Problem: Intermittent or erratic stepper motor or stepper driver function.
Solution: This is the most common cause of failure and one of the most difficult to detect. Start by checking to insure that all connections are tight between the stepper motor and the stepper driver and controllers. Evidence of discoloration at the terminals / connections, may indicate a loose connection. When replacing a stepper motor, stepper driver or driver pack, or controller in a motion control system, be sure to inspect all terminal blocks and connectors. Check cabling / wiring for accuracy. Stress stepper motor wiring and connections for worse conditions and check with an ohmmeter. Whenever possible, use ATO shielded cables for stepper motor wiring.
Problem: Stepper motor wires were disconnected while the driver was powered up.
Solution: Avoid performing any service to the stepper motor, driver or controller while the power is on, especially in regard to the motor connections. This precaution is imperative for both the driver, as well as the technician / installer.
Problem: Poor system performance.
Solution: Check to see if the wire/cables are too long. Keep wire/cable to the stepper motor under 25 feet in length. For applications where the wiring from the stepper motor to the stepper driver exceeds 25 feet, please contact the factory for instructions, as it is likely that transient voltage protection devices will be required. Another possibility is that the stepper motor lead wires are of a gauge that is too small. Do not match your cable wires to the gauge size the stepper motor lead wires. This is a common mistake, so ATO suggests using its shielded cable for such wiring (purchased separately). Additionally, check the age of your stepper motor, as with time and use, stepper motors lose some of
their magnetism which affects performance. Typically one can expect 10,000 operating hours for stepper motors (approximately 4.8 years, running one eight‐hour shift per work day). Also, make certain that your stepper motor and driver combination is a good match for your application. Contact the factory, should you have any concerns.
Problem: The stepper motor has a shorted winding or a short to the motor case.
Solution: It is likely that you have a defective stepper motor. Do not attempt to repair motors. Opening the stepper motor case may de‐magnetize the motor, causing poor performance. Opening of the stepper motor case will also void your warranty. The motor windings can be tested with an ohmmeter. As a rule of thumb, if the stepper motor is a frame size of Nema 08, Nema 11, Nema 14, Nema 15, Nema 17, Nema 23, or Nema 34 and the warranty period has expired, it is not cost‐effective to return these stepper motors for repair.
Problem: The stepper motor driver or Driver Pack is over‐heating.
Solution: Ventilation and cooling accommodations are essential – failure to provide adequate airflow will affect the stepper motor driver’s performance and will shorten the life of the driver. Keep driver temperatures below 60 degrees Celsius. To maintain good airflow, use fans, heat sink material, and base plates, so not to exceed the maximum temperature rating of the stepper motors, drivers or controllers. Be mindful of temperatures inside cabinets and enclosures where stepper drivers may be mounted.
Note: Painted surfaces do not make good heat sink material for stepper motor drivers and controllers. Also, be certain that the environment is free from dust and debris that can clog a fan‐cooled system.
Problem: Environmental factors are less than ideal.
Solution: Environmental factors, such as welding, chemical vapors, moisture, humidity, dust, metal debris, etc., can damage both the electronics and the stepper motor. Protect drivers, controllers and stepper motors from environments that are corrosive, contain voltage spikes, or prevent good ventilation. Anaheim Automation offers products in several line voltage ranges, as well as splash‐proof, IP65 rated stepper motors. For wash‐down or explosion‐proof motors, contact the factory direct. For AC lines that contain voltage spikes, a line regulator (filter) will likely be required.
Note: If your application requires welding, or if welding is done in the same work environment, contact the factory for advice on how to protect the stepper motor driver and controller.
Problem: Pulse rates (Clock or Step) to the driver are too high.
Solution: The typical half‐step driver can drive a stepper motor at a maximum rate of 20,000 pulse per second. Pulse rates of above 60,000 pulses per second can damage the driver. See individual specification sheets for the motor and driver combination for best performance.
Problem: The stepper motor is stalling.
Solution: In some cases, stalling the stepper motor causes a large voltage spike that often damages the phase transistors on the driver. Some drivers are designed to protect itself from such an occurrence. If not, transient suppression devices can be added externally. Consult us for further information.
Problem: The stepper motor is back‐driving the stepper driver.
Solution: A stepper motor that is being turned by a load creates a back EMF voltage on the driver. Higher speeds will produce higher voltage levels. If the rotational speed gets very high, this voltage might cause damage to the driver. This is especially dangerous when the motor is back‐driven while the driver is still on. Put a mechanical stop or brake in applications that might be subject to these phenomena.