Most Prototype Quotes Are Read the Wrong Way
Buyers usually compare the bottom line and pick the lowest number. That works for catalog parts and fails for prototypes, because two quotes for the same drawing can differ by a factor of three for reasons that are visible in the line items if you know what to look for. This is a short guide to reading the quote rather than the total.
The Four Lines That Matter
| Line item | What it really covers | When it should be zero |
|---|---|---|
| Programming | CAM work, toolpath strategy, fixture design | Never on a new geometry, but it should not repeat on a revision of the same part |
| Setup | Machine time to prepare jaws, tools and offsets | Spread across a batch, so a single unit carries all of it |
| Material | Stock plus cutting allowance, not finished weight | When the customer supplies certified stock |
| Finishing | Anodizing, plating, bead blasting, masking | If the prototype is functional only and will not be shown to end users |
Setup Is the Line Buyers Underestimate
On a one-off part, setup can be half the price. That is not padding: soft jaws have to be bored, tools have to be assembled and measured, and the first part has to be inspected before the run continues. The useful question is not "why is setup so high" but "how many setups does this part need", because a design that can be machined in one clamping is genuinely cheaper than the same shape requiring three.
- Ask how many setups the quote assumes. Two quotes with different setup counts are not comparable.
- Ask whether five axis work was considered. It often removes a setup and lowers the total even at a higher hourly rate.
- Ask what happens on a revision. A good shop reuses the program and charges only the delta.
Material Is Quoted as Stock, Not as Part
A 200 gram bracket may start as a 900 gram block. You pay for the block, and the chips are not refundable. This is why near net shape stock, extrusion or a different process can beat machining on cost at surprisingly low volumes. A supplier who never mentions stock efficiency is either not looking or not telling.
Finishing and the Hidden Cost of Tolerance
Anodizing adds days and a masking step on functional faces. Tolerances tighter than the process can hold add inspection and rework, not accuracy. When a drawing calls for 0.005 mm on a feature that does not need it, a good supplier will flag it rather than quietly quote the risk into the price.
Our own quotation format, the tolerances quoted by default and the revision policy are described on the low volume prototype machining page.
Three Questions That Expose a Weak Quote
- Which features drive the price, and what would you change to reduce it?
- What is included in inspection, and do I receive the report?
- What is the lead time from drawing approval, not from order date?
A supplier who can answer all three in writing is quoting a process. One who cannot is quoting a hope.
