Developing a part together with the customer: when to call the machine shop

The cheapest changes to a turned part are the ones made while the drawing is still open. Once it is released, the same change costs a re-approval — and by then nobody wants to hear about it.

Most drawings reach us finished. The part works, the tolerances are defensible, and the only remaining question is the price. That is a normal way to buy machining, and it also leaves money on the table, because the decisions that set the cost were taken weeks earlier by someone who had no reason to think about a lathe.

Five things that move the price, decided at the drawing stage

• Where the part is parted off. A shoulder that lets the component be cut shorter can drop it below the slenderness threshold and change which machine it belongs on.
• Sharp internal corners. A relief groove instead removes a form tool and a pass. The function is identical.
• Tolerances on non-functional features. Opening one from ±0.01 to ±0.05 mm can remove an inspection step from the routing entirely.
• Material chosen out of habit. Stainless where free-cutting steel would serve can double the cycle time. Sometimes the application demands it; often nobody re-examined it.
• Features reachable in one setup. A cross hole or a flat is nearly free if it can be made while the part is still in the first clamping, and expensive if it cannot.

What we actually do in development

We do not design your product. We take the drawing or the 3D model and say what the process would do with it: which features drive the cycle, where a tolerance is buying nothing, what the material choice costs, and what we would change if it were ours. Then, once the design is settled, we build the process, prove its capability and document it for the series.

When to involve us

Earlier than feels necessary — while the geometry can still move. A change agreed before release costs a conversation. The same change after release costs a re-approval, new samples and, in a regulated industry, a re-qualification of the assembly.

Note that this is series work: we engineer the process around a repeat part, not around a one-off. Samples for approval are part of qualifying a series.

More on product development, or send a drawing to info@kovinski-izdelki.si.