Plainly put: when 3D printing isthe wrong choice

Additive manufacturing is often sold as a magic answer to everything. It isn't. As engineers we know every manufacturing method has physical limits. Choosing 3D printing (FDM/FFF) at the wrong time gives weak parts, high costs and needless frustration. Here is when to choose something else.

1. Mass production (over 5,000 units)

3D printing is hard to beat for prototypes, fixtures, spare parts and low-volume production (1–500 units). But machine time per part barely drops just because you print 10,000 of them.

Our advice: If your design is finished and you need tens of thousands of units, have a mould made and use injection moulding. The tool costs around SEK 100,000, but the unit price drops from hundreds of kronor to almost nothing.

2. Extreme isotropic strength

An FDM print is built layer by layer. However strong the material (e.g. PAHT-CF), the Z axis, where the layers meet, will always be the weakest link. This means the material isanisotropic.

Our advice: If you have extreme tensile loads coming from several unexpected angles, or the part must pass certified pressure vessel tests, a solid metal block (CNC machined) or SLS printing is the better choice. FDM requires the designer to understand and design for the load direction.

3. Micrometre tolerances (±0.01 mm)

We hold ±0.05 mm tolerance, which is very good for plastic. But thermoplastics shrink and expand with temperature and geometry. That matters if you are designing a high-precision bearing housing where the fit must be within hundredths of a millimetre (H7/h6 fits).

Our advice: Use additive manufacturing for the housing and frame (to save weight and money), but plan a finishing step where a metal bushing is pressed in, or machine that specific surface on a CNC.