Servo Motors and Amplifers
Motors
 |
Matched perfectly with DeskCNC Motion control card and software and our Amplifiers |
| Matched perfectly for use with the Mach 1 control |
| Constant Torque: 170oz-in (don't compare this number to that of a stepper motor. Because this motor runs 8.4 times faster than a stepper motor, it actually has about .6HP. A 720oz-in stepper motor will have only about .36HP and a maximum full torque speed of 500rpm. |
| Peak Torque: 850oz-in |
| Speed at 90VDC: 4200 |
| Continuous Current: 7.6 A |
| Peak Current: 38A |
| Torque Constant 25oz-in/A |
| Voltage Constant: 18.4V/KRPM |
| Resistance: .66ohms |
| Inductance: 2.35mH |
| Inertia: .003 oz-in-sec-sec |
| Weight: 8.8 lbs |
| Motor Price: $350 each + $10 shipping |
| Encoder: 200 count quadrature (yields a positional resolution of .45 degrees) |
| Encoder Options: other encoder counts are available |
| Encoder Cable: 20' long, Shielded (other lengths available) |
| Encoder/Cable Price: $80 + $5 shipping |
Amplifiers
| Matched perfectly with our Servo Motor (see above) and motion control
card.
| Run DC servos with stepmotor software | 20A motor output
| 18V to 80V power supply
| PID closed loop operation
| Step and Direction control inputs
| Quadrature encoder feedback
| Anti-dithering circuit keeps motor silent
| +5VDC, 50mA encoder supply
| Pulse by pulse motor current limiting
| 0 to 20A current limit adjust range
| 25 kHz PWM frequency
| +/- 128 count servo lock range
| No tachometer feedback needed
| 250 kHz max step rate
| Latched Fault protection
| 0C to 70C operating temperature
| LED Fault indicator | Price: $145 each + $5 shipping |
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Why run servos vs. steppers?
Servos will run with full torque to speeds over 4,000 RPM. Steppers loose virtually all torque over 550 RPM. This results in more power delivered to the load. Servos and their Amplifiers run cool. They don't need large heat sinks or fans and feel cool to the touch; even under full load. Servos are closed loop. They utilize an encoder that sends information back to the Amplifier indicating whether the motor made it's position or not. Power is then adjusted to keep the motor in the correct position at all times. Bottom line......no lost steps due to stalling stepper motors.
The down sides of servos!
They are a little more complicated to get going; you need to tune them to the load they are attached to so you get perfectly square corners in your moves without under/overshooting. They will cost about $150 more per axis than a comparable stepper motor. This is due to a higher cost in the motor and the requirement for the encoder and encoder cable. If the machine runs a rack and pinion drive mechanism you will probably need a gear reduction of about 6:1 to keep the motor speed up while maintaining a reasonable travel speed. Timing belts and pulleys make excellent and low cost gear reducers!