What is a servo press?

A servo press uses servo motors for precise force and position control during forming operations.

How do I calculate servo press tonnage?

Use our free tonnage calculator at servopress.club/tonnage-calculator.html

12-point checklist for inspecting a used servo press

ray_shopfloor

After buying one used press that turned out to be a money pit, I put together this inspection checklist. Would've saved me about $40k if I'd had it the first time.

**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
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\n**Edit:** added point about checking the encoder battery age. Learned that one the hard way after this post.

pete_retro

I'd add a 13th point: run the press empty at full speed for 30 minutes and monitor motor temperature. A healthy press should stabilize below 60?C ambient + 40?C rise = 100?C. If it's climbing past that on air strokes, something is wrong —usually gib binding or counterbalance issues.

carlos_mx

Negotiation tip: use the inspection findings to negotiate price. Every issue you document is a bargaining chip. We bought a used 200T with worn gibs and a noisy gearbox. Used the inspection report to negotiate $25K off the asking price —more than enough to cover the repairs.

mchen_servo

Solid checklist. The one thing I always add: check the encoder feedback during the test run. Put the drive in monitor mode and watch the position feedback waveform for one full revolution. A healthy press shows a smooth sinusoidal curve. If you see flat spots, spikes, or noise, the encoder is going bad or has a cable issue. Encoder replacement on most servo presses is $3-8K depending on the brand, so that is a significant hidden cost on a used machine.

Also worth checking: pull up the drive fault history if the controller allows it. On Fanuc and Siemens systems you can usually access the last 50-100 faults. Look for patterns. Occasional overcurrent faults during production might just be tooling issues, but repeated encoder faults or bus voltage errors point to electrical problems that are expensive to fix.

One more thing on the gearbox: drain a small oil sample and send it to a lab. Costs about $35 and tells you more about gear condition than any visual inspection. Iron content above 100ppm means the gears are wearing fast.

anna_plc

Coming back to this — we just finished evaluating a used Aida 200T last month and I want to add something about the DC bus capacitors that nobody checks. Pull the drive cabinet open and look at the electrolytic caps on the DC bus board. If the tops are bulging or there's any brown residue, walk away. Those caps are $800-1200 each and there are usually 4-6 of them. On a 10+ year old press they're the most likely failure point.

The other thing: ask the seller to run the press at rated tonnage, not just air strokes. Any press looks good running empty. We test with a calibrated load cell at 80% rated capacity and watch for BDC position repeatability — should be within 0.02mm over 50 cycles. The used Minster we almost bought was fine on air strokes but drifted 0.08mm under load. Turned out the ball screw had 0.05mm backlash that only showed up under thrust loading.

Also worth checking the drive's hour meter vs what the seller claims. On Yaskawa drives it's Un00C, on Fanuc check the diagnostic screen. We've caught sellers claiming "low hours" when the drive showed 28,000 hours of run time.