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#315 Know-how on automation: Designing high-speed automation devices-2

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November17, 2017
(1) Issues in designing high-speed equipment

- The following points must be kept in mind when developing an automation device that drives at a high speed:
a) Selecting an appropriate actuator that supports high-speed driving and how to use it efficiently
b) Characteristics of the mechanical components that support high-speed driving

- Since the two issues a) and b) are correlated, it is critical to incorporate both of them when developing an optimal design for high-speed equipment.
- If the two issues are handled separately, the engineer working on b) tries to develop a high-precision and high-rigidity mechanism, which tends to be a heavier structural object, while another engineer working on a) will develop an expensive system as he plans to adopt high-precision control and high-power driving design.
- To develop an optimal design by considering the both issues, the equipment development can be carried out in line with the concept introduced hereinafter. By following this concept, it is possible to develop a lightweight yet highly rigid design by incorporating both the actuator's motion characteristics and optimal mechanical structure.

Optimal equipment concept for high-speed design ---- High-speed equipment realizing minimum energy consumption

(2) Vital points in designing high-speed equipment

- The following six points are important in designing high-speed mechanical design:

  1. Adopt a rib structure for the movable components to the extent without affecting the rigidity.
    Description: Develop a lightweight design for the movable body without decreasing the strength.
  2. Keep the point of effort and the center of gravity on the movable body as close as possible, and minimize the effect of the moment of inertia.
  3. Simplify the structure and reduce the number of the components of the transmission drive mechanism to develop a highly rigid structure, thereby increasing the servo stiffness.
    Description: Reducing the number of components used for the motion area (especially the number of joints between the actuator and the movable body) can prevent servo stiffness from being degraded and can also minimize unstable vibration during control, etc.
  4. For the triple axis drive using the X, Y, and Z shafts, the load placement must be optimized, such as by moving the load applied on a shaft used for high-speed driving to the other shafts.
    Description: To use the Y-axis for high-speed driving, design the structure so that a large portion of the load will be applied to X-axis and Z-axis, while reducing the load on the Y-axis movable body.
  5. Safety measures for limiting a driving range of the high-speed movable part
    Description: Installing runaway stoppers (Fig.1) or a safety cover for the movable body
  6. Select flexible and highly reliable wiring for connecting the drive actuator
    Description: For the mechanism used for repeated reciprocating motion, the actuator joint of the movable body is prone to fracture. Thus, selecting an appropriate cable carrier (Fig.2) is critical. If an inappropriate cable carrier was adopted, it hinders the cable carrier motion, which may degrade the positioning accuracy or cause cable disconnection or abrasion of carrier components (made of plastic). Ultimately, unexpected problems, such as the equipment contamination by wear debris, could occur.

[Fig.1] Example of two stoppers for movable body

[Fig.2] Cable carrier

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