Challenge

Lead wires normally pass directly through the wall of the motor housing and can be subjected to sharp pull forces or vibration that can degrade the solder connections if the wires are not properly secured.

Irregularities in solder joints, such as solder balls or sharp peaks, can also cause the wire insulation to wear resulting in shorts if the wires are free to move within the motor. To prevent these issues, grommets, specialty clamps and adhesives are often used to secure the lead wires.

In the case of step motors, using grommets or specialty clamps is challenging due to the small size of the motor.

The physical size of the grommet or clamp may require a larger frame housing to be used for a given motor, which is highly undesirable.

The assembly of the grommet or clamp in the small step motor housing can also be a tedious process that slows the manufacturing processes.

The added cost of grommets and clamps also reduces the desirability of these two methods.

Solution

Lin Engineering determined that adhesively tacking the lead wires to the stator with Loctite® 352™ light cure adhesive was the optimum method for securing the lead wires.

To accomplish this, the operator manually dispenses a bead of Loctite® 352™ over the wire connections on the stator wires using a hand held syringe dispenser (See Figure 1). The viscosity of the adhesive makes the dispensing process quick and easy to operate.

After the adhesive is dispensed, the coated motor assembly is then placed on a light cure conveyor. A 30 second exposure to light fully cures the adhesive.

After the light cure process, the lead wire is fully reinforced and immediately ready for subsequent handling.

Results

• Using the Loctite® 352™ light cure adhesive to secure the lead wires.The bonded joint has proven to prevent wire failures, while the long open time and fast cure of this adhesive has resulted in a very user friendly, efficient assembly process.Since the adhesive can be dispensed in any pattern, the process is very flexible: usable for all motor sizes and configurations without any tooling changes.
• Bonding the molded stators into custom housings using Loctite® 3942™ light cure adhesive as shown in Figure 2.
• Sealing Wire Connectors with Loctite® 352™ Light Cure Adhesive was the optimum adhesive for this application. (See Figure 3)