PRACTICAL PROJECT GUIDE
3D printing, CNC machining or injection moulding?
Choose around the requirements of the part, the stability of the design and the quantities you need. There is no universal quantity at which one process becomes the best choice.
The three processes at a glance
| Consideration | 3D printing | CNC machining | Injection moulding |
|---|---|---|---|
| How it works | Builds a part in layers. | Cuts material from stock. | Forms parts in a mould. |
| Where to consider it | Prototypes, complex shapes and selected short runs. | Metal or plastic parts with important material and dimensional requirements. | Repeat plastic production with an established design. |
| Design changes | A revised model can be used for a later build. | Changes may require revised machining setup. | Changes can require tool modifications. |
| Main constraints | Process, material, orientation and finish. | Tool access, geometry and machining time. | Tooling cost and mouldability of the design. |
When flexibility matters
For an evolving design, 3D printing can let you explore a physical model without committing to a production mould. Use that model to answer a specific question about shape, fit or assembly. Printing is not automatically suitable for every final-use requirement.
Before choosing a process, record the function of the part, expected quantities and important constraints. That gives a supplier more useful information than a request for the cheapest possible material.
When material and fit matter
CNC machining removes material from a solid workpiece. It is worth considering when a particular stock material or a critical fit is central to the part. Tool access and geometry can limit what is practical to machine.
Identify the dimensions and surfaces that matter to function. Avoid applying a demanding requirement to every feature unless the application calls for it; discuss the drawing with the manufacturer.
When repeat production matters
Injection moulding uses a tool to form repeat parts. Tooling adds an initial commitment, so expected reorders and design stability matter alongside the first batch quantity.
A printed prototype may need geometry changes to become mouldable. Discuss wall thickness, draft, part release and cosmetic requirements before treating a prototype file as a tooling-ready design.
Ask these questions before ordering
- What must the part do, and what would count as a successful result?
- How many do you need now, and what might you reorder?
- Is the design still changing?
- Which material properties, fits and finishes are essential?
- What does the total cost include: design, setup, tooling, finishing and delivery?
You can use different processes at different stages. Allentronics offers 3D printing and manufacturing support to help discuss a suitable route.
Further reading
General process guidance: NIST’s additive manufacturing FAQs, Protolabs’ machining and printing comparison, and Protolabs’ injection moulding guide.
These sources describe manufacturing generally. Their equipment, materials and delivery promises are not Allentronics service specifications.
Explore the next step
Let’s talk about your project.
Share your idea, requirements and any useful files. We’ll review the project and get in touch to discuss the next step.