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Our Guide to Rewinding Servo and Spindle Motors

There are a number of steps that should be followed for rewinding spindle and servo motors, and adhesion to these is the most effective way to ensure success.

• The old copper windings first need to be removed and this process starts in the burn out oven. Heating the old coils softens the enamel and makes them more pliable and easier to remove. This is also the time to gather data on the motor, such as schematic drawings as all information available will assist in the rewinding process. Taking photographs of the windings as they are removed is a useful, graphical form of data.

• Once stripped of copper, the stator can be cleaned and sprayed with insulating paint, and phase paper fitted to protect against ground faults.

• Coil heads can now be fitted, ensuring that they have the correct curvature and will fit into the housing without fouling.

• The information gained during the burn out phase now becomes important. The size and type of wire, the number of windings; and shape need to correct to allow the duplication of the motors magnetic properties.

• Once installed, the coils must be internally connected with lead wires fitted. These must be connected correctly as per the original to ensure correct operation and alignment. Incorrect assignment in a three phase motor could lead to it operating in reverse.

• Once installed, the coils are tied off with specialist string and quality checked for form, winding accuracy and stray wires. All the windings should be grouped together and follow the form of the old windings. A comparison photograph is useful at this point.

• Once checked the motor can be dipped in varnish and cured in an oven, electrically sealing the coils and reducing the chances of vibration in the finished motor.

• The final element of the process is testing. This involves a surge check, resistance check and a test on polarity.

• Once tested, the motor is reassembled and a back EMF check is carried out to check that the motor is operating within its required parameters and producing the correct level of torque at the required RPM. On passing this, the motor can then be forwarded to the next stage of the rebuild.

The key to this process is accuracy, as each stage is essentially a duplication of a previous set up. Having high quality data initially will help ensure a successful spindle and servo motor rewind.

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