Work Order and Traveller Control

A work order authorises a build, and the traveller that accompanies it records what happened. Between them they answer the questions that arise whenever something goes wrong: which revision was built, which material lots were used, which processes were applied and who verified each step. When they are accurate, an investigation is a lookup; when they are not, the same investigation becomes a reconstruction exercise that consumes days of engineering time.

What the Work Order Defines

The work order states the product, the revision of the documentation, the quantity to be built, the delivery date and any specific instructions that apply to that batch. It should be released from the same system that controls the drawings, so that the revision on the order and the revision of the build package cannot diverge. Where the order is produced manually, that link is the first thing to break, and the result is a build made to the previous revision with nobody noticing until test.

The order should also carry the material allocation where the product requires specific lots, such as a customer-approved component or a laminate with a particular property. Recording that at the point of release is much easier than tracing it afterwards, and it is what makes a document control system useful rather than ceremonial.

The Traveller and What It Records

The traveller is the physical companion of the boards through the process, and its purpose is to show, at a glance, what has been completed and what remains. Each operation records a result, a quantity and a signature or an electronic equivalent, and any deviation is noted where it happened rather than remembered at the end. Rejects and rework are recorded on the same document, because they change the quantity and sometimes the material used.

Paper travellers still work well in many factories, particularly where the process involves manual stations, but they are vulnerable to loss, damage and illegible entries. Electronic travellers remove those problems and make the data analysable, at the cost of terminals at each station and a system that must stay available. The choice is practical rather than ideological, and the requirement is the same either way: the record must reflect what actually happened. Work instruction practice assumes that record exists.

Revision Control in the Build

The most valuable single control is the revision check at the start of the build and at each changeover. The operator confirms that the documentation in hand matches the revision on the order, and that any obsolete paperwork has been removed from the line. Where a change is implemented mid-build, the split point should be recorded on the traveller, so that the boards before and after the change can be identified and treated differently if necessary.

Material changes follow the same rule. A component substitution approved during production should be recorded with the quantity affected and the approval reference, not merely noted in a conversation. Where the substitution changes the product’s performance, the customer may need to be informed, and that decision depends entirely on whether the record exists. Traceability is built from these small entries rather than from a single database field, and it is only as good as the weakest entry in the chain.

Sign Offs and Their Meaning

A sign-off should mean that a defined check was performed, not merely that the station was reached. The traveller should state what is being confirmed at each point: that the material matches the order, that the first article conforms, that the parameters were recorded, that the inspection was completed. Ambiguous sign-offs produce records that look complete and carry no information, which is the worst of both worlds.

Self-verification versus independent verification is a design decision for the process. Where a mistake at a station would be caught at the next one, self-verification may be adequate; where an error would be invisible until the product is in the field, an independent check is justified. Writing that logic into the traveller makes the reason for each sign-off clear, which helps the operator take it seriously. Delivery documentation is the last sign-off in the same chain.

Traceability Requirements

Traceability means being able to relate a finished unit to the material lots and processes that produced it. The level of granularity should be decided deliberately: tracing to a batch is usually sufficient for a defect investigation, while tracing to an individual serial number is needed where a unit must be recalled precisely. Building more traceability than the product needs costs time at every station, so the requirement should be defined by the product and the customer.

Where serialisation is used, the number should be applied at a point in the process where the unit is already identifiable and the marking cannot be lost. A label applied before reflow will not survive, and one applied after coating must adhere to the coating. The traveller should record the range of serial numbers in the batch so that the link between the physical unit and the paperwork is never in doubt.

Handling Deviations and Rework

Deviations are normal, and the process should make them easy to record. A quantity shortfall, a substituted component, a parameter that was adjusted outside its window: each is a deviation, and each should be recorded with the disposition and the approval. The value of that record is not administrative; it is the only way to know later whether a defect cluster correlates with a deviation that seemed harmless at the time.

Rework sits in the same category and deserves the same treatment. Reworked units should be identified on the traveller, with the operation that caused the rework and the repair performed, because a reworked board carries a different risk profile from a first-pass board. Where rework changes the quantity of good product, the order should be updated rather than adjusted at the end of the build. Shift handover should carry the open items so that the next shift does not rework the same unit twice.

Reviewing the Records

Records are only worth keeping if somebody reads them. A periodic review of a sample of travellers, checking that the entries are complete, the deviations are disposed and the quantities balance, finds the drift in the system before it becomes a defect. The review is also a useful measure of whether the process documents are practical, because a traveller that is consistently incomplete is usually a sign that the form asks for information nobody can obtain at the station.

Where the records are electronic, the same review can be automated: missing entries, unusual quantities and deviations without dispositions can all be flagged. The purpose is the same as the paper review, which is to confirm that the system describes reality. A traceability system that records what was supposed to happen rather than what did happen provides comfort and no protection.

FAQ

Is a paper traveller still acceptable? Yes, where the process suits it. The requirement is that the record is complete and reflects what happened, not which medium is used.

What must a sign-off mean? That a specific, defined check was performed. A signature against an ambiguous box records nothing.

How much traceability is enough? Enough to identify the material lots and processes behind any unit under investigation. More than that costs time at every station.

Should rework be recorded on the traveller? Yes, with the cause and the repair, because a reworked unit carries a different risk from a first-pass one.