off topic question on 3D printing

[Huntindave McCann]

Thought I start a new thread.
Quoting benp
"In my experience, there are a lot of factors into how strong the print can be. It matters at what temperature the print bed is and the nozzle, it matters on how thick each layer is, if it's thick parts it matters on how hollow the infill is and how thick the walls are. I have found typically the weakness is in shear load applied along print layers. I combat this by printing higher percentage infill with alternating print path.

I had to do a repair at work and where my piece of metal was attaching to there was an odd angle on both sides of the part that would not allow any clamp to attach to without sliding off. There was a tiny lip on the corner of the angle so I 3d printed pieces that would lock into that lip and go over the repair to create a square space for the clamps to hold onto. I applied a lot of force but I did 100% infill so that it would be the strongest possible while making sure the print orientation wouldn't allow the layers to separate under pressure.

Not trying to hi-jack the thread just like the cool technology and application this tool allows us to do.

Like the use of the printer Dave, the mind of the limit on what can be created."

Question;
I have been told that increasing wall thickness is way more beneficial than 100% infill. Right or wrong? I have a part where a bolt goes down thru and I am crushing the top layer, down into the infill. 5/16 bolt down thru a 1 inch dia. boss about 3.75 inches tall. I am thinking of increasing the walls from 2mm to 12mm (5 walls to 30 walls)
This would make the 1 inch dia boss all solid walls with no infill.
Should be my strongest option? (staying with my limitation of PLA)

 

[benp]

Depending on your slicer and its capabilities it might not make a difference. I looked at mine and if I increase wall count to create a solid block then it creates the same print pattern as if I increase infill to 100%

In theory if it keeps the same print pattern of infill then it would have more isotropic shapes that would be stronger than print lines in simpler geometric shapes to create a solid piece. I don't see where I can fiddle with mine to create that options but I am just using a free software.

Something you could do to make a truly solid piece would be to use a grid infill pattern and then design and print it taller than you need, then cut it in half and pour epoxy into it and glue it back together. Or print two half's and do the same thing.

 

[benp]

I just figured out a way to get an almost solid block with the infill. I chose to have infill at 90% and that makes it virtually all infill with the lines infill pattern I have. Sometimes I use cubic or triangle, under compression I would use grid or lines.

This is a butt plate I made for my sons BB gun that shows the line infill pattern At 25%



And this one is the cubic infill at 25%



Here is the line pattern at 90%

 

[benp]

Could also make the part with an oversized bolt hole and make a metal bushing to slip into it to take on some of the compressive load, would help in shear application as well.

 

[Huntindave McCann]

Could also make the part with an oversized bolt hole and make a metal bushing to slip into it to take on some of the compressive load, would help in shear application as well.

That is a good option, provided I have the room. There are two 1 inch dia. cross holes running 90 degrees adjacent to the bolt hole in question. I may be able to shift them or modify their shape. Thanks for your expertise.