Project:
Create a proposal to automate ultrasonic degating of an injection moulded medical device component.
Solution to be used within a class 8 cleanroom environment.
Concept developed using Solid Edge.
Design Considerations:
Client preference not to use a PLC controller with this solution.
Client has robot to remove components from the mould.
Robot currently drops components into a bin for manual degating.
Injection moulding machine produces other components.
Mould position may vary slightly between changeovers (+/- 1mm).
Solution to be mounted on a rolling cage.
Cage position subject to horizontal positioning tolerances.
Cage position subject to vertical positioning tolerances due to unevenness of floor, caster orientation etc.
Nest Design:
- Nest design- negative of gate
- Hole for lowest point of sprue tapered to allow part to engage with nest if there is a horizontal misalignment of up to +/- 2mm
- Compensate for slight differences in alignment between changeovers
- Robot calibrated to mould position during changeover
- Slight differences in moveable cage alignment
Vertical Misalignment Compensation:
- Prevent robot crashing into nest due to variations in floor height/castor position
- 10mm vertical travel
- Nest suspended by springs within hollow vertical guides (shown gold here for clarity)
- Bezel washer bolted to end of tie rods compress spring when no load applied
- Nest reaches bottom of travel when ultrasonic press actuates.
- Any fragments due to metal on metal contact from spring are contained within the housing by bushing (cleanroom suitable).
X-Axis Misalignment Compensation:
- Linear bearing allows nest to slide parallel to robot x-axis
- Pushed by part sprue engagement with tapered hole in nest
- Spring plungers return nest to central position when robot releases part
Y-Axis Misalignment Compensation:
- Linear bearing allows nest to slide parallel to robot y-axis
- Pushed by part sprue engagement with tapered hole in nest
- Spring plungers return nest to central position when robot releases part
Nest Positioning:
- Use guided cylinder to position nest for part insertion by robot
- Cylinder positions part under ultrasonic press for degating
Error Detection & Rework:
- If part degating unsuccessful, whisker switch is triggered
- Whisker switch causes cylinder to actuate
- Cylinder diverts part into bin for manual rework
Normal Sprue/Runner Disposal:
- If part degating successful, path taken by robot with sprue doesn’t trigger whisker switch
- Rework diversion cylinder remains retracted
- Sprue & runner falls into disposal bin
Machine safety:
Rolling cage connection with moulding machine is confirmed using Schmersal safety interlock switch.
Similar switch to be used on doors of rolling cage to ensure operator safety at all times.
Other considerations:
Rolling cage shown with door closed (guarding omitted for clarity)
Rolling cage shown with door open
Accurate location of cage relative to the moulding machine using ball lock pin.
Quick reliable connection to moulding machine achieved using pull action latch clamps.
