Page 9 of catalogue Recirculating bearings of PM Bearings B.V.

1. Technical Data
1.1 General The PM range of linear guides for unlimited travel are available in various sections with matching ball, and roller-, and needle roller diameter in a wide range of standard lengths. The choice of sizes (cross-sections) and lengths caters for almost all load capacities, enabling the designer to solve most linear motion problems with virtual frictionfree movements, free from play, with adjustable pre-load. Due to these features PM linear guides are almost complete free from wear, needing only minimum lubrication and maintenance, and are used successfully in a wide range of industries, e.g.: Packing machinery Machine Tools + other metal working machinery Automation applications Special purpose Machines + special purpose tooling Due to the high linear accuracy, which PM Linear bearings offer, they are also used widely for: Measuring instruments Tool setting equipment Robotic devices Space applications Research projects Semiconductor equipment 1.2 Friction Friction is the force necessary to move the carriage along a horizontal plane or track (Figure 1.1) The coefficient of friction (µ) is mostly depending on the ratio C/P1). For recirculating systems with a ratio between 4 and 20 the coefficient of friction is 0.002 to 0.004. (measured without endseals) Other important factors which affect the friction are the quality of running surface, quality of rolling element, amount of preload and type of grease. Figure 1.1 1.3 Maximum Velocity and Acceleration Linear motion recirculating bearings are suitable to operate at below mentioned speeds and accelerations under standard operating conditions. Miniguide DSU and DSU 30.15F: Max. recommended speed v=180m/min Incidental speeds up to 300m/min are possible. Max. acceleration a=300m/sec2 Linear recirculating bearing DS equipped with recirculating units UK or UR: Max. recommended speed v=120m/min Max. acceleration a=50m/sec2 Linear recirculating bearing PNUA: Max. recommended speed v= 120m/min Max. acceleration a= 60m/sec2 1.4 Lubrication PM precision guides are a main part in the construction of machines. The standardized high quality has to be secured during the calculated lifetime. Nevertheless dust and moisture are the main enemies of the precision bearings. Lubrication creates a film between the rolling surfaces and gives a sufficient protection against corrosion. Other benefits are for example: Friction reduction Reduction of wear Prolongation of lifetime Cooling We prefer lubrication by oil CLP (DIN 51517) or HLP (DIN 51524). During operation the temperature has to be between -30°C till +120°C while the viscosity is between ISO-VG32 and ISO-VG150 in accordance with DIN 51519. In case of grease, lubrication on lithium soap base is recommended like KP2K or KP1K in accordance with DIN 51825. Recirculating units type UK and UR are standard supplied with lubrication holes to add lubrication easily to the units. PNUA guide bearings are supplied with an oil lubrication port. Proper lubrication helps the bearings to reach their projected operational lifetime. PM recirculating bearings are supplied ex factory with a sufficient amount of oil lube, and can be used as delivered. This initial lubrication can reach a maximum of 3000 km or 1 year of travel, whichever comes first, under normal operating conditions in which the load ration C/P=10 and velocity V=1m/s.

µ = Coefficient of friction Fn = Normal force F = Frictional resistance
1)

C:dynamic loadrating, P: applied load.

8