Linear motion system: profile rail and polymer slide guidance for a carriage table

01

Size guide life and preload from the load on each carriage

HIWIN's linear guideway catalogue defines the basic dynamic load rating as the load giving a nominal life of 50 km for a ball-type guideway and 100 km for a roller type, the distance that 90% of identical guideways reach without flaking. Its nominal life is L = (fh·ft·C ÷ fw·Pc)³ × 50 km for ball types and the same with 10/3 and 100 km for roller types, where fh is a hardness factor, ft a temperature factor and fw a load factor. [1]

In HIWIN's worked example an HGH30CA block (C = 38.74 kN) under a 15 kN table and a 1 kN acting force carries 2.29 kN per block; with fw = 2 and Z0 preload the nominal life is 30,258 km. HIWIN notes that a larger preload (ZA, ZB) raises rigidity but lowers nominal life, and that raceways need HRC 58–62 hardness to keep full load ratings. [1]

HIWIN gives the friction coefficient of ball-type guideways as about 0.004 and of roller types as about 0.003, as little as 1/50 of a traditional slide. [1]

Editorial calculation: doubling the load per block cuts ball-guide life by 2³ = 8 times, so in the example a load of 4.58 kN per block instead of 2.29 kN would give about 30,258 ÷ 8 ≈ 3,780 km. [1]

Give the supplier the moving mass and its centre of gravity, external forces and their positions, stroke, speed and acceleration, duty cycle and required life in km or hours, environment, and whether the guides must run without lubrication.

02

Machine the rail mounting surfaces to the guide's tolerances

For its HG series HIWIN tabulates the maximum parallelism tolerance between the two rail reference surfaces by size and preload: from 25 µm (Z0), 18 µm (ZA) and 13 µm (ZB) for HG15 up to 80, 60 and 55 µm for HG65. The permissible height difference between reference surfaces runs from 130, 85 and 35 µm for HG15 to 350, 250 and 200 µm for HG65, proportional to the axial distance. [1]

HIWIN describes installing a master rail against a reference edge and a subsidiary rail, with or without push screws or a side surface, so that the two rails stay parallel, and tightening the table bolts in sequence. [1]

Plain polymer guides handle misalignment differently: CSB's LMS design rules use floating bearings with controlled extra play in the direction of the expected parallelism error to avoid jamming. [2]

Editorial calculation: moving an HG20 pair from Z0 to ZB tightens the allowed parallelism from 25 µm to 18 µm, about 28% less, so a heavier preload also asks more of the machined base. [1]

03

Compare rolling and plain-sliding guidance

CSB's LMS polymer linear motion systems slide on liners of TEFPLAS B, listed for operation to 200 °C and a maximum speed of 4 m/s without lubrication. Their design rule limits the distance from the guide to the driving force or load to twice the bearing separation (2:1), based on a static friction value of 0.25; exceeding it causes uneven motion or blockage. [2]

04

Rail, carriage or polymer slide, table, seals, lubrication and drive interface

05

Stroke, dynamic load rating, speed and rail size for a guided carriage table

Positioning accuracy and repeatability depend on the drive as well as the guides, so ask for them on the complete axis; the guide data here cover load ratings, friction and running parallelism.

06

Send the load, life and mounting data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Load: [moving mass; centre of gravity; external forces]
Motion: [stroke; speed; acceleration; duty cycle]
Life: [required km or hours]
Guidance: [ball, roller or polymer; preload]
Mounting: [base material; machined surfaces; parallelism achievable]
Environment: [temperature; dust; washdown; lubrication allowed]
Drive: [screw, belt or motor; interface]

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