Used Injection Molding Machine Inspection Checklist
A comprehensive inspection checklist for evaluating used injection molding machines. Know what to look for, what questions to ask, and how to identify potential problems before you buy.
Before You Inspect: Key Tips
- •Always see the machine run under power before committing
- •Request wear measurements—don't accept "good condition" without data
- •Review maintenance records for patterns of recurring issues
- •Check alarm history on the control for hidden problems
- •Consider hiring a professional inspector for high-value machines
- •Factor rebuild costs into your purchase decision
1. Documentation & Records
2. Injection Unit
3. Clamp Unit
4. Hydraulic System
5. Control System
6. Electrical System
7. Operational Test
Screw & Barrel Wear Reference
Understanding screw and barrel wear measurements is critical. Here are typical values:
| Condition | Clearance (inches) | Action |
|---|---|---|
| New / Excellent | 0.003" - 0.005" | No action needed |
| Good / Acceptable | 0.005" - 0.010" | Monitor; budget for future replacement |
| Worn | 0.010" - 0.015" | Plan replacement; negotiate price |
| Excessive | > 0.015" | Requires immediate replacement; factor into price |
Note: Clearance is measured as (Barrel ID - Screw OD) / 2. Values vary by machine size and manufacturer— consult OEM specifications for exact tolerances.
Red Flags to Watch For
Mechanical Issues
- • Heavy scoring on tie bars or platens
- • Cracks in castings or frame
- • Excessive play in toggle joints
- • Signs of crash damage (bent components)
- • Unusual noises during operation
Hydraulic Issues
- • Active leaks (especially at pumps/cylinders)
- • Dark, contaminated oil
- • Pump whining or cavitation noise
- • Slow or jerky movements
- • Overheating during operation
Control System
- • Recurring alarms in history
- • Non-functional screens or menus
- • Temperature control inaccuracy
- • Missing or corrupted recipes
- • Obsolete software with no update path
Documentation
- • No maintenance records available
- • Unwillingness to provide measurements
- • Machine hasn't run in extended period
- • Unknown history or ownership gaps
- • Missing critical manuals/schematics
Frequently Asked Questions
What are the most important things to check on a used injection molding machine?
The three most critical inspection areas are: 1) Screw and barrel wear - affects shot consistency and quality, 2) Clamp mechanism and platen condition - affects mold protection and part quality, 3) Control system function - determines machine capability and maintainability. These items most directly impact production performance.
How do I check screw and barrel wear on an injection molding machine?
Request wear measurements from the seller - reputable sellers measure screw OD and barrel ID at multiple points. New clearance is typically 0.003-0.005 inches; wear beyond 0.010-0.015 inches usually requires replacement. Look for spiral patterns or grooving on the screw and any signs of galling.
Should I run the machine before buying?
Absolutely. Always insist on seeing the machine run under power, preferably making parts if possible. Observe cycle times, listen for unusual noises, watch for hydraulic leaks, and verify control functions. A machine that's been sitting unpowered may have issues that only appear when running.
What documentation should I request when buying a used injection molding machine?
Request: maintenance records, machine manuals/schematics, shot count/hour meter readings, any rebuild documentation, service history, and electrical drawings. Good documentation indicates the machine was professionally maintained and simplifies future service.
How important is the machine's age vs. hours of operation?
Hours of operation and maintenance history matter more than age. A well-maintained 15-year-old machine with moderate hours may outperform a neglected 5-year-old machine. Focus on condition indicators like wear measurements, maintenance records, and operational testing rather than just the year built.
Ready to Buy?
Browse our inventory of inspected used injection molding machines. Every listing includes detailed specifications, photos, and condition information. Our team can answer your questions about any machine.
