Custom Plastic Parts: A Complete Guide to Getting Parts Made

Four Ways to Make Custom Plastic Parts

Whether you need one prototype or ten thousand production units, there’s a manufacturing process that fits your needs and budget. Here’s how they compare:

1. 3D Printing (Additive Manufacturing)

Best for: 1-100 parts, complex geometries, fast turnaround

Lead time: 1-5 business days

Tooling cost: $0

Materials: ABS, PLA, Nylon, ULTEM, PC, photopolymers

Tolerances: ±0.005″ to ±0.020″ depending on technology

3D printing is the fastest path from CAD file to physical part. No tooling, no minimum quantities, and design changes cost nothing. The tradeoff is higher per-unit cost and limited material options compared to injection molding.

2. CNC Machining

Best for: 1-500 parts, tight tolerances, engineering plastics

Lead time: 3-10 business days

Tooling cost: $0 (fixtures may be needed for complex parts)

Materials: Delrin, UHMW, Nylon, PEEK, Polycarbonate, Acetal, PTFE

Tolerances: ±0.001″ to ±0.005″

CNC machining gives you the tightest tolerances and broadest material selection. It’s ideal for functional parts that need specific engineering plastics. The limitation is geometric — undercuts, internal channels, and thin walls are difficult or impossible.

3. Urethane Casting

Best for: 10-200 parts, production-like quality at prototype prices

Lead time: 5-15 business days

Tooling cost: $500-2,000 (silicone mold from master pattern)

Materials: Polyurethane resins simulating ABS, PP, rubber, clear

Tolerances: ±0.010″ to ±0.020″

Urethane casting bridges the gap between prototyping and production. A silicone mold made from a 3D printed master can produce 20-50 parts that look and feel like injection molded parts — at a fraction of the tooling cost.

4. Injection Molding

Best for: 500+ parts, production quality, lowest per-unit cost

Lead time: 4-8 weeks (including tooling)

Tooling cost: $3,000-50,000+ depending on complexity

Materials: Almost any thermoplastic (ABS, PP, PE, Nylon, PC, etc.)

Tolerances: ±0.002″ to ±0.005″

Injection molding is the gold standard for production plastic parts. Once the mold is built, parts are fast and cheap — often under $1-5 each. The barrier is tooling cost and lead time.

How to Choose the Right Process

Ask yourself these questions:

1. How many parts do I need? (1-100 → 3D print, 100-500 → CNC or urethane, 500+ → injection mold)
2. How fast do I need them? (Days → 3D print, weeks → any process)
3. What tolerances do I need? (Tight → CNC, moderate → any process)
4. Is the design finalized? (No → 3D print, yes → consider tooling)
5. What material do I need? (Engineering plastics → CNC, production plastics → injection mold)

Not Sure Which Process Is Right?

PartSnap offers all four manufacturing processes under one roof. Send us your CAD file and we’ll recommend the best process for your application, timeline, and budget — with a free quote.