Model scale: how to change the size before printing

Why change the scale

There are two reasons. First, the file has the wrong units. The STL format does not carry unit information, so a model designed in inches opens 25.4 times too small in millimetres, and a model in metres opens huge. Second, you want a bigger or smaller print than the author intended, for example a figurine as a gift or a holder for a different object.

The general idea of scale is explained on Wikipedia. For 3D printing a percentage is enough: 100% is the original size, 50% is half, 200% is double.

What happens when you resize

Note that weight and time do not grow like the dimensions. At double scale the dimensions are twice as large, but the volume, and so the material used, is about eight times larger. The price therefore rises sharply when you enlarge, and falls faster than you might expect when you shrink.

• Shrinking. Thin walls and details may drop below what can be printed, see smallest feature. With a 0.4 mm nozzle, fine details simply will not print.
• Enlarging. The part has to fit in 246 × 246 × 256 mm. Anything bigger has to be split.
• Joints and holes. The clearance changes with the scale too. Better not to scale models with snap-fit joints or print in place.

Example: a part that weighs 20 g weighs about 68 g when scaled up to 150%. The price therefore rises more than it might seem. If you do not know the dimensions, open the model in a viewer and look at its size in millimetres.

How it works with us

You set the scale in the calculator after uploading. The model is prepared for printing on our server again at the new size, so the grams, the time and the number of pieces on the bed are real. You see the price and the delivery date straight away.

If your model looks like a grain of sand after uploading, it was saved in different units. You bring it back from inches with a scale of 2,540%, from centimetres with 1,000%. Always check the dimensions in the calculator before you order.