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Support material question

Posted: Wed Mar 28, 2018 12:27 pm
by jon_bondy
I sometimes create a solid object in my CAD software and then make it hollow in the slicer by making the infill 0%. When I do this and also ask IdeaMaker to generate support, support is generated for the solid object, not the hollow object. For example, if I create a solid hemisphere and then print it without infill, support will be required for the top of the dome to print correctly, but support is not generated.

Whether this is "correct" behavior or not I cannot say. I can say that the result is a print that will fail.

Comments?

Re: Support material question

Posted: Wed Mar 28, 2018 3:15 pm
by Squenz
uh, might be a smart a.. comment, but anyway, did you try create automatic support and uncheck "touching build plate" ?

Re: Support material question

Posted: Wed Mar 28, 2018 4:33 pm
by Noren
An example image would be good.

Re: Support material question

Posted: Wed Mar 28, 2018 9:31 pm
by Jetguy
No, automatic or even manual support will not be generated inside an infill area.
This is just lack of understanding of basic 3D printing rules, how an STL is formed and how slicers in general work.
This thread and the multiple posts on down with pictures is a must read viewtopic.php?f=14&t=3290&p=18599&hilit=boolean#p18600

Infill is the area between an outward facing "wall" or shell.
When you set 0 percent infill- this is meant to be a solid object and we have the option to make less.
Support material is a structure built on the OUTSIDE of the shell- exactly opposite of infill. This is why automatic supports will never build there (inside an infill area) and even manual placement will generally fail because again, massive rules violation.

Re: Support material question

Posted: Wed Mar 28, 2018 10:02 pm
by Jetguy
You have to design the STL in such a way that no room for alternate interpretation exists.
If you want a hollow object, you design a proper hollow object that has 2 shells(no, I'm not talking about the # of shells in the slicing settings), one inward and one outward.
That defines an infill area with thickness between the 2 shells and also defines a proper surface in the hollow part that if you were crazy enough to try this and put in support (because how the heck are you going to get support out of a sealed sphere???) at least the slicer could generate the support you think you should be able to make.

0% infill is not the same as a properly designed and exported STL hollow CAD object.

Re: Support material question

Posted: Thu Mar 29, 2018 12:00 pm
by jon_bondy
Makes sense.