Choosing the Correct Timing Belt
Explosive growth in 3D printing and rapid prototyping has increased demand for after-market parts such as timing belts. Whether it’s an industrial prototyping unit or home desktop printer, timing belts play an essential role in performance and the accuracy of the 3D printed object.
Quality construction, accurate fit, and material considerations for timing belts will help increase 3D printer accuracy and resolution while eliminating degradation and backlash. A properly selected timing belt and pulley combination will result in improved 3D printer axis drive motion and efficiency.
Timing Belts for Linear Axial Movement
The key factor when considering the precision of a belts axial movement is the tooth profile. To achieve the precision required for 3D printing, a properly designed and manufactured profile is crucial. Good design and quality construction will guarantee accuracy, repeatability, and long service life.
Timing Belt Material Selection
There are different permutations of timing belt materials that will enhance service life, durability, and strength. 3D Printer timing belts are typically made using polyurethane, neoprene, molded urethane, and welded urethane.
Each belt is produced with “tensile strings” embedded inside the length or teeth of the belt for added strength and reinforcement. Tensile strings typically consist of materials such as steel, fiberglass, polyester, or Kevlar for reinforcement.
Since there is a constant tension imposed as the belt is driven back and forth along its axis, it needs to maintain its form and not exhibit any stretching. Lack of belt tension or degradation in length could result in the belts loosening, thus reducing performance. Proper belt tension will result in smooth drive motion, and longer performance life.
For specialized requirements, customized timing belts can be engineered with specific characteristics tailored to your design needs. This includes self-lubricating timing belts, timing belts with anti-static properties for electronics sensitivities, dust resistant belts, double sided, and belts designed with high or low coefficient of friction.
Choosing Timing Belts for 3D Printers
Timing belts are offered in a variety of pitch and tooth profiles. Tooth profile refers to the shape of the belt’s teeth. Pitch refers to the distance between each tooth. When selecting a timing belt, both the pitch and tooth profile should precisely match the tooth and pitch profile of the pulley.
There are numerous types of timing belts to choose from in either standard or metric pitch, but several belt profiles are traditionally used in 3D Printers. The most popular are the T2.5, T5 and Gates PowerGrip GT2. Other belt profiles include the FHT (curvilinear), MXL, XL, and HTD.
The T5 offers trapezoidal shaped teeth and larger pitch distances. However, the GT2 is growing in popularity due to a smaller, more rounded tooth profile and closer pitch distance. This ultimately contributes to a higher degree of grip between the timing belt and pulley. It results in smoother axial translation and increased torque while reducing backlash, noise, and vibration.
Timing Belt Lengths
Timing belts are supplied in open lengths and sized according to your needs, using processes such as welding or molding. Other manufacturing configurations include wrapping, punching, grinding, slitting, and vulcanizing.
Belt Performance Considerations
In terms of 3D printing, there’s always a small margin of error when a timing belt engages with the pulley. Frictional forces between the belt’s teeth and pulley teeth are experienced at the moment of engagement and separation, resulting in a pulse of vibration traveling through the length of the timing belt.
Since the belt and pulley experience constant forward and reverse motion, this has the potential to periodically affect the drive rate of the belt. This will potentially cause problems in the surface finish of a 3D print. It is crucial that belt tension be checked and maintained for both the X and Y axes on a regular basis.
Another important factor is fit. There should be no room for the belt to slip or move when around the pulley. Slippage will cause deviation from the theoretical straight line the belt should travel. Having a stable belt with positive grip on the pulley will help eliminate this and produce smooth surface finishes in your 3D prints.
Timing belts rarely break during 3D printer operation, but will gradually wear down, causing increased slippage and inconsistent timing between forward and reverse motions. This can also result in degradation in accuracy. Improper handling of timing belts will also cause internal fracture or disconnection of the tensile material embedded inside the belt. Always avoid bending, twisting, or stretching timing belts beyond their designed axis.
Timing Belt vs. Pulley Relationship
The relationship between pulley and belt is one of the most significant factors for producing quality 3D prints.
Once a belt is chosen, you’ll need to select a pulley that matches the profile and pitch of your timing belt. Remember to follow these key rules:
- The timing belt teeth should fit snug within the teeth of the pulley. Any minute gap or slippage between the belt teeth and pulley teeth could result in noise and vibration, inevitably leading to poor 3D printing drive performance.
- Choose a pulley that will make contact with at least six teeth on the belt at any moment during rotation. Typical pulleys will be between 12 to 18 teeth. This will minimize slippage and help to increase torque for smooth belt drive motion.
It is vital to make sure your timing belt matches the belt tooth profile. Besides precision and performance problems, mixing and matching timing belt tooth profiles with different pulleys will result in ratcheting and delamination of your timing belt, in addition to possible increased operating temperatures for your drive system.
Timing Belt Applications
While timing belts are used in industrial and home rapid prototyping equipment, they’ve historically been seen in a wide variety of mechanical devices.
From robotic automation to photocopy machines, timing belts are used to transfer mechanical motion for different applications. Timing belts are built into machine tools, printing presses, packaging systems, conveyors, plotters, and even medical appliances.
Timing Belts for the 3D Printer Revolution
Timing belts are an essential component to your 3D printer or rapid prototyping system design. For servo motors to translate accurate linear motion to the printer’s hot end, timing belts must be properly selected, installed, and tuned.
The growing market for 3D printer timing belts has opened a new front for their design in teeth and pitch profiles, material composition, and service life. Timing belts are a cost effective way to provide excellent motion control accuracy, smooth operation, low noise, and vibration. To learn more about how we can help you with all your product handling needs, contact us today.