jobs are considered too hazardous to be performed by hand. Up until the 1960’s, it was not possible to avoid the dangers involved, which placed welders at risk. Concerned for the safety of workers, and wanting to improve the production process, research and development for auto manufacturers began to investigate other methods to complete the welding process.

In 1962, two gentlemen developed a robotic method that was able to spot weld car bodies on the General Motors’ production line. Though the process was proven to be safe and productive, it didn’t come into general use by other auto producers until the 1980’s. Two forms of welding are used by robotic welders: resistance and arc. The arc welding type uses methods that include MIG, TIG, FCAW, and plasma.

The methods of welding described here are a few of the many types used by industry, hobbyists, repairmen, and others to join metals. Society relies on metals as a part of construction and the production of products. For that reason, welding is very likely to be a needed skill for many years to come.

The welding profession, as with any skilled trade, requires training and experience to be proficient and employable. Though certification is not a requirement, it is recommended since some employers will not hire uncertified craftsmen. The nature of welding equipment makes it imperative that a future welder understand the implications and power of their tools. Having an education beyond high school is not a necessity, but the American Welding Society recommends getting some form of post-secondary or associate degree. Several community colleges offer classes in welding, which include certification upon completion.

In 2018, close to a half million skilled tradesmen were working as welders, cutters, solderers, and brazers, as recorded by the United States Bureau of Labor Statistics. It is projected, in the next ten years, there will be a steady increase in the required number of welders as the methods of welding become more technical and manufacturing requires highly skilled laborers. As certain skills and trades are replaced by technology, all indications are that welding is one skill that will be needed regardless of advancements in computer controlled processes.