Screw Drive Test

Simplifying the system: Replacement of three devices with one linear rotary actuator.

The use of a SMAC actuator as a screwdriver has expanded to disc drive assembly. Typical screw sizes are M2 & M3 using STAR socket heads. A common method is the use of an electric, brushless rotary screwdriver which is attached this to a high precision pneumatic slide. Electronic screwdrivers can be programmed with a maximum torque level, monitoring torque and using a Hall Effect sensor for rotary rpm.

A couple challenges with this method are related to both the linear and rotary axis. As for the linear, precise height alignment is necessary at pick and place locations. Since the end of stroke is a physical adjustment and not programmable, the manual tuning is a nightmare. Sometimes, two pneumatic slides are used to accommodate these two locations, long stroke for pick position and second slide for force controlled extension during threading. A proportional valve is used to control the extended force but it remains difficult to keep accuracy.

The rotary axis is not able to determine position or the linear movement, thus neither the pitch, the number of rotations nor the first thread CCW can be confirmed. The cost of this combination can run up to US$10,000. In comparison, the SMAC linear rotary electric actuator is an all in one, off the shelf solution, providing a long stroke with fast approach, Soft-Land function at both positions pick and place, constant accurate force control while threading, monitoring the torque, pitch verification. Good, shallow, cross, or no threads as well as the precision of the thread are detected through linear position feedback. SMAC provides this at 50% less the cost of the previous method.

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