Routing

A routing records, per part, which operations are needed, in what order, on which machine or at which supplier, and how much setup time and run time each step takes. Outside steps such as hardening or surface treatment appear as lines of their own, with their own lead time.

What it means for the calculation

The routing is the bridge between the calculation and the shop floor. The sum of the times times the rates per step is the machining cost; the sum of the steps plus the waiting times is the lead time. Moving a step can change the amount without changing anything about the part: milling after hardening needs different tooling than milling before it. And a routing that is right becomes the starting point of the calculation on the next order.

Where this comes up

In a shop's own system, tied to the part number, and on the works order that travels with the part through the shop.

Common mistakes

Writing one line for the whole part instead of a line per operation, which leaves nothing to trace back when the time turns out different. Also entering an outside step as a short line without its round-trip time, which makes the delivery promise too tight.

Is a routing the same as a bill of materials?

No, a bill of materials says what something is made from; a routing says how and in what order.

Does the routing change with batch size?

The steps usually do not, the machine choice and the times sometimes do.

Does an outside step belong in the routing?

Yes, with its own cost and its own lead time, otherwise the delivery promise does not hold.