prevent right angle travel when bridging voids?
 
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ga
 ga
(@ga)
Trusted Member
prevent right angle travel when bridging voids?

I have a print which has some small bars spanning 6mm over a void -- holes with two bars across them at right angles, crossing in the center.  The slicer generates a path that goes up one leg to the center, turns a right angle, then goes back out to the edge.  On the first pass, this drags the filament across the void.  Is there an easy way to tell it not to generate this kind of path?  It would be great if it would only generate straight edge-to-edge paths and not take a right angle turn.  I've already told it not to cross voids.

Posted : 13/02/2021 8:22 pm
ga
 ga
(@ga)
Trusted Member
Topic starter answered:
RE: prevent right angle travel when bridging voids?

Another option might be to tell it to slow down for that particular layer / parts of the layer, similar to the way you can now select different layer heights and paint seams, but I don't see a way to do that.

Posted : 13/02/2021 8:45 pm
towlerg
(@towlerg)
Noble Member
RE: prevent right angle travel when bridging voids?

You need to attach your .3MF project files.

Two things you can do to change the bridging direction, rotate the part before slicing or change Bridging Angle (print setting/infill/advanced)

Posted : 13/02/2021 10:06 pm
ga
 ga
(@ga)
Trusted Member
Topic starter answered:
RE: prevent right angle travel when bridging voids?

@towlerg

Sorry, the .3mf for a test showing the problem attached.  Rotating the part won't work for printing.  I don't understand what the bridging angle has to do with the path, or how it can help.

 

Posted : 14/02/2021 4:15 am
towlerg
(@towlerg)
Noble Member
RE: prevent right angle travel when bridging voids?

@ga-3

I don't see any attachment. Surely no reason not to rotate the part leaving the same face on the bed but I have no idea what the part looks like.

"I don't understand what the bridging angle has to do with the path, or how it can help." I didn't say it would, only that it was a way to change bridging direction.

You really need to attach a .3MF file.

This post was modified 10 months ago by towlerg
Posted : 14/02/2021 8:50 am
ga
 ga
(@ga)
Trusted Member
Topic starter answered:
RE: prevent right angle travel when bridging voids?

@towlerg

Hmmm, not sure how that attachment got discarded.  Trying again.

What does "bridging direction" mean?  Direction relative to what?  I couldn't find a good explanation for what the bridging angle controlled anywhere.  Sorry if this is a bit basic.  Thanks for your persistence.

 

Posted : 14/02/2021 7:36 pm
bobstro
(@bobstro)
Illustrious Member
RE: prevent right angle travel when bridging voids?

Attachments must be zipped.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 14/02/2021 7:40 pm
ga
 ga
(@ga)
Trusted Member
Topic starter answered:
RE: prevent right angle travel when bridging voids?
Posted by: @bobstro

Attachments must be zipped.

A 3mf file is already in zip format.  I just changed the name, will see if that works.

Attachment removed
Posted : 14/02/2021 7:48 pm
towlerg
(@towlerg)
Noble Member
RE: prevent right angle travel when bridging voids?

Can't read you attachment. Can you?

Posted : 14/02/2021 9:15 pm
ga
 ga
(@ga)
Trusted Member
Topic starter answered:
RE: prevent right angle travel when bridging voids?

@towlerg

I clicked on the link and saved it as a .3mf and it opened in prusa-slicer fine.  Is that what you tried?

Posted : 14/02/2021 10:19 pm
towlerg
(@towlerg)
Noble Member
RE: prevent right angle travel when bridging voids?

"I clicked on the link and saved it as a .3mf..."

I must be stupid because that did not occur to me.

BTW as you have Supports none and don't detect bridges true, you don't have any bridging.

I assume the issue starts a layer 15 where a circle with diameter lines is sliced as 4 90deg arcs with radii?

If that is the issue I don't see how you could slice it any other way. Bear in mind the inter layer path can't cross so if instead if doing a radius followed by a right angle radius, it did a diameter the other bar of the "cross" would still have to be two separate radii.

 

 

Posted : 15/02/2021 10:04 am
Neophyl
(@neophyl)
Famed Member
RE: prevent right angle travel when bridging voids?

The part design NEEDS support on that layer.  If you were to make one of the cross members start 1 layer lower and then have the other one start 0.2 further up then the slicer could do that without support.  Its basically the same problem as an unsupported hole for a cap head screw, with the same solution.

 

Posted : 15/02/2021 1:28 pm
ga
 ga
(@ga)
Trusted Member
Topic starter answered:
RE: prevent right angle travel when bridging voids?

@towlerg BTW as you have Supports none and don't detect bridges true, you don't have any bridging.

I assume the issue starts a layer 15 where a circle with diameter lines is sliced as 4 90deg arcs with radii?

If that is the issue I don't see how you could slice it any other way. Bear in mind the inter layer path can't cross so if instead if doing a radius followed by a right angle radius, it did a diameter the other bar of the "cross" would still have to be two separate radii.

 

I thought if I had detect bridging on it would generate supports, but now I think that must be incorrect.  Does detect bridging only cause changes in the extrusion rate, fan speed, and travel rate?

Yes, the problem is where the circle is crossed by two 90 deg bars.  If one is a diameter and the other are two separate radii, would it still do a 90 degree turn, or backtrack?  I don't know if I can get it to generate a mesh that way, but can try.

 

@neophyl The part design NEEDS support on that layer. If you were to make one of the cross members start 1 layer lower and then have the other one start 0.2 further up then the slicer could do that without support. Its basically the same problem as an unsupported hole for a cap head screw, with the same solution.

 

Thanks, that will probably work in this case.  I'll try it also.

Sorry the formatting sucks, I don't see how to quote from two messages in the same reply.  Maybe it doesn't like my browser (firefox)

Posted : 15/02/2021 4:27 pm
ga
 ga
(@ga)
Trusted Member
Topic starter answered:
RE: prevent right angle travel when bridging voids?

Just a followup. 

Offsetting one crossbar by one layer perfectly.  The first crossbar was laid down straight across.  The second took a right turn but apparently the filament adhered to the layer below sufficiently to keep it from pulling in. 

Breaking one crossbar into two halves didn't work, even when they barely touched the full crossbar.  The nozzle travel still turned the corner on the first layer and dragged the filament over the void.

Thanks again for all your help.

Posted : 16/02/2021 3:12 pm
towlerg
(@towlerg)
Noble Member
RE: prevent right angle travel when bridging voids?

Looks like I was wrong about print paths not crossing on the same layer. Apparently Grid infill does just that.

"Due to the way this infill is printed, the paths cross and cause the material to accumulate in these spots. You may hear a specific noise as the nozzle hits these parts. This may even lead to a failed print."

Posted : 18/02/2021 12:06 pm
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