How does cutting mesh work?

[petronel 0]

I am trying to make a hole into the bottom of a normal object using a cylinder set as cutting mesh. I'm assuming that's how it's meant to be used since i haven't found any info about it. The result is not as expected: i get the cut part transposed above the cutting mesh:

 

I tried all kinds of settings for the cutting mesh but none produces the expected result. What's wrong here?

 

 

[ahoeben 1,948]

If you want to use the Cutting mesh to cut a hole, normally just adding the "Wall line count", "Top layers", "Bottom Layers" and "Infill density" settings and setting them all to 0 should suffice. I'm not entirely sure why it is not working for you. Do you perhaps have ironing turned on? If not, save a project and share it here, so I can take a look at what settings prevent you from making a hole.

[petronel 0]

I'm not using ironing but i am using a filled object in a custom vase mode which seems to be the problem. If i use "spiralize outer contour" it works fine, but i need multiple walls.

CE3_LampaCreponata.3mf

[GregValiant 1,249]

The good news is that the cutting mesh works fine.  The bad news is that all it is doing is creating a pocket in a solid model.  Those walls and roof that appear around the cutting mesh are not part of the cutting mesh, they are walls and floor of the main part around the pocket.  Extending the cutting mesh through the roof of the part eliminates it's top because it's a floor.  The walls remain.

 

You have 3 options.

Shell the model and then thicken the floor and put a hole in it.  Your settings for walls and floor may remain the same.

 

Move to a .8 nozzle.  It would allow you to push the line width to 1.0 or even 1.2.  Then you could use spiralize and get at least somewhat thicker walls in 1 pass.  In that case the cutting mesh would work since Cura is throwing out the inside volume of the model.  It would require the cutting mesh to be 3.84 tall (12 layers at .32) and resting on the build plate or it will still grow walls.

 

Another alternative is to slice the model twice.  One would be the skirt and bottom 12 layers with a cutting mesh to make the hole, and a huge cutting mesh covering the rest of the part.  The second slice would be the rest of the model except for the first 12 layers which you would expand your 1st cutting mesh to cover, and delete the huge mesh, and set bottom layers to 0.  Then you could copy and paste file #2 starting at layer:0 into file #1 at the end of extrusions for the top layer (delete the end of file stuff like shutting off the heaters).  There would likely be a G92 to sync the extruder at the splice.  The Z would work out.  You aren't moving the base model so the X's and Y's would work out.  There is no additional homing required.  Nice.

[GregValiant 1,249]

And then I looked at it again...

REV_CE3_LampaCreponata.3mf

[petronel 0]

10 hours ago, GregValiant said:

And then I looked at it again...

REV_CE3_LampaCreponata.3mf 89.49 kB · 0 downloads

 

Works perfect, thanks a lot!

 

May i ask what you did with the eraser object?

[GregValiant 1,249]

I use other peoples questions and problems as tools.  I do some research, play with the software, and see if there is a way around, through, over or under a problem.  It helps me to develop my own skills as a designer and printer of plastic craptastic.  It also gives me something to do while waiting for a color change or other pause event.

 

So I had played with your situation for a while and really couldn't come up with anything except "slice twice & splice".  Several hours later I decided to try again, and there it was.  A big blocker on top resting on the little blocker in the hole.  I think it was the height of the hole blocker being set to 3.84 that made the difference.  Then the big blocker bottom is at 3.84 so it takes over from there and doesn't block the walls.  Or something like that.  Anyway, it worked.

The 3mf file has the settings for the blockers as well as the rest of the Cura settings.

Have a good holiday.

[giedzinski 0]

This issue here seems relatively resolved, but I'd like to add a note for anyone (like me) who landed on this thread with a similar issue.

 

I am using a cutting mesh to subtract an irregular shape from the top of a model (normal mesh). I found that three additional roof layers generated on the very top of the normal mesh, inside the cutting mesh—which otherwise worked fine. I removed those excess floating roof layers by:

 

- setting global roof layers and thickness to 0

- setting cutting mesh specific roof layers (along with infill, bottom layers, and walls) to 0

- setting normal mesh part's specific roof layers and thickness to my standard settings

 

This seems to circumvent the initial issue, or at least a similar issue I had.