Shenzhen Alu Rapid Prototype Precision Co., Ltd.
Industry News
Short answer: Choose 3D printing for the fastest, cheapest visual or fit check in plastic. Choose CNC machining when the part must work in its final material or hold real tolerances. Choose vacuum casting when you need 10–50 parts that look and feel like production. For metal prototypes, CNC is the default.
Every prototype exists to answer a specific question. The right process is whichever answers that question fastest and cheapest — without giving you a misleading answer.
At a Glance
| Factor | 3D Printing | CNC Machining | Vacuum Casting |
|---|---|---|---|
| Lead time | 1–3 days | 3–7 days | 4–8 days |
| Cost for 1 part | $10–$100 | $50–$300 | Master + tooling |
| Cost for 20 parts | Linear (×20) | Falls slowly | Falls sharply |
| Materials | Photopolymers, thermoplastics, some metals | Essentially any machinable metal or plastic | Polyurethane resins |
| Tolerance | ±0.2–0.5 mm | ±0.02–0.1 mm | ±0.1–0.3 mm |
| Surface finish | Layer lines, needs finishing | Machined, functional | Near-injection-molded look |
| Best for | Form and fit, speed | Function, real material, tight tolerance | Appearance models, pilot runs |
3D Printing: Fastest to a Physical Part
Additive processes build the part layer by layer, so there is no tooling and no set-up. That makes it the cheapest and quickest route for a single part — often same day or next day.
Use it when: you are checking form, fit, or ergonomics; the part is a non-structural housing or cover; or you need a visual model for a presentation. Avoid it when: the decision depends on the mechanical behaviour of the final material, or on tolerances tighter than ±0.2 mm.
CNC Machining: The Functional Prototype Standard
CNC removes material from a solid block, so the prototype is made of the same alloy or plastic as production and holds the same tolerances. If your prototype must pass a load test, survive heat, or fit a real bearing, this is the process that gives a trustworthy answer.
Use it when: the part is metal; tolerance matters; the prototype will be tested to failure; or the design will eventually be machined in production. See our CNC machining capabilities.
Vacuum Casting: Appearance and Pilot Batches
A master pattern is used to make a silicone mold, which then yields 15–25 polyurethane parts that are difficult to distinguish from injection molding. It is the standard way to produce a small batch of identical, presentable units for beta testing, trade shows, or investors.
Use it when: you need 10–50 matching parts; appearance and texture matter; or you are validating a design before paying for steel tooling. See our vacuum casting capabilities.
Which Question Are You Trying to Answer?
| Your question | Best process |
|---|---|
| Does the shape and size feel right in the hand? | 3D printing |
| Do the parts assemble without interference? | 3D printing or CNC |
| Will it survive the real load, heat, and vibration? | CNC machining |
| Does it fit a real bearing, seal, or mating part? | CNC machining |
| What does it look like in the final finish and color? | Vacuum casting |
| Can I send 20 units to beta testers? | Vacuum casting |
The Typical Development Sequence
3D print — confirm shape and fit in days, at low cost
CNC machine — validate function, tolerances, and final material
Vacuum cast 10–50 — produce matching units for real-world testing or display
Injection mold or production run — once the design is frozen
Skipping step 2 is the most common mistake: teams go straight from a printed model to tooling and discover a functional problem after the mold is cut. See our rapid prototyping services for the full route.
FAQ
What is the cheapest way to make a prototype?
For plastic parts and simple geometry, 3D printing. For metal or functional parts, CNC — there is no cheap substitute.
Can 3D printing replace CNC for prototypes?
For shape and fit, often yes. For mechanical performance, tolerance, and material behaviour, no.
How fast can I get a CNC prototype?
Typically 3–7 days, and faster with expedited handling.
When is vacuum casting worth it?
Whenever you need more than a handful of parts that must all look identical and production-like, without paying for a steel mold.
Should I prototype in the final material?
Yes, at least once before committing to production tooling. Material behaviour is the most common source of late-stage surprises.
Not Sure Which Route Fits?
Send your CAD file and tell us the question you are trying to answer. We will recommend the process and quote it.