You uploaded your CAD file. You waited for the quote. And the number came back much higher than expected. Before you blame the vendor, know this: the problem often starts with the design itself.
Here are the most common reasons your CNC quote is inflated, and what you can do about each one.
1. You Are Asking for Tighter Tolerances Than You Need
Tight tolerances cost money. A part with a tolerance of +/-0.01mm requires slower machining speeds, more tool passes, and skilled operators. If your part does not need that level of precision, you are paying for nothing.
Most mechanical parts work fine with +/-0.1mm. Reserve tight tolerances only for mating surfaces, press fits, or critical functional interfaces. Review your drawing and loosen wherever the function allows.
2. Your Design Has Features That Are Expensive to Machine
Deep internal pockets with narrow widths, sharp internal corners, undercuts, and thin walls all require extra tooling or setups. Each extra setup adds time and cost.
Common problem features include: internal corners without radii, pockets deeper than 6x the tool diameter, undercuts requiring 5-axis machining, and thin walls below 1mm in metal parts. Adding a simple fillet to an internal corner can reduce machining time and bring the quote down noticeably.
3. You Chose the Wrong Material for the Job
Material selection directly affects machining cost. Harder materials like SS316 or titanium take longer to cut and wear down tools faster. This pushes your quote up significantly.
| Material | Machinability | Relative Cost |
|---|---|---|
| Aluminium 6061 | Excellent | Low |
| Mild Steel | Good | Medium |
| SS304 | Moderate | High |
| SS316 | Difficult | Very High |
| Brass | Good | Medium-High |
If strength is the goal, check whether aluminium or mild steel can do the job instead of stainless steel. It often can.
4. Low Volume Orders Have High Per-Part Costs
CNC machining has fixed setup costs. When you order 5 parts, those setup costs are divided by 5. When you order 50, they are divided by 50. Small batch sizes mean high per-unit prices.
If you are prototyping, that is expected. But if you need parts regularly, consolidating orders into larger batches can cut per-part costs by 30% or more.
5. You Are Not Getting DFM Feedback Before Quoting
DFM means Design for Manufacturability. Most vendors quote exactly what you send. They do not tell you that a small design change could save you significant money. That is a missed opportunity for you.
A DFM review before you finalise your drawing can save 20 to 40% on machining cost by eliminating features that add time without adding function.
How ProtoMandi Helps You Reduce Cost
ProtoMandi reviews every uploaded file for DFM issues before production starts. If our engineering team spots a feature that is increasing your cost unnecessarily, we flag it. You can modify the design or proceed as-is with full transparency.
Our quote breakdown shows material, machining, and shipping costs separately. You see exactly where your money is going. No hidden charges, no guesswork.
Upload your CAD file on ProtoMandi, get a free DFM review, and find out how much you can save before placing your order.