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Used servo presses can offer excellent value, but they also carry hidden risks. This 12-point inspection checklist helps you evaluate a used press before purchase.
## Before the Site Visit
1. Request maintenance records: ask for the last 3 years of maintenance logs. Look for recurring faults, major repairs, and whether scheduled maintenance was performed on time.
2. Check the drive firmware version: older firmware may have known bugs. Ask for the drive model and firmware version, then check the manufacturer release notes.
3. Verify the encoder type: absolute encoders are standard on modern servo presses. If the press uses incremental encoders, homing is required after every power cycle - a significant operational disadvantage.
## Mechanical Inspection (On-Site)
4. Gib clearance: measure with a dial indicator. Clearance above 0.15mm indicates worn gibs that need replacement (budget $2,000-$8,000 depending on press size).
5. Slide parallelism: place a precision level on the slide at TDC and BDC. Difference above 0.05mm per 300mm indicates frame distortion from overloading.
6. Crankshaft end play: on eccentric-drive servo presses, check crankshaft axial play. Above 0.1mm indicates worn thrust bearings.
7. Noise during slow-speed run: run the press at 5 SPM and listen for knocking, grinding, or irregular sounds. Knocking at BDC indicates worn connecting rod bearings.
## Electrical Inspection
8. Drive condition: check the drive cooling fans (replace every 3-5 years), capacitor age (replace every 7-10 years), and look for signs of overheating (discoloration, burnt smell).
9. Motor insulation: measure motor winding insulation resistance with a megohmmeter at 500V. Should be above 100 megaohm. Below 10 megaohm indicates moisture or winding damage.
10. Encoder battery: check the encoder battery voltage. Replace if below 3.2V. Budget for replacement batteries ($20-$50 each, typically 2-4 per press).
## Operational Test
11. BDC repeatability test: run 20 strokes at production speed and log the BDC position. Standard deviation above 0.02mm indicates worn mechanical components or drive tuning issues.
12. Overload test: run 3 strokes at 110% of rated tonnage (if the press has a tonnage monitor). The press should complete the strokes without fault. Any fault at 110% indicates the press is already running near its limit.
## Price Negotiation Points
Use inspection findings to negotiate:
- Worn gibs: deduct $3,000-$8,000
- Drive capacitors due for replacement: deduct $2,000-$5,000
- Motor insulation below 50 megaohm: deduct $5,000-$15,000 (motor rewind or replacement)
- No maintenance records: deduct 10-15% from asking price