When assessing a secondhand or surplus Doosan DNM-500II, the goal is to determine whether the machine still meets high-precision manufacturing standards and offers a good return on investment. This guide provides a step-by-step technical evaluation checklist—ideal for professional resellers, consultants, and buyers in the used-machinery market.

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1. Key Technical Specifications (for Benchmarking)

Specification	Typical Value
Travel (X / Y / Z)	1,020 mm / 540 mm / 510 mm
Table size	1,200 × 540 mm
Max table load	800 kg
Spindle speed	8,000 – 12,000 rpm
Spindle taper	BT-40 or ISO-40
Tool magazine capacity	30 tools (ATC carousel)
Spindle motor	~ 11–18.5 kW
Rapid traverse (X/Y/Z)	30/30/30 m/min
Machine weight	≈ 6,500 kg
Origin	South Korea

These figures serve as baseline references. Variations may occur depending on production year and optional equipment (e.g., through-spindle coolant, chip conveyor, or probing system).

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2. Pre-Inspection Preparation

Before visiting or inspecting the machine:

• Request the serial number, production year, and origin certificate (confirm “Made in South Korea”).
• Ask for total power-on and cutting hours.
• Obtain all service logs, repair invoices, and calibration certificates.
• Confirm the installed CNC control (usually FANUC i-Series or Siemens 828D).
• Prepare a dial indicator, alignment bar, and vibration analyzer if possible.

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3. Physical and Structural Condition

3.1 Exterior & Frame

• Inspect for cracks, impact marks, or welded repairs.
• Check paint consistency—uneven or fresh paint may conceal structural repairs.
• Verify that doors, guards, and covers operate smoothly.

3.2 Guideways & Ball Screws

• Visually inspect linear guideways for scoring, pitting, or discoloration.
• Move each axis at slow and fast feedrates—listen for grinding or chatter.
• Use a dial indicator to test backlash on X, Y, and Z axes.
• Ensure the lubrication system is active; look for oil film on guideways and no leaks under the machine.

3.3 Spindle & ATC System

• Run the spindle at low, medium, and maximum rpm—note any abnormal noise or heat.
• Check spindle run-out using a precision test bar.
• Inspect the taper for scoring or corrosion.
• Test automatic tool change for all pockets (no mis-alignment, sticking, or slow operation).

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4. Electrical, Hydraulic, and Control Systems

• Open the electrical cabinet—verify cable routing, labeling, and absence of burned connectors.
• Ensure fans and filters are clean.
• Power up the machine and confirm the control boots properly without alarms.
• Test all panel buttons, MPG handwheel, and emergency stop.
• Check hydraulic and pneumatic circuits for pressure stability and leaks.
• Review system logs for historical alarms or servo overloads.

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5. Functional & Accuracy Tests

Perform live tests to evaluate machine integrity:

Test	Purpose	Acceptance Criteria
Axis movement test	Smoothness, noise	No vibration or stuttering
Spindle thermal run test	Bearing condition	< 0.01 mm run-out
Circular interpolation test	Geometric accuracy	± 0.005 mm deviation
Tool-change cycle test	ATC performance	< 3 seconds, no jams
Power-off recovery	Control reliability	Position memory retained
Coolant & chip conveyor	Auxiliary system check	No leakage, proper flow

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6. Maintenance & Parts Availability

• Confirm periodic maintenance (lubricant and filter replacement intervals).
• Ask if any major overhauls were done (e.g., spindle rebuild, ball-screw replacement).
• Verify availability of spare parts and service support from DN Solutions (Doosan).
• Ensure the installed CNC version still receives software updates.

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7. Suitability & Value Assessment

Evaluate based on your production needs:

• Does the table size and axis travel suit your part envelope?
• Is the spindle speed adequate for your materials (aluminum vs steel)?
• Does the machine include valuable options like through-spindle coolant or probing?
• Compare its market price with similar-age units on platforms.
• Estimate setup, transport, and re-alignment costs before finalizing the purchase.

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8. Contract and Documentation Checklist

• Specify in writing whether the machine is sold “as-is” or “fully serviced.”
• Define acceptance tests (accuracy, tool-change, spindle noise).
• Include delivery, installation, and training responsibilities.
• Attach an inspection report signed by both buyer and seller.
• Ensure payment terms protect both parties (e.g., deposit + balance after installation).

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9. Quick Final Checklist

✅ Machine exterior free from cracks or corrosion
✅ Guideways lubricated and backlash minimal
✅ Spindle runs quietly with low run-out
✅ Tool changer fully operational
✅ Control system error-free
✅ Cooling and lubrication systems functional
✅ Maintenance records complete
✅ Power and control components original, not modified
✅ Test part meets tolerance
✅ Transport and re-installation costs calculated

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Conclusion

A well-maintained Doosan DNM-500II remains one of the most reliable 3-axis vertical machining centers in its class—offering a strong spindle, rigid casting, and wide global parts availability. When inspected thoroughly according to this guide, it can provide years of productive service at a fraction of the cost of a new unit.