A polyurethane bushing is a friction reducing component that is placed between moving and stationary components as a replacement for lubricants. The use of polyurethane for the production of bushings is due to...
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This article will take an in-depth look at urethane wheels.
The article will bring more detail on topics such as:
This chapter will discuss what urethane wheels are, their construction, and how they function.
Urethane wheels are wheels made of molded urethane, also known as polyurethane. Urethane is an elastomer that comprises urethane carbamate linkages and is a portmanteau phrase for "elastic polymer."
All of the advantages of metal, plastic, and rubber wheels are integrated in urethane wheels. They are more cost effective, more flexible, have better noise reduction, higher resilience, and are more resistant to impact, abrasion, and corrosion than metal.
In terms of low temperatures, impact, cold flow, abrasion, and radiation resistance, urethane outperforms plastic. They can also reduce noise, are more resilient, have superior elastic memory, and are less expensive than plastic. Finally, due to its wider range of hardness, ease of customization, and superior impact resistance, urethane surpasses rubber. Polyurethane wheels can also be retooled and recoated, reducing the need for costly fine tuning.
Urethane wheels come from polyurethane molding is the process of placing a urethane polymer system into a tool or mold and allowing it to cure in order to fabricate or manufacture plastic items. Polyurethane's exceptional processability makes it a particularly effective material in the manufacture of typical consumer goods and industrial parts, just like any other type of plastic. Polyurethane molding can readily attain tight tolerances and complex shapes, which include urethane wheels.
Polyurethanes are incredibly adaptable materials that may be formulated in a variety of ways to produce a variety of plastic characteristics. They can have a wide range of mechanical qualities, from soft and malleable to hard and rigid. They can also be made into high-performance, engineering-grade goods using certain compounds.
This section will discuss the construction of urethane wheels.
In the fabrication process urethane wheels are constructed by combining typically standardized parts using two individual processes.
Urethane is melted to a liquid state and then poured into a wheel-shaped mold to cool and harden. In this procedure, synthetic resins can also be used. The liquid casting method is commonly used for prototyping and small-scale manufacturing.
It entails melting the urethane to a liquid state and injecting the liquid material into a wheel-shaped mold through fill holes with a low-pressure pneumatic injection gun. Injection molding machines are made up of a complex network of motors, heaters, and other moving parts that consume a lot of energy to run. However, research has been done to improve the energy efficiency of this process. Regardless, injection molding takes for around 32 percent of all plastic processing applications and is one of the most prominent plastic processing techniques today.
Secondary methods can also be used to make urethane wheels from molded urethane. Urethane wheels can be produced from solid urethane or a mixture of urethane and metals including cast iron, aluminum, and steel. For heavier-duty applications, these wheels are ideal. The core of a bonded-to-metal wheel is constructed of metal, while the tread is made of urethane. Urethane wheels are extremely cost-effective to manufacture, and the FDA has allowed their usage in clean rooms and other sterile situations.
Although polyurethane is a polymer variant of urethane, the two materials are essentially the same. Polyurethanes are made up of several components. Polyols and diisocyanates are the primary components. Other components include curatives and additives that give a polyurethane polymer composition its distinctive qualities. Blowing agents, surfactants, and catalysts are further components unique to polyurethane foams that aid in the generation of gasses needed to form the foam's structure.
Polyurethanes are made up of many materials. Polyols and diisocyanates make up the majority of the mixture. Curatives and additives are other components that give a polyurethane polymer composition some of its particular qualities. Blowing agents, surfactants, and catalysts are another group of components unique to polyurethane foams that assist in the generation of gasses necessary for the foam's structure.
An organic molecule with one or more hydroxyl (OH) groups is known as a polyol. Polyether or polyester polyols are the two types of polyols used in urethane casting.
The interaction of organic oxides with glycol produces these. Polyether is distinguished by its strong impact resistance, minimal heat build-up for dynamic applications, hydrolysis resistance, and low-temperature performance. PTMEG and PPG are two forms of polyether often utilized in the polyurethane industry. PTMEG is the better of the two, but it is also the more expensive.
The polycondensation reaction of di-acids and glycol produces these. Polyesters have better abrasion resistance, oil resistance, heat aging resistance, shock absorption qualities, solvent resistance, and tear resistance than polyether.
Polycarbonate and polycaprolactone polyols are the most frequent. Polyesters are a type of polyol that includes these two polyols. Because of their strength and hardness, polycarbonates are employed as engineering materials. Polycaprolactone, on the other hand, provides excellent water, oil, solvent, and chlorine resistance to cast urethane.
Diisocyanate compounds, like polyols, make up the resin side of the polyurethane system. Aliphatic and aromatic diisocyanates are the two basic forms of diisocyanate.
The non-yellowing appearance of this type is its most appealing feature. They also have a lower reactivity, making them suitable for chemical-resistant coatings. Where color stability is required, aliphatic diisocyanates are commonly employed in polyurethane coatings, castings, and films. Hexamethylene (HMDI), Hexamethylene (HDI), and isophorone are the most frequent ADIs (IPDI).
Aromatic diisocyanates represent more than 90% of total diisocyanate consumption. This kind is further divided into TDI, NDI, and MDI.
These are features that are specific to polyurethane foams. Aside from the prepolymer system of polyols and diisocyanates, blowing agents, surfactants, and, in some blends, catalysts are required to manufacture the product. These additional raw components produce foaming gasses and manage them in order to get the desired foam structure.
Blowing agents are employed to generate gas, which is then used to create the foam’s cellular structure. Gas can be introduced into the polymer system chemically or physically. CFC-11, often known as trichlorofluoromethane, was the first blowing agent utilized. Because of its non-combustibility, acceptable boiling point, good compatibility with polyurethane, and lack of toxicity, this was regarded as an ideal blowing agent. However, the molecule, along with other hydrochlorofluorocarbons, was banned by the Montreal Protocol in 1987 due to its ability to deplete the ozone layer. Water, pentane, methylene chloride hydrocarbons, halogen-free azeotropes, and other zero ozone depletion-potential blends are currently replacing CFCs.
Surfactants are additives that aid in the formation, stabilization, and setting of polyurethane foams. Silicone-based surfactants are the most commonly utilized. Silicone surfactants perform critical roles such as lowering surface tension, preventing foam collapse till cross-linking, managing cell size, limiting cell shrinkage after cure, and compensating for any deformities caused by the addition of particles to the solution.
Catalysts are used to control the rate of isocyanate and hydroxyl group reaction as well as the rate of gas generation. These polymerization and gas generation operations must normally take place at the same time. If the polymerization process is faster than the gas generation process, the cells tend to stay close together, causing the foam to shrink as it cures and cools. As a result, if the gas generation rate is faster, the cells expand before the polymer can cure and sustain them. To produce uniform open cells, the speeds of these two reactions must be balanced.
Curatives and chain extenders are used to crosslink the lengthy, chained molecules generated by the polyol-diisocyanate process. They are combined with the prepolymer system of polyol and diisocyanate to form a solid or semi-solid elastomer. They are present in the majority of thermosetting polyurethane compositions. Hydroxyls and amines are the two most common forms.
The hydroxyl groups at the molecule terminals that link prepolymers are present in these curatives. At room temperature, the standard hydroxyl curative is 1,4-butanediol (BDO), which is often employed in MDI prepolymer systems.
Aside from hydroxyl groups, amine groups can also link to the prepolymer terminals. As the basic curative for TDI prepolymer systems, the most commonly used amine curative is 4,4-methylenebis (2-chloroaniline) or MOCA. OSHA, on the other hand, designated this type as a carcinogen. Other amine chain extenders, such as 4,4-methylenebis (3-chloro-2,6-diethylaniline), are currently in use.
Additives are used to give the polyurethane product additional properties. The kind and amount of additive are chosen based on the formulation of the polymer system and the intended use. Some polyurethane additives are fillers, plasticizers, stabilizers, antistatic agents, degassing aids, flame retardants, pigments, and colorants.
When opposed to tougher wheels such as steel or cast iron, urethane wheels are a preferred option in industrial applications due to their quiet operation. The urethane functions as a shock absorber and cushioning agent. It also absorbs the bumps caused by uneven terrain. When OSHA rules apply, adopting urethane wheels instead of steel or cast iron wheels can dramatically lower noise levels, helping to protect employees' hearing.
When compared to rubber, urethane tires are commonly used for their load-bearing capabilities. Urethane has a higher load-bearing capability while still offering the advantages of a rubber tread, such as shock absorption, noise reduction, and floor protection.
Urethane deflects and leaves a much bigger presence than tougher wheel materials like nylon. This increased surface area reduces shear force on floors and keeps them in excellent shape for longer durations. Urethane wheels also function by providing better traction and grip, reducing the load on the wheel to provide the required driving force.
If these specifications are considered, a good experience with urethane wheels is likely in industrial use.
When utilized properly, polyurethane is an extremely robust substance. However, when utilized in high environmental temperature applications or applications that create heat, the urethane's durability is drastically reduced. Most ordinary urethane cannot survive temperatures above 110 degrees Celsius for more than 60 to 90 minutes without being damaged. Internally generated heat (from cyclic urethane deflection) in the 121 degree range will liquefy the material in 15 minutes.
Polyurethane utilized in industrial applications must have qualities that outperform many urethanes being used in non-dynamic applications. In order to get the best urethane for needed purposes, the following factors must be considered: tensile strength, tear strength modulus, and abrasion resistance.
The only way to produce an industrial wheel is by hot casting. Hot cast urethanes (poured at 60 to 76 degrees Celsius and cured at 87 to 114 degrees Celsius) produce a stronger wheel for demanding dynamic applications. Room-temperature produced and cured urethanes rarely provide the physical qualities required in an industrial wheel application.
Some of the considerations when choosing urethane wheels include:
Each wheel has a minute point of contact with the surface it is rolling on. As a result, weight distribution is crucial. An overloaded wheel will deform over time, increasing friction and resistance and eventually failing. Understanding and preparing for the highest load will aid in the selection of the appropriate wheel.
Urethane wheels, despite being robust and forgiving on rougher surfaces, are influenced by the surface on which they are running. A different material or diameter may be preferable depending on whether the wheel is operating on smooth concrete or over rougher terrain. Aside from mechanical problems, wheels may come into contact with chemicals. Although urethane performs extraordinarily well in this climate, it is still a factor to consider.
Braking and acceleration are expected and may impact the specification, especially if these parameters are extreme or precise. It is necessary to maintain regular, predictable traction while maintaining stable contact with the rolling surface. Urethane wheels provide superior traction. However, traction can be reduced in particular circumstances where maintenance issues cause dust, grease, or oils to accumulate. These environmental concerns should be addressed throughout the planning stage. A consistent cleaning strategy for surfaces and tracks helps extend the life and efficiency of wheels.
Urethane wheels, like rubber, will expand and contract in reaction to environmental conditions. These temperature ranges are useful in cases where short-term exposure to severe temperatures is required, such as moving in and out of a deep freezer or a mining operation. Special formulas are offered in extreme circumstances to extend wheel life.
Extreme temperatures outside of the normal range are frequently reversible. Extreme heat will permanently destroy a urethane wheel. Operating outside of the low-temperature spectrum might result in brittleness, which can cause irreversible damage.
When moving wheels from indoor to outdoor situations, every environmental variable is introduced into the equation. Temperature, humidity, and the physical limitations of diverse surfaces are all factors to consider. Transition points frequently have saddles or other seams that might wear or harm the wheel. Even though urethane wheels are quite robust and resilient, it is critical to restrict the changes from one environment to the next. This helps to keep the wheel's integrity and prevents delamination. A smoother work area with fewer surface changes can help to increase the life of a wheel.
Unexpected environmental circumstances are frequently to blame for traction loss or wheel deformation. These can cause accumulation on the wheel, caster, or even the track. Any urethane wheel can be affected by build-up, resulting in premature wheel failure. The simplest method to avoid these scenarios is to thoroughly examine the ventilation system, where air motion could be shifted away from tracks, or perform routine track cleaning.
Wheels may be subjected to bumps, sudden loads, or lowering in a more demanding environment. Within the parameters of the formulation, urethane is stiff enough to bear impact. However, as with any other problem, this might cause wear to the axle, wheel, or load bearings. The impact is measured in a different way than the load. And, even if the wheel is well-designed for the specified load, it is adequate for impact, lowering, or shock. In some circumstances, this may result in a new material design that is more tolerant of damage.
There are numerous machines available to produce urethane wheels in the United States and Canada. These machines are important in today's society because they enable the manufacturing of high-quality, durable, and customizable wheels used in various industries, contributing to innovation and technological advancement. We discuss many of these leading machines below.
Features: Wabash MPI Compression Molding Presses are popular for their ability to mold urethane wheels with high precision and consistency. They utilize compression molding techniques to create durable and high-quality products.
Features: These injection molding machines known for their efficiency and automation in producing urethane wheels, allowing for high production rates and accurate control over wheel dimensions.
Features: These machines are popular for manufacturing urethane wheels with various profiles as a result of their ability to produce various sizes and offer flexibility in the production process.
Features: Haas VF Series Vertical Machining Centers are utilized for precision machining of urethane wheel molds, enabling the creation of intricate designs and smooth surfaces.
Features: Baulé machines are employed for small to medium-scale production of urethane wheels due to their excellent repeatability and efficiency.
It's important to note that the popularity and advancements in technology can change rapidly in the manufacturing industry. For the most current and accurate information on leading machines used for urethane wheel production in the United States and Canada, it is recommended that you contact industry-specific sources, manufacturers, or equipment suppliers directly.
The types of urethane wheels include:
Crowned poly wheels have significantly reduced rolling resistance than standard flat treaded wheels. These wheels range from 100 to 200mm and consist of a silent running urethane tire wrapped around a lightweight aluminum center.
They are also resistant to solvents and abrasive wear and have precision ball bearings for long bearing life. They can hold up to 600kg in load capacity and are typically used in conveyor systems.
These feature engraved patterns such as brand names, identification marks, or serial numbers. Rolling resistance is higher than that of crowned wheels since they are standard flat treaded wheels. They come in various sizes and have low load capacity.
These can be found in document processing equipment. They aid in the orientation of your documents for better optical readings. Desk wheels are commonly seen in light roller applications. Desk Wheels can be utilized as soft touch wheels with varying spring rates achieved through the use of varying urethane harnesses.
Due to the ability to adapt urethane to any hardness required for the application, urethane drive wheels are particularly common. A key slot or bolt to a hub will be used to drive urethane drive wheels. Urethane drive wheels are widely used in various industries where huge things must be moved quickly. When shifting direction is required in the application, urethane drive wheels work well.
Compliant wheels help make industrial machinery resistant to abrasion. Compliant Wheels are employed in applications that process documents or materials of various thicknesses. Compliant Wheels, with their spring-like motion, enable your gear to process papers of varying thicknesses without the use of costly spring mechanisms.
Compliant wheels are also known as no crush wheels, zero crush wheels, and compliance wheels.
Benefits of urethane compliant wheels include:
This chapter will discuss the applications and benefits of urethane wheels.
The applications of urethane wheels include:
Overhead conveyors, like many other objects, frequently employ wheels to move items. These wheels are used to transfer products down the rails of overhead conveyors and in conjunction with various carrying devices. These rails frequently contain joints in their construction, which, like expansion joints in a floor, can cause chunking and tearing. Urethane wheels can withstand a wide range of load requirements while also resisting wear, chunking, and tearing. They are designed to be exactly round and smooth, eliminating wear and wobbling.
Carts are available in a variety of sizes and strengths to suit a variety of uses. Urethane wheels are utilized on equipment carts that move parts and pieces manufactured on automotive assembly lines. For the hefty products they transport, the carts and wheels must have a high load capacity.
Urethane wheels are also suitable for railroad applications. For example, urethane wheels manufactured by Stellana are used in tugger systems to drive boxcars over train rails. This material can run directly on the tracks while providing grip on a very limited surface.
A few components work together to dry the clothing inside giant industrial dryers. Urethane wheels are used to rotate the drum's idler wheels. As the load dries, these components tumble it.
This equipment is used in the metal construction sector to shape metal sheets into rain gutters, siding, metal roofing, and other products. On the equipment, urethane wheels provide two functions. The drive wheel is utilized to draw through the aluminum sheets, while the idler wheels aid in the formation of the necessary angles and bends.
Elevator contractors prefer the material urethane for their elevator guide wheels. Guide rails are installed along the elevator shaft to move the vehicles during regular operation and to provide backup safety systems. If the cable snaps, elevators have numerous safeguards in place to swiftly halt the car where it is on the rail. The guide wheels are small wheels that help the elevator car travel smoothly up and down the rail bars during normal operation.
Hyperloop is a high-speed transport system being developed by Tesla and SpaceX. If pressure is ever lost by the Hyperloop system, interrupting the vacuum formed, urethane wheels would stabilize the vehicle while slowing it down from high speeds. Even though the vehicle is designed to never touch the ground, urethane wheels perform an important role as a safety feature. This is an application that truly tests the limitations of polyurethane!
Carrying case wheels, conveyor bearings, grocery carts, skateboard wheels, forklift drive, roller coaster wheels, and load wheels are more of the applications for urethane wheels. Medical, athletic equipment, retail, transportation, industrial manufacturing, and material handling are among the industries that benefit from urethane wheels.
Molded urethane advantages include exceptional durability due to its resistance to cuts and rips. It is also heat resistant and chemical, noise reduction, and elastic memory. The hardness of urethane wheels can vary. They might be sponge soft, iron-hard, or any hardness level in between. Aside from hardness, they can also be made in a number of colors, sizes, and shapes.
They are resistant to ultraviolet radiation, ozone, oxygen, and a variety of other environmental conditions. They are resistant to the effects of abrasive substances. Urethane wears slower than other materials under the same conditions, making it last longer. Because the material has higher tensile strength, it can withstand heavier loads.
Because urethane is manufactured chemically, a variety of variants are possible. The density and physical properties of the material can be altered depending on the ultimate usage. The load capacity of urethane wheels is 6 to 7 times that of rubber caster wheels with the same dimensions. Urethane has a high elastic memory. Because of the material's flexibility, it may be employed in a variety of situations where plastic falls short.
It can attain automatic and continuous production with low waste in the use processes and manufacturing. More essentially, some of the waste residues can be recycled for new urethane products, which will not pollute the environment. Liquid casting is a simple manufacturing procedure belonging to the new no cord casting wheel, also known as the green wheels of the twenty-first century. Urethane wheels will be the future developing trend in automotive tires, with numerous applications in the auto sector.
Failures of urethane wheels on drive wheels, industrial rollers, and industrial caster wheels cost companies not only money to replace the wheels but also equipment downtime. Most of these failures are avoidable, including:
Polyurethane is often chemically attached to a plastic or metal substrate in a wheel or roller application. Delamination happens when the tread separates from the wheel or hub of the roller. In some circumstances, this might be attributed to a poor administration of an adhesive prior to the application of the polyurethane to the hub. Overheating the wheel or exposing it to water and/or solvents at the bonding line can also cause it. Furthermore, some hub materials are difficult to bond. If adhesive was properly placed, no external conditions interfered with the bonding process, and the tread is still delaminating, a mechanical bond may be a preferable alternative.
When the wheel is loaded in a stationary position, a flat area on the polyurethane tread can occur. When the wheel resumes spinning, this area may or may not "roll-out." It will be more difficult to move the wheel from a halt in either case. The compression set value of a polyurethane material determines its susceptibility to flat-spot. The problem could be solved by using polyurethane with lower compression set settings. Another option is to utilize a larger diameter or breadth wheel, which minimizes the stress on the urethane.
When urethane treads are subjected to cyclic loading and unloading, heat is created by friction within the material due to the urethane's mechanical hysteresis. If the heat accumulation is too great (more heat created than can be dispersed), the urethane tire will melt internally, causing pressure to build up as the material expands, resulting in a blow-out. Most of the time, this is caused by operating the wheel or roller at an excessively fast speed or overloading the part. It may also be caused by unequal wheel or roller loads. The remedy would be to switch to urethanes with lower heat generation properties, raise the diameter, width, or adjust other operation parameters of the wheel.
If the wheel is loaded too heavily in a dynamic posture, the polyurethane tread may crack. This can be mitigated by replacing the tire material with material better suited for this application. Another option is to distribute the weight differently by increasing the width of the wheel or by expanding the diameter of the wheel.
However, the benefits of urethane wheels far outweigh the urethane wheel’s drawbacks.
Urethane wheels are made of molded urethane. They come from polyurethane molding which is the process of placing a urethane polymer system into a mold and allowing it to cure in order to fabricate or manufacture plastic items. Polyurethane's exceptional processability makes it a particularly effective material in the manufacture of wheels. Polyurethane molding can readily attain tight tolerances and complex shapes, which include urethane wheels.
Types of urethane wheels include crowned, drive, engraved, compliant, and desk. All benefits of metal, plastic, and rubber wheels are found in urethane wheels. They are more affordable, more flexible, have better noise reduction, are more resilient, and are more impact resistant, abrasion, and corrosion than metal. In terms of low temperatures, impact, cold flow, abrasion, and radiation resistance, urethane outperforms plastic. They can also reduce noise, are more resilient, have superior elastic memory, and are less expensive than plastic. However like any other material they have their disadvantages as discussed above.
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