Technical documentation

Technical documentation (also called engineering or manufacturing documentation) is the set of documents that precisely describes a product and how it is made. It is the common language through which the designer communicates with the manufacturer, suppliers and the customer.

The core elements of technical documentation are 2D production drawings with dimensions, tolerances and surface requirements, 3D CAD files (STEP, SolidWorks), a bill of materials (BOM) listing all components, process sheets, material and surface finish specifications, assembly instructions and test reports.

Well-prepared technical documentation is the foundation of efficient manufacturing. Unclear or incomplete drawings lead to quality claims, rework or parts that cannot be used. The rules for creating technical documentation are set by standards such as ISO 128 (presentation on technical drawings), ISO 1101 (geometrical tolerancing) or ASME Y14.5.

Technical documentation is also essential for conformity assessment and certification (CE, FDA), for quality management system audits (ISO 9001), for repeat production without having to measure parts again, and for transferring production to another supplier if needed.

You need complete technical documentation as soon as a product is to be made outside your own workshop, repeatedly or by different suppliers. It is the basis for requests for quotation and price quotes, for manufacturing and inspection, for purchasing bought-in parts and for assembly.

It is also required when placing a product on the market. For CE marking in the EU, for example, the manufacturer must keep technical documentation that demonstrates compliance with the applicable regulations. It is also worth creating documentation for older products that exist only as physical parts or with incomplete drawings.

The most common problem is a mismatch between the model, the drawing and the BOM after changes. Introduce revision numbering and engineering change control, and always send suppliers a complete, current set. If the drawing does not state the material, general tolerances, surface finish or heat treatment condition, the manufacturer will make its own assumptions.

Another risk is documentation written for one specific supplier that relies on their unspoken conventions. Check whether an independent manufacturer could make the part from it. When you commission documentation, agree in advance on the standards, the output formats and who will own the source data.