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Strengthen hole walls?

Posted by StlLooking 
Strengthen hole walls?
February 12, 2019 01:24PM
Hi, does anyone have some ideas on strengthening the walls just for holes so they don't crush down when bolted to something?

Using Cura I have set Wall-count to 6 or more and it works OK, but it takes forever to print as all other walls are printed at 6 too.

I tried using Slic3r and variable layer heights but same issue. By the time I have defined the appropriate layer-ranges, it is 80% of the full print. A little quicker but not much.

Thanks
Re: Strengthen hole walls?
February 12, 2019 02:10PM
If you want the holes stronger, you have to put more material around the hole and yes, it will increase print time.

Use modifier meshes in slic3r to increase fill density around the holes. You can either create the modifiers in CAD (the most flexible option) and export as a separate STL(s) from the main part(s), or create them in slic3r.

In slic3r, import your object stl file. Click on it so it is green. In the menu bar select object>settings and then select load or create modifier. See: slic3r.org/blog/modifier-meshes

Fine point is using modifier meshes: if the mesh contacts the outer wall, top or bottom of a print, you will see it in the print. If you put the modifier mesh completely inside the part, you won't see it on the outside surface. For top/bottom holes, if I use 4 top/bottom solid layers and layer thickness is 0.2 mm, I put the modifier mesh 0.4 mm above the bottom of the part and make it 0.4 mm shorter in Z than the part.

Edited 2 time(s). Last edit at 02/12/2019 02:14PM by the_digital_dentist.


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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Strengthen hole walls?
February 12, 2019 04:05PM
I have a few things where I wanted to reinforce the wall strength like you describe.

My solution was to put a set of 1mm diameter holes spaced 1.6mm from the main hole and from each other around the hole that I wanted reinforced.

At 0.4mm extrusion width, this makes the space between the holes 4 lines wide, and the tiny triangles between them get filled solid. I put them in a set of 6 pairs (12 in total) spaced around a 10mm hole, so it doesn't do a complete ring, but it was enough to hold a piece with a 3/8" lag bolt under enough torque to hold a handrail onto a deck. (The piece was a set of 13mm spacers between a 2X4 handrail and the uprights on a staircase, done in ABS and painted with a UV resistant coating.)


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Re: Strengthen hole walls?
February 12, 2019 05:41PM
Quote
the_digital_dentist
Use modifier meshes in slic3r to increase fill density around the holes.

OK thanks, I will check that out. I figured the solution would take a little longer to print, but a lot less time than the multiple walls. I assume doing it in CAD means merging the files within Slic3r?

I'd prefer to use Cura as I am more familiar with it, but if Slic3r will do the holes, then I will use it for that and live with the angst of finding my way around it. grinning smiley
Re: Strengthen hole walls?
February 12, 2019 05:51PM
Quote
SupraGuy
My solution was to put a set of 1mm diameter holes spaced 1.6mm from the main hole and from each other around the hole that I wanted reinforced.

Thanks, I had done some messing around like that but it was a pain with a lot of holes to draw. I found that 5 small radial holes as you described forced enough fill in with Cura to do what I needed. But with a lot of holes it has become a real issue to incorporate. Like you, I am designing and buildng a new printer (CoreXY) and there are dozens of parts attaching to the 2020. I was hoping for a "magic bullet" solution but looks like I'll have to put in the hours.

I had created a channel around a hole that also did a similar thing and that was a lot easier to draw for each hole compared to the radial holes. But I will give the Dentist's suggestion a look at. I really like Slic3r, but I can get Cura to print on my Delta in much less time for the same quality results. Slic3r has zillion mini-retractions per layer that eats up the time.
Re: Strengthen hole walls?
February 13, 2019 12:41PM
@Dentist: The Slic3r thing is a good idea, but execution is abysmal.

Using Cura I have found "Extra infill wall count," that is a halfway thing between extra walls. It seems to still add to extra exterior walls, but the print time is quicker than just using the main "wall count" for the same total walls.

I don't care why, but Wall Count = 3 and Extra infill wall count=3 is about 10% faster than just Wall Count = 6 and Extra infill wall count=0

I'll live with that for the convenience. smiling smiley
Re: Strengthen hole walls?
February 14, 2019 12:18AM
Cura can do modifier meshes similar to how Slic3r does it. They call it infill meshes. I created a set of primitive shapes using Tinker Cad and just use those STLs as modifier meshes in either Cura or Slic3r. Usually a simple square works fine since you can scale it in the slicer to fit what you need. Once you have the modifier STL in place, select it and click Per Model Settings. You can then customize how the modifier mesh will be applied and what settings to change. The interface is far easier than Slic3r currently. Hopefully the next version of Slic3r makes that easier.
Re: Strengthen hole walls?
February 14, 2019 06:48AM
I usually just create the modifier(s) in CAD when I design the part that's going to be printed. You can't really do that if you're getting an stl file from thingiverse, though, so having the capability in the slicer is good, too.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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