The limits of 3D printing in rapid prototyping

The 3D printing process has several advantages over traditional rapid prototyping techniques. However, using this technology also has limits if you want to prototype a future plastic part that will then be produced by injection.

No limits in terms of shapes, but no information on manufacturability

One of the principal advantages of 3D production is that it is possible to imagine all shapes without the limits of the constraints of the plastics industry, such as undercuts, hollowness, respect for thicknesses, etc. The flip side of this advantage is that 3D printing does not offer information on the manufacturability of parts for series production, which will be subject to these constraints. In other words, plastic parts that can be produced with 3D printing will not necessarily be able to be produced by thermoplastic injection. With CNC machining or vacuum duplication, although these techniques differ from a series injection, the technical production constraints are closer than 3D production.

Cheap, but not always

For large quantities (in excess of 5-10 parts), 3D additive production will be less cost-effective and slower than CNC machining or vacuum casting due to the lack of economies of scale.

Large series parts (measuring more than 200 mm) or very heavy ones (more than 500 g) are also financial barriers to additive production.

No visual limits but physical limits

Finally, the biggest disadvantage comes from the material used. This is often an ABS or PA resin used as a substitute for the right material in many cases. This limits the physical properties of the part. Examples include:

• Standards: 3D printing does not allow the production of food-grade parts or parts that meet fire-proofing standards such as UL-94 V0

• Mechanical properties: Mechanical properties such as impact strength, bending, etc. will be less close to series parts.

• Transparency: The transparency of parts produced with 3D is less than PMMA machining of parts.

• Finish: Without manual retouching, 3D-printed parts are less attractive than parts created by vacuum duplication. In fact, the material addition lines are visible and the part is slightly grainy to the touch.

In conclusion, the advantages of 3D printing are also the limitations of this additive technique when it comes to prototyping a thermoplastic injection part. The visual and mechanical properties are less close to series parts with 3D production than with CNC machining using the right material or vacuum duplication.

For more information on the limitations of 3D printing compared to other rapid prototyping processes, we advise you to read our news on this subject, as well as our page comparing the techniques of obtaining rapid prototypes.