The plastic industry relies on injection molding machines to produce part after part. To endure the high demand, the motors on injection molding machines are manufactured to withstand extreme environments.
The motors are water-cooled and are unique compared to a standard motor. When repairing these motors, users should consider how to repair shop strips the motor of its coils, how it is rewound and how the windings are varnished.
Burnout Oven method
The stripping methods used by standard motor shops can be detrimental to water-cooled motors
The stripping methods used by standard motor shops can be detrimental to water-cooled motors. These shops use the Burnout Oven method, where the motors are placed in an incineration oven to heat up the varnish to make the coils pliable. Burnout oven temperatures exceed 680°F which compromise the integrity of the core with frame damage & distortion.
While distortion of any motor housing is unacceptable, a unique problem with water-cooled motors is the warping of the motor housing causing a leak in the water jacket. A faulty water jacket can allow the coolant to leak and contaminate other components of the motor.
Effects of contamination
Similar to the issues with a distorted water jacket, water-cooled motors may have rubber o-rings that are susceptible to the high heat of the Burnout Oven. When introduced to high temperatures, the o-rings can melt causing leakage of the coolant. This leakage can contaminate the windings, bearings, electronic components, etc.
This contamination can result in a slew of problems, including but not limited to damaged bearings, imbalance of rotating equipment, and breakdown of insulation. To learn more about the effects of contamination and how to prevent it, read the article Electric Motor and Generator Failures from Contamination.
MotorSafe Stripping Method
The method of motor stripping protects the motor housing and specialized elements of a motor
Unlike other motor repair shops, Dreisilker uses its MotorSafe Stripping method in place of the Burnout Incineration Method. In the MotorSafe Stripping method, they gently warm the outside diameter of the laminations to 400 degrees F with induction or non-contact natural gas.
Once heated, they hydraulically remove coils preserving 3 phase groups for data. The method of motor stripping protects the motor housing and specialized elements of a motor, such as a water jacket or o-rings.
OEM specifications
After stripping of a motor, rewinding the motor is a critical step of the repair process. They make sure to wind the motors back to OEM specifications or better using computer-controlled technology.
The original wire size and wiring data are recorded so that they can replicate the motor’s winding with uniformity and accuracy. Other shops may change specifications, substitute with inferior materials, or modify the original design.
Varnish water-cooled motors
When a motor is rewound, the windings need to be varnished to protect the motor windings from contamination and ensure electrical conductivity. The typical repair shop method for varnishing a motor is the dip-and-bake method.
While they use this method for common motor applications, they trickle varnish water-cooled motors to match the OEM standards (for water-cooled motors).
Traditional dip and bake process
The varnish follows the wire into the entirety of the slot, eliminating chances for partial discharge
Trickle varnishing is accomplished by connecting the windings to a rotating table and using electrical resistance to heat the windings during rotation. Once at temperature, a tiny stream of varnish is trickled onto the winding head. The varnish follows the wire into the entirety of the slot, eliminating chances for partial discharge in random windings.
Once fully saturated, the current is increased in the windings, resulting in the varnish curing while on the machine. This process is faster and better than the traditional dip and bake process because it cures on the machine – making it ideal for emergency repairs.
Reliability and lifetime of the motor
How water-cooled injection molding machine motors are repaired is very important to the reliability and lifetime of the motor. If they need their water-cooled motor repaired, make sure they consider which method is used for stripping the motor, how the motor is rewound and how the windings are varnished.
If they have any questions on how the repair method for water-cooled motors is different, feel free to call now.
