We had given the impression it could not be printed without supports

We are preparing to sell 3D-printed parts that customers specify by dimension. Looking at one of those pages, I stopped.

Surely this shape cannot be printed without supports.

Whether supports are needed is decided by orientation

A 3D printer stacks material from the bottom up. Nothing can be stacked in mid-air, so temporary pillars are printed alongside to hold the overhanging material. Those are supports. They are snapped off afterwards, leaving marks and taking time. From the buyer's side, whether supports are needed is how easy the part is to make.

And that is not settled by the shape alone. The same shape changes answer depending on how it is laid down.

Measured, it came down to orientation

So we measured the part.

Printed upright it needs not one support. All 350 layers have an identical cross-section, so there is nothing that can overhang.

Which means the shape was fine, and my reading of it was not wrong either. What was wrong was neither of those.

The cause was the picture we were showing

The page carried one picture: the part in the orientation it is used in — fitted in place.

People assume a part prints the way the picture shows it. Printed that way, it genuinely does need supports. So my reading was correct on the information I had been given. What was missing was on our side.

We could have added a sentence saying it prints upright without supports. But adding words does not help much: the picture is read first.

What we did — added one picture

We added a picture of the orientation the part is printed in. The part we released the following day carried that picture from the start; laid flat it would have 50mm of material hanging in mid-air, which simply cannot be printed. Without the picture, the same misreading was waiting to happen.

We did not add it to every product. Only two have a printing orientation that differs from the orientation of use. Putting a "print it this way" picture on products where the two match would tell readers that orientation is something to worry about here — so the picture goes only on the two where it differs.

In summary

• When something is not getting across, look at the picture before adding words. The picture is read first
• A correct shape does not mean the user will set it down that way. An assumed orientation belongs in an image, not a sentence
• Not marking everything can communicate better. A mark means something because it appears only on the exceptions

The figures here come from measuring the geometry by machine. They are not from a printed part in hand.

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