Mechanical System
Clamping Unit
Toggle-Type Clamp
| Component | Maintenance | Frequency |
|---|---|---|
| Toggle pins and bushings | Grease via central lubrication | Every cycle |
| Toggle pin axial play | Measure with dial indicator | Yearly (replace if > 0.3 mm) |
| Crosshead guide rails | Clean and grease | Weekly |
| Clamp cylinder seals | Inspect for leakage | Monthly |
| Mold height adjustment mechanism | Grease threads | Yearly |
| Moving platen guide shoes | Adjust clearance (0.05–0.10 mm) | Quarterly |
Two-Platen Clamp
| Component | Maintenance | Frequency |
|---|---|---|
| Tie bar nut clamping mechanism | Check lock/unlock function | Weekly |
| Axial displacement sensors | Check zero point | Monthly |
| Platen guide rails | Clean and grease | Daily |
| Clamp cylinder rod seals | Inspect for leakage | Monthly |
Injection Unit
| Component | Maintenance | Frequency |
|---|---|---|
| Screw | Pull and inspect flights | Monthly |
| Non-return valve (check ring) | Measure ring gap | Quarterly (replace if > 0.1 mm) |
| Barrel | Measure I.D. at feed, transition, metering zones | Yearly |
| Screw drive gearbox | Check oil level | Weekly |
| Screw drive gearbox oil change | Replace gear oil | Yearly |
| Injection cylinder rod seals | Inspect for leakage | Weekly |
| Carriage guide rails | Grease | Weekly |
| Nozzle / sprue alignment | Check alignment to mold | Monthly |
| Heater bands | Measure current draw per zone | Quarterly |
| Thermocouples | Compare to calibrated reference | Quarterly |
Tie Bar Maintenance
Tie bars are the most critical structural components of the clamping unit. Uneven tie bar stress causes mold damage, poor part quality, and machine frame fatigue.
Tie Bar Elongation (Stretch) Measurement
- Install dial indicators or ultrasonic sensors at the outboard end of each tie bar.
- Apply clamp force at the normal set point.
- Record the stretch for each bar.
- Target: all four bars within ±5% of each other.
- If out of tolerance, re-torque the nut on the low-stretch bar to increase its load.
Tie Bar Inspection Schedule
| Inspection | Frequency |
|---|---|
| Visual check for thread damage | Monthly |
| Nut alignment mark check | Weekly |
| Elongation measurement | Monthly (first 6 months), then quarterly |
| Magnetic particle (MT) crack inspection | Yearly |
| Ultrasonic (UT) for internal cracks | Yearly (high-cycle machines) |
Ejector Unit
| Task | Frequency |
|---|---|
| Cycle full stroke, check smoothness | Weekly |
| Inspect ejector rods for bending | Monthly |
| Lubricate ejector guide bushings | Weekly |
| Check ejector return function | Weekly |
Screw / Barrel Wear Limits
| Screw Diameter | New Clearance | Replace at |
|---|---|---|
| ≤ 30 mm | 0.08–0.12 mm | > 0.30 mm |
| 31–60 mm | 0.10–0.18 mm | > 0.40 mm |
| 61–90 mm | 0.15–0.25 mm | > 0.50 mm |
| > 90 mm | 0.20–0.30 mm | > 0.60 mm |
Screw and barrel wear accelerates once the nitrided case is worn through. Regular measurement helps plan replacement before wear causes shot weight instability.