We Walked Away From a 10,000-Piece Order. Here's the Engineering Behind It.
A buyer asked us to quote ten thousand pieces of a part that, on closer reading, was never going to be happy as a CNC machined component. We said no — and explained the process-selection reasoning, because that explanation is more useful to you than the order would have been.
The Order
It was one of the largest single orders we'd been asked to quote — ten thousand pieces, a steady annual requirement, the kind of volume that most shops would move mountains to win. The drawing arrived as a STEP file and a PDF, and at first glance it looked like a normal machined bracket: a few holes, a couple of pockets, some threaded features.
We ran it through the usual quoting pass. And then we ran it through our heads, because the numbers didn't sit right.
The part had thin walls that would want to distort the moment the clamp came off. It carried tolerances on faces that the fit didn't actually need, which would force slow finishing passes and climate-controlled inspection on every piece. And the overall shape — long, flat, with fine cosmetic detail on one face — was the kind of geometry that other processes make in a single shot for a fraction of the time.
None of that is visible in a quote line item. But all of it shows up at 10,000 pieces: in scrap, in cycle time, and in a unit price the customer would have resented the instant a competitor quoted the same part done the right way.
Why We Said No
Three reasons, and they all point the same direction.
1. The part would drift at volume
Thin walls and tight tolerances on a part that fights its own material are manageable at ten pieces. At ten thousand they become a reliability problem. The first article might be perfect; the five-thousandth, machined on a Friday afternoon with a tool that's done its time, will not be. We were not prepared to ship a part we knew would drift in the field, because the cost of that lands on the customer first and the shop second.
2. The unit price would have been a lie
A CNC quote on a part this shape, at this volume, is an honest number about an inefficient process. We could have quoted it — and the customer would have paid a premium for the wrong method, then wondered why we were "expensive." That's not a sale, it's a misunderstanding we'd be profiting from. We don't do that.
3. There was a better process, and we said so
The geometry was a strong candidate for die casting, or in places sheet-metal forming. Those processes are built for exactly this kind of thin, detailed, high-volume shape. Telling the customer "this should be cast, and here's who does good die casting" lost us the order and gave them the right answer. That's the trade we'll make every time.
| Feature on the drawing | CNC machining | Better-suited process |
|---|---|---|
| Long, thin, flat walls | Warp on unclamp; need fixtures | Die cast / sheet metal form |
| Fine cosmetic detail on one face | Slow, costly to hold | Moulded in the tool |
| Tolerances on non-fitting faces | Forces inspection everywhere | Relaxed to standard class |
| Volume of 10,000 / year | Unit cost dominated by cycle time | Amortised tooling wins |
| Verdict | Wrong process for the volume — say so, don't quote it blind | |
The interesting part is that the customer took the news well. They had assumed "CNC shop" meant "will make anything from metal," and learning that process selection is its own discipline was more valuable to them than a quote would have been. They went away knowing more about their own part than they did that morning.
How to Tell If Your Part Should Be CNC'd
You don't need to be a process engineer to sanity-check this. Three questions cover most cases:
- Is the wall thickness fairly uniform and thin? That favours casting or forming, not machining a solid block away.
- Is the shape mostly two-dimensional with bends? That's sheet-metal territory, where CNC would waste material and time.
- Is the geometry 3D, low-volume, or needing fast iteration? That's exactly what CNC is for — no tooling, no waiting.
Below a few thousand pieces, CNC usually wins on lead time and tooling cost. Above that, a process matched to the shape usually wins on unit cost. The line moves with the part, but a good shop will tell you which side you're on — and the ones who won't are the ones to worry about. We wrote up the crossover in detail in our process comparison guide and our notes on what actually moves a machining quote.
If you're not sure, the cheapest step is also the earliest one: send the drawing before you freeze the design. For how a shop reads a print for manufacturability, see our CNC design guide and the GD&T notes for buyers.
Process Selection
When should a part NOT be CNC machined?
CNC, die casting or sheet metal — how do I decide?
Will a CNC shop really refuse a large order?
How do I know if my drawing is CNC-appropriate?
Send the Drawing Before You Freeze It
If you're about to send a part out for quote and you're not sure it's a CNC job, send it to us first. We'll tell you whether we're the right shop — and if we're not, we'll tell you which process is. No charge, no pressure, and usually a useful conversation about your own design.