CNC Machining vs 3D Printing: Which One Actually Costs Less

Where the Cost Curves Cross

The chart everyone draws looks like this: 3D printing starts low and stays nearly flat; machining starts high (because of programming and setup) then falls as the fixed cost spreads over more parts. The crossover depends mostly on material.

Plastic parts

For a plastic bracket or enclosure, machining can beat printing somewhere around 20 to 100 pieces. Below that, printing's zero setup wins. Above it, the machined part is faster to repeat, holds tighter dims, and you're not paying for build volume per part.

Metal parts

For metal, machining often wins even at one piece once the part is structural. Printed metal powder is expensive per gram, the print is slow, and you usually still machine datums and bores afterwards — so the "no setup" advantage shrinks fast. The exception is a complex, low-load metal shape where printing genuinely saves material.

Above a few hundred plastic parts, injection moulding enters and beats both — but that's a tooling investment, a different decision entirely.

Material: the Quiet Dealbreaker

3D printing is brilliant for a handful of polymers and a short list of metals. CNC machining handles essentially any solid that can be cut — and that includes engineering plastics most printers struggle with. Our plastic CNC machining guide covers POM, PEEK, PTFE and nylon, which are common in real assemblies but awkward to print well.

If your part must be 7075 aluminium, 17-4PH stainless, Titanium Grade 5 or a specific PEEK grade with certified properties, machining is usually the only route that gives you the actual material — not an approximation of it.

Tolerance and Sealing Surfaces

Printed parts carry tolerance that varies with build orientation and feature — a hole printed vertically is rarely as true as one printed horizontally, and post-cure shrinkage moves things. Machining holds ±0.01–0.05 mm on a boring bar regardless of shape. For a bearing bore, a hydraulic seat or a sealing face, machining is the default. Our tolerance chart shows what each process realistically holds.

Strength: Anisotropy Is the Part Nobody Shows

Most metal printing is layer-based. The bond between layers is the weak direction, so a printed bracket is stronger along the layers than across them — and porosity hides inside unless you pay for hot isostatic pressing. A machined part comes from solid stock and is isotropic: it behaves the same in every direction. For a part under load, vibration or fatigue, that difference is not academic. Why two quotes for the same drawing can be five times apart often comes down to exactly this kind of hidden requirement.

The Hybrid That Usually Wins

You don't have to pick one. The common pattern: print near-net, then machine the precision features. Print the complex geometry to save material and time, then put true datums, bores and sealing faces on a mill to drawing tolerance. We do this for customers who need both the shape freedom and a real ±0.01 mm bore. It beats printing-then-living-with-the-tolerance, and it beats machining-the-whole-complex-shape-from-solid.