TL;DR
A longer-than-normal cycle on the Roboshot is most often a cooling circuit problem or a slow valve response. Log each phase of the cycle to isolate where the time is being lost.
What you might see
- total cycle time above validated baseline
- cooling timer running longer than nominal
- clamp open or close time increased
- ejector dwell time unexpectedly extended
Likely causes
Cooling circuit blockage or scaling in the mold reducing heat removal rate
Cooling water temperature or flow rate outside specification
Hydraulic valve response slowed by contaminated fluid or worn spool
Cooling timer set too long, not recalibrated after a tooling change
Required tools
- Thermometer or temperature data logger (mold cooling water)
- Flow meter or bucket-and-timer test for cooling circuit flow
- Milacron Roboshot controller diagnostic screen access
- Process validation documentation
Safety first
- Hot mold surfaces cause burns. Wear heat-resistant gloves when handling mold cooling connections during or after a run.
- Lock out the main disconnect and verify zero clamp pressure before reaching into the mold area for any inspection or hose connection.
- Do not exceed the validated cooling time reduction during optimization. Premature ejection causes part distortion and potential tooling damage.
Procedure
- 1
Log the time for each cycle phase: clamp close, injection, pack, cool, clamp open, ejection. Compare to the validated cycle time breakdown.[1]
- 2
Identify which phase is adding time. The cooling phase is the most common source of creep.
- 3
Measure the mold cooling water inlet and outlet temperature difference (delta-T). A delta-T above Milacron specification means flow rate is too low or heat load is too high.[1]
- 4
Check the cooling water flow rate at the press manifold. Confirm each mold cooling circuit is open and flowing.
- 5
Inspect cooling water hoses and quick-connects for partial blockage. Disconnect and flush each circuit individually.
- 6
Check the cooling tower or chiller setpoint supplying the press. Supply temperature above spec requires a plant-level investigation.
- 7
If the clamp or ejector phase is slow, check hydraulic pressure and valve response time on the Roboshot controller diagnostic screen.
- 8
If cooling circuits are clear and temperatures are in range, review the cooling timer parameter. Reset to the value from the validated process sheet.
Sources
Milacron Roboshot All-Electric Injection Molding Machine Operator Manual, Milacron
Milacron Roboshot Injection Molding Machine Operation and Maintenance Manual, cycle time optimization and cooling system procedures (general)
View source
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