Operation & Maintenance
A pre-shipment inspection is decided largely before anyone travels. The acceptance criteria, the measurement method, the test part and the document set all belong in the purchase order, written when the machine is specified rather than when it is finished. The inspection then does four things in one visit: it confirms the machine’s identity and configuration, checks function and safety devices, records geometry against the specified tolerance, and proves performance on a real part. What it is not is a last chance to renegotiate a specification that was never agreed — an inspection commissioned after the machine is packed can only confirm what has already happened.
Why the preparation matters more than the visit
Two pre-shipment inspection visits can look identical on paper and have completely different outcomes. The difference is not the length of the visit or the number of people in the room; it is whether the criteria being measured against were agreed before the machine was built.
When they were, the inspection is mechanical. The machine is identifiable against the order, the configuration is checked against a list, the geometry readings are compared against a stated tolerance, and the test part is measured against a drawing. Every result is a pass or a fail, the record is a document, and the balance payment can be released on the strength of it.
When they were not, the inspection becomes a discussion. A tolerance is described as “high precision”, a test cut is whatever the machine happens to produce, and the acceptance criterion quietly becomes the performance of the machine in front of you. That is not a conspiracy; it is what happens when a criterion does not exist. The remedy is entirely procedural, and it costs nothing at the specification stage: state the numbers, the method and the artefact in the order. The same discipline applies to the machine’s specification as to the commercial offer, and the two documents should be read together — what a machine tool quotation includes and leaves out is the commercial half of the same exercise.
The test to apply to your own order
Read the acceptance section of the purchase order and ask whether a stranger could use it to decide pass or fail. If the answer depends on knowing what the machine normally does, the criterion has not been written yet.
Writing the acceptance criteria into the order
A pre-shipment inspection measures against criteria, so those criteria have to exist first. Three kinds of accuracy have to be distinguished, because they are measured three different ways and a machine can be strong in one and ordinary in another. Geometric accuracy covers the straightness, squareness and parallelism of the axes and is checked statically against the machine’s alignment specification. Positioning accuracy and repeatability describe how close an axis gets to a commanded position and how tightly it returns, and they are measured over a stated travel with a stated instrument. The third, and the one that decides whether the machine is fit for the job, is the production tolerance held on your part, demonstrated on a real part over a run of pieces rather than a single measurement.
Each of those needs a stated method, not just a number. Write down the instrument, whether readings are taken cold, after the warm-up routine, or both, and the ambient condition. Two parties measuring the same machine with different instruments at different temperatures will produce different results, and the disagreement costs more than the measurement ever did.
Then define the artefact. The cleanest arrangement is an acceptance test part: a drawing supplied with the order, produced on the machine, measured and recorded, with the number of consecutive parts that must fall within tolerance stated. Where the part is confidential, define a test cut instead — a specific turning or milling operation, on a specific material, with named features to be measured — and state clearly in the order that this substitution is agreed. Improvising the substitute on the day is how an acceptance test becomes a demonstration.
Finally, decide who witnesses it and where. Acceptance may take place at the builder’s works, by video with the machine identification read from the control, or partially again on arrival at your site. All three are workable, and each has to be written down, because the alternative is discovering on the day that the people who need to sign are in different countries.
What the inspection actually covers
An inspection visit covers five groups of checks. Working through them in a fixed order keeps the day short and makes the record complete.
| Group | What is verified | Evidence produced |
|---|---|---|
| Identity and configuration | Model, machine number and control against the order; every option, accessory and workholding item against the agreed list; the components actually fitted identified by brand | Photographs of nameplates and the control identification screen, plus the configuration list marked line by line |
| Function and safety devices | The machine powered and cycled; spindle, axes, turret or tool changer and coolant functioning; door interlock, emergency stop, guard switches and limit switches tested rather than assumed | Signed functional check sheet, with any device that failed to operate recorded with the action taken |
| Geometry | Leveling and alignment of the bed; straightness, squareness and parallelism of the axes; positioning accuracy and repeatability, measured with the agreed instrument and in the agreed thermal condition | Readings recorded against the tolerance in the alignment specification, with the instrument and the thermal state noted |
| Performance | The acceptance test part or the agreed test cut, run on the real material, measured feature by feature against the drawing, over the stated number of consecutive parts | Measurement report per part, with the surface finish check and the cutting conditions used |
| Documentation and packing | The document set present and in the right language; the packing specification followed; the machine braced and protected as agreed; accessories packed and marked | Photographs of the packed machine, the packing list, and the document set checked off |
Two of those groups are frequently left until they cannot be fixed. Safety devices have to be tested while the machine is powered and accessible, which means before packing, and a failed interlock discovered afterwards is a delay at the worst possible moment. Documentation has the same character: a manual in the wrong language, or a declaration of conformity for the wrong market, cannot be produced retrospectively at the destination. Both belong in the inspection scope for that reason alone.
Running the inspection day
Start with identification, because everything else depends on the machine being the one that was ordered. Read the nameplate and the control identification, match them to the order, and photograph both. Then confirm the configuration against the list: options, accessories, chuck and jaws, steady rest, tailstock, tool holders, the control series and any automation interface. This is also the moment to note the components fitted by brand, since those identifications will be needed for every future parts enquiry.
Move to function and safety with the machine powered. Test the interlocks deliberately, watch the machine complete a cycle, index the turret or tool changer through several positions, and check the lubrication and coolant systems are delivering rather than merely present. A function check that consists of watching the spindle turn is not a function check.
Geometry comes next, with the machine in the stated thermal condition. The readings should be taken by whoever has the instrument and the competence, and they should be written down as numbers rather than as pass or fail, because the numbers are what allow a comparison later if the machine’s behaviour changes. Only then run the acceptance part or test cut, and measure it feature by feature.
If something fails, the response is not to sign and hope. Write the failure into the record with the reading that failed, agree the corrective action and the date it will be completed, and agree how the corrected item will be re-verified — another test cut, another measurement, or a witnessed re-test. Then re-inspect that item specifically. Where the failure is in the packing or documentation group, it is resolved before dispatch rather than on arrival; where it is in geometry or performance, the re-test is the release criterion.
What should not be signed on the day is a blank or conditional acceptance. A record that says the machine was accepted subject to unspecified further work is not an acceptance, and it removes the leverage that the balance payment provided.
The document set released against the balance
The inspection and the payment are one process: the balance is normally released once the machine has been verified and the documents exist. Name the documents in the order rather than accepting a general promise, and check each one on the day.
| Inspection record | The signed checklist for all five groups, with the readings, the test part measurements and the list of any item deferred with its corrective action |
|---|---|
| Configuration list | The agreed option and accessory list, marked line by line against what is fitted, with the component brands identified |
| Geometry and performance report | The readings taken, the instrument used, the thermal condition, and the tolerance they were compared against |
| Documentation set | The operating and maintenance manual, electrical drawings, parameter backup, lubrication schedule and component list, in the agreed language |
| Conformity documents | The declaration or certificate required for the destination market, checked for the correct machine identification before dispatch |
| Packing record | The packing specification applied, photographs of the braced and protected machine, and the packing list for the accessories |
| Shipping documents | The invoice, packing list and transport document consistent with the delivery term in the order — the terms themselves are defined in the ICC Incoterms 2020 rules and decide where responsibility transfers |
| Release note | A short statement naming what was verified, what remains open, and who authorised dispatch |
Before you travel
A pre-shipment inspection visit is expensive and the preparation is cheap. This is the list worth completing a week before the date rather than the morning of the flight.
- The acceptance criteria, test part and measurement method confirmed as written in the order
- The instrument to be used for geometry agreed, and available on site — do not assume it is there
- The test part material and the blank available, and the program to run it already proved
- The configuration list carried in printed form, so it can be marked off line by line
- The document set required for the destination market listed, with the language specified
- The person who will sign on each side named, and their authority to release the balance confirmed
- A photographic record plan agreed, since photographs are the most useful part of the file afterwards
- The thermal condition for the readings decided: cold, after warm-up, or both
The same discipline continues after dispatch, because the machine has to be set up again on arrival. The readings taken at the factory are the baseline that the installation is compared against, and the working method on site is covered in the leveling and alignment procedure and in the commissioning checklist. A machine that was inspected properly in the factory and installed properly on site is a machine whose accuracy can be traced from the day it was built.
Frequently asked questions
Do I need to attend the inspection in person?
Not necessarily, but somebody with the authority to accept or reject does. Attendance in person gives the strongest outcome because measurements can be repeated on the spot and questions answered immediately. Where travel is impractical, a live video inspection with the machine identification read from the control, plus a third-party inspection for the geometry readings and the test part measurement, is a workable substitute — provided the criteria and the record format were agreed in the order. What does not work is accepting a set of readings without knowing who took them, with what instrument, and in what thermal condition.
What should happen if the machine fails the acceptance test?
The failure is recorded with the reading that failed, the corrective action and the completion date are agreed in writing, and the method of re-verification is agreed at the same time. Where the failure is in geometry or performance, the re-test is the release criterion and the balance should not be released until it is passed. Where the failure is in packing or documentation, it is corrected before dispatch and confirmed by photograph. A conditional acceptance with unspecified further work leaves the buyer with neither the machine nor the leverage.
How long does a pre-shipment inspection take?
A pre-shipment inspection takes long enough to do the five groups properly: typically a day, and two where the acceptance part needs to run over a number of pieces or the geometry readings require several thermal states. The variable is not the machine but the preparation. An inspection where the criteria, the test program and the instrument are all in place moves quickly; one where the acceptance part has to be designed on the day takes much longer and produces a weaker record. This is why the useful work happens at the order stage.
Who should carry out the geometry measurements?
Whoever has the instrument and the competence, and this is worth agreeing rather than assuming. The machine builder’s own inspection department will have the equipment and the procedure, and their readings should be recorded with the instrument identified. Where the buyer wants independent verification, a third-party inspection body can take the readings or witness them. In both cases the reading is only meaningful against a stated tolerance and a stated thermal condition, which is why those two items belong in the order rather than in the discussion.
Does the inspection replace installation checks on site?
No, and the two are not comparable. Factory acceptance verifies that the machine was built, configured and performing as ordered, on the builder’s foundation and in the builder’s environment. Installation acceptance verifies that the machine still does that on your foundation, after transport, when it has been levelled, aligned, connected and commissioned. Both are necessary, and the second is measured against the readings taken at the first — which is the strongest argument for recording the factory numbers properly rather than treating the inspection as a formality to be completed before dispatch.
Next step
Write the acceptance criteria now, not at dispatch. Send the workpiece, the tolerance you must hold and the market the machine will be installed in, and we will return the acceptance section that belongs in your order — the geometric and positioning values, the thermal condition for the readings, the test part or agreed test cut, the number of consecutive parts in tolerance, and the document set released against the balance. The manufacturing and testing steps those criteria are measured against are documented at how DAHUI MT builds and tests its machines.
Request the acceptance criteria list
WhatsApp: +86 15502628547 · Email: info@dhlathe.com
Send the part drawing for the acceptance part if you have one, and tell us which market the machine is going to. Both decide what the inspection will look like.
