The limits of rapid plastic prototyping

The technologies used for rapid plastic prototyping are limited due to the production processes used. The principal techniques used are 3D printing and its variants (3D stereolithography, powder sintering, SLA, etc.), CNC machining and vacuum silicone molding.

The wide range of materials and finishes available with these technologies makes it possible to create prototypes that are very close to series parts. However, the production processes for 3D plastic prototypes do not make it possible to obtain parts that are completely identical to injected parts. Below is a presentation of the four principal limitations of rapid prototyping compared to thermoplastic injection used in series production.

4 limitations of rapid prototyping compared to thermoplastic injection

1. Quantity:

The quantities of parts to be produced: units (1-10 parts), small series (10-200 parts) or large series (>200 parts) can be an obstacle to the use of plastic prototyping technologies. In fact, the techniques to prototype a part or to produce in small quantities reach an economic and production efficiency limit rather rapidly. In fact, beyond 2-3 3D-printed parts or 5-10 plastic machined parts or 100-200 parts vacuum-cast in silicone, it is necessary to switch to series injection. Thermoplastic molding is thus more advantageous than vacuum silicone molding for the production of large series.

2. Geometry:

Thanks to certain techniques such as 3D printing, shapes that cannot be produced with injection, such as hollow parts or parts with undercuts, are conceivable with plastic prototyping. A similar situation exists with 3D plastic machining since it is possible to obtain parts by cutting and sticking sections. Thus, the parts resulting from these productions may not be representative of series parts. Rapid prototyping, therefore, imitates plastic series parts as close as possible, but certain techniques make it possible to produce components that cannot be produced during the industrialization phase. For more information on the limits of the machining of plastic parts and vacuum silicone molding, read our news about tapers and undercuts.

3. Physical properties:

Plastic prototyping uses equivalent materials, or substitutes, or materials that are very close to the right material. As a result, the mechanical properties cannot be entirely similar to those of injected parts.  In addition, 3D plastic machining uses the right material, but the production method is different from the injection. Consequently, the mechanical characteristics cannot be totally identical.

4. Finishes:

In rapid plastic prototyping, it is possible to obtain parts with technical and visual characteristics that are very close to those of injected parts. The difference may be difficult to perceive between a machined part made from the right material and an injected part. However, there will always be some difference because the method of production of plastic parts in small quantities is different from large series production. For example, the arbor and mold-tech grains are difficult to imitate.

In conclusion, the mechanical and visual characteristics of 3D plastic parts are not completely identical to those of injected parts. The information obtained during validation testing of the prototypes will always have a limit. A production of plastic parts in small quantities or plastic prototypes will be close but not identical to the production of injected parts.

For more information, our page Identify your needs offers a comparison between the technologies of rapid prototyping, production of small series and large series.