Linear Slide Design DataView Our Design Criteria for Our Low Profile Linear Slides Linear Slide Tolerances
- 0.001″ per 12″ – Flatness of base
- 0.001″ per 12″ – Flatness of saddle top
- 0.001″ per 12″ – Flatness of saddle top to base
- 0.0005″ per 12″ – Tracking parallelism of base and saddle
- Nominal to +/- 0.005″ – Slide overall height tolerance
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Linear Slide Design Criteria Bearing Pressure Bearing pressure is measured in pounds per square inch (psi).It is calculated by distributing the total load in pounds that the bearing is carrying by the projected area (length x width in inches). This gives the average pressure, psi, that the bearing must support. Elevated temperatures reduce load capacity; lower temperatures generally increase static load capacity. Bearing Speed Sliding or surface velocity is measured in surface feet per minute (SFM). DuraBond bearings are generally limited to 400 feet per minute under dry, low-load operation. Higher speeds are possible with lubricants or liquid coolants. Bearing PV The third parameter is the product of operating pressure and surface velocity, defined as PV. P x V = PV. It is in effect a measure of the work the bearing is doing. While it is not the final answer, PV is an invaluable general guide in matching bearing to application. Design Criteria for DuraBond Low Profile Linear Slides (All values are for dry running conditions – ambient temperature)
Recommended Operating Limits
Temperature – Typical Range Fo
Maximum PV (continuous)
Maximum P – PSI (static)
Maximum V – SFM (no load)
Slide Hardness – Minimum
Slide Finish Recommended RMS
Friction-Static & Dynamic
Water Absorption ASTM D570
Flammability ASTM D635
BTU/hr/sq. ft./ F/in.
Linear Coefficient of 78oF – 200oF
78oF – 300oF
Performance Considerations For continuous non-lubricated service, DuraBond Linear Slides are capable of operating at PV values up to approximately 10,000. Fig. 1 shows wear rates as a function of time at various PV values. For intermittent or short-time duty, higher PV values can be used. Use of lubricants permit higher PV values. Slide hardness. DuraBond Linear Slides are designed to operate against surfaces that have minimum hardness and finish requirements; however, performance is optimized when the hardest possible running surface is used. Softer materials such as stainless steel or aluminum are not recommended. DuraBond Slide bearing surfaces are hardened to Rc 58-62. Friction and wear. DuraBond Slides utilize custom compounds of PTFE. Like PTFE, they exhibit very low friction at low speeds, and low friction at high loads. These properties are diametrically opposed to most other materials and give DuraBond Slides their smooth start/stop characteristics. They eliminate most stick-slip problems. Wear rate. DuraBond Linear Slides are self-lubricating because a small quantity of Durabond or PTFE material is transferred to the mating surface during start-up. After initial break-in, the wear rate levels out. Surface finish. Best performance is achieved with a surface finish in the range of 8–16 microinches RMS, however, acceptable performance can be obtained with finishes up to 32 microinches. DuraBond Slide surface finish is 10-16 RMS. Load. DuraBond Linear Slides are generally limited to 1,000 psi. However, actual bearing deformation is a function of thickness, temperature, and load. Refer to Fig. 4. At elevated temperatures and heavy load, RULON will not shatter, but will merely deform. This eliminates sudden breakdowns and possible damage to other components. Friction Friction decreases rapidly with increase in load, because friction at start-up (static friction) and very slow speeds is extremely low. Stick-slip is virtually non-existent in DuraBond Linear Slides. This makes them ideal for oscillating or start/stop applications. When fully lubricated with oil, DuraBond compounds exhibit a coefficient of friction in the .05–.08 µ range of lubricated metal bearings. (See Fig. 5 & 6) Corrosion resistance. DuraBond material is practically inert to all acids, bases, and solvents. Lubrication. Although Durabond Slides can operate without lubrication, a small amount of lubrication applied to the slide facilitates break-in. Recommended lubricants include natural, petroleum based, way lube oils such as MOBIL Vactra #2, 3-in-1 oils and lighter weight oils for speeds over 400ft./min. Caution: Do not use fluorocarbon or silicon based oils, grease or WD40™! The additives in these lubricants create a barrier and can cause a stick slip and or binding condition in the slide. Clearance. Durabond Linear Slides are set up with 0.0005″ to 0.0015″ clearance depending on slide size. If your application requires less clearance, or as additional clearance develops over time, the adjustable gib can be tightened to achieve the desired rigidity. Care should be taken to adjust all setscrews equally throughout the full range of travel to achieve optimum performance. Accuracy. Straight line accuracy is 0.0001″/inch