Working from your drawing, not a catalogue
OEM manufacturing starts with the customer's own drawing or specification rather than a standard part number. A supplier equipped for this needs to review that drawing for manufacturability — flagging, for example, a bend radius that's tight for the specified wall thickness — before committing to tooling, not after a batch has already been produced.
Tooling and first-article approval
Custom geometries usually require dedicated tooling: bending dies, brazing fixtures, or forming tools specific to the part. A structured OEM relationship includes a first-article inspection stage, where an initial sample run is measured against the drawing and formally approved before full production begins — protecting both sides from a large batch of parts that turn out to be slightly off-spec.
Volume, lead time and consistency
Once production is running, the value an OEM supplier adds is consistency at volume: the hundredth part should measure the same as the first. That depends on documented process parameters (braze temperature, bend program, torque specs) rather than operator judgement alone, and on quality checks built into the line rather than only at final inspection.
What to ask before placing a production order
Before committing volume to a new supplier, it's worth asking for mill certificates on the copper being used, sample test reports from a pilot run, and clarity on lead time under normal and surge demand. These questions matter more than the unit price quoted on a first sample, since they're what determine whether the relationship holds up once real production volumes start.