3.6 Printing over air gap

[beatlemaniac 1]

Hello all!

 

I've been away from the 3D Printing world for a while and am just now getting back into it.  I haven't upgraded to 4.x yet and I'm still running Cura 3.6.  I'm planning to upgrade.  Hopefully my issue is fixed in a newer version.

 

I'm doing a 45-degree test print of a circular model.  It's a tip jar and will eventually be printed in transparent PETG.  I will have LEDs underneath projecting light out to the sides and bottom of the jar so the model will have air gaps in it as "light-pipes" that I wont be able to get supports to when I print the full model.  My problem comes when I get to the first layer of the bottom of the jar.  Cura has the extruder start printing the layer directly over the air gap, as seen in the pic I've included.

 

Is there a way to correct this in 3.6, or 4.x?  

 

Many thanks!!

 

Steve Hurd

Floyds Knobs, IN

 

 

[gr5 2,268]

I don't understand the question.  You are talking about that small triangle - right where the nozzle is - in the photo above.  Right?

 

If so:

1) Is that the begining of some kind of support?  If so then there is something called "support blocker".  I'm pretty sure it existed back in 3.6 as well.

2) Or is that part of the model in which case... what do you want cura to do?  Is your model a tiny triangle hanging over nothing?  And if so how would you expect it to get printed?

 

3) Or is that entire region supposed to be filled in but you haven't shown us that yet?  If so, that shouldn't happen - there's a feature called "bridging" that spans areas like that with long straight lines supported on each end.  Or maybe your part bottom isn't level here and that's the issue.

 

Anyway, we need to know a little bit more about the level you are showing now - what does it do next?  And is it printing model?  Or infill?

[beatlemaniac 1]

Hi!  Thanks for the reply.  I'm not concerned about the edges where the tree supports are.  they are just supporting the sides of the "slice" of the model.  In the pic is the start of the print of the layer.  You can see the triangle outline and then the gcode moves to the air gap and starts printing in mid air.  I'm going to fix part of the problem by extruding the "floor" of the jar downward so it touches more of the model, but I'd like to have the gcode start at the inner edge of the outside triangle and work in.  That way the plastic has something to adhere to.  I've add a few pics for clarification.  One is what it's doing in my test print.  The other is a "core" piece I printed that shows what the effect is supposed to look like.  The core was printed upside-down so the air gap wasn't an issue with that print.  Please let me know if you need more pics or have more questions.

 

Thanks!

 

Steve Hurd

 

 

[gr5 2,268]

I don't see any pictures. Okay - it looks like they are hosted on google and we don't have authorization to see them.  Maybe if you modify the pics so they are visible to anyone?

 

 

I still don't understand what I'm seeing in the first picture.  I think of jars (and tip jars) as very simple cylinders.  I understand you mention led light channels but no clue on the 3d path for those.  Why doesn't the bottom of the jar touch the print bed?

 

It might help if you use "line type" for your coloring because right now it's almost all dark gray and hard to tell what is support, what is shell, what is infill.

[beatlemaniac 1]

Apologies!

 

The mock-up has finished printing.  Can you see these pics?  I think I can fix my immediate issue by extruding the floor down a few mm.  Each square in the base will have an LED in it.  

 

 

 

 

[gr5 2,268]

Still no photos above.  The only photo is from the original post.  Log out of gmail and any other google services and then look at this post.  There will be no photos.

[beatlemaniac 1]

Sure thing.  It will be a little bit.  Sorry about this!

 

Steve Hurd

[beatlemaniac 1]

Try these (I copied them to my pc and re-uploaded them):

From my second post:

 

 

 

From my third post:

 

[gr5 2,268]

Okay I think I see what you are talking about.  In the first photo of the first post, ALL the gray area is support.  Except the lighter gray area in the rear left.  If that first photo was taken with "line type" as the coloring (maybe you should still do that for other people to understand!) then most of what is visible in the first photo would be teal colored and it would be obvious what was support and what was model.

 

So it looks like you have this pyramid shaped point that goes down into those square holes in the other part which is a cylinder.  Although why is it triangular here but square in the cylinder???  I'm still confused.

 

Okay, I'm still quite confused but if that triangular spot is the problem then it's not getting support because by default it looks at the angle of surfaces and if they are vertical they don't get support.  If they are horizontal they do.  There is an angle in between that either gets or doesn't depending on the angle of the surface.  The angle is typically around 60 degrees (from vertical) I think.  I'm thinking that because that little pyramid doesn't have a flat bottom it doesn't get any support.  Try changing the angle to like 10 degrees to see if the pyramid gets support - just as a quick test.  If that's the problem then it's not easy to fix because 10 degrees will put support *everywhere*.

 

Instead you could design your own support in CAD.  That's the way I would go.  Or alternatively maybe give the pyramid a flat bottom.

 

Or I could be wrong about why there is not support.  Or I could be wrong about what the issue you are having is.

 

[gr5 2,268]

Support Overhang Angle is the setting in Cura I'm talking about.  Set that to 10 degrees to see if it starts supporting your pyramid.

[beatlemaniac 1]

Hi!

 

Here are some better pictures of what's happening.  The first 2 are Cura layers 8 & 9.  This is the spot with the air gap in the cross-section in picture 2 in my third post.   I never used Line Type before.  These shots have it turned on.

 

The next few are from the printer. The thin lines (spokes) toward the center are the tops of the edges between the "pyramid" sections - as you call them.  Then there are several layers where nothing is printed on them.  Once I get to layer 9 I get the problem since there is nothing for the extruded plastic to adhere to.  There will never be any support underneath this area because in the full model the space is fully enclosed with plastic.  

 

I'm going to rework the model so those edges between the pyramids are high enough to reach layer 8.  

 

My main question here is:  Is there a way for Cura to start drawing the inner disc at either the center or outer edge where there IS plastic at layer 8?  That way the new plastic will have something to stick to as it comes out.  Right now, it draws the perimeter (in the air), Goes to the middle of the disc and prints out to the perimeter (in the air), and then moves to the center and works to the middle.  There is plastic on layer 8 in the center so that's why the center is round in the shots from the printer.

 

Hope that helps!

 

 

 

 

 

 

 

[gr5 2,268]

100% I don't see how your latest post has anything to do with the first screenshot.  There was a pyramid there but don't see that on these newer pics.  Anyway...

 

You must have put some very thin walls from the center to the spokes as those very thin red lines indicate "shell".  I guess I would get rid of those walls.  They look like you are creating your own support.

 

Instead I would have layer 9 be a hollow cylinder for 1 layer (or two layers) that rests/connects to the tips of all those spokes.  Maybe overlapping each tip of each spoke by 5mm or so.  That way cura will slice it such that there is a stable ring all the way around on all those spokes.  Then make the cylinder solid on layer 10 (or 11) as it is in your existing design.

 

That temporary ring on layers 9 or 9&10 will create a nice structure to bridge across from the outer ring into the center post.

 

 

[beatlemaniac 1]

Changing the model fixed my issue.  I'm still curious about the logic behind how Cura generates the gcode.  for instance, why does it start at the middle of a shape (a solid circle in this instance) work in one direction, then go back to the middle and go the other way?  Anyway, I appreciate the help!

 

[Vizitechusa 0]

Hi

 

I may have a similar problem ...

 

I am VERY new to printing.  I printed this thing last week, and by fiddling with some preference I successfully printed it without this infill structure. I "lost the reference" (forgot) how I did that. 

 

What preference would allow me to "not print that infill" structure again?

 

TIA,

Carroll   🙂

 

[gr5 2,268]

34 minutes ago, beatlemaniac said:

then go back to the middle and go the other way?

For the same reason there is a circle here.  Something about your model has an extra wall here in the middle of the solid.  That shouldn't be there.  It's something in CAD.

 

 

[gr5 2,268]

@Vizitechusa 

There's lots of ways to disable some but not all support.  That's support.  If you change your display settings - right now you have color scheme: material color.  Not very helpful.  Instead make it "line type".  Then you would clearly see that the thing you point to is support.

 

1) You can disable all support: "generate support"

2) You can set support to print only touching build plate:  "support placement"  to "touching buildplate".  That will disable the thing you arrow as it's not touching build plate.

3) You can change the angle of what needs support or not.

4) You can use support blockers - click on your part and then there is a button on the left side to add a support blocker.  Click that and click on your part then use the buttons on the left side to scale it, and position it in 3 dimensions and voila you can disable support for one small area of your part.

5) Lots of other support features

[Vizitechusa 0]

Thanks gr5. I got some of what you said.

I don't want to disable all support.

 

Where's the setting for "not touching build plate?"

I think I used that previously - but don't know where to find it.

As well, how exactly do I change the angle of what needs support or not?

 

I would also like to understand support blockers.  I clicked on the part and hovered on all ?buttons? but none said support blocker.

 

Thanks,

Carroll

[gr5 2,268]

17 hours ago, Vizitechusa said:

Where's the setting for "not touching build plate?"

support placement.  It has a dropdown with 3 or so choices.

 

Support blocker is the bottom of the section of 5.  I don't see any hover text anymore.  Click the part.  Click that.  Click somewhere on the bed and a cube appears.   Wait - I shouldn't have to describe this - there are youtube videos and other pages to help you with support blocker.  Try some of the youtube videos.  Please let us know which youtube video worked well for you by posting a link in your next post for the next person searching for this.

[Vizitechusa 0]

ok, I've spent a few hours trying to get the support blocking to work but wanted some guidance please?

 

When I (think that I have) put a support blocker in the area I want, shouldn't it "not display" the light blue structure inside that blocking cube?

 

Am I missing other settings that do that?

 

Thanks,

Carroll

 

[Vizitechusa 0]

Disregard.  I found my answer.

Thanks!

[gr5 2,268]

For others - support blocker is the next icon down.