Precision linear guide rail

01

Size the guide from load ratings and nominal life

HIWIN defines nominal life as the distance 90% of identical guides travel without flaking; at the basic dynamic load rating C it is 50 km for ball guides. For ball types L = (C/P)³ × 50 km; for roller types L = (C/P)^(10/3) × 100 km. Hardness, temperature and load factors reduce the result in real conditions. [1]

THK warns that when comparing catalogues you must check whether C was defined on a 50 km or 100 km basis and convert under ISO 14728-1, and that these formulas may not apply when the stroke is no more than twice the block length. [2]

Editorial calculation using PYG's published rating for its PEGH25CA block (C = 16.27 kN): at a steady 3 kN per block, L = (16.27/3)³ × 50 km ≈ 8,000 km, before applying hardness, temperature or load factors. Halving the load multiplies the life by eight. [3]

HIWIN also defines the static load rating C0 as the load that leaves permanent deformation of 0.0001 times the rolling-element diameter; the maximum static load, including shocks, must stay below it with a safety factor. [1]

Give the supplier the loads on each block (including moments), stroke, speed, acceleration and duty cycle, and ask on what basis its C is stated.

02

Check raceway hardness and the load factors

HIWIN states that "in general, the raceway surface in contact with the rolling elements must have the hardness of HRC 58~62 to an appropriate depth"; below that, load ratings and life are reduced by a hardness factor. THK adds that vibration, shock, fluctuating load, temperature and blocks mounted close together all have a decisive effect on service life. [1] [2]

PYG lists S55C rail steel and 20CrMo block steel for its PEG series. Ask for the hardness and case depth actually achieved, not only the steel grade. [3]

03

Choose accuracy class, preload and interchangeability

HIWIN offers accuracy classes C, H, P, SP and UP chosen for the equipment, and preload classes Z0, ZA and ZB: heavier preload raises stiffness but reduces nominal life, and the internal preload must be included in the life calculation. Preload depends on the stiffness needed and the accuracy of the mounting surface. [1]

Interchangeable blocks and rails can be ordered separately, but HIWIN advises ordering matched, non-interchangeable block-and-rail sets for high precision grades; PYG makes the same distinction for its PEG series. For butt-jointed rails, HIWIN advises installing them in their marked order and staggering joints on paired rails. [1] [3]

04

Plan lubrication and installation

HIWIN states that guides must be greased with lithium-soap grease before installation and re-lubricated about every 100 km; grease is applied, in its words, "for speeds that do not exceed 60 m/min", while faster speeds need oil of about 30–150 cSt fed at around 0.3 cm³/h. Insufficient lubrication greatly reduces service life. [1]

HIWIN notes that accurate motion comes from ground or milled mounting surfaces, the recommended installation sequence and bolts tightened to the specified torque. Convert the life in km to hours with the stroke and reciprocations per minute. [1] [2]

05

Standard, flange, low-profile and miniature ball rails from listed suppliers

PYG publishes load ratings, block and rail weights and five accuracy grades for its PEG series; Asia FON lists miniature guides with ball screws and modules; Pinsi lists HG and EG-style series; CSK, ALM, Jiesheng and JLCMC list linear guideways among wider motion-component ranges. Where a supplier describes a series as equivalent to another brand, ask for its own load ratings and tolerances rather than assuming identical values. [3] [4] [5]

06

Rail, carriage block, balls or rollers, end caps and seals, and lubrication fitting

The rolling element sets how life is counted: HIWIN rates ball guides on a 50 km basis with a cube law and roller guides on 100 km with a 10/3 exponent, so the element type fixes which formula applies. [1]

07

Rail size, load ratings and their km basis, accuracy, preload, speed and hardness for a guide order

Ask for the dynamic rating together with its basis: THK warns that C may be stated on 50 km or 100 km and must be converted under ISO 14728-1 before two catalogues are compared. [2]

08

Send the loads, motion and accuracy needs together

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

Axis: [horizontal, vertical or wall-mounted; number of rails and blocks; span]
Loads: [mass; cutting or process forces; moments; shocks]
Motion: [stroke; speed; acceleration; duty cycle; required life]
Accuracy: [class; parallelism; mounting surface preparation]
Guide: [ball or roller; size; block style; preload; interchangeable or matched]
Environment: [temperature; dust, chips or coolant; seals; lubrication method]
Documents: [load rating basis; drawing; accuracy inspection record]

See manufacturer records Send an enquiry through CNFX