he DMG DMU 35 M is a compact, high-precision universal machining center known for its rigidity, accuracy, and multi-side machining capabilities. However, buying one on the second-hand market requires disciplined evaluation. The following steps help ensure you make a smart, safe, and profitable investment.

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1. Confirm Model Identity & Machine Configuration

The DMU 35 M family includes variations across production years. Start with:

What to Verify

• Exact model: DMU 35 M (not confused with DMU 35 eVo, DMU 35 monoBLOCK, or early Deckel Maho versions)
• Year of manufacture
• Control type:
  • Heidenhain TNC 426 / 430 / 530
  • Siemens 840D
• Spindle version (rpm rating and power)
• Whether the machine has:
  • 3-axis configuration or 3+1 with swivel table
  • Integrated tool changer and tool storage size
  • Coolant through spindle (CTS) or external coolant only

Why it matters: Configurations differ widely. Controls, spindle ratings, and options affect price, accuracy, and maintenance cost.

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2. Inspect the Mechanical Condition Thoroughly

The mechanical structure is the backbone of the DMU 35 M. Pay close attention to:

Key Inspection Points

• X/Y/Z ball screws: Listen for rattling or inconsistent movement.
• Linear guides / slideways: Check for wear lines or vibration marks.
• Spindle bearings:
  • Run at low, medium, and high rpm
  • Listen for humming, grinding, or heat buildup
  • Measure spindle runout with a dial indicator
• Axis backlash test:
  • Ensure positioning accuracy remains within spec
• Machine geometry:
  • Perform a ballbar test
  • Check orthogonality using granite square or laser measurement

Why it matters: These components determine long-term stability, cut quality, and service cost.

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3. Evaluate the Spindle Health

The DMU 35 M typically features high-speed spindles in the 12,000–18,000 rpm range.

Checklist

• Noise levels at incremental speeds
• Spindle warm-up behavior
• Drawbar force measurement (critical for tool retention)
• Taper condition (HSK or SK/ISO taper)
• Vibration analysis if possible

Red flags

• Overheating after a few minutes
• Metallic noise
• Low drawbar force

Spindle repair costs can be high—do not skip this evaluation.

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4. Review the Control System (Heidenhain or Siemens)

The control is the machine’s brain. Evaluate:

Check These Elements

• Boot time and error messages
• Condition of keyboard, buttons, CRT/LCD screen
• Servo amplifiers and drive modules
• Backup battery status
• Presence of manufacturer parameters and PLC programs
• Smoothness of axis jogging
• Functionality of handwheel / MPG
• Tool change cycle test

Ask the seller for:

• Machine parameter backups
• Original manuals
• Control diagnostics reports

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5. Inspect the Table, Fixtures & 4th Axis (if included)

Critical Points

• Table wear, scratches, or drill marks
• Runout of rotary table
• Clamping force of the table
• Condition of pneumatic/hydraulic connections

If the machine has a swivel rotary table, verify:

• Smooth rotation
• Accurate positioning
• No backlash in the A-axis

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6. Check the Tool Changer System

Evaluate

• Condition of tool magazines
• Smoothness of ATC arm movement
• Sensors and pneumatic valves
• Tool pocket wear

Test:

• Tool change with a full cycle
• Emergency stop during tool change to ensure recovery works properly

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7. Review the Electrical Cabinet and Wiring

Electrical issues can be expensive. Open the cabinet and inspect:

What to Look For

• Cleanliness and absence of burnt smell
• Proper cooling and ventilation
• No loose connectors or corrosion
• Module fans working correctly
• Servo drives free from error logs

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8. Inspect Hydraulic, Pneumatic & Coolant Systems

Checklist

• Leaks in hoses and fittings
• Hydraulic pump noise
• Pressure consistency
• Coolant tank contamination
• Chip conveyor operation
• Mist collector & coolant chiller (if equipped)

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9. Verify Machine Hours & Maintenance Records

Ask for:

• Spindle hours
• Cutting hours
• Axis hours
• Complete maintenance folder
• Service reports from DMG or independent engineers

Machines with low cutting hours but high idle hours may indicate extended non-use, which can also cause issues.

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10. Run a Real Cutting Test

Always request a cutting demonstration:

Measure

• Surface finish quality
• Dimensional accuracy on a test block
• Repeatability across multiple passes
• Circularity test (boring / interpolated circle)
• Stability during heavy milling

Cutting tests reveal what static inspections cannot.

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11. Confirm Tooling, Accessories & Software Included

Evaluate the value of included extras:

• Tool holders
• Collet chucks
• Vises, clamps, fixtures
• Probing system (Renishaw, Blum)
• 3D measuring probe
• Coolant through spindle pumps
• Chip conveyor
• Manuals & documentation
• CAM post-processor availability

Even small accessories can save thousands.

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12. Assess the Total Cost of Ownership

Before buying, calculate the total investment:

Consider

• Transport costs
• Loading/unloading
• Foundation requirements
• Installation & calibration
• Control retrofit options
• Annual maintenance cost
• Potential spindle rebuild estimation
• Warranty availability

If buying from abroad, include:

• Customs fees
• Insurance
• Packing cost
• Export documentation fees

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13. Check the Seller’s Credibility

Before finalizing the deal:

Investigate

• Seller’s track record
• Customer reviews
• Photos and videos from the actual machine
• Ownership documents
• Machine is fully paid and not leased/encumbered

Never rely solely on stock photos.

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Final Recommendation

A used DMG DMU 35 M is an excellent investment when the mechanical accuracy, spindle condition, control integrity, and accessories are verified. These machines are built with German precision and can deliver years of trouble-free production when properly assessed before purchase.

Following these proven steps will help you confidently analyze any pre-owned DMU 35 M and negotiate the best possible deal.