9.1 LOW-SPEED OPERATION
Synchronous drives are especially well-suitable for low-speed, high torque applications. Their positive traveling nature prevents potential slippage associated with V-belt drives, and even allows significantly greater torque carrying ability. Little pitch synchronous drives operating at speeds of 50 ft/min (0.25 m/s) or less are believed to be low-speed. Care should be taken in the drive selection procedure as stall and peak torques can sometimes be high. While intermittent peak torques can frequently be carried by synchronous drives without unique considerations, high cyclic peak torque loading ought to be carefully reviewed.

Proper belt installation tension and rigid travel bracketry and framework is essential in avoiding belt tooth jumping in peak torque loads. It is also helpful to design with more than the normal the least 6 belt tooth in mesh to ensure sufficient belt tooth shear strength.

Newer era curvilinear systems like PowerGrip GT2 and PowerGrip HTD should be used in low-acceleration, high torque applications, as trapezoidal timing belts are more prone to tooth jumping, and have significantly much less load carrying capability.

9.2 HIGH-SPEED OPERATION
Synchronous belt drives tend to be found in high-speed applications despite the fact that V-belt drives are usually better appropriate. They are often used because of their positive traveling characteristic (no creep or slide), and because they might need minimal maintenance (don’t stretch significantly). A substantial drawback of high-velocity synchronous drives is certainly drive noise. High-swiftness synchronous drives will almost always produce more noise than V-belt drives. Small pitch synchronous drives operating at speeds more than 1300 ft/min (6.6 m/s) are believed to end up being high-speed.

Special consideration ought to be directed at high-speed drive designs, as a number of factors can significantly influence belt performance. Cord fatigue and belt tooth wear are the two most crucial factors that must definitely be controlled to have success. Moderate pulley diameters ought to be used to lessen the rate of cord flex exhaustion. Designing with a smaller sized pitch belt will most likely offer better cord flex exhaustion characteristics when compared to a bigger pitch belt. PowerGrip GT2 is particularly well suited for high-swiftness drives due to its excellent belt tooth entry/exit characteristics. Clean interaction between your belt tooth and pulley groove minimizes wear and noise. Belt installation stress is especially crucial with high-acceleration drives. Low belt pressure allows the belt to ride from the driven pulley, leading to rapid belt tooth and pulley groove wear.

9.3 SMOOTH RUNNING
Some ultrasensitive applications require the belt drive to use with only a small amount vibration aspossible, as vibration sometimes impacts the system procedure or finished manufactured product. In such cases, the characteristics and properties of all appropriate belt drive products should be reviewed. The final drive program selection ought to be based upon the most critical design requirements, and could need some compromise.

Vibration is not generally considered to be a issue with synchronous belt drives. Low levels of vibration typically derive from the process of tooth meshing and/or as a result of their high tensile modulus properties. Vibration caused by tooth meshing is normally a standard characteristic of synchronous belt drives, and can’t be completely eliminated. It could be minimized by staying away from little pulley diameters, and instead selecting moderate sizes. The dimensional precision of the pulleys also influences tooth meshing quality. Additionally, the installation stress has an effect on meshing quality. PowerGrip GT2 drives mesh very cleanly, leading to the smoothest possible operation. Vibration caused by high tensile modulus can be a function of pulley quality. Radial run out causes belt stress variation with each pulley revolution. V-belt pulleys are also produced with some radial run out, but V-belts have got a lesser tensile modulus resulting in less belt pressure variation. The high tensile modulus within synchronous belts is necessary to maintain correct pitch under load.

9.4 DRIVE NOISE
Drive noise evaluation in virtually any belt drive system should be approached with care. There are several potential sources of sound in something, including vibration from related elements, bearings, and resonance and amplification through framework and panels.

Synchronous belt drives typically produce even more noise than V-belt drives. Noise results from the procedure of belt tooth meshing and physical contact with the pulleys. The sound pressure level generally boosts as operating velocity and belt width increase, and as pulley size decreases. Drives designed on moderate pulley sizes without extreme capacity (overdesigned) are generally the quietest. PowerGrip GT2 drives have already been discovered to be significantly quieter than additional systems due to their improved meshing characteristic, see Figure 9. Polyurethane belts generally create more sound than neoprene belts. Proper belt installation tension can be very important in minimizing travel noise. The belt should be tensioned at a level which allows it to perform with only a small amount meshing interference as possible.

Drive alignment also has a significant effect on drive noise. Special attention ought to be given to reducing angular misalignment (shaft parallelism). This assures that belt teeth are loaded uniformly and minimizes aspect monitoring forces against the flanges. Parallel misalignment (pulley offset) isn’t as crucial of a concern so long as the belt is not trapped or pinched between opposing flanges (start to see the particular section coping with drive alignment). Pulley materials and dimensional precision also influence drive noise. Some users have found that steel pulleys are the quietest, followed closely by lightweight aluminum. Polycarbonates have already been found to become noisier than metallic components. Machined pulleys are generally quieter than molded pulleys. The reason why for this revolve around materials density and resonance characteristics along with dimensional accuracy.

9.5 STATIC CONDUCTIVITY
Small synchronous rubber or urethane belts can generate an electrical charge while operating on a drive. Elements such as humidity and working speed influence the potential of the charge. If identified to become a issue, rubber belts could be produced in a conductive building to dissipate the charge in to the pulleys, and also to surface. This prevents the accumulation of electrical charges that might be harmful to materials handling processes or sensitive consumer electronics. In addition, it greatly reduces the prospect of arcing or sparking in flammable environments. Urethane belts cannot be produced in a conductive construction.

RMA has outlined requirements for conductive belts in their bulletin IP-3-3. Unless normally specified, a static conductive building for rubber belts is certainly available on a made-to-order basis. Unless in any other case specified, conductive belts will be built to yield a resistance of 300,000 ohms or less, when new.

non-conductive belt constructions are also available for rubber belts. These belts are usually built particularly to the customers conductivity requirements. They are generally found in applications where one shaft must be electrically isolated from the other. It is necessary to note a static conductive belt cannot dissipate an electrical charge through plastic pulleys. At least one metallic pulley in a drive is required for the charge to be dissipated to surface. A grounding brush or very similar device may also be used to dissipate electric charges.

Urethane timing belts are not static conductive and can’t be built in a special conductive construction. Unique conductive rubber belts ought to be used when the presence of an electrical charge can be a concern.

9.6 OPERATING ENVIRONMENTS
Synchronous drives are ideal for use in a wide selection of environments. Particular considerations could be necessary, nevertheless, based on the application.

Dust: Dusty environments do not generally present serious problems to synchronous drives provided that the contaminants are fine and dry out. Particulate matter will, however, act as an abrasive producing a higher rate of belt and pulley use. Damp or sticky particulate matter deposited and loaded into pulley grooves can cause belt tension to increase significantly. This increased stress can effect shafting, bearings, and framework. Electrical fees within a travel system will often entice particulate matter.

Debris: Debris should be prevented from falling into any synchronous belt drive. Debris caught in the travel is generally either pressured through the belt or outcomes in stalling of the machine. In any case, serious damage occurs to the belt and related travel hardware.

Water: Light and occasional connection with drinking water (occasional clean downs) shouldn’t seriously have an effect on synchronous belts. Prolonged get in touch with (continuous spray or submersion) results in significantly reduced tensile power in fiberglass belts, and potential duration variation in aramid belts. Prolonged contact with water also causes rubber substances to swell, although less than with oil contact. Internal belt adhesion systems are also steadily broken down with the existence of water. Additives to water, such as for example lubricants, chlorine, anticorrosives, etc. can possess a far more detrimental influence on the belts than clear water. Urethane timing belts also have problems with water contamination. Polyester tensile cord shrinks considerably and experiences loss of tensile strength in the presence of water. Aramid tensile cord keeps its power fairly well, but experiences size variation. Urethane swells a lot more than neoprene in the existence of water. This swelling can increase belt tension significantly, leading to belt and related hardware problems.

Oil: Light connection with oils on an occasional basis won’t generally harm synchronous belts. Prolonged connection with essential oil or lubricants, either directly or airborne, outcomes in considerably reduced belt service lifestyle. Lubricants cause the rubber substance to swell, breakdown inner adhesion systems, and decrease belt tensile power. While alternate rubber compounds might provide some marginal improvement in durability, it is best to prevent essential oil from contacting synchronous belts.

Ozone: The presence of ozone can be detrimental to the substances found in rubber synchronous belts. Ozone degrades belt materials in much the same way as extreme environmental temperature ranges. Although the rubber materials used in synchronous belts are compounded to withstand the effects of ozone, ultimately chemical substance breakdown occurs and they become hard and brittle and begin cracking. The amount of degradation depends upon the ozone focus and duration of publicity. For good efficiency of rubber belts, the next concentration levels should not be exceeded: (parts per hundred million)
Standard Construction: 100 pphm
Nonmarking Construction: 20 pphm
Conductive Construction: 75 pphm
Low Temperatures Structure: 20 pphm

Radiation: Exposure to gamma radiation could be detrimental to the compounds used in rubber and urethane synchronous belts. Radiation degrades belt materials quite similar way excessive environmental temps do. The amount of degradation depends upon the strength of radiation and the publicity time. For good belt performance, the next exposure levels should not be exceeded:
Standard Construction: 108 rads
Nonm arking Building: 104 rads
Conductive Construction: 106 rads
Low Temperatures Structure: 104 rads

Dust Era: Rubber synchronous belts are known to generate small quantities of fine dust, as a natural consequence of their procedure. The amount of dust is typically higher for new belts, as they run in. The period of time for run directly into occur is dependent upon the belt and pulley size, loading and speed. Elements such as for example pulley China Air Compressor surface surface finish, operating speeds, installation tension, and alignment influence the quantity of dust generated.

Clean Space: Rubber synchronous belts might not be ideal for use in clean space environments, where all potential contamination must be minimized or eliminated. Urethane timing belts typically generate significantly less particles than rubber timing belts. However, they are recommended only for light operating loads. Also, they cannot be produced in a static conductive structure to permit electrical costs to dissipate.

Static Sensitive: Applications are occasionally delicate to the accumulation of static electrical charges. Electrical fees can affect material handling functions (like paper and plastic film transportation), and sensitive electronic gear. Applications like these require a static conductive belt, to ensure that the static charges produced by the belt can be dissipated in to the pulleys, and also to ground. Regular rubber synchronous belts usually do not meet this requirement, but could be produced in a static conductive structure on a made-to-order basis. Normal belt wear resulting from long term procedure or environmental contamination can impact belt conductivity properties.

In sensitive applications, rubber synchronous belts are favored over urethane belts since urethane belting can’t be produced in a conductive construction.

9.7 BELT TRACKING
Lateral tracking qualities of synchronous belts is definitely a common area of inquiry. While it is normal for a belt to favor one side of the pulleys while operating, it is abnormal for a belt to exert significant pressure against a flange resulting in belt edge use and potential flange failure. Belt tracking is usually influenced by many factors. In order of significance, conversation about these factors is really as follows:

Tensile Cord Twist: Tensile cords are formed into a one twist configuration throughout their manufacture. Synchronous belts made with only solitary twist tensile cords track laterally with a significant push. To neutralize this monitoring push, tensile cords are produced in right- and left-hand twist (or “S” and “Z” twist) configurations. Belts made out of “S” twist tensile cords monitor in the opposite path to those built with “Z” twist cord. Belts made out of alternating “S” and “Z” twist tensile cords track with minimal lateral force since the tracking characteristics of the two cords offset each other. This content of “S” and “Z” twist tensile cords varies somewhat with every belt that’s produced. Because of this, every belt comes with an unprecedented inclination to monitor in either one direction or the additional. When a credit card applicatoin takes a belt to track in a single specific direction only, an individual twist construction is used. See Figures 16 & Figure 17.

Angular Misalignment: Angular misalignment, or shaft nonparallelism, cause synchronous belts to track laterally. The position of misalignment influences the magnitude and path of the tracking pressure. Synchronous belts tend to monitor “downhill” to circumstances of lower stress or shorter middle distance.

Belt Width: The potential magnitude of belt monitoring force is directly related to belt width. Wide belts tend to track with more force than narrow belts.

Pulley Size: Belts operating on small pulley diameters can have a tendency to generate higher monitoring forces than on large diameters. That is particularly accurate as the belt width approaches the pulley size. Drives with pulley diameters less than the belt width aren’t generally suggested because belt tracking forces may become excessive.

Belt Length: Due to just how tensile cords are applied to the belt molds, brief belts can tend to exhibit higher monitoring forces than longer belts. The helix angle of the tensile cord decreases with increasing belt length.

Gravity: In drive applications with vertical shafts, gravity pulls the belt downward. The magnitude of the force is usually minimal with small pitch synchronous belts. Sag in lengthy belt spans should be prevented by applying adequate belt installation tension.

Torque Loads: Sometimes, while in operation, a synchronous belt can move laterally laterally on the pulleys instead of operating in a constant position. Without generally regarded as a significant concern, one description for this is usually varying torque loads within the drive. Synchronous belts sometimes track in a different way with changing loads. There are several potential known reasons for this; the primary cause is related to tensile cord distortion while under pressure against the pulleys. Variation in belt tensile loads may also cause adjustments in framework deflection, and angular shaft alignment, resulting in belt movement.

Belt Installation Pressure: Belt tracking may also be influenced by the level of belt installation pressure. The reasons for this are similar to the result that varying torque loads have got on belt tracking. When issues with belt monitoring are experienced, each of these potential contributing elements ought to be investigated in the purchase that they are detailed. Generally, the principal problem is going to be identified before moving totally through the list.

9.8 PULLEY FLANGES
Pulley guideline flanges are essential to preserve synchronous belts operating on their pulleys. As talked about previously in Section 9.7 on belt tracking, it really is normal for synchronous belts to favor one aspect of the pulleys when working. Proper flange design is important in stopping belt edge wear, minimizing sound and avoiding the belt from climbing out of the pulley. Dimensional recommendations for custom-made or molded flanges are included in tables coping with these problems. Proper flange positioning is important to ensure that the belt is usually adequately restrained within its operating-system. Because design and design of small synchronous drives is so varied, the wide variety of flanging situations possibly encountered cannot very easily be covered in a straightforward group of rules without locating exceptions. Despite this, the following broad flanging suggestions should help the developer in most cases:

Two Pulley Drives: On simple two pulley drives, either one pulley should be flanged about both sides, or each pulley ought to be flanged on reverse sides.

Multiple Pulley Drives: On multiple pulley (or serpentine) drives, either every other pulley should be flanged on both sides, or every pulley should be flanged in alternating sides around the machine. Vertical Shaft Drives: On vertical shaft drives, at least one pulley should be flanged on both sides, and the rest of the pulleys ought to be flanged on at least underneath side.

Long Span Lengths: Flanging recommendations for small synchronous drives with long belt span lengths cannot quickly be defined because of the many factors that may affect belt tracking qualities. Belts on drives with long spans (generally 12 times the diameter of small pulley or more) often require more lateral restraint than with short spans. Because of this, it is generally smart to flange the pulleys on both sides.

Huge Pulleys: Flanging large pulleys could be costly. Designers frequently wish to leave huge pulleys unflanged to reduce price and space. Belts generally tend to need less lateral restraint on large pulleys than small and can frequently perform reliably without flanges. When deciding whether to flange, the previous guidelines is highly recommended. The groove encounter width of unflanged pulleys also needs to be higher than with flanged pulleys. See Table 27 for recommendations.

Idlers: Flanging of idlers is generally not necessary. Idlers made to bring lateral aspect loads from belt tracking forces can be flanged if needed to offer lateral belt restraint. Idlers utilized for this purpose can be utilized inside or backside of the belts. The previous guidelines also needs to be considered.

9.9 REGISTRATION
The three primary factors contributing to belt drive registration (or positioning) errors are belt elongation, backlash, and tooth deflection. When evaluating the potential registration capabilities of a synchronous belt drive, the system must first be decided to become either static or powerful with regards to its registration function and requirements.

Static Sign up: A static registration system moves from its initial static position to a secondary static position. During the procedure, the designer is concerned just with how accurately and regularly the drive arrives at its secondary position. He/she isn’t concerned with any potential registration errors that happen during transportation. Therefore, the primary factor contributing to registration error in a static registration system is certainly backlash. The consequences of belt elongation and tooth deflection do not have any impact on the registration precision of this type of system.

Dynamic Registration: A powerful registration system is required to perform a registering function while in motion with torque loads different as the system operates. In this instance, the designer can be involved with the rotational placement of the get pulleys regarding one another at every time. Therefore, belt elongation, backlash and tooth deflection will all contribute to registrational inaccuracies.

Further discussion about each of the factors adding to registration error is really as follows:

Belt Elongation: Belt elongation, or stretch, occurs naturally whenever a belt is placed under stress. The total tension exerted within a belt results from set up, in addition to working loads. The amount of belt elongation is a function of the belt tensile modulus, which is certainly influenced by the kind of tensile cord and the belt construction. The typical tensile cord found in rubber synchronous belts is certainly fiberglass. Fiberglass has a high tensile modulus, is dimensionally stable, and has superb flex-fatigue characteristics. If an increased tensile modulus is needed, aramid tensile cords can be viewed as, although they are usually used to supply resistance to severe shock and impulse loads. Aramid tensile cords used in little synchronous belts generally have just a marginally higher tensile modulus compared to fiberglass. When required, belt tensile modulus data is normally obtainable from our Software Engineering Department.

Backlash: Backlash in a synchronous belt drive outcomes from clearance between the belt tooth and the pulley grooves. This clearance is required to allow the belt teeth to enter and exit the grooves easily with a minimum of interference. The amount of clearance required depends upon the belt tooth account. Trapezoidal Timing Belt Drives are known for having relatively small backlash. PowerGrip HTD Drives possess improved torque holding capability and withstand ratcheting, but possess a significant quantity of backlash. PowerGrip GT2 Drives have even more improved torque carrying capability, and have as little or less backlash than trapezoidal timing belt drives. In unique cases, alterations could be made to drive systems to further decrease backlash. These alterations typically lead to increased belt wear, increased travel noise and shorter travel life. Get in touch with our Application Engineering Division for additional information.

Tooth Deflection: Tooth deformation in a synchronous belt drive occurs as a torque load is put on the machine, and individual belt teeth are loaded. The quantity of belt tooth deformation is dependent upon the amount of torque loading, pulley size, installation stress and belt type. Of the three major contributors to sign up error, tooth deflection may be the most challenging to quantify. Experimentation with a prototype get system may be the best means of obtaining reasonable estimations of belt tooth deflection.

Additional guidelines that may be useful in developing registration essential drive systems are as follows:
Select PowerGrip GT2 or trapezoidal timing belts.
Style with large pulleys with an increase of teeth in mesh.
Keep belts restricted, and control stress closely.
Design frame/shafting to be rigid under load.
Use top quality machined pulleys to minimize radial runout and lateral wobble.