Is it cheaper to CNC machine or 3D print a single prototype? (Economic breakdown)

You’ve got a STEP file, a deadline, and one question:

“For this one prototype, do I send it for CNC machining or 3D printing?”

1. The very short answer

Most articles say:

• “3D printing is cheaper for prototypes.”
• “CNC machining is cheaper for batches.”

That’s not wrong, but it’s incomplete.

For a single prototype, the picture usually looks like this:

• Plastic parts, moderate strength, normal tolerances → Outsourced FDM/SLA/SLS is usually cheaper than CNC machining because there’s no programming and minimal setup.
• Functional metal parts (aluminum, steel) → Conventional CNC machining is almost always cheaper than metal 3D printing for one-offs. Metal printing machine time and finishing are expensive.
• High-tolerance or “customer-facing” prototypes → Even if 3D printing wins on price, CNC machining often wins on “usable sample that won’t mislead the test”.

So price is not just “process vs process”. It’s process + risk + number of spins you expect to do.

Now let’s unpack costs the way your machinist and print bureau actually see them.

2. How a CNC machining shop builds the price for one prototype

Most CNC machining quotes can be roughly reduced to this formula:

Total CNC cost = Material cost + (Machine time × Hourly rate) + Setup / programming + Finishing + Shipping

For a single part, the nasty part is that setup/programming is not diluted by volume. It lands almost fully on that first piece. That’s why many sources say a CNC prototype can be 5–10× the cost of a printed part, even when the geometry is simple.

Typical ranges you’ll see in the market:

• 3-axis CNC machining rate: about $20–50 per hour in many regions.
• 4/5-axis CNC machining: frequently $75–150 per hour.

So for one prototype, the CNC machining quote is heavily driven by:

• Programming (CAM, workholding decisions, maybe fixture design)
• Setup (tooling, zeroing, test cuts)
• Real machining time
• Manual steps: deburr, tapping, inspection report if you asked for it

You know this already. But it matters when you compare a $90 printed part to a $220 machined one and wonder why there’s that gap.

3. How a 3D printing shop builds the price

For outsourced 3D printing (especially plastics), the cost model is simpler:

Total 3D printing cost = Material + (Build time × Machine rate) + Post-processing + Setup/admin

Key differences vs cnc machining:

• Geometry complexity Complex organic shapes don’t explode the price the way they do on CNC. Cost follows volume, height, support, not “number of ops”.
• Setup/programming There is prep work, but it’s usually much lighter. No fixtures, fewer decisions about tool access.
• Post-processing For simple prototypes, this might just be support removal and a bit of sanding. For “presentation” or functional parts, surface work or painting can dominate the quote.

This is why many comparison guides state that for prototyping and one-offs, 3D printing tends to win on cost and lead time, with CNC machining taking over at higher volumes.

But that’s still general. Let’s put numbers to a situation you probably face weekly.

4. Numeric example 1 – simple plastic bracket, one-off

Assume:

• ABS-like material
• ~100 × 50 × 20 mm part
• No crazy tolerances, but needs to be reasonably clean and dimensionally stable

CNC machining quote – 3-axis, ABS block

Plausible cost build (outsourced to a mid-cost region):

• Programming & CAM: 1.0 h × $40/h = $40
• Machine cutting time: 0.5 h × $40/h = $20
• Deburr / basic inspection: 0.25 h × $40/h = $10
• Material stock: $8

Raw internal cost ≈ $78. Add shop margin and overhead and you get something like $80–100 as the quoted price for one CNC-machined ABS prototype.

3D printing quote – FDM plastic

Now the same part on a decent FDM machine, outsourced:

• Build time: 4 h × $10/h = $40
• Material (about 60 g at $0.05/g): ≈ $3
• Support removal / light cleanup: 0.2 h × $30/h ≈ $6

Raw internal cost ≈ $49. With margin, a realistic quote is $50–60.

Quick comparison table

These are indicative numbers, not a formal quote. But they match what many purchasing teams see.

For this case, 3D printing is cheaper. Not by a thousand dollars. But enough that if you’re doing multiple iteration loops, cost adds up.

If you know you’ll print three revisions, the math tilts even more:

• 3 × printed bracket: maybe $150–180 total
• 3 × CNC bracket (no re-programming, some setup reused): still roughly $180–240, depending how the shop discounts later pieces

5. Numeric example 2 – one aluminum bracket

Now swap material and purpose:

• 6061-T6 aluminum
• Similar geometry, but drilled holes, tapped features, functional use
• Needs real mechanical strength

CNC machining quote – aluminum

Example cost build:

• Programming & CAM: 1.0 h × $50/h = $50
• Machine time (heavier cuts, tool changes): 2.0 h × $50/h = $100
• Deburr, inspection, maybe edge breaks: 0.5 h × $50/h = $25
• Material stock: $20

Raw internal ≈ $195 → quoted $180–220 is very normal.

Metal 3D printing quote – e.g., laser powder bed

Approximate structure, based on typical cost drivers: long machine time and finishing.

• Build time: 6 h × $100/h ≈ $600
• Powder usage: ≈ $60
• Support removal, heat treatment, finishing: 2 h × $60/h ≈ $120

Total ≈ $780, then commercial realities on top. Even with aggressive pricing, you’re rarely under $400–500 for a metal-printed functional bracket of that sort.

So here, CNC machining is cheaper by a wide margin for a single prototype.

This is why, when buyers quietly compare metal printing quotes to cnc machining quotes for the same bracket, machining often wins even at a volume of one.

6. Where the “one-off” economics flip

There are a few edge cases where CNC machining is not obviously more expensive than 3D printing even for one piece.

6.1 Very simple geometry, tight tolerances

If your part is:

• Mostly 2.5D
• Reasonable size
• Tolerance-driven (fit testing, sealing surfaces)

Then:

• CNC programming is quick
• Setup is straightforward
• Machining time is low

Some shops will quote aggressively on these, and the gap to printing shrinks. Especially if you’re in a region with lower CNC labor rates.

6.2 When post-processing dominates the quote

3D printing surface finishing, painting, smoothing, or support removal can easily blow out the cost.

If the print house has to:

• Remove complex internal supports by hand
• Sand multiple surfaces
• Paint or coat to hide print layers

You’re not buying “one printed part” anymore. You’re buying a chunk of manual work, and that narrows the gap with cnc machining.

6.3 Multiple near-identical CNC spins

One big difference from printing: CNC setup cost amortizes across the batch.

Example from a real-style cost breakdown: the first CNC part might be ~$240, while the 25th part of the same batch drops to ~$130, over 50% cheaper, just because setup is spread across more pieces.

If you expect:

• Several prototype spins with micro-changes
• Or a quick pilot run after the first part looks good

Then you can think in terms of “family of prototypes” rather than a single one, and cnc machining starts to look less brutal.

7. Quick rules of thumb for purchasing and engineers

You don’t always have time to model every cost term. So use simple rules.

7.1 Start with the material + risk equation

• Plastic, early concept, you mainly care about shape → Default to 3D printing.
• Metal, functional loading, or tight tolerance fits → Default to CNC machining, unless metal printing is strategically required (internal channels, weight reduction you actually need now).
• Customer demo where the part will be handled a lot → lean toward CNC machining or high-end printing with proper finishing. Cosmetic rework on a rough print quickly eats your “savings.”

7.2 Ask two simple questions in RFQs

When you send RFQs for cnc machining vs 3D printing, ask suppliers:

1. “What drives most of the cost here: setup, machine time, or finishing?”
2. “If I order five pieces instead of one, how does unit price change?”

From the answers, you’ll see:

• If CNC is mostly setup-heavy, the first unit will look harsh but follow-ons cheap.
• If 3D printing is post-processing-heavy, the price won’t scale linearly with volume.

You’re not trying to negotiate yet. You’re trying to see which process responds better to the way your project will actually run.

7.3 Don’t ignore internal costs

If you have:

• Internal printers (FDM, resin) but no internal cnc machining
• Or the reverse

Then even if vendor pricing favors one process, your internal overhead might push the decision the other way.

Example: It might be “cheaper on paper” to 3D print outside, but if the engineering team would print it overnight in-house at near-zero marginal cost, the real decision isn’t the vendor quote.

8. What to send suppliers so quotes are actually comparable

To get clean CNC machining and 3D printing quotes for a single prototype, include:

• Neutral CAD (STEP/IGES) + drawing if tolerances matter
• Material and acceptable substitutes
  • e.g. “Any 6000-series aluminum is fine” or “ABS / ABS-like, doesn’t have to be exact grade”
• Functional requirements instead of vague labels
  • “These bores need H7 fit; this face is sealing; these surfaces are cosmetic only”
• Surface and finishing requirements
  • For 3D printing: state if you accept as-printed surfaces on non-critical areas
  • For cnc machining: specify if you need anodizing, bead blasting, etc.
• Expected next step
  • “This is a one-off” vs “If this works, there’s a 50–100 piece run behind it”

Suppliers will quietly adjust their pricing if they know there’s likely follow-on work. That changes your real cost for today’s “single” prototype.

9. So which is cheaper for your one prototype?

Stripped down:

• Most plastic concept parts → 3D printing is cheaper on the invoice and faster on your desk.
• Most metal functional parts → cnc machining is cheaper than metal 3D printing, and usually more representative of final manufacturing.
• Highly cosmetic or tolerance-driven parts → cost is often closer than you expect; cnc machining may be slightly more expensive, but reduces test risk.

If you’re unsure, a good pattern is:

1. Print the first rough iteration (especially plastics, and especially internal reviews).
2. Switch to cnc machining when you’re close to the final design, or as soon as tolerances and surfaces start to matter.

That combination uses 3D printing where it wins on cost and speed, and cnc machining where it wins on realistic behavior.

10. FAQ – CNC machining vs 3D printing for a single prototype