3D printing is often spoken of in similar terms to rapid prototyping. It is common to hear the terms: “3D prototype” or “3D proto part”. In fact, printing is one of the technologies used in rapid prototyping and forms part of so-called additive techniques. The process it uses has existed for around forty years. In fact, the technology of stereolithography that appeared in the 1970s is the ancestor of 3D printing.
Stereolithography: has long been used in rapid prototyping (see how does rapid prototyping work?). It uses an equivalent material and does not allow the production of functional or visual parts. However, it offers the advantage of producing simple parts for visualisation rapidly and at low cost.
3D printing: just like stereolithography, the resin used in 3D printing does not allow the prototypes to be designed using the right materials. Therefore, parts obtained via this technology are often not functional or visual. Consequently, 3D printing and the range of additive techniques can be separated from the so-called traditional techniques of rapid prototyping, CNC machining and vacuum casting.
Principal differences between 3D printing and traditional techniques
- Production speed: the production of a unit is generally more rapid in 3D printing. However, CNC machining and vacuum duplication are more relevant to production of multiple parts. In fact, 3D printing machines require an incompressible production time; the use of a mould with vacuum casting results in a more rapid production rate for small series.
- Material: 3D printing uses a substitute material, an epoxy resin. New generations of machines allow the printing of so-called “series” materials, but the rendering is not yet finished and relatively porous. CNC machining, on the other hand, uses the right material and polyurethane vacuum casting that is very close to the right material.
- Visual quality of the parts: the finishes in CNC machining and vacuum casting are almost identical to those of the series parts. Conversely, the visual rendering in 3D printing is often more mediocre because the lines of the printing layers are visible.
- Price: While 3D printing offers an attractive production cost for parts to be produced per unit, the many human interventions it requires make it less worthwhile than vacuum casting for small series.
- Functionality: Due to the material used, parts produced by 3D printing are not functional. Unlike CNC machining and vacuum casting, they are very limited in terms of their end use:
>> They cannot meet important technical standards and requirements. For example, the prototypes cannot withstand high temperatures or ensure compliance with food grade requirements.
>> In addition, the parts obtained are relatively fragile due to the substitute materials used. Therefore, prototypes made by 3D printing cannot be used for mechanical testing.
Consequently, 3D printing is essentially suitable for unit production of parts not subject to significant mechanical stresses. To simulate the future injection part as closely as possible, which is the principal aim during the prototype phase, traditional techniques (machining and silicone moulding) still have advantages.