Part sizes

Four figures decide whether your part fits the machines: weight, outer dimensions, projected area in the parting plane, and minimum wall thickness. The third is the least known and the most important — it is the projected area, not the weight, that decides how much clamping force is needed to hold the die shut.

We make parts from a few grams to several kilos. That is the phrasing that has stood on our site for a long time, and it is true — but it is too coarse to be useful to you.

Note also that the limit is not the same in the two metals. Zinc is 6.6 g/cm³ and aluminium 2.7. The same geometry weighs 2.4 times more in zinc, so a weight limit in grams is reached on a physically smaller part.

Wall thickness runs the other way: zinc handles thinner sections than aluminium, because the lower melt temperature gives a fluid melt that reaches into tight features before it freezes.

Projected area is easy to work out yourself: lay the part down as it sits in the die, look straight down on it, and measure the area of the shadow. That is the area the injection pressure acts against, which is why a flat, wide, light part can need more clamping force than a compact, heavy one.

Wall thickness should be as even as the geometry allows. Large steps in thickness give uneven solidification, and where the thick section freezes last, shrinkage porosity forms. If a thicker section is needed for strength, a rib is almost always a better answer than a lump — it gives the same stiffness with less metal and without the heavy section.

The precise figures are being verified. If you have a part you are wondering about, send it — we will look at the actual geometry and tell you whether it runs, and in which machine.