A custom line is handed over only once, and that single window decides whether problems are found while a builder can still change the machine or after the machine is already yours. Quality checks during commissioning are not a list of go/no-go switches. They are the place where a made-to-order line has to prove the behaviour it was bought for, under your material, your utilities and your people. The checks worth insisting on are the ones that separate a line that runs from a line you can rely on and keep running.
Start with the checks that prove the machine was built as specified
Before anything moves, confirm that what is standing on your floor matches what was agreed. The useful question at this stage is not whether the equipment looks complete, but whether the parts that carry quality were built to the stated requirement: the stations that position, join, coat, inspect or handle your product, the vision or sensing hardware that makes decisions, and the interfaces between them. Ask for the build records behind those parts and check them against the drawings you approved, because the difference between design-issue drawings and as-installed reality usually shows up here, not later.
Walk the line with an engineer who was not on the build and read the safety arrangement as a behaviour rather than a parts list: what stops a station, who can reset it, what the operator sees when a process drifts, and what happens to in-process product when the line halts. A guard that exists is not the same as an interlock that behaves the way your operators will need it to behave at shift change.
Then prove the line behaves correctly on your product, not on the builder's
Most commissioning failures are behaviour failures, and behaviour can only be tested with the material that will actually run. Insist on a staged sequence: each station proved on its own with your part, the handoffs between stations proved next, then the whole line running continuously. The station-level pass matters because a defect introduced upstream is usually detected downstream, and until you can tell which station produced it, you cannot fix it.
The handoff checks are the ones buyers most often skip. Position at a transfer point, the way a part is gripped or released, and the timing window a station expects from the one before it are all custom decisions, and they are exactly where a made-to-order line misbehaves weeks after a successful demonstration. Run the awkward cases on purpose: an undersized part, an out-of-position part, a deliberately missing part, a station taken out of service. A line that only runs when everything is perfect has not been commissioned, it has been shown a favourable day.
Treat the process window as the measurement, not the average result
A single good output proves nothing. During commissioning the record you want is how the line performs across the range it will actually see: your tolerance extremes in the material, a change of operator, a change of consumable lot, a planned stop and restart, and a restart after an unplanned one. For each critical process step, agree before the run which parameters are recorded, who reads them, and what value or range counts as a pass. Without that written definition, the commissioning log becomes a collection of numbers nobody can argue about later.
Ask specifically what the line does at the edges of its recipe. Custom machines are often commissioned at their comfortable centre, and a production line earns its keep in the marginal hours. The parameter set the machine ships with is a process claim until you have seen it reproduced on your material under your conditions, so the parameter list, the meaning of each field and the recipe change procedure belong in the same conversation as the run results.
Do not let the utility and cleaning boundary fall between two contracts
On any line, some equipment belongs to the integrator and some belongs to the site. Utilities, supply quality, drainage, run-off handling, compressed air, and the cleaning or surface-preparation step ahead of a joining process are frequently assumed to be somebody else's responsibility. List them station by station and name the owner of each, because a line that fails a quality check because of what arrives at its inlet is still a line that failed. Where surface cleanliness governs bonding, coating or inspection results, the cleaning step and its inspection evidence need a defined place in the process rather than an informal habit.
Ask the same question about the cleaning equipment you may add later. Steam and hot-water units are usually sold as equipment a buyer configures for a duty, so the checks that matter at commissioning are whether the supply and drainage the machine needs exist at the station, whether the surface and the deposit it carries will accept the method, and who signs off the cleaning route before it runs against production product. A cleaning step commissioned after the line is live inherits every boundary problem the handover did not settle.
Close on the signed record, not on a successful demonstration
Commissioning ends when an open-item list is empty, or when the items you have consciously accepted are written down with an owner and a date. Keep the run records that let you repeat a result later: which parts ran, which parameters were recorded, which defects appeared and what closed them. A line that passed a demonstration and a line that passed a documented run differ in one respect only, and it is the documented one you can maintain, audit and improve.
Close-out is where an integration partner's work either becomes usable knowledge or disappears with the crew that built it. Ask for the as-installed drawings, the parameter and recipe list with the meaning of each field, the version scheme for software and documents, a restore procedure that has actually been tested, the spares and consumables list, and a training record that names who was trained on which station. Where your line has a surface-preparation or degreasing step ahead of a joining or inspection process, that step also needs a defined cleaning method and an inspection habit. If the site has no such step, the production line equipment degreasing category pages show the cleaning equipment options available for that duty, and each supplier should be asked for the same written set so the comparison rests on evidence rather than promises.
For the line itself the discipline is identical one level up. The partner delivering the automated production line solutions you are commissioning should be the party generating that evidence, and your job as buyer is to ask every supplier for the same record set before the contract, so the comparison rests on documents you can verify instead of on assurances you have to trust afterwards.
