The process decision comes before the supplier decision
Most first-time buyers of custom plastic parts start by collecting supplier quotes. The smarter sequence is to decide the manufacturing process first, because the process determines the cost structure you will be quoted against. CNC machining and injection molding are not competing versions of the same thing — they are two different economic models, and choosing the wrong one can multiply your landed cost by an order of magnitude at the wrong volume.
One clarification worth making before anything else: die casting is a metal processing technique, while injection molding is the equivalent process for plastics. Buyers who see "die casting" and "CNC machining" discussed together in supplier conversations should separate the two families immediately — molten metal is never involved in plastics processing.
How the two processes actually differ
CNC machining cuts finished parts directly from solid plastic stock. There is no tooling in the mold sense: the "tool" is the cutting program. That makes it the natural fit for low-volume production (roughly 1–200+ parts), with no tooling costs and tight tolerances of ±0.001 inches.
Injection molding melts resin into a steel or aluminum mold. The mold is the entire cost story: once it exists, each additional part is cheap. The source is explicit that molding becomes cost-effective at 10,000+ parts, despite higher initial tooling costs of USD 3,000–15,000 per mold.
Cost comparison at every volume that matters
| Cost component | CNC machining | Injection molding | Notes |
|---|---|---|---|
| Initial tooling | USD 0 | USD 3,000–15,000 (standard mold) | Aluminum soft tooling: USD 2,000–5,000 for 3–4 weeks production |
| Setup cost | USD 50–200 per batch | USD 500–1,500 per production run | CNC needs minimal setup; molding needs mold installation |
| Unit cost (1–100 pcs) | USD 15–50 per part | USD 50–150 per part (amortized) | CNC more economical at very low volumes |
| Unit cost (500+ pcs) | USD 10–30 per part | USD 2–8 per part | Injection molding becomes significantly cheaper |
| Unit cost (10,000+ pcs) | USD 8–25 per part | USD 0.50–3 per part | Molding achieves maximum economies of scale |
| Lead time | Same day – 3 days | 1–15 days (plus 2–8 weeks for mold) | CNC offers faster initial delivery |
| Design changes | Immediate (program update) | USD 500–5,000 (mold modification) | CNC provides superior flexibility |
Cost ranges are industry data compiled in the source, not quotes. Two rows decide most projects:
- The tooling row. If your total order is below roughly 1,000 pieces, a USD 3,000–15,000 mold amortizes into a tooling surcharge per part that can exceed the molding savings. Aluminum soft tooling at USD 2,000–5,000 exists precisely for the middle ground — short production runs of 3–4 weeks' worth of parts, before committing to a steel mold.
- The design-change row. During prototype iterations, mold modification at USD 500–5,000 per change is the line item buyers forget. A program update on a CNC machine is free. If your design is still moving, machine the prototypes.
The break-even, stated plainly
The crossover sits between 500 and 10,000 pieces depending on part size and complexity. A practical reading of the unit-cost rows: at 500+ pieces molding already beats machining on unit price (USD 2–8 vs USD 10–30), but the mold still needs to be paid for. At 10,000+ pieces the unit cost collapses to USD 0.50–3 per part and the tooling is a rounding error. Between those anchors, run the arithmetic with your own numbers — total cost, not unit cost, is the comparison that matters.
For buyers with uncertain demand, the standard risk-reduction ladder is: CNC prototypes (days, no tooling) → aluminum soft tooling for the first production run (USD 2,000–5,000) → steel mold only after the design and the demand are both proven.
Where the parts come from: Southeast Asia sourcing map
The source's regional data (Mordor Intelligence, South-East Asia Plastics Market Report) is useful context for buyers building an Asian supply base. The regional plastics market is growing from 33.09 million tonnes in 2026 to 40.49 million tonnes in 2031, a 4.12% CAGR.
| Country | Market share | Growth (CAGR) | Key manufacturing sectors |
|---|---|---|---|
| Indonesia | 34.26% | 4.23% | Packaging, automotive, construction |
| Singapore | 18.45% | 3.87% | Electronics, medical devices, precision components |
| Thailand | 16.82% | 4.05% | Automotive parts, consumer goods, recycling |
| Malaysia | 12.34% | 4.18% | Electronics, packaging, industrial components |
| Vietnam | 9.67% | 4.56% | Consumer goods, textiles — fastest growing |
| Others | 8.46% | 4.01% | Philippines, Cambodia, Myanmar |
Indonesia dominates on domestic consumption and export-oriented manufacturing, while Vietnam shows the fastest growth at 4.56% CAGR on foreign investment in plastics processing infrastructure. For process selection, the practical takeaway: precision-component buyers (electronics, medical) will find the deepest supplier benches in Singapore and Malaysia; high-volume packaging and automotive work concentrates in Indonesia and Thailand.
A process-selection checklist for your RFQ
- Lock the volume band. Below 200 pieces: CNC. 200–10,000: aluminum tooling or CNC depending on geometry. Above 10,000: steel mold.
- Freeze the revision count. More than two design iterations still expected? Machine the prototypes first.
- Ask for the tolerance you need, not the best available. CNC at ±0.001 inches costs more per part; molding at ±0.005 inches may be entirely sufficient.
- Request both quotes for ambiguous projects. At mid volumes, a CNC quote and an aluminum-tooling molding quote often land within 20% of each other — the difference is lead time and per-part trajectory if volumes grow.
- Confirm the material form. CNC requires stock compatible with your part geometry; molding accepts almost any pelletizable resin.
Figures in this guide are compiled from the cited industry sources and are indicative planning references, not quotations. Always validate current pricing and capability with your shortlisted suppliers.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
Sources:
- Alibaba.com Seller Blog — "CNC Machining vs Injection Molding for Plastic Parts" (process guidance, cost ranges, Mordor Intelligence regional data): https://seller.alibaba.com/blogs/2026/southeast-asia/plastic-stocks/cnc-machining-injection-molding-process-guide-alibaba-b2b
This article is original content by China Plastic Factory. Data points are cited to the sources above; we do not republish third-party text, images or descriptions.
