Profile Rail Accuracy Standards and Recommendations

NOOK Precision Profile Rail Systems are available in six standard classes. The selected accuracy grade should match the positioning accuracy and parallelism requirements of the equipment.

The grade of the Profile Rail System should be matched to the ball screw if used. (See Image 1 in Figure 1 Below)

Accuracy

Please select the most suitable grade of NOOK Precision Profile Rail System for your application. For accuracy requirements beyond the tolerances indicated or for any special requirements, please contact NOOK application engineers.

Running Parallelism

Running Parallelism is defined as the error in the parallelism between the datum planes of the rail and the runner block as the runner block is moved along its entire travel length.

Differences in Height "H"

This defines the difference between the maximum and minimum heights "H" of the runner blocks that are mounted on the same rail. (See Image 2 in Figure 1 Below)

Rail Accuracy Grade (units = µm) C001 Ultra Precision C01 Super Precision C1 Precision C3 High Precision C5* Standard Precision C7 Commercial Precision
Rail Length
Min (mm) Max (mm)
- 315 1.5 2 2.5 8 16 52
315 400 2 2.5 3.5 10 20 57
400 500 2 3 4.5 11 24 63
500 630 2 3.5 6 14 27 70
630 800 2.5 4 8 16 32 80
800 1,000 3 4.5 9 19 38 90
1,000 1,250 3 6 11 22 43 105
1,250 1,600 4 7 14 25 50 125
1,600 2,000 4.5 8 16 29 57 150
2,000 2,500 6 9 18 30 60 170
2,500 3,150 6 10 18 30 60 210
* Stocked Accuracy - C5

Difference in Widths "N"

This defines the difference between the maximum and minimum widths of "N" between each runner block mounted on the same rail. (See Image 2 in Figure 1 Below)

Rail Length

The maximum lengths of rail for NOOK Precision Profile Rails are shown in table below. Longer lengths can be achieved by butt joining rails.

Maximum length of rail track Unit: mm

MODEL NO. MAX LENGTH
NH-15 3000
NU-15 1500
NH-20, 45, 55, 65 3000
NU-20 thru 55 3000
NH-25, 30, 35 4000
Unit = mm

Rail Straightness

To obtain high accuracy guidance, the rail itself must be straight. It is very diffi cult to mount a distorted rail on a straight mounting surface. NOOK rail manufacturing processes ensure straightness for ease of assembly and long life. Distortion free end cuts are achieved through an automated, wet, abrasive cut-off saw system.

Preload and Rigidity

For correct operation under complex loading conditions, the selection of a suitable preload for linear motion bearings is essential. For extended life and accuracy under conditions of vibration and shock, the best results are usually achieved by using NOOK Precision Profi le Rails with heavy preload.

In general, if preload is applied to the NOOK Precision Profi le Rails, rigidity of the Profi le Rail will be doubled compared to that of a non-preloaded Profi le Rail.

The preloaded condition is effective for operating loads of up to approximately 3 times the value of preload. Therefore, as a guide, one half to one third of the operating load should be considered for preload and specifi ed according to tables below. (See Image 3 in Figure 1 Below)

Selection of Preload

Preload Conditions of use Application
T3 Heavy Heavy cutting or forming work with heavy impact and vibration. Machining center
T2 Medium Overhung load or alternate load applied. Milling machines
Vertical axis of machine tools
T2 Medium Medium cutting or forming light work with medium impact and vibration. Electrical discharge machines
T1 Light Light overhung load or alternate load applied. Surface gridinging machines
Robots
Jig grinding machines
Laser processing machines
Printed circuit board drilling machines
High speed punching machines
T1 Light Precise movement with very light vibration. Precision positioning tables
T0 Very Light No overhung or no measuring equipment alternate load applied. Tables of optical
Automatic Tool Charger for machining centers
Welding machines
; Material feeding devices
T0 Very Light Extreme changes in temperature. High precision not required. Tool changers Material feeding devices
T Clearance Plasma cutting machines

RUNNER BLOCK & STYLE PRELOAD
NH-L NH-NU NU-SER T T0* T1 T2 T3
    15 - 0 15 30 45
  15 20 - 0 25 50 75
      - 0 30 60 90
  20 25 - 0 40 80 120
25     - 0 50 100 150
  25 30 - 0 55 110 165
30     - 0 70 140 20
  30 35 - 0 80 160 240
      - 0 95 190 285
  35   - 0 110 220 330
      - 0 120 240 360
35     - 0 135 270 405
  45   - 0 180 360 540
45     - 0 210 420 630
  55   - 0 270 540 810
55     - 0 310 620 930
  65   - 0 420 840 1,260
65     - 0 520 1,040 1,560
*Stocked Preload - T0
Figure 1