I believe that the GT2 is the superior belt for precision registry when all factors are taken into consideration.
The GT2 uses a fiberglass cord which is very close in performance to steel.
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For the sake of completeness, the three additional belt profiles shown in
Figure 19j, 19k, and19l are used in Europe and are sometimes found on machinery imported from Europe and Japan.
They are not produced in the U.S.A. and are not covered by RMA standards.
The belts are made of polyurethane, and steel is usually used as the tension member.
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In Figure 2, the photoelastic pattern shows the stress distribution within teeth of different geometry. There is a definite stress concentration near the root of the trapezoidal belt tooth, with very low strains elsewhere. For the curvilinear tooth, there is a uniform, nearly constant, strain distribution across the belt. The load is largest in the direction of the tension member to which it is transferred. Because of their superior load carrying capabilities, the curvilinear belts are marketed under the name of Gates' HTD drives. This is an abbreviation of High Torque Drives. As a result of continuous research, a newer version of the curvilinear technology was developed by Gates, which was designated as Gates' PowerGrip GT belt drives.
The trapezoidal shape timing belt was superseded by a curvilinear tooth profile which exhibitedsome desirable and superior qualities.
Advantages of this type of drive are as follows:
•Proportionally deeper tooth; hence tooth jumping or loss of relative position is less probable.
•Lighter construction, with correspondingly smaller centrifugal loss.
•Smaller unit pressure on the tooth since area of contact is larger.
•Greater shear strength due to larger tooth cross section.
•Lower cost since a narrower belt will handle larger load.
•Energy efficient, particularly if replacing a "V" belt drive which incurs energy losses due toslippage.
•Installation tension is small, therefore, light bearing loads.
The PowerGrip GT System, featuring a modified curvilinear belt tooth profile, provides timing and indexing accuracy superior to the conventional PowerGrip Trapezoidal Belt System. Plus, PowerGrip GT Belts have a higher capacity and longer belt life than trapezoidal belts.
It's difficult to make a true quantitative comparison between the backlash of a trapezoidal tooth drive and PowerGrip GT drive due to the difference in "pulley to belt tooth" fit.
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Steel
Tensile Strength 360,000 lbs/in^2
Elongation at break 2.5%
Modulus (approx.)15,000,000 lbs/in^2
Fiberglass
Tensile Strength 350,000 lbs/in^2
Elongation at break 2.5 – 3.5%
Modulus 10,000,000 lbs/in^2
The most important advantages are:
1.High strength.
2.Low elongation or stretch.
3.Excellent dimensional stability.
4.Excellent chemical resistance.
5.Absence of creep, 100% elongation recovery.
Disadvantages:
1.High modulus (difficult to bend).
2.Brittleness of glass. Improper handling or installation can cause permanent damage.
3.Poor shock resistance. No shock absorbing quality when used in timing belts
Polyester
Tensile Strength 160,000 lbs/in^2
Elongation at break 14.0%
Modulus (approx.)2,000,000 lbs/in^2
One of the main advantages of polyester cord over higher tensile cords is the lower modulus of polyester, enabling the belt to rotate smoothly over small diameter pulleys. Also, the elastic properties of the material enable it to absorb shock and dampen vibration. In more and more equipment, stepping motors are being used. Polyester belts have proven far superior to fiberglass or Kevlar reinforced belts in these applications. High-speed applications with small pulleys are best served by polyester belts under low load.
Kevlar
Tensile Strength 400,000 lbs/in^2
Elongation at break 2.5%
Modulus 18,000,000 lbs/in^2
High tensile strength and low elongation make this material very suitable for timing belt applications.
Kevlar has excellent shock resistance and high load capacity.
T-5 The main stress line in a trapezoidal tooth timing belt is at the base of the teeth. During operation, this stress greatly reduces belt life. The PowerGrip GT system overcomes this condition with its complete tooth flank contact which eliminates the tooth stress line area. This greatly increases belt life and prevents tooth distortion caused by drive torque. In addition, the conventional timing belt has a chordal effect as it wraps small pulleys. This is significantly reduced in the PowerGrip GT system because there is full tooth support along the pulley.
Full support improves meshing, reduces vibration and minimizes tooth deformation. On drives using a low installation tension, small pulleys, and light loads, the backlash of thePowerGrip GT system will be slightly better than the trapezoidal timing belt system. However, with increased tension and/or loads and/or pulley sizes, the performance of the PowerGrip GT system becomes significantly better than the trapezoidal timing belt system.
The PowerGrip GT system is an extension of the HTD system with greater load-carrying capacity. HTD was developed for high torque drive applications, but is not acceptable for most precision indexing or registration applications. The HTD design requires substantial belt tooth to pulley groove clearance (backlash) to perform.As smaller diameter pulleys are used, the clearance required to operate properly is increased. HTD drive clearance, using small diameter pulleys, is approximately four times greater than anequivalent GT timing belt drive.
The PowerGrip GT system's deep tooth design increases the contact area which provides improved resistance to ratcheting. The modified curvilinear teeth enter and exit the pulley grooves cleanly, resulting in reduced vibration. This tooth profile design results in parallel contact with the groove and eliminates stress concentrations and tooth deformation under load. The PowerGrip GT design improves registration characteristics and maintains high torque carrying capability. PowerGrip GT belts are currently available in 2 mm, 3 mm and 5 mm pitches.
Specific advantages of the PowerGrip GT system can be summarized as follows:
•Longer belt life
The strong fiberglass tensile cords wrapped in a durable neoprene body provide the flexibility needed for increased service life. The deep tooth profile provides superior load-carryingstrength and greatly reduces ratcheting when used with pulleys provided by a licensed supplier.
•Precision registration
PowerGrip GT belts provide timing and synchronization accuracy that make for flawless registration, with no loss of torque carrying capacity.
•Increased load-carrying capacity
Load capacities far exceed HTD and trapezoidal belt capabilities making PowerGrip GT belts the choice for accurate registration, heavy loads and small pulleys.
•Quieter operation
The PowerGrip GT belt's specially engineered teeth mesh cleanly with pulley grooves to reduce noise and vibration. Clean meshing and reduced belt width result in significant noise reduction when compared to Trapezoidal and HTD belts.
•Precise positioning
PowerGrip GT belts are specifically designed for applications where precision is critical, such as computer printers and plotters, laboratory equipment and machine tools.
[www.scribd.com]
REFERENCE LIBRARY
[www.sdp-si.com]
T5 slightly stiff so it requires a higher tension
[forums.reprap.org]
Belts and Pulleys
[www.reprap.org]
The GT2 uses a fiberglass cord which is very close in performance to steel.
For the sake of completeness, the three additional belt profiles shown in
Figure 19j, 19k, and19l are used in Europe and are sometimes found on machinery imported from Europe and Japan.
They are not produced in the U.S.A. and are not covered by RMA standards.
The belts are made of polyurethane, and steel is usually used as the tension member.
In Figure 2, the photoelastic pattern shows the stress distribution within teeth of different geometry. There is a definite stress concentration near the root of the trapezoidal belt tooth, with very low strains elsewhere. For the curvilinear tooth, there is a uniform, nearly constant, strain distribution across the belt. The load is largest in the direction of the tension member to which it is transferred. Because of their superior load carrying capabilities, the curvilinear belts are marketed under the name of Gates' HTD drives. This is an abbreviation of High Torque Drives. As a result of continuous research, a newer version of the curvilinear technology was developed by Gates, which was designated as Gates' PowerGrip GT belt drives.
The trapezoidal shape timing belt was superseded by a curvilinear tooth profile which exhibitedsome desirable and superior qualities.
Advantages of this type of drive are as follows:
•Proportionally deeper tooth; hence tooth jumping or loss of relative position is less probable.
•Lighter construction, with correspondingly smaller centrifugal loss.
•Smaller unit pressure on the tooth since area of contact is larger.
•Greater shear strength due to larger tooth cross section.
•Lower cost since a narrower belt will handle larger load.
•Energy efficient, particularly if replacing a "V" belt drive which incurs energy losses due toslippage.
•Installation tension is small, therefore, light bearing loads.
The PowerGrip GT System, featuring a modified curvilinear belt tooth profile, provides timing and indexing accuracy superior to the conventional PowerGrip Trapezoidal Belt System. Plus, PowerGrip GT Belts have a higher capacity and longer belt life than trapezoidal belts.
It's difficult to make a true quantitative comparison between the backlash of a trapezoidal tooth drive and PowerGrip GT drive due to the difference in "pulley to belt tooth" fit.
Steel
Tensile Strength 360,000 lbs/in^2
Elongation at break 2.5%
Modulus (approx.)15,000,000 lbs/in^2
Fiberglass
Tensile Strength 350,000 lbs/in^2
Elongation at break 2.5 – 3.5%
Modulus 10,000,000 lbs/in^2
The most important advantages are:
1.High strength.
2.Low elongation or stretch.
3.Excellent dimensional stability.
4.Excellent chemical resistance.
5.Absence of creep, 100% elongation recovery.
Disadvantages:
1.High modulus (difficult to bend).
2.Brittleness of glass. Improper handling or installation can cause permanent damage.
3.Poor shock resistance. No shock absorbing quality when used in timing belts
Polyester
Tensile Strength 160,000 lbs/in^2
Elongation at break 14.0%
Modulus (approx.)2,000,000 lbs/in^2
One of the main advantages of polyester cord over higher tensile cords is the lower modulus of polyester, enabling the belt to rotate smoothly over small diameter pulleys. Also, the elastic properties of the material enable it to absorb shock and dampen vibration. In more and more equipment, stepping motors are being used. Polyester belts have proven far superior to fiberglass or Kevlar reinforced belts in these applications. High-speed applications with small pulleys are best served by polyester belts under low load.
Kevlar
Tensile Strength 400,000 lbs/in^2
Elongation at break 2.5%
Modulus 18,000,000 lbs/in^2
High tensile strength and low elongation make this material very suitable for timing belt applications.
Kevlar has excellent shock resistance and high load capacity.
T-5 The main stress line in a trapezoidal tooth timing belt is at the base of the teeth. During operation, this stress greatly reduces belt life. The PowerGrip GT system overcomes this condition with its complete tooth flank contact which eliminates the tooth stress line area. This greatly increases belt life and prevents tooth distortion caused by drive torque. In addition, the conventional timing belt has a chordal effect as it wraps small pulleys. This is significantly reduced in the PowerGrip GT system because there is full tooth support along the pulley.
Full support improves meshing, reduces vibration and minimizes tooth deformation. On drives using a low installation tension, small pulleys, and light loads, the backlash of thePowerGrip GT system will be slightly better than the trapezoidal timing belt system. However, with increased tension and/or loads and/or pulley sizes, the performance of the PowerGrip GT system becomes significantly better than the trapezoidal timing belt system.
The PowerGrip GT system is an extension of the HTD system with greater load-carrying capacity. HTD was developed for high torque drive applications, but is not acceptable for most precision indexing or registration applications. The HTD design requires substantial belt tooth to pulley groove clearance (backlash) to perform.As smaller diameter pulleys are used, the clearance required to operate properly is increased. HTD drive clearance, using small diameter pulleys, is approximately four times greater than anequivalent GT timing belt drive.
The PowerGrip GT system's deep tooth design increases the contact area which provides improved resistance to ratcheting. The modified curvilinear teeth enter and exit the pulley grooves cleanly, resulting in reduced vibration. This tooth profile design results in parallel contact with the groove and eliminates stress concentrations and tooth deformation under load. The PowerGrip GT design improves registration characteristics and maintains high torque carrying capability. PowerGrip GT belts are currently available in 2 mm, 3 mm and 5 mm pitches.
Specific advantages of the PowerGrip GT system can be summarized as follows:
•Longer belt life
The strong fiberglass tensile cords wrapped in a durable neoprene body provide the flexibility needed for increased service life. The deep tooth profile provides superior load-carryingstrength and greatly reduces ratcheting when used with pulleys provided by a licensed supplier.
•Precision registration
PowerGrip GT belts provide timing and synchronization accuracy that make for flawless registration, with no loss of torque carrying capacity.
•Increased load-carrying capacity
Load capacities far exceed HTD and trapezoidal belt capabilities making PowerGrip GT belts the choice for accurate registration, heavy loads and small pulleys.
•Quieter operation
The PowerGrip GT belt's specially engineered teeth mesh cleanly with pulley grooves to reduce noise and vibration. Clean meshing and reduced belt width result in significant noise reduction when compared to Trapezoidal and HTD belts.
•Precise positioning
PowerGrip GT belts are specifically designed for applications where precision is critical, such as computer printers and plotters, laboratory equipment and machine tools.
[www.scribd.com]
REFERENCE LIBRARY
[www.sdp-si.com]
T5 slightly stiff so it requires a higher tension
[forums.reprap.org]
Belts and Pulleys
[www.reprap.org]