Line commissioning: readiness and test order

An engineer's arrival date does not confirm that a line is ready for start-up. You need the assembly status, utilities, documentation and the people responsible for each device. One missing item can block the next test. A commissioning plan should identify what can be checked, what remains blocked and the conditions required to proceed to the next stage.

Confirm readiness before trials

Establish which devices are installed, which inspections are complete and which points remain open. Prepare current PLC and HMI projects, drawings, drive configurations and signals exchanged between machines. Record engineering software versions and baseline backups. A project in a folder may differ from the last version downloaded to a device. Resolve that discrepancy before making changes.

Readiness also includes people and decision-making. Identify who confirms assembly, who handles mechanical issues and who authorises product trials. Responsible personnel need to confirm utilities and material availability. Mark work by other disciplines that prevents a test. Software readiness alone should not be presented as confirmation that the complete line is ready for automatic operation.

Check signals and individual devices

Separate I/O checks from complete sequence trials. For an input, confirm the physical device, address and signal interpretation. Output checks follow the agreed procedure with responsible personnel and an assessment of machine conditions. Resolve label or address discrepancies at this stage, before they affect several linked process steps.

Direction, position and feedback tests need prepared conditions and a person responsible for the device. Record the expected and observed results, rather than a general checked entry. For a drive, compare the command, device state and feedback. For analogue measurements, verify units, range and plausible values. These trials must not rely on arbitrary signal forcing or bypassing safeguards to speed up commissioning.

Communication and station permissions

Confirm connections and actual data exchange. Establish what each machine means by ready, request, busy and complete, including when those states are set and cleared. Matching addresses do not resolve a handshake in which one side waits for new confirmation while the other retains the previous cycle's signal. Test the agreed behaviour after communication loss and recovery as well.

Permissives and interlocks should match the process description. For each important transition, identify the enabling conditions and the conditions that inhibit it. Missing conditions should have understandable HMI messages. Safety-function testing is a separate responsibility and documentation scope. Completing a normal sequence is not acceptance of those functions, even when the machine stops at the expected point.

Dry runs and product trials

Where the machine design allows it, a dry run can check action order, permission exchange and selected software responses without product. It does not establish process quality or behaviour under real load. Keep those results distinct in the line commissioning plan. Unavailable material is a reason to mark a product trial outstanding, not to record it as completed.

Product trials need entry conditions, settings, expected results and responsibility for judging the outcome. Include the normal cycle, interruption, restart and agreed missing-material situations. Alarms should identify the device and unmet condition. When a trial reveals a fault, return to the last verified stage rather than inserting an unexplained timer so that the line completes one more cycle.

Control changes and open points

Back up the project before a correction. Record the change, reason, author and version tested. Include device parameters and connections, not just PLC logic. After several days, this distinguishes a new discrepancy from a previously identified issue. Work by another discipline may also require part of the test plan to be repeated.

Open points, often called punch items, need an impact description, owner and date. Distinguish blockers from changes that can be completed later. A limitation affecting operation should not be hidden in an informal note. Agree which tests must be repeated after closure and who will confirm the result. This makes the list actionable rather than a collection of comments.

Hand over the final baseline

Deliver current PLC and HMI projects, configurations, change records and test results. Identify the installed version and create the final backup after the last accepted correction. Separate verified functions from those that could not be tested. For scheduling, provide assembly status, the trial scope and available dates. Acceptance refers to agreed functions and results, not simply to the line having completed one cycle.