CNC Machining vs. 3D Printing: Which Is Faster & Cheaper for a Custom Prototype?
Complete 2024 comparison of CNC machining vs 3D printing for custom prototypes: speed, cost, tolerance, materials, MOQ, design tips.
Why read this guide?
If you Google “rapid prototyping services near me”, “low-cost CNC prototype”, “fast 3D printing quote”, “aluminium machining tolerances” or “SLA vs SLS strength”, you land on thousands of scattered pages. We combined every keyword, FAQ and stop-watch test into one evergreen article so you can pick the cheapest and fastest process for your custom prototype in under five minutes.
1. Quick glossary
● Rapid prototyping – turning a CAD file into a physical part within 1–3 days.
● CNC machining services – subtractive manufacturing using mills, lathes or 5-axis centres.
● 3D printing services – additive manufacturing including FDM, SLA, SLS, SLM, DMLS, MJF, PolyJet.
● Tolerance – allowable deviation from the nominal dimension; CNC ±0.025 mm, SLA ±0.05 mm, FDM ±0.2 mm.
● MOQ – minimum order quantity; CNC and 3D printing both accept 1 piece.
2. Keyword-rich comparison table
| Search Keyword | CNC Milling Aluminium 6061 | FDM 3D Printing PETG | SLA Resin | SLS Nylon PA12 | SLM Stainless 316L |
| prototype cost per piece | $28–$45 | $8–$15 | $18–$28 | $25–$35 | $110–$150 |
| lead time in days | 1–2 | 0.3–1 | 1–2 | 2–3 | 3–5 |
| tightest tolerance | ±0.01 mm | ±0.15 mm | ±0.05 mm | ±0.1 mm | ±0.05 mm |
| surface finish Ra | 0.8 µm (as-milled) | 15 µm (layers) | 1 µm (smooth) | 6 µm (grainy) | 12 µm (shot-peen) |
| best wall thickness | 0.5 mm | 1.0 mm | 0.4 mm | 0.7 mm | 0.4 mm |
| material strength | 310 MPa UTS | 50 MPa | 65 MPa | 48 MPa | 580 MPa |
| minimum order | 1 | 1 | 1 | 1 | 1 |
| scraper risk / rework | 2 % | 10 % | 8 % | 5 % | 15 % |
| internal channels | ❌ (add EDM) | ✅ | ✅ | ✅ | ✅ |
| anodise colours | clear, black, red, blue | n/a | dyeable | n/a | n/a |
| recyclability | chips remelted | landfill | landfill | powder reuse | powder reuse |
3. Speed shoot-out: which process is really “overnight”?
● Same-day CNC prototype
11 a.m. upload STEP → 11:30 a.m. CAM → 12:30 p.m. 3-axis mill → 3 p.m. anodise → 6 p.m. DHL pick-up → 10 a.m. next day USA. Total 23 h.
● Same-day 3D printing (FDM)
11 a.m. upload STL → 11:15 a.m. slicer → 12 p.m. print 5 h → 5 p.m. support removal → 6 p.m. ship → 10 a.m. next day USA. Total 23 h.
● Metal 3D printing SLM
Print alone 14 h → heat-treat 2 h → cut supports 1 h. Absolute best 26 h + courier. Winner: CNC for metals, FDM/SLA for plastics when geometry is simple.
The above time is based on the most ideal premise, omitting the time for design complexity, material preparation, equipment debugging and testing, etc.
4. Cost Analysis
● Plastic prototype
FDM cheaper from 1–30 pcs; CNC becomes cheaper >30 pcs thanks to low material cost ($2/kg PETG vs $25/kg 6061 plate).
● Metal prototype
CNC cheaper from 1–200 pcs; SLM never catches up unless geometry is impossible to mill.
5. Material selector
| Google Search | Recommended Process | Notes |
| clear plastic prototype | SLA, PMMA CNC | SLA 1 day, CNC 2 days |
| high temperature plastic prototype | CNC PEEK, SLS PA12GF | PEEK 250 °C |
| rubber-like prototype | PolyJet TPU, SLA Elastic | Shore 30 A |
| conductive prototype | CNC copper, DMLS copper | DMLS \$300/pc |
| food safe prototype | CNC 316L, SLA Dental resin | FDA certified resin |
6. Design-for-prototype tips
1. “How to reduce CNC machining cost?”
– Use standard end-mill radii (1, 2, 3 mm).
– Depth ≤ 3 × diameter.
– Avoid undercuts; use split part if needed.
2. “How to reduce 3D printing cost?”
– Hollow the part, 15 % infill.
– Orient largest face down to minimise supports.
– Nest multiple parts in one print bed.
3. “How to hold ±0.01 mm on a prototype?”
– Choose CNC, leave 0.2 mm finish pass, use carbide cutters <0.1 mm wear.
7. FAQ schema
Q: Is CNC machining faster than 3D printing?
A: For metals, yes—1–2 days vs 3–5 days. For plastics, FDM/SLA can match CNC if geometry is simple.
Q: Is 3D printing cheaper than CNC?
A: For 1–30 plastic pieces, yes. For metals, CNC is 2–4× cheaper at all quantities.
Q: Can you CNC machine ABS plastic?
A: Absolutely; ABS machines in 1/3 the time of aluminium and gives glossy faces after vapour polish.
Q: What is the cheapest rapid prototyping service?
A: FDM PETG for cosmetic models; CNC 6061 for functional metal parts.
8. How to get an “instant CNC machining quote online”
