Manufacturing drawing or performance specification?

Choose what to fix and what to leave open

A manufacturing drawing specifies how the product is built. A performance specification describes what it must achieve under stated conditions. Choose by asking whether your team has already validated the design or needs the supplier to develop it. The product specification guide covers the basic contents; this choice determines who develops the solution.

A mixed brief often works best: fix mounting points, connection sizes, external envelope and essential materials, while allowing proposals for the internal mechanism or manufacturing process. Mark each requirement as fixed or open to proposals. Do not send a drawing and an outcome requirement that conflict without stating which takes precedence.

Allocate design work explicitly

For manufacture to drawing, ask the supplier to review manufacturability and identify ambiguities before quoting. Keep design validation with your named technical owner unless additional work is expressly agreed. A factory saying it can make the part is not evidence that the part will work in your application.

For supplier development, name who selects materials, performs calculations, develops prototypes and resolves failed tests. Define what your approval covers: appearance, interfaces, test results or the complete design. Record who investigates and pays for redesign when agreed performance is missed. These are project allocations to agree, not conclusions about legal liability.

Give innovation a controlled route

Invite alternatives separately from the compliant quotation. Ask the supplier to explain the proposed change, expected benefit, trade-offs and evidence needed to validate it. A different wall thickness, component or process may help production, but it can also change fit, repairability or performance.

Approve a proposal against the same acceptance criteria before updating the production documents. Keep a revision record and identify the authorised approver. If translated drawings are involved, use the drawing approval guide before releasing the revised brief.

Make performance capable of failing a test

Replace words such as strong, quiet or durable with a measured characteristic, an agreed limit and a test method. For a bracket, specify the load, mounting arrangement, loading direction and permitted deformation. For a pump, specify delivered flow at the required pressure, fluid and operating conditions. Ask the supplier to quote against limits your technical owner has approved.

Agree equipment, sample selection, conditioning, test duration, reporting and retest rules. Distinguish prototype design validation from production acceptance: a successful prototype does not establish consistency across a batch. Record raw results and the tested revision, and agree what happens after failure before releasing production.

Agree design-file access before development

List the deliverables: editable models, manufacturing drawings, component lists, calculations, test records and relevant software source files. Specify formats, revision status, delivery milestones and passwords or dependencies needed to open them. Ask for a trial file and check that your engineer can edit it. A viewable drawing alone may be insufficient to modify or reproduce the product.

Treat file delivery and permission to use the design as separate items. UK Intellectual Property Office guidance stresses establishing copyright ownership through a contract. Ask for clear terms covering modification, maintenance and manufacture by another supplier, with any excluded supplier background designs identified. Have the proposed rights reviewed for your project rather than assuming development payment settles them.

Before final development acceptance, check that the delivered files describe the approved, tested product and contain the agreed information. If future transfer matters, use the second-supplier qualification guide to plan the practical handover. File access still needs to be supported by usable production information and an agreed scope of use.