Exposed gyroid infill

[Jens_Kristensen 0]

I am currently printing a part with an embedded magnet. My 3D model contains a cylindrical groove for the magnet. The 3D printer is programmed to pause when it reaches the top of the groove. The magnets can then be inserted, and printing  continued.

In order to make the model stronger and seal the magnet the infill is made of gyroids. After printing, a hole is drilled into the gyroids in the base and top of the model and epoxy is injected with a syringe. All that works fine. However, it would be an advantage if the grove was printed without any walls, so the gyroids were exposed. That would ensure that the magnet would be covered it the injected epoxy and thereby better protected. Is that possible?

[gr5 2,167]

Just to be clear - the gyroid is for porousness to spread the glue.  Not for strength, right?

 

So in cura you can wall thickness to zero.  That should to it.  Double check that the wall lines also ends up being zero automatically.  You might want to up your infill percentage - really not sure.

 

but if you do that you will lose the outer shell as well and I assume you need that to keep the epoxy in.

 

SO INSTEAD you want to remove walls *only* where magnet(s) go.  So:

1) Make sure in "prepare/preferences/config cura" you have "ensure models are kept apart" unchecked.

2) add a cube (one for each magnet) to your build plate, right click on it, on left side of screen click the "per model setting" icon and change the cube to "modify settings for overlap of other models".  Then select the settigs and choose anything related to walls.  Then modify "wall thickness" and "wall line count" to be zero.  Now position this cube in the area where the magnet will go.  When positioning this "cube" you can scale the x,y,z axes independently.  You can position it *above* the build plate a bit.

 

You might want to add a cylinder to your build plate instead of a cube to get more accurate control.

[bagel-orb 61]

It's not really possible to make a hole in the shell at a specific place only at the moment.

 

[gr5 2,167]

Really?  The setting is there - I didn't try it.  You can't turn off shell in certain areas?

[Jens_Kristensen 0]

23 hours ago, bagel-orb said:

It's not really possible to make a hole in the shell at a specific place only at the moment.

 

So does that mean that you can not make exposed gyroids inside the model as I would like to?

BR

Jens

[gr5 2,167]

Try it.  See what happens. Follow my directions above.  You can change all kinds of things in certain areas of your prints.  "shell" is on the list of things you can change so try it.  It only takes 2 minutes to try it and even if it doesn't work you will learn about a LOT of new tricks you can do with Cura.  It's a very powerful feature.

[bagel-orb 61]

I implemented the modifier mesh settings. I am fairly sure it's not possible.

 

If you use an infill mesh (modifier mesh with Infill Only ticked) the outer wall will not be modified,

but if you use a cutting mesh (modifier with Infill Only unticked) you will get a wall at the boundary between the modifier mesh and the normal mesh, so the epoxy wouldn't be able to spread.

 

It would definitely be an interesting feature to be able to make holes in the shell.

 

However, I'm not sure how this feature should be implemented.

If you want a hole in the vertical walls you would have to interrupt the Outer Wall print lines, which are normally always closed polygons. This means that there will be a lot of interaction with other code dealing with walls and it will affect the printing as well.

If you want a hole in the Top/Bottom skin it would be a lot easier to implement, but then it would be difficult as a user to configure a hole in a nearly horizontal surface, because the walls would then still be printed as bridges accross the hole.

[gr5 2,167]

Well you can change the model so the round holes for the magnets aren't quite round -the cylindrical hole could have star like projections into the model where you can add glue/epoxy.

 

Or you can use your drill as you said earlier to drill holes in the magnet cylinder so the epoxy can flow there.

[Framar 38]

gr5, 

 

It does not work since the primary model still has outer walls that would block the expoxy to flow in. See picture (this is in Cura 3.6)

Thi

[geert_2 557]

You could design a sort of venting hole from the top of the magnet, to the hole in which you pour-in the resin. Or better two holes: one filling-canal, and one venting canal. Similar to those used in metal casting.

 

However, if the magnet is totally surrounded by plastic, and that is impregnated with resin, I don't see how the magnet could be damaged. It might rattle a bit, but metal is harder than plastic.

 

Another approach might be if you design a sort of springs or vanes into the hole. So, when you push-in the magnet, these vanes keep it centered and gently clamp it. Sort of snap-fit mechanism. That might be easiest? Try this fitting on small test pieces first, before doing a big model.

 

[cresquin 0]

I was also thinking about something similar. I'd like to print a part that would have 2-3 structural walls, filled with loose gyroid infill (10% or less). Then I would like to fill the interior with polyurethane or epoxy resin to create a PLA-reinforced resin matrix. It could save dozens of hours per part over printing with 100% infill, and would likely increase strength in the z-direction since the internal structure would end up as one homogeneous chunk of plastic instead of fused layers.

 

My current solution is also to use a drill, but that is error-prone, inconsistent and requires time that could be saved and automated if the part could be designed/printed with the ports to start.

 

For proof of concept I could go in and modify the g-code by hand to remove the walls created by the overlapping modifier, but that's not really sustainable.

 

Perhaps I could make a post-processing script if the walls created around the hole were marked in g-code? Maybe a feature in preview mode where I could select and delete individual g-code segments?

Edited May 1, 2020 by cresquin