Tumbling Machines

Chapter 1: Principle of Tumbling Machine

This chapter will discuss what tumbling machines are, their components, working principle and process.

What is a Tumbling Machine?

A tumbling machine is a durable deburring and metal-polishing machine designed for finishing large parts or batches of smaller parts. A tumbling machine is also known as a barreling machine or a mass-finishing machine. A tumbling machine processes the parts by rotating them in a multi-sided, urethane-lined barrel filled with the processing media and a liquid compound. The parts are deburred by the tumbling action inside the barrel.

This occurs during the continual sliding down of the top section of the media over the incline created from the barrel rotation. Tumbling machines are mostly used in the jewelry industry for stone tumbling, jewelry polishing, metal parts deburring, etc. The most commonly used vibrating machines are the rotary barrel tumbling machine and the vibratory tumbling machine.

Components of a Tumbling Machine

The components of a tumbling machine include:

Machine

This part consists of various parts including the vibratory tub, a motor, an electric control panel, and a network of springs. These parts are combined to help create the vibratory motion that aids in the finishing process of parts.

Water

Water is used in the case of the wet deburring process. Water is an essential ingredient since it reduces the friction between the parts and the media (see below for further definition), and also helps in the removal of dirt and grease from the parts. The water is used for carrying the scrap materials from the part. This, in turn, effectively cleans the parts.

Media

These are substances that are added to the parts inside the bowl. Their purpose is to enhance the polishing or deburring effect achieved during the vibratory process. These media contain abrasive content that helps in the deburring of the parts. The amount of deburring is directly proportional to the percentage of abrasive content that is contained in the media.

Compound

These are substances that are added to the media as a part mixture for polishing or some other purpose. Compounds are generally available in a liquid state or, occasionally, also in the form of a paste. Some compounds are useful for inhibiting any potential corrosive action.

How a Tumbling Machine Works

The tumbling machine comprises barrels where the media, abrasive pastes, and pieces to be treated are inserted. The tumbler sets the barrel in motion with a constant and regular movement. The barrel is then filled with media, abrasive pastes, as well as the materials to be treated. This movement creates friction that grinds, smooths, and polishes the surface of the objects that are to be treated.

Depending on the inherent features of the substance being treated, every material has a specific cycle. Stronger materials require specific media as well as abrasive pastes that are different from those utilized in the tumbling of softer materials. The tumbling action is always performed mechanically on the surface to be treated. The tumbler creates a level of friction based on the type and quantity of deburring media used when set in motion for vibration or rotation.

The Working Principle of a Vibratory Deburring Machine

A vibratory deburring machine has a circular tumbler that is used to hold the parts, as well as the media mixture. This type of tumbler has a PU (polyurethane) lining inside. The bowl of this machine is connected to a motor for the drive. The entire bowl is balanced by a network of springs. The bowl is filled with media and parts for finishing. Once the machine is powered on, the bowl starts to vibrate because of the motor.

The media that is contained inside the bowl begins to rub against the parts for finishing. Thus, the parts inside are deburred by the vibratory motion of the tumbler. Tumblers employ a toroidal motion as a means to ensure that the parts will be cleaned, deburred, and polished.

Chapter 2: The Tumbling Processes of Tumbling Machines

The tumbling process is utilized on an industrial scale. It is used to remove the surface flaws that are caused by previous working processes. It is also used for polishing the surfaces of various materials.

Such tumbling and vibratory finishing processes are normally employed for the polishing of metal alloys, plastics, natural materials, and precious metals.

Vibratory Tumbling

The vibratory tumbling process is used by tumbling machines to effectively create smooth and polished surfaces on plastic as well as metal parts. This type of process works by combining the water and abrasive media in a machine called a vibratory tumbler. This form of tumbling has been used for years. It has been used by many companies for providing incredibly smooth surfaces on even the most fragile plastic and metal parts.

This type of tumbling machine is capable of creating fast vibrations for promoting powerful collisions between the parts, water, and the abrasive tumbling media. Vibratory tumbling is a method that is preferred for finishing, with vibratory tumblers available in both small and large sizes.

High-Energy Tumbling

The high-energy tumbling process is similar to the vibratory tumbling process. It is also called centrifugal barrel finishing. High-energy tumbling uses the combination of water, as well as abrasive media, for creating extremely smooth surfaces. This process is faster than vibratory tumbling and is typically preferred when there is limited time.

High-energy tumbling requires sealed barrels to be filled together with the parts that are to be finished, water, and the abrasive tumbling media. The barrels are placed on a carousel that serves to create a centrifugal force by spinning in a single direction while pushing the barrels in the opposite direction. Also, like the vibratory tumbler, high-energy tumbling machines are available in both large and small sizes. The range of the sizes available ensures that even batches of larger quantities can be efficiently serviced.

Vibratory Tumbling vs. High-Energy Tumbling

There are a few aspects to consider while choosing between vibratory tumbling and high-energy tumbling. Time management comes first and foremost. High-energy tumbling may require more human input and often needs more time to finish the task. This is due to the fact that vibratory tumblers are designed for the best automation compatibility. Processes that are automated, as opposed to those that involve human interaction, are frequently more productive and economical.

Complexity is another thing to take into consideration. Because the machinery needed for the vibratory tumble deburring process is sometimes more complex, these devices can occasionally be more expensive. In the end, vibratory tumbling and high-energy tumbling are both very successful in producing smooth, resilient, and polished surfaces that successfully increase the lifespan of metal and plastic parts.

The Tumbling-Vibro Finishing Process

The tumbling-vibro finishing process has four different steps which include grinding, smoothing, polishing, and shining. The purpose of this process is to obtain a shiny and flat surface that contains no flaws. The grinding is the initial step of the tumbling process. This is where the removal of the most accentuated flaws occurs.

The second stage is smoothing. At this stage, the smaller flaws as well as the residuals of the grinding process are removed. The third step of the tumbling process is polishing. Then comes the last step which is the shining. This is the final phase of the whole process. Shining is where the piece to be treated becomes brilliant and the surface shiny as a mirror – containing no surface flaws.

The Materials That can be Tumbled by Tumbling Machines

There are a lot of materials that can be tumbled by tumbling machines including the following:

• Plastic materials especially polyamides, polymethylmethacrylate, polyesters, and cellulose acetate
• Natural materials, such as wood, corozo, horn, and mother-of-pearl
• Precious metals
• Metal alloys

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Chapter 3: Types of Tumbling Machines and Tumbling Media

The different types of tumbling machines include:

Centrifugal Barrel Tumbler

The centrifugal barrel tumbler has a working principle that is similar to a Ferris wheel. This wheel contains smaller baskets that are mounted on the edges of a large wheel. A centrifugal barrel tumbler consists of four barrels. Each barrel represents a seat on a Ferris wheel, as well as one large flywheel. When the flywheel completes a revolution, a complete rotation of each barrel occurs. Because of the fast turning speed of the flywheel, extremely high centrifugal forces are generated.

These forces will be up to 15 – 20 times higher than gravitational force. This in turn causes the contents to slide against each other under high pressure. The increased pressure allows for fast processing times of metal parts, and smooth and consistent finishes. The operator of the centrifugal barrel tumbling machine is capable of adjusting the speed of the tumbling. This level of control allows for finer finishing, as well as polishing at lower speeds. It also provides for aggressive deburring, as well as edge smoothing at higher speeds.

Centrifugal tumbling machines are typically well-adapted for removing the significant burrs, as well as blending lines, that are left by machining. These types of tumbling machines also offer excellent performance in polishing and burnishing applications. When employed with different types of ceramic, as well as organic media, centrifugal barrel tumbling machines are capable of achieving virtually any level of part finishing ranging from super-fine surface finishing to burr removal.

These types of tumbling machines are industry workhorses and they are employed with a wide variety of metals including aluminum, brass, chrome, steel, titanium, and stainless steel. This type of tumbling system is not used for the deburring of plastic parts since plastic is too pliable for this process.

Common Configurations for Centrifugal Barrel Tumbling Machines

Typical configurations of centrifugal barrel tumbling machines include:

Barrel Divider

A barrel divider allows an operator to easily separate each barrel into smaller compartments. This step helps in the prevention of part-on-part impingement as well as damage during the processing.

Part and Media Separator

This option is often utilized in larger systems for separating the tumbling media from the metal parts after processing. When there is no separator, an operator is forced to hand-pick the parts out from the tumbling media. This can become very time-consuming with smaller parts. The separator employs a vibratory screen for separating the parts from media, and screens of various sizes are capable of being swapped out for accommodating media and parts of different sizes.

Processing Table and Sludge Tank

This option is often utilized with smaller systems for trapping sediment from the process of tumbling. The sludge is removed from the processing table by a cascading feature and trapped, while the water gets pumped out of the tank using a sump pump. Eventually, the sludge will build up and will need to be cleaned out at regular intervals.

Industrial Parts Tumbler

An industrial parts tumbler performs work that can be put into three categories based on an ascending order of smoothness. The first category is the deburring process. This process involves the removal of sharp edges or burrs from the surface of a metal that are often left after machining. A very popular example of deburring is to smooth a sharp corner into a rounded corner on a metal piece.

The second category of work performed through an industrial parts tumbler is the blending of machining lines, which is similar to deburring. This process smooths the finish on a metal piece. Blending is employed for the removal of machine lines that are left in the process of milling as well as cutting the metal into the correct shape and size.

The third category of action performed through an industrial parts tumbler is the polishing process (also called burnishing). This process takes the part to the next level of smoothness. With this process, polished parts are made to become shiny and they are capable of achieving a mirrored look.

Vibratory Tumbling Machine

A vibratory tumbler is a large, donut-shaped drum. It consists of parts that rotate in a circular direction while the drum is shaking at a high speed. This motion causes the tumbling media and the parts to scrub against each other which results in the removal of burrs from, and the abrading of, the parts treated within. After this production step, the tumblers empty into a conveyor belt and the contents are sent through a dryer and cleaner. The dryer and cleaner contain rust inhibitor ingredients that serve to extend the shelf life of plain finish parts.

The shelf life of these parts is sometimes adversely affected by environmental factors, as well as improper handling and storage. Efforts must be made to avoid the dropping of parts from high distances where the edges can ping. These parts must not be handled with bare hands since impurities and oils present on skin can damage the "plain" finish on the parts. For this reason, personnel must wear gloves to handle plain finish parts.

Drum Tumbling Machine

A drum tumbling machine utilizes rubber strips as a lining. It has a drum tilt that can be adjusted for regulating the number of collisions which the items contained within have against each other. The working principle of the drum tumbling machine is based on the collision of the workpieces with approximately identical hardness against each other. The drum’s diameter will depend on the productivity that is required.

Drum tumbling machines can be equipped with an automatic system for loading workpieces and an automatic loading system for finished products. Through such automation, the finished pieces can be directly loaded onto a pallet and then packaged. Although it is best to take steps to remove dust after each use since dust buildup can give an aged look to finished products or, worse, damage the machine, a dust removal system can be equipped on the tumbling drums to help fight this issue if installed by the user.

Linear Tumbling Machine

The linear tumbling machine is available in various options. This machine is different from a drum tumbling machine in that another object hits the surface of the product in a linear tumbling machine. While in the drum tumbling machines, the products collide with each other during the rotation of the drum. In a linear tumbling machine, crank-type drive spikes or chains are utilized as beaters.

There is one disadvantage with this version of a tumbler which is that beaters wear out and require replacement more often. The rubber lining of the drum tumbler is super wear-resistant and lasts longer. The main benefit associated with linear tumbling machines is that they finish only one surface of the product, thus leaving corners as well as edges on other surfaces intact. Such an installation can be employed to finish the paving or facade tiles’ surface.

Vibratory Tumblers vs. Barrel Tumblers

Barrel tumblers employ rotary motion with abrasive tumbling media for creating sliding friction. The polishing or deburring occurs during the sliding of the parts against the media and other parts. The centrifugal barrel tumblers are a specialized form of barrel tumbler. Its centrifugal force adds to the effects of the process of barrel tumbling. Vibratory tumbling machines utilize a side-to-side motion for shaking a bowl or tub in a circular path. This is similar to the rock- polishing kits that are played with by children. Here,the finishing occurs through a scrubbing action during the shearing of the parts and the media against each other.

Ceramic Tumbling Media

The addition of ceramic tumbling media is recommended for general purpose polishing, light as well as heavy deburring, ultra-aggressive metal removal, and fast and extra fast deburring. Ceramic tumbling media is most suited for harder metals like steel and stainless steel, but may also be utilized on softer metals like aluminum. Ceramic media best suits very heavy parts. This type of media is inexpensive, durable, and highly versatile. It is the most popular media utilized in mass finishing. It is made with ceramic material, silica, and other minerals or abrasive substances combined and fired together to create a grinding and finishing agent that works extremely well on all types of workpieces.

This recipe produces an extremely hard and cement-like product. Most shapes that are ceramically performed like stars, triangles, and ellipses, are extruded and then cut to the desired length. The density of the shapes that are created is often determined by the quantity of abrasive material incorporated into the mix before firing – the more abrasive material added, the higher the density. This is very important since the higher the density, the more aggressive the ceramic tumbling media will be, and the quicker it wears at workpieces.

Carbon Steel Tumbling Media

Carbon steel tumbling media is utilized for burnishing as well as polishing metals. The high-bulk density of the carbon steel media exerts a lot of pressure on the mass of parts, thus producing a high shine in very short finishing times. Carbon steel tumbling media also has its use in surface work-hardening. This tumbling media improves the wear resistance of parts. It is capable of producing multiple sizes and shapes, and it is associated with very short cycle times.

High-Density Ceramic Tumbling Media

High-density ceramic tumbling media is heavier and longer-lasting than regular ceramic tumbling media. It is best suited for use when there is a requirement for reduced cycle times, as well as a low-residue process. High-density ceramic tumbling media delivers quicker deburring and a higher level of polishing in all types of tumbling equipment. It is extremely durable and fracture resistant. This type of tumbling media also has a fast-cutting action resulting in an increased product throughput.

Premium Ceramic Tumbling Media

Premium ceramic tumbling media is designed for specific applications that require precision deburring and polishing. Its smaller sizes are well suited for intricate finishing jobs. It gives a very smooth surface finish. It provides an intricate polishing of parts and there are also fast-cutting versions. Premium ceramic tumbling media is available in a wide variety of shapes and sizes.

Hardwood Tumbling Media

Hardwood tumbling media is a type of tumbling media that is specifically chosen and cut for dry tumbling applications for optimal performance. It is employed in combination with finishing creams. This type of tumbling media is used for surface smoothing, deburring, and polishing. It is well-suited for plastic parts. Hardwood tumbling media is capable of achieving near-mirror finishes. It does not require any water and it's long-lasting.

Plastic Media

Plastic tumbling media is utilized for general metal deburring, precision deburring, burnishing, and polishing. It is utilized on softer metals like brass or aluminum as well as on threaded parts.

Chapter 4: Applications and Benefits of Tumbling Machines

This chapter will discuss the applications and benefits of tumbling machines.

Applications of Tumbling Machines

Tumbling machines are utilized in a wide variety of industries. The different sectors in which tumbling machines are used include the buttons sector, eyewear sector, and jewelry sector. These machines are also utilized for the surface treatment of small metal parts and, especially, for the surface treatment of fashion accessories like accessories for hair, and costume jewelry.

Medical Devices

The customers of medical devices expect consistent, high-quality finishes on metal parts, mostly with complex geometry. Centrifugal barrel tumbling machines deliver fast performance for polishing. They also deliver fast performance for the deburring of titanium, cobalt-chrome, and stainless steel implants and surgical parts. Centrifugal barrel tumbling machines are also used for polishing dental implants and dental tools.

Aerospace and Defense

Metal smoothness is often a crucial requirement for the high performance of aerospace parts. The deburring of aerospace equipment by hand is not cost-effective. Therefore, manufacturers utilize centrifugal barrel tumbling machines for this task. Many parts benefit from the process of centrifugal barrel tumbling including turbine blades and jet engines.

Automotive

The automotive industry is another type of business that benefits from centrifugal barrel tumbling machines for smoothing metal parts surfaces. In particular, the automotive industry employs centrifugal barrel parts tumblers for polishing engine heads, fasteners, and gears.

General Job Shop

At these shops, centrifugal barrel tumbling machines deliver fast, cost-effective performance for polishing as well as deburring metal parts.

Benefits of Tumbling Machines

• Tumbling machines, specifically the vibratory deburring machines, are utilized for removing the rough edges from parts. This helps in fitting the parts efficiently after the finishing process.
• Tumbling machines are involved with a lower part-rejection rate when the vibratory deburring machine is used for polishing the parts.
• Vibratory deburring machines help in the preparation of parts before coating and painting. The part's surfaces are properly cleaned to ensure that the paint adheres to the part correctly.
• Tumbling machines help to improve the overall aesthetics by creating good-looking parts.
• Vibratory deburring machines enhance the reliability, as well as the life expectancy, of the part. This helps to save money for product manufacturers that employ these devices.

Other benefits include:

Precision Finishes

Depending on the size and type of the workpieces, the process of tumble finishing is capable of being completed in a very short time ranging from a few minutes to a few hours. This process is much faster than more traditional technologies and it provides a consistent and repeatable production finish.

Simple Deburring

Tumbling machines that are utilized in the deburring process can provide a precise method of deburring parts, eliminating sharp edges, cleaning up drill holes, or improving a product’s overall surface roughness.

Cost-Efficient Finishing

The devices that were traditionally used before today’s tumbling machines to perform the smoothing and polishing of metal and plastic materials were very complex and, therefore, costly to use. The tumbling process nowadays is efficient and affordable through today’s machines. Vibratory deburring machines enhance the reliability, as well as the life expectancy, of the part. This helps to save money for product manufacturers.

Low Maintenance

Today’s tumbling machines require little maintenance. Their reliability means that one can take on more work without the hindrance of frequent repairs, as well as far fewer cleanings. This maximum uptime results in better cost savings, as well as the ability to fulfill more orders.

Mass-Finishing Capabilities

Most of the machines used for performing the tumbling process can service large quantities of pieces at a time and, additionally, very small items. This ultimately saves a lot of time as well as money.

Versatility

Tumbling machines, specifically vibratory tumbling machines, are incredibly versatile. They are capable of polishing ceramics, plastics, steel, stainless steel, aluminum, copper, and many other materials. These machines can also be customized according to the needs of the user.

Compatibility with Fragile Products

The vibratory finishing process requires high friction levels for cleaning and deburring parts. It’s designed for protecting more-sensitive materials that can easily break or lose their shape. Vibratory tumbling machines offer smooth finishes while maintaining the integrity of the product.

Consistency

In mass production, consistency is key. However, metal parts do not always come off the line looking completely uniform. The barrel tumbling machine is an efficient machine that can be utilized for smoothing imperfections that stand in the way of a consistent batch. Mass metal finishing offers much more consistent results than polishing by hand.

Considerations for Getting Optimal Results with Industrial Tumbling Machines

Some of the factors to include when working with industrial tumbling machines include:

Avoid Cycle Times

One must be aware that centrifugal barrel tumbling machines generate a significant amount of heat within each barrel. For example, at a speed of 150 rpm, a 120-liter (@32 gallons) centrifugal barrel tumbling machine boils water in 15-20 minutes. Operators must keep this level of heat in mind for safety reasons and also for how it impacts the surface-finishing process. Due to the heat generated, very long cycle times are usually categorized as 5-15 minutes for many parts. A cycle that goes beyond an hour is considered an extremely long one and is not recommended.

Avoid Overloading

Placing too many parts in a tumbler’s barrels will result in part-on-part contact. This can damage the parts. For cosmetically-sensitive parts, barrel dividers can be employed as a solution. Other important factors to consider are the part-to-media ratio in each barrel, as well as utilizing an appropriate amount of water and cleaning compound.

Balance the Machine

A typical barrel centrifugal tumbling machine has four barrels. Filling only one barrel must be avoided as this practice is hard on the bearings; the same is true when loading three of the four barrels. It can cause the machine to be off-center. If there must be the use of an odd number of barrels, then the empty barrel(s) opposite it must be counterbalanced. If nothing else, the opposite barrel(s) must be filled with water to help counterbalance the machine.

Conclusion

A tumbling machine is a machine that is utilized for the finishing processes of parts. There are different types of tumbling machines that are used including the vibratory tumbler, centrifugal barrel tumbler, parts tumbler, drum tumbler, linear tumbler, etc. These machines are utilized for smoothing and polishing products. The process utilized by these machines is called the tumbling process. There are also different types of tumbling media used by tumbling machines in the tumbling process. These media include ceramic media, hardwood media, stainless steel media, carbon steel media, plastic media, etc. Tumbling machines have different applications in a wide range of industries. For example, a tumbling machine is used in the aerospace industry for smoothing jet engines, as well as blades. In the automotive industry, tumbling machines are also utilized for polishing engine heads and gears. Tumbling machines also help produce a number of other items with great consistency. These machines are an efficient, durable, low- cost, low-maintenance solution for the deburring, polishing, and finishing of numerous parts.

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