Here’s a professional, practical step-by-step guide to help you evaluate a used Mitsubishi M-VS20/15 CNC Gantry Double Column Mill (5 meters) — plus the key technical specifications you must verify before buying. This is designed for engineers, buyers, and workshop managers who need actionable, reliable guidance.

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How to Evaluate a Used Mitsubishi M-VS20/15 CNC Gantry Mill

Buying a large CNC gantry machine is a serious investment — and mistakes can cost tens of thousands of dollars. The steps below help you avoid hidden issues, judge real condition, and ensure you pay a fair price.

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1. Prepare Before You Inspect

Before visiting the machine:

• Request full machine history and documentation:
  • Purchase invoice
  • Maintenance logs
  • Repair history
  • Previous load tests
• Ask for recent high-resolution photos and videos of the machine idle and running.
• Get the machine’s serial number and year of manufacture to verify age and factory configuration.

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2. Visual Inspection – Structural Integrity

Start with a comprehensive visual check:

Inspect the main structure:

• Columns — look for cracks, welds, heavy surface corrosion, or misalignment marks.
• Cross rail — check for wear or cracks around the way covers.
• Table and base — inspect leveling pads and base welds for fatigue.

Check all covers and guards:

• Way covers, accordion bellows, chip guards — these wear out over time. Missing or damaged covers allow chips to scratch ways.

Look for signs of impact or accidental damage:

• Dents in columns or beam
• Replacement plates/welds

Check condition of paint and corrosion:

• Large areas of blistering paint can hide corrosion
• Rust on guideways or screws = expensive repair down-the-line

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3. Mechanical Components

Inspect core motion parts:

Linear Guideways / Ways

• Check if guides show uniform wear — inconsistent wear often means improper lubrication or past overload.

Ball Screws / Leadscrews

• Slowly turn them by hand (with machine powered OFF).
• Feel for stiff spots, looseness, backlash or binding.

Drive Components

• Inspect servo motors and encoders — look for:
  • Burn marks
  • Loose connectors
  • Water/oil contamination

Spindle System

• Check spindle taper and nose for wear
• Ensure no excessive end play

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4. Electrical & CNC Control System

Control Panel & Display

• Verify the CNC powers up cleanly — no scrambled graphics, dead segments, or checksum errors.
• Test operator buttons for responsiveness.
• Ask for the last backup of the CNC parameters.

Cables & Wiring

• Avoid machines with brittle, unprotected cable bundles.
• Look for repaired or mismatched cables.

Servo Drives / Inverters

• Check for blown capacitors around drives
• Ensure drives match the machine model

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5. Hydraulic / Pneumatic Systems

• Check for oil leaks around pumps, rails, and valves.
• Foggy or milky hydraulic oil often means water contamination.
• Test air pressure and regulator consistency.
• Inspect filters and conditioners — dirty filter = neglect.

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6. Coolant System

• Run coolant pump and check:
  • Flow rate
  • Hose condition
  • Coolant quality
• Rusty tanks and clogged lines reduce tool life and finish quality.

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7. Test Run

A good evaluation must include a running test.

Jog Axes

• Move each axis individually across full travel — listen for abnormal noise.
• Watch for jerky motion, backlash, or vibration.

Check Accuracy

If possible, use:

• Dial indicators
• Test bars
• Laser interferometer

Perform basic tests:

• 90° corner cut
• Test circle
• Align with edge finder

Compare results with original machine tolerances (listed below).

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8. Wear & Tear Indicators

Typical Red Flags

• Machines with unreported crashes
• Way covers missing or heavily patched
• Ball screws with deep grooves or inconsistent backlash
• Spindle oil leaks
• Replaced parts with different brands (may indicate past failures)

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9. Price Justification

After inspection, compare:

• Book value (200-300% below new for age & running hours)
• Repair budget (bear in mind cost of ball screw replacement, guide way scraping)
• Value of control upgrade if any

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10. Transport & Installation

Before final purchase:

• Verify foundations — large gantry machines often require special leveling pads.
• Ask for disassembly and transport plan.
• Ensure re-assembly experts are available in your region.

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Key Technical Specifications You Must Verify

Here are the most important parameters you should see on the machine nameplate or technical manual:

Specification	Typical Value
Machine Type	CNC Gantry Double Column Mill
Model	Mitsubishi M-VS20/15
Origin	Japan
Table Size	~5,000 mm X Axis (verify actual)
Y-Axis Travel	~2,000–2,500 mm (machine dependent)
Z-Axis Travel	~1,200–1,500 mm
Rapid Traverse	8–15 m/min (confirm on machine)
Spindle Speed	3,000–5,000 RPM (depends on head)
Spindle Taper	Typically BT50 or MST50
CNC Control	Mitsubishi M-Series (e.g., M80 / M800)
Drive Type	Servo motors with ball screws
Table Load Capacity	Often > 10,000 kg
Column Width	Large gantry for heavy parts

(Exact specification can vary with factory options — always confirm against the serial number and technical manual.)

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Final Tips

• Always bring a trusted technician to the inspection.
• Do not accept “it ran fine last week” without test data.
• Always power the machine and run it under load if possible.
• Keep expectations realistic — used large CNC mills rarely have OEM tolerance unless well maintained.