Key decisions
- Separate one-time preparation from costs repeated for each component.
- Compare the complete delivered scope, including inspection and finishing.
- Ask for design alternatives with defined savings mechanisms and explicit approval.
Start with the scope behind the unit price
A CNC quotation combines several kinds of work: interpreting the drawing, planning the route, preparing tools and holding, machining, finishing, checking and delivering the components. Some effort occurs once per job or setup. Other effort repeats for each part. A unit price without that context says little about where an improvement is possible.
The NIST design-for-cost paper supports breaking manufacturing and delivery into identifiable elements. For purchasing, the practical lesson is to distinguish a cost estimate from a selling price and to compare the same scope. A supplier may bundle labor, machine overhead and tooling differently; adding separate allowances without understanding the quotation can double-count them.
Start the comparison with a controlled model and drawing, material condition, quantities and acceptance requirements. If one quote assumes a different finish or omits a report, its lower price is not necessarily evidence of a more efficient machining process.
Connect each cost driver to a practical question
The table helps identify useful questions. It does not imply a standard cost percentage or a fixed saving for any Beigain process.
| Cost driver | Why it changes the order | Useful question |
|---|---|---|
| Programming, setup and fixtures | Preparation is spread across the quantity using that setup | Which charges are one-time, recurring per batch or included in the unit price? |
| Cycle time and handling | Work repeats for each component | Which feature or transfer dominates time, and can its design be revised? |
| Material and blank yield | The purchased blank can be much larger than the finished part | Would an approved stock form reduce waste without creating a new qualification problem? |
| Surface finishing | Batch minimums, masking and cosmetic control can add separate work | What finish, thickness, color approval and final checks are included? |
| Inspection and documentation | A few checks and a full characteristic report are different scopes | Which features, how many pieces and what records are covered? |
| Packaging and delivery | Protection and shipment terms affect landed cost | Are separators, identification, transport and any additional charges defined? |
Worked example: separate quantity savings from process savings
The following simplified calculation uses invented inputs solely to explain cost behavior. The figures are not a supplier quotation or market benchmark. Assume setup costs 240 currency units per batch, machining takes 12 minutes per part at an inclusive rate of 60 per hour, and material, finishing and inspection add 5, 3 and 2 per part respectively.
The model deliberately omits scrap, additional batch minimums, freight, financing, taxes and supplier margin. It also assumes one setup can serve the full quantity. Real quotations must include relevant terms and may change route at different quantities, so the example should not be used to predict an actual price.
Ten parts versus one hundred parts
The repeated cost is 12 × 60 / 60 + 5 + 3 + 2 = 22 per part. At a quantity of 10, setup contributes 24 per part, giving 46. At 100 parts, setup contributes 2.40, giving 24.40. Now assume an approved design change reduces cycle time from 12 to 8 minutes without changing the other inputs. The repeated cost becomes 18, producing totals of 42 and 20.40 respectively. Larger quantity spreads preparation; the design change saves four units on every part. These are different mechanisms and should not be confused in negotiations.
Optimize the whole route rather than one machine rate
A lower hourly rate can be offset by longer cycle time, additional handling or a more difficult inspection plan. Conversely, a more capable setup can cost more to prepare while reducing repeated work. Sandvik discusses machining economy in terms of production cost, supporting a total-process view rather than judging a cutting tool or operation by its purchase price alone.
Identify the feature responsible for the extra effort. A deep corner, awkward cross hole or cosmetic surface may contribute more than the overall part size suggests. Ask for one or two specific alternatives, with the changed geometry and acceptance requirements clearly stated. A generic request to make the part cheaper often produces assumptions rather than an engineering proposal.
Inspection can also have fixed and repeated elements. A measurement program may be prepared once, while loading, probing and report review repeat according to the plan. NIST describes measurement-equipment selection as part of inspection planning. The appropriate question is which method supports the required decision, not whether every feature can be checked with the cheapest available instrument.
Distinguish a forecast from a release quantity
An annual forecast helps a supplier evaluate potential fixtures and material planning, but it is not the same as a committed batch. Request price breaks for realistic releases and clarify whether preparation charges recur. A quote based on one continuous production run cannot automatically be applied to many small deliveries spread across a year.
Design changes can also invalidate some previous preparation. Keep the revision history clear and identify whether a repeat order is genuinely unchanged. Material substitutions, coating changes and new report requirements may alter the route even when the CAD outline looks identical.
For an RFQ to Beigain, provide the required delivery date as a planning input and ask for a confirmed schedule based on the full scope. Do not infer lead time from cutting minutes alone: material, programming, outside finishing, inspection and shipment all have their own sequence.
- Align all quotations to the same files, revision and material condition.
- Request realistic quantity breaks and distinguish forecasts from releases.
- Separate one-time tooling or programming charges from recurring batch costs.
- List finishing, deburring, reports and packaging explicitly.
- Record any proposed design change and the operation it simplifies.
- Confirm payment, shipment and delivery assumptions before comparing totals.
- Evaluate accepted-part cost and scope, not a machine-hour figure in isolation.
Questions about this topic
Why can a prototype cost much more per part than a repeat batch?
Preparation and setup are distributed across fewer pieces, and a new design may need additional route development. The difference should be explained through the actual scope rather than a universal prototype markup.
Will doubling the quantity halve the unit price?
No. It may reduce the setup share, but material, machining, finishing and inspection still recur. Batch minimums and route changes can also make the relationship nonlinear.
Should the cheapest hourly machining rate win?
No. Compare total cycle time, preparation, secondary operations and acceptance evidence. An hourly rate is only one input to the cost of an acceptable delivered component.
How can a buyer request cost reduction without weakening the part?
Identify negotiable geometry and ask for specific alternatives. Have the drawing authority assess each change against fit, loading and service requirements before releasing a revised specification.
Technical references
- NIST: Design-for-Cost — An Approach for Distributed Manufacturing Cost Estimation — Primary research on cost breakdown and supplied-component estimation. The numerical machining example is original and uses invented inputs.
- Sandvik Coromant: Tips film — Machining Economy — Toolmaker explanation of machining economy and the broader production-cost perspective.
- NIST: A Rule Model for Selecting Dimensional Measurement Equipment in Inspection Planning — Primary metrology research supporting inspection-equipment selection as a planned engineering decision.
Continue reading
- How to Order Custom CNC Parts
- Preparing a CNC RFQ that suppliers can quote accurately
- Defining CNC inspection requirements before production
- Request a Manufacturing Quote
READY TO SOURCE YOUR PART?
Get a machining quote for your drawing.
Send your drawing, material and quantity. Beigain reviews the machining features, finish and inspection requirements with your quotation.
Upload drawing for a quoteDownload the RFQ checklist (PDF)
