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

Evaluating a used servo press - 10 point inspection

chris_auto

Went to look at a used servo press last week. Here's my 10-point inspection process and what I found.

Before You Visit:
- Request maintenance records and alarm history from the drive
- Ask for the original tonnage monitor calibration certificate
- Check if the OEM still supports the control system

10-Point On-Site Inspection:
1. Slide parallelism: Measure at four corners. Reject if >0.05mm on presses under 500 tons.
2. Gib clearance: Clearance >0.1mm means liner replacement needed.
3. Brake stopping time: Should be within 10% of OEM spec.
4. Drive alarm history: More than 5 overcurrent faults in the last year is a red flag.
5. Encoder cable condition: Inspect the full cable run for repairs, tight bends, and oil contamination.
6. Counterbalance pressure: Check against OEM spec.
7. Lubrication system: Run the lube pump and check flow at each lube point.
8. Control system response: Run 10 strokes and check position repeatability. Should be +/-0.02mm or better.
9. Frame cracks: Inspect crown, uprights, and bed. Any cracks are disqualifying.
10. Tooling compatibility: Verify shut height, bolster dimensions, and T-slot pattern.

Price Negotiation: gib liner replacement (~$2,000-5,000), encoder cable (~$500-1,500), drive capacitors (~$1,000-3,000) are legitimate deductions from asking price.

pete_retro

Point 11 that should be on every list: check the press frame for cracks. Use dye penetrant inspection on the stress concentration areas —column-to-crown joints, tie rod threads, and bed-to-column connections. Frame cracks are a deal-breaker. I've found hairline cracks on 3 out of the last 20 used presses I've inspected.

carlos_mx

Also check the electrical cabinet for signs of water damage or rodent activity. Open every panel and look at the wiring. Corroded terminals and chewed wires are expensive to fix and indicate the press was stored or operated in poor conditions. If the cabinet is clean and well-maintained, the rest of the press probably is too.

jim_apps

Dye penetrant inspection is key ??frame cracks are the one thing that can turn a bargain into scrap metal.

I would add: check the encoder and position feedback system carefully. Put the press in inch mode and watch the position readout. It should be rock-steady at any point in the stroke. If you see the position value flickering or jumping, the encoder is failing. Replacement encoders for older servo presses can be $8K-15K and have 12-week lead times.

Also run the press at full speed with no die and watch the tonnage monitor. An unloaded press should show near-zero force through the stroke. If you see force spikes, the gibs are too tight, bearings are worn, or the slide is binding. Any of those means a rebuild.

One more: ask to see the drive parameter backup. If the previous owner never saved parameters and the drive fails, you are starting from scratch on tuning. That can be weeks of work on a complex servo system.

raj_pm

One thing I forgot to mention in my earlier post ??bring a thermal camera if you can borrow one. Even a FLIR One phone attachment works.

Run the press at full speed for 30 minutes unloaded, then scan the motor, drive cabinet, and bearings. Hot spots tell you things that visual inspection can't:
- Motor bearing running 20C above ambient on one side = bearing wear starting
- One drive module significantly hotter than others = power stage degradation
- Crown bearing housing hot = lubrication issue

The other big one for used servo presses specifically: ask to see the drive's internal hour meter and cycle counter. Compare against what the seller claims. I looked at a "low hours" Komatsu H1F last year ??seller said 8,000 hours. Drive showed 23,000. That's not a red flag by itself (23K hours on a well-maintained press is fine), but the dishonesty told me everything I needed to know about the maintenance records they provided.

Also worth checking: does the press still have its original servo motor, or was it replaced? Look at the motor nameplate date vs press build date. A replaced motor isn't necessarily bad, but you want to know WHY it was replaced and whether the replacement is OEM spec or a "close enough" substitute. Wrong inertia ratio on a replacement motor causes tuning problems that show up as position overshoot at high SPM.