Machine Design

Smooth driver eliminates stepper resonance problems

Requirements coming out of semiconductor manufacturing have resulted in the development of a stepmotor driver able to generate up to 500,000 steps/rev. This high resolution effectively eliminates vibration and motor resonances that lead to missing steps. Among the first applications for the new motor driver is in a positioning gantry that places precision parts on an assembly line.

Called nanospeed drivers, the INS50 and INS500 series are both bipolar constantcurrent chopper units programmable down to 0.001 step. This means the smallest degree of step when operating with a five-phase motor would be 0.00072. For comparison, a five-phase stepper operated with an industry-standard driver would hit 0.18 resolution at best.

The nanospeed drivers are designed to work with NEMA-17 to 34 high-torque fivephase motors rated 1.4 to 2.8 A. The dc series operates from a 24-V supply.

According to driver developer Nyden Corp., a subsidiary of Mycom Inc., San Jose, a torque chip in the driver maintains maximum holding and running torque during each nanostep. It also generates a correction value for each operating position as the motor runs. In addition, it calculates values for PWM outputs and d/a conversion outputs for presentation to driver circuitry.

Thermal management is an ancillary benefit, says Nyden. An auto current-down-disable feature in the INS50 keeps motor temperature to just 80F after three hours of operation. A built-in cooling fan also helps.

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