Content
Understanding Rotation Stage Specifications
Specifications | Description | |
Model Number | RA07A-W | 1. Kohzu's significant alpha-numeric model numbers offer quick product insight. |
Table Size | 68mm | 2. Table size refers to the stage's upper-most mounting surface. |
Guide Mechanism | Bearing | 3. Type of bearing mechanism used on this stage. |
Motion Range | ±135° | 4. Stage travel range in the positive and negative directions from it's centered or neutral position. |
Lead Mechanism | Worm & Worm Wheel | 5. Feeding Mechanism and feed screw pitch. |
Ideal Resolution | 0.002° / step (Half Step) | 6. Ideal Resolution of standard stage (half step). |
Maximum Speed | 20°/sec | 7. Maximum Speed of standard stage (half step, 10kpps). |
Accumulated Lead Error | ≦ 0.015°/ 360° | 8. See "Kohzu Stage Inspection Standards" section |
Lost Motion | ≦ 0.006° | 9. See "Kohzu Stage Inspection Standards" section |
Angular Repeatability | ≦ 0.01° | 10. See "Kohzu Stage Inspection Standards" section |
Pitch Error | ≦ 0.01° / 4° | 11. See "Kohzu Stage Inspection Standards" section |
Backlash | ≦ 0.02° | 12. See "Kohzu Stage Inspection Standards" section |
Surface Run out | ≦ 0.02° / 360° | 13. See "Kohzu Stage Inspection Standards" section |
Eccentricity | ≦ 0.01mm | 14. See "Kohzu Stage Inspection Standards" section |
Moment Load Stiffness | 7 arcsec / kgf-cm | 15. Moment load stiffness is measured in a direction perpendicular to the motion axis |
Load Capacity (Horizontal) | 6kg | 16. Maximum load capacity is for a horizontally orientated stage with load centered on top-plate. |
Material | Aluminum Alloy | 17. Material specification is for stage's main body components only. |
Finish | Clear-Matte Anodizing | 18. Surface finish type and color. |
Weight | 1.65kg | 19. Stage weight includes all components depicted in product photograph. |
Standard Motor | Five (5) phase stepper motor PX535MH-B | 20. Actuator type of standard stage. |
Standard Connector | RP13A-12RA-20PC | 21. Connector type of standard stage |
Guide Mechanism Type
Angular Bearing
The angular bearing has a contact angle appropriate to receive a unidirectional axial load or a combined radial and axial load (see Fig. 1). To use this bearing as a guide system, set two bearings face-to-face on opposite sides. This arrangement provides rigidity for loads both in the radial and axial directions.
Cross-Roller Bearing
In cross-roller bearing guides,,, quench hardened and precision ground bearing surfaces move upon loose hardened steel cylinders (rollers) with rotation axes oriented in alternating 90 degree angles (Ref. Fig.1). Having rollers arranged in an alternating cross pattern allows preloading and operation at any angle. The roller bearings are held apart from one another by a bearing cage, which prevents adjacent rollers from touching. Since cross-roller bearings have little difference between static and dynamic friction they minimize start-to-stop slip-motion typical of other bearing types. The line contact of roller bearings along with precise roller-to-race gap management provide larger load-bearing surfaces, higher preloads and meet verytight run out and stiffness specifications.
Feeding Mechanism
Worm Shaft & Worm Wheel
The worm wheel is ground at high precision and the worm shaft was processed with a precision abrasive finish (see Fig. 3).
Tangent-Bar System (Ball Screw)
This is the optimum feed system when the rotation range is small (5 to 10°) but a fine rotary movement at a high resolution is required. Rotary movement is generated by applying linear displacement to the bar tip extending from the rotary axis in the tangential direction by means of a ball screw.
Ideal Resolution
Ideal Resolution of stage RA05A-W, RA07A-W, RA10A-W are calculated based on the following formula.
ΔΘ = Δθ / n*m | ΔΘ： Ideal Resolution※ |
Δθ： Basic step angle of motor | |
n ： Reduction ratio of Worm shaft and Worm wheel | |
m： Division number of micro-step |
※ The minimum resolution described in this catalog is calculated with two (2) divisions of the standard motor step (half-step, where the value of m is 2).
Model Number | n | m | Δθ（°/pulse） | Resolution (° / p) |
RA05A-W | 90 | 2 | 0.36 | 0.002 |
RA07A-W | 90 | 2 | 0.36 | 0.002 |
RA10A-W | 180 | 2 | 0.72 | 0.002 |
RA16A-W | 180 | 2 | 0.72 | 0.002 |
Ideal Resolution of tangent-bar style stage RA10A-T is calculated based on the formula below.
ΔΘ = tan-1( Δθ・P / 360・R・m ) | ΔΘ： Ideal Resolution※ |
Δθ： Basic step angular of motor | |
P ： Feed screw pitch | |
R： Length of tangent-bar (mm) | |
m： Division number of micro-step |
In the case of RA10A-T : R=108mm.
※ The minimum resolution described in this catalog is calculated with two (2) divisions of the standard motor step (half-step, where the value of m is 2).
Maximum Speed
Maximum speed depends on individual motor torque characteristics. However, we calculate maximum speed at 10kpps with motor in half-step mode.