CNC Machine Tool After Repair — How to Accept the Machine from Service

Short answer

Repair, ball screw rebuild, spindle bearing replacement, or guideway replacement changes the machine condition — but only measurement shows what that condition is after reassembly. Acceptance of a machine tool after repair is the moment when oversights are easiest to catch: the service provider is still engaged, and a protocol with numbers ends the “works / does not work” discussion. An independent inspection at acceptance protects the customer and gives an honest service provider confirmation of well-done work.

Typical situations after repair

• the machine returns from a general overhaul and must be formally accepted,
• the service replaced the ball screw but did not update compensation tables — dimensions do not hold despite the new part,
• after spindle regeneration runout or heating appears at higher speeds,
• after guideway or slide replacement axis geometry has changed,
• control parameters that nobody documented have changed after intervention in the CNC control.

What to check at acceptance after repair

1. Scope of work performed — service protocol: what was replaced, what was rebuilt, what parameters were changed.
2. Axis positioning — whether errors are within the values declared for the machine after repair.
3. Repeatability and backlash — especially in axes covered by the repair; see backlash.
4. Geometry — straightness, squareness, parallelism in the scope relevant to the repaired assemblies.
5. Spindle — runout, heating, noise after regeneration.
6. Machining trial — a test part machined under production conditions, measured after machining.

What an independent inspection can assess at acceptance

• measurement of positioning and repeatability of axes covered by the repair,
• assessment of machine geometry in the scope agreed with the customer,
• verification of whether the service provider’s declarations are confirmed by numbers,
• comparison with the pre-repair condition if an earlier report exists,
• technical report as an attachment to the acceptance protocol — neutral for both parties.

The scope depends on the machine, purpose, on-site conditions, and available equipment — we qualify the measurement scope before arrival so that acceptance takes one day, not a week.

How to talk to the service provider at acceptance

Best before the repair starts: agree which parameters will be subject to acceptance (e.g. positioning of axes covered by the repair, spindle runout) and what reference values apply. A service provider who knows that acceptance will be measured usually documents work more carefully. If the repair has already taken place — an independent measurement protocol still closes the matter: it either confirms the condition or indicates what needs correcting under warranty. In both variants numbers work in the customer’s favour.

What the result does not determine

An inspection at acceptance documents the measured condition — it does not replace the service provider’s warranty and does not guarantee that the machine will maintain parameters over time. We do not perform formal ISO calibration or issue calibration certificates; the technical report is a document describing the condition, not a certificate.

When service is needed immediately

• the first parts after repair are out of tolerance,
• new noises, vibrations, or drive errors have appeared,
• the service provider left no protocol of work performed,
• the machine additionally underwent relocation or a collision during repositioning after the repair.

FAQ

The service provider claims the machine is ‘checked’. Is that enough? It is worth asking what exactly was checked and whether the results are recorded. “Checked” without numbers is an opinion; acceptance with measurement gives values referenced to the machine documentation or ISO 230 standards.

Who should commission the acceptance measurement — us or the service provider? Preferably the customer: then the report is independent of the repair contractor. An honest service provider has no reason to object.

Are you accepting a machine tool after repair? Submit it for inspection — we will qualify the acceptance scope. Similar rules apply to CNC inspection before purchase of a used machine.