Support material don't touch the object.

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Support material don't touch the object.

Postby Ebzorg » 2015-Jan-Tue-09-Jan

Hey there fellow 3D people.

I'm quite new to 3D printing - assembled my simple metal in December, and have printed quite some stuff succesfully, with flaws though.

I decided to try out printing a bearing - thing no 19836 on thingiverse.

I tried printing it, but the printer messed up the balls in the bearing. The filament simply did not attach to the support material as supposed to. I therefore took a closer look at the sliced model, and realized that there were several layers of air between the support and the balls. I tried to mess around with the settings in slic3r, but none seemed to do the job.

So my question is, what am i doing wrong here? How can i make the support material actually support the objects its supposed to. Ill post two pics, one of my support settings and one closeup of the sliced model.

Thanks for an awesome forum btw, i found alot of help in here thanks to you guys.

/E
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Support material don't touch the object.

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Re: Support material don't touch the object.

Postby plexus » 2015-Jan-Tue-12-Jan

I tried slicing this with KISSlicer (KISSlicer forum) which does a pretty good job with support. I tried my default 60 degree trigger (if the slop from horizontal is greater than 60 degrees, print support). I was getting a 1 layer gap between the support and the first layer of the bearing. I dropped this down to 30 and 10 degrees and also tried 80 degrees just to see. in all cases there is still a 1 layer gap.

This suggests to me that the issue is with the model in the context of the way Slic3r and KISSlicer compute support. If it were me, I'd change the model to try and get the slicer to not skip a layer. if this was not possible I would use the narrowest layer height so that the gap was as small as possible and hope that it is deposited well enough that the bearing can build up on it with as little roughness as possible.

I think this is a good example of how the original model, the slicing and the printer are all inter-realted and sometimes its not possible to print something because the original model was not designed to address issues in the later steps.
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Re: Support material don't touch the object.

Postby musk » 2015-Jan-Tue-16-Jan

slic3r purposely puts a gap between support and your model. From the photo, it looks like you are printing with a fairly thin layer height which in my experience is difficult to use with slic3r. Because the gap between support and the model does not adapt to the small layer heights slic3r can be inappropriate for certain models. (There should be less air gap with .1mm layers because they will not extrude into the air in the way a .3mm layer will.)
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Re: Support material don't touch the object.

Postby Ebzorg » 2015-Jan-Tue-16-Jan

Do you know why slic3r does this on purpose? It seems quite odd to me.

I enden up printing another bearing (Emmett's Gear Bearing), which doesnt need support, so that solved the problem :D

Interesting how you two disagree on the layer heigth, it calls for an experiment in my opinion!

Thanks for responding.
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Re: Support material don't touch the object.

Postby plexus » 2015-Jan-Wed-12-Jan

Ebzorg wrote:Do you know why slic3r does this on purpose? It seems quite odd to me.
I enden up printing another bearing (Emmett's Gear Bearing), which doesnt need support, so that solved the problem :D
Interesting how you two disagree on the layer heigth, it calls for an experiment in my opinion!
Thanks for responding.


Slicing is tricky. the idea is to take a 3D model defined by polygons and convert it into tool moves, layer by layer. if you think about it, its not trival. there are many ways to do it too. the slicer software has to determine the best tool moves to make for a given model. since the geometry of models can vary so much and since everyone has their own way of modelling, its just not possible for one piece of software to cover all use cases. the developers of slic3r and KISSlicer have to make decisions about how to address various kinds of geometry and in doing so, ideally, come up with a solution that works for most cases. but it won't work for all cases. this is why its important to gain experience with how a given slicer slices so you can make your models work the way you expect.

so, I am not sure why both KISS and Slic3r skip a layer before extruding the object. it could be that the geometry of the bearings is between that which would otherwise trigger the right layer being generated. you could try slightly increasing or decreasing the model's scale in all dimensions (in order to preserve spherical shapes) and see if that helps.
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Re: Support material don't touch the object.

Postby RetireeJay » 2015-Jan-Wed-13-Jan

Is it possible that there is a missing layer intentionally?

In other words, when you print "normally" the new layer is actually squished against the underlying layer, and the combination of heat and pressure from the new layer welds it to the previous layer. When you want to print removable support, maybe the best way is to leave a one-layer gap, so that the upper layer simply falls upon the underlying layer without any pressure. Its natural round shape will mean that the area of contact is very very small, so it's not firmly welded to the underlying layer.

Maybe this gets tricky when trying to print spheres!
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Re: Support material don't touch the object.

Postby knightrider » 2015-Jan-Wed-18-Jan

I believe jay is correct, a layer is intentionally left out so the support is easier to remove. I think in cases like spheres, the support material must be modeled into the part.
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Re: Support material don't touch the object.

Postby musk » 2015-Jan-Wed-18-Jan

An air gap between support and model is a feature designed to allow easier removal of support material. While it's true that the air gap does make removal easier, it causes more surface roughness in my experience and is incompatible with some models.

When using .3mm layers for example, the first layer of your model over supports will "fall" through the air gap onto the support scaffolding instead of being pressed down into it. This reduces adhesion between support and model, making the support easier to remove. This is especially helpful when supports are used in cramped areas and you'll need all the assistance you can get to remove the supports. Supporting a small sphere like in your design is a perfect example of how this feature doesn't work well for all models. The first layer of the sphere would be a small dot which "ideally" would fall down and become lightly adhered to the supports. (this will not happen at .1, and is more likely to happen at .3 though not guaranteed) Even if the dot did get properly half-adhered to the support, subsequent layers will suffer the same problem trying to stick to the dot while wildly overhanging the dot. It'll be a mess unless you can slice without the air gap.

Other slicers like simplify3d allow you to manually set the width of the air gap. They call it "upper vertical separation layers" with a default value of "1". That software also allows you to create very low density infill which is capped by high density infill, so that you don't waste hours printing high-density posts just to support a small object 10 centimeters above the print bed.
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Re: Support material don't touch the object.

Postby Ebzorg » 2015-Jan-Fri-06-Jan

musk wrote:Other slicers like simplify3d allow you to manually set the width of the air gap. They call it "upper vertical separation layers" with a default value of "1". That software also allows you to create very low density infill which is capped by high density infill, so that you don't waste hours printing high-density posts just to support a small object 10 centimeters above the print bed.


That sounds smart. I'll defenitely try that out next time!

Thanks for the responses everyone.
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