What an assembly scope covers

Outsourcing a complete machinery assembly means the supplier builds a finished, ready-to-use unit from your drawings rather than a single machined part. The scope usually combines welded fabrication, machined interfaces, mechanical assembly and inspection. Before you issue an RFQ, decide which parts the supplier makes and which you supply.

Buyers often source proprietary items such as bearings, seals, hydraulic cylinders, motors or sensors themselves and ask the supplier to fit them during assembly. Alternatively, the supplier can procure catalogue components against an approved specification. The division of responsibility should be written into the RFQ so the quote, the inspection plan and the delivery boundary all match.

This is different from buying a finished machine off the shelf. Contract manufacturing follows your drawings, your bill of materials and your acceptance criteria. The supplier adds fabrication and machining capability, not a proprietary product design, so the buyer keeps control of the engineering.

Drawings and bill of materials to prepare

A usable RFQ starts with a complete assembly drawing set. That includes the overall assembly with datum references, the individual part drawings, a bill of materials with quantities and materials, weld symbols, and the machined interface tolerances. Dimensioning should follow a recognised scheme such as the ASME Y14.5 dimensioning standard so that geometric tolerances are unambiguous.

State the material grades for every plate, section and casting, and name any incoming material certificate level you require, for example EN 10204 3.1. Where a part must mate with existing equipment, give the mating interface drawing and the allowable fit. Missing or inconsistent drawings are the most common cause of RFQ rework and price change, and they slow the technical review that every order needs.

Keep a revision letter on every drawing and state which revision the quote is based on. If you issue a change after the supplier has started, expect a revised price and lead time, so freeze the package before release wherever you can.

Welding and machining scope

For the welded structure, state the welding code that applies. Structural steel frames are commonly built to AWS D1.1, while a European-specified project may require ISO 3834 together with EN 1090. The code drives procedure qualification, welder qualification and acceptance criteria, so naming it early avoids a mismatch later when the shop has already planned its work.

Machined interfaces such as bore patterns, mounting faces and shaft seats need their own tolerance block. Define the datum scheme, the surface finish where seating matters, and the acceptance band. If the assembly must be trial fitted before shipping, say so and state which subassemblies are joined for the check. Clear machining scope prevents arguments about who corrects a misfit discovered during build.

Inspection evidence and trial assembly

Agree the inspection records before production. Typical evidence includes welding procedure specifications and procedure qualification records, welder qualification records, visual and non-destructive test reports where specified, material certificates, and a dimensional report against the drawing datums.

For large welded frames, a trial assembly in the supplier's workshop catches fit-up errors before the unit is shipped and reworked on site. Define which interfaces are checked, which gauges or fixtures are used, and who signs the report. The cost of a workshop trial is almost always lower than the cost of field correction, and it protects the installation schedule.

Packaging, logistics and handover

An assembled unit is harder to pack and move than loose parts. State the lifting points, the centre of gravity if the unit is unbalanced, and any export packaging requirement such as vapour corrosion inhibitor wrapping or a steel crate. Clarify who arranges freight and who is responsible for on-site installation or functional testing, because these boundaries change the quote and the delivery date.

Buyers sometimes underestimate the handling plan. Agree the unpacking and lifting method at the destination, and confirm that the crate or sling points suit the receiving crane, so the unit arrives ready for the next stage without a surprise.

For export, confirm the incoterm and the point at which risk transfers, because that decides who books freight and who carries loss in transit. State the destination port and any site access limits so the supplier can size the crate and the method.

How Realjet supports contract manufacturing

Realjet builds custom machinery components and assemblies to customer drawings, combining steel fabrication, machining, mechanical and hydraulic integration, workshop assembly and inspection. Final dimensions, functions, interfaces and delivery boundaries are confirmed through technical review before manufacturing begins. You can review the contract manufacturing services page for the overall scope, and see an example of a contract-manufactured and machined structure on the crane boom head product page.

Next step

When your assembly drawings and bill of materials are ready, prepare the RFQ around the points above and confirm the welding code, machined tolerances and trial-assembly requirement with the supplier. Realjet can review your package and return a scoped manufacturing proposal built to your drawings.