Definition
Pre-calculation is the estimate made before a part is produced: the process plan, the setup and run time per operation, tooling and material cost, combined into a price. It is the estimator's or work preparer's prediction, later checked against reality in post-calculation.
What a pre-calculation depends on
A pre-calculation is only as good as the process plan and time standards behind it; see process planning and setup time and run time. Its accuracy is measured against production actuals afterwards.
Where pre-calculation happens
Not on the drawing; it is produced from the drawing, the 3D model, the routing and the factory's own time standards, typically before a quotation is sent.
Common mistakes
Treating a pre-calculation as a guaranteed price rather than an estimate built on assumptions about process, setup count and material. Also never comparing it against what actually happened, which means the same errors repeat on every similar order.
A pre-calculation is only as good as the process plan and time standards behind it; see process planning and setup time and run time. Its accuracy is measured against production actuals afterwards.
See how Blake reviews a partFrequently asked questions
Is pre-calculation the same as a quotation?
A quotation is the price offered to a customer; pre-calculation is the underlying cost estimate that quotation is based on, often with a margin added.
What is the difference with post-calculation?
Pre-calculation happens before production and predicts; post-calculation happens after and compares the prediction with what was actually booked.
Why does a pre-calculation go wrong?
Usually because the assumed process plan, setup count or material behaviour differs from what actually happens on the shop floor.