Buy against documented condition and an agreed acceptance test, not appearance or low operating hours. Verify the machine identity, inspect it under power, measure a representative test part and price any untested items as unresolved risks.
What should a pre-purchase CNC inspection include?
Start with the part you need to produce: material, drawing, tolerance, surface finish, batch size and required tooling. A machine can run normally yet be unsuitable for your work. Ask a qualified technician familiar with the model and controller to set the inspection method. Use the manufacturer’s procedures and model-specific limits rather than a universal accuracy number.
| Check | Evidence to request | Decision point |
|---|---|---|
| Identity and configuration | Clear nameplate, serial number, controller version, fitted options and accessory list. | Match the physical unit to the quotation and acceptance record. |
| Spindle | Manufacturer-prescribed warm-up, operation at agreed speeds, abnormal noise observations and appropriate runout measurement. | Investigate damage, taper condition, vibration or thermal concerns before accepting. |
| Axes and lubrication | Full agreed travel, lubrication operation, way covers, leaks and qualified backlash/repeatability measurements. | Record method, instrument, setup, temperature and results. |
| Tool changer and accessories | Repeated safe tool changes, coolant, chip removal, probing and other purchased options. | A fitted option is not automatically a working or licensed option. |
| Machining capability | Representative test cut with drawing, material, tooling and measured results. | Agree tolerances before testing; distinguish machine effects from tooling and setup. |
| Controller and records | Alarm history, available service logs, permitted parameter backups and manuals. | Confirm transferability of software, options and support with the relevant provider. |
Do low spindle hours prove good condition?
No. Counters are context, not proof of accuracy or remaining life. A low-hour machine may have suffered a collision, corrosion, poor storage or missing maintenance. A higher-hour unit may still suit the application after proper assessment. Compare counters with service records, visible wear and test results. Missing history is uncertainty; it is not evidence that a machine has never crashed.
What should make a buyer pause?
- Serial numbers or included options do not match the quotation.
- The seller refuses agreed powered testing or independent inspection without a clear reason.
- Visible impact damage, unexplained geometry corrections, recurring alarms or unsafe electrical modifications remain unresolved.
- No practical route exists for controller support, backups or replacement parts in the destination country.
Some defects are repairable. Obtain a written diagnosis, repair scope and re-test plan before deciding whether the adjusted total cost is acceptable.
What belongs in the acceptance report?
Identify the exact machine, inspection date, participants, tested functions, test method, measurements, defects and exclusions. Separate observed facts from seller statements. Attach photos and videos to the same serial number. Document what was not tested and agree whether each item requires repair, a price adjustment or rejection before payment and dispatch.
Technical references
Manufacturer documents below illustrate maintenance and inspection areas. They are not acceptance standards for every CNC model.