Contact Inspection of Soft Contact Lens Mold

Objective: Each prescription for a soft contact lens is embodied in a single plastic mold. The mold costs less than one dollar but by the time a lens is made, several dollars may have been expended, so it's prudent to check the mold for the correct measurement before it is used to make a lens. The critical dimension is the distance from the plane of the parting line to the spherical surface of the lens. Since the parting line is very sharp and the mold material is quite soft, it is necessary to make that measurement with a controlled light touch.

Solution: The SMAC actuator is equipped with a tip which is the same diameter as the parting line plane. The actuator rod can be driven through a hole in the center of the tip. A second actuator with a spherical seat on its tip is used to contain and raise the mold up against the tip of the first actuator. The force used to seat the mold against the tip is set at 30 grams. With the mold in place, the rod from the first actuator is driven towards the spherical surface of the mold and lands softly on the mold, making the measurement.

Key Operations:

• Bottom actuator lifts up, lands softly (30 grams) on the measuring tip
• Top actuator extends, lands softly on contact lens mold
• Measurement is taken
• Pass/fail status is signaled

SMAC Advantages:

• 100% parts inspection
• Linear actuator in a single ready-to-mount package
• Reproducible force setting to get consistent measurement