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)
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 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|
|Min (mm)||Max (mm)|
- * 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)
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-20, 45, 55, 65||3000|
|NU-20 thru 55||3000|
|NH-25, 30, 35||4000|
- Unit = mm
To obtain high accuracy guidance, the rail itself must be straight. It is very difï¬ 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 Proï¬ le Rails with heavy preload.
In general, if preload is applied to the NOOK Precision Proï¬ le Rails, rigidity of the Proï¬ le Rail will be doubled compared to that of a non-preloaded Proï¬ 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 speciï¬ 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|
|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|
|;||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|
- *Stocked Preload - T0