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| Question: Which motor is right for you? |
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| Answer: |
Two types of motor technology exist in the market, one is a Stepper motor and another is a Servo motor. Both technologies are employed to laser engraving machines. What exactly is the difference between these two control approaches? Which one is better for your equipment?
Servo control technology applies a higher quality motor and controller to send command to the motors and utilises an encoder to feedback location values to the controller, so the motors always verify their positions. This continual link allows the motors to run faster with higher acceleration and speed that the laser engraver can cut or engrave and also you can move the laser carriage to any position and resume working precisely. Adopting the servo control technology, LaserPro provides a completed line of servo-controlled laser engravers that have an exceptional reputation to produce some of the highest 2D and 3D engraving effects with superior accuracy.
Stepper motors means the motor moves step by step. This is an open-loop device without any feedback information. Thus, the motor cannot accelerate too fast or it will miss steps. Furthermore, the carriage cannot be moved freely by hand since the stepper motor does not have position feedback device to track carriages.
The following comparison sheet presents a clear and thorough examination between servo motor and stepper motor. |
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Servo motor |
Stepper motor |
| Accuracy (1) |
High |
Low |
| Throughput |
High |
Low |
| Acceleration (2) |
High |
Low |
| Speed (3) |
High |
Low |
| Cutting quality (4) |
High |
Low |
| Oscillation |
Low |
High |
| Cost |
High |
Low |
| Size |
Big |
Small |
| Noise |
Low |
High |
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Remark:
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(1) The servo motor provides constant positional feedback to the controller, which corrects any discrepancy between desired and actual position. When told to move 10 inches down and 10 inches right from home position, it would go exactly to (10,10) position as what it is told. The stepper motor applies the open loop communication with the controller, any steps missing would not be automatically corrected and thus accrue poor positional accuracy.
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(2) The acceleration would be the crucial factor to decide the throughput of laser engravers instead of the speed value. The acceleration defines how much time the machine takes to reach the maximum speed. One 100ips laser engraver with stepper motor has much lower throughput than one 80ips machine with servo motor because of the acceleration differences. The stepper motors cannot have the high acceleration as the servo motors, due to the excessive high acceleration would lose steps and accuracy.
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(3) A laser engraver equipped with a stepper motor have certain speed limitations due to the stepper motor’s poor torque characteristic under high speed movement, and the result is losing steps and precision.
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(4) The stepper motor would lose steps and movement accuracy due to resonance of the motor at low speed movement. While cutting through material under very slow speed, any missing step would break the path movement harmony and destroy the cutting quality. The resonance also makes the stepper much noisier than the servo motor.
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