How does auto orient work in PreForm?

General Discussion
1

My question is: how does auto orient work in PreForm?
What is taken into consideration when calculating the object’s angle?
Sometimes I use this function, and the results are not always consistent. As shown in the picture, a slightly larger object has a much higher angle than a smaller one.

All objects on this screen were oriented using auto-orient:

image
image1920×919 112 KB

My usual workflow for resin 3D prints (on Formlabs and Anycubic printers): I take the pixel size (in the case of Form 3, the laser spot size) and calculate the tangent of layer thickness divided by laser spot size. For the Form 3 by layer thickness:

  • 0.1mm = 49.6355°

  • 0.05mm = 30.4655°

  • 0.025mm = 16.3895°

2

Ah yes, good ole arctan angles. I’m not sure how auto orient figures it out, and only when I do auto orient will it sometimes change a little. When I use the 1-click feature, models always orient in the same way, no matter if I delete the file and reopen it - it’s been consistent. I get better results with my prints using the 1 click than if I were to orient and edit support points myself. I know that not everyone has that experience, but for the most part it’s been solid

3

I feel that some of the variables to the auto-orientation are:

  • Reduce the area of the printing layer (mainly the first ones) to minimize the peeling force. So the the angle of the part will be a consequence, not taken really in count for the software;
  • Try to avoid cups;
  • Optmize supports spending less material;

But as you just realized, it is not a consistent method, if you take the same part and auto-orient it, the software will not always orient it in the same way.

My tip is not to use this tool hahaha orienting parts is a subjective skill that is easy to learn, and there is not always a “best” way to do it, sometimes is just your feeling. In my case I prioritize the accuracy and geometric characteristics.

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4

Hi @strojano,

The auto-orient algorithm can converge on different local minima and uses random optimization. This is why running auto-orient multiple times may yield different results. The algorithm itself is trying to:

  • Make sure the result fits into the given build volume

  • Minimize the number of minima vertices

  • Avoid small angles with build platform

  • Minimize build platform parallel surfaces

  • etc…

4 Likes
5

Thank you. This is exactly what I want to know.

BR,
Sebastian

1 Like