Having Single Parts CNC-Milled: Process, Data and Cost Logic
Knowledge · CNC machining
When is it worth having single parts milled?
Whenever a part cannot be bought: the discontinued spare part, a prototype before the series decision, a fixture for your own assembly, or the one special component in a project. Small batches of 5 to 50 pieces run through the same channel.
Which data does the manufacturer really need?
The short answer: a PDF drawing and a STEP file, plus material, quantity and target date. The drawing carries tolerances, surface data and thread specifications and remains the legally binding document; the 3D model speeds up programming and quoting considerably. State the material precisely (S355J2, 1.4301, EN AW-7075) and mention surface treatment. If no model exists, manufacturing from a sample or sketch is possible, it just takes longer to quote.
Why is a one-off so much more expensive than the same part in a series?
Because preparation dominates the price: drawing review, CAM programming, tooling, material procurement, machine set-up and first-article inspection are nearly identical for one part and for fifty. A worked example: two hours of preparation plus 30 minutes runtime means the single piece carries 2.5 hours; at ten pieces the share drops to 42 minutes per part. Second and third parts are always disproportionately cheap, so consider ordering foreseeable spare demand at the same time.
How do designers reduce the cost of a milled part?
Four levers matter most: tolerances only where they have a function (ISO 2768-m as the default), generous internal radii (R ≥ 4 mm allows rigid standard tools; sharp internal corners force EDM), standard materials that are on stock, and part dimensions that fit common raw material sizes. A practical tip: send the drawing to the manufacturer before final release; ten minutes of shop-floor feedback regularly saves a double-digit percentage of the part price.
Comparison: online platform or manufacturer with technical review?
| Criterion | Online platform | Contract manufacturer with review |
|---|---|---|
| Quote | instant, automatic | after review, usually 1–2 days |
| Drawing review | limited, risk with buyer | professional review, queries before production |
| Complex parts, tight tolerances | quickly at the limit | core business |
| Spare parts from samples | usually impossible | possible |
| Downstream processes (welding, painting, assembly) | rarely integrated | from one source |
Frequently asked questions
Can you really order from quantity one?
Yes. Single-part production to drawing is a core business of contract manufacturing. The only requirement is that the part is technically clearly defined; the manufacturer checks that free of charge during quoting.
What does a one-off CNC part cost?
There is no flat rate, because programming and set-up dominate and depend on geometry. Simple plates start in the low three-digit range; complex parts with tight tolerances sit well above. A reliable quote follows the drawing review, usually within 48 hours.
Which file formats are ideal?
PDF for the drawing, STEP for the 3D model. DXF helps with sheet parts. STEP is the vendor-neutral standard and speeds everything up.
Is manufacturing without a drawing possible?
Yes, from a sample or sketch. The manufacturer measures the original and confirms critical dimensions. For fits, a short technical discussion is worthwhile because a worn sample only tells half the truth.