Several starting points in one layer

[joki1 0]

Hello together,

I print with a 0.6mm nozzle and i made a CAD with a broad at the top of 0.6mm. I was hoping that the nozzle just goes through layer by layer. instead, it has two starting points in a layer. and prints a part, then it goes over it again and starts to print on the other side and then goes around again very strangely, instead of pulling once properly over the layer. With the slicer Slic3r it works exactly as I want it, but I have problems with the retraction of multiple objects. In addition, I find the Ultimaker Cura slicer very appealing from the user interface. 

I have tried several z seam alignments but unfortunately it did not work to create only one starting point.

Does anyone here know further?

Best Jonas

Edited April 7, 2022 by joki1

[gr5 2,173]

The short answer is that thin walls print much better in Cura beta arachne:

https://github.com/Ultimaker/Cura/releases/tag/Arachne_engine_beta_2

 

It can do that trick where it only prints the walls once.  It still might jump from one spot to another.

 

To stop the jumping try turning off all infill.

 

If you are making a cookie cutter some people do another trick to make the walls perfect.  It's a bit of a hack.  You make your cad model solid.  For example for round cookies you model a cylinder.  A solid cylinder.  Then in cura you make the walls the same width as your nozzle with (e.g. you can do 1mm walls with a 0.4mm nozzle just fine).  Then you disable infill, top and bottom skin.  You can turn on brim for some strength.  It's not a perfect solution.  The cookie cutter may be weak.  You can't do dual level cookie cutters (I love those) that cut on the outside and add impressions (like eyes) on the inside.  But you get perfect walls.

 

The jumping might be because the walls get slightly thinner in spots.  Even if the walls are perfect in cad, when the model gets converted to triangles, now the walls vary in width slightly.  I'm not sure what causes the jumping.

[joki1 0]

I must say, super great anser and so fast, I did not expect this!
Cura beta arachne is really top, and within a layer there is no longer jumping. It is only jumped between the layers from time to time, but that does not bother me.
Since I want to design the cookie cutter tool I think your hack is not so helpful. 

Another question:
As soon as the single top wall is printed, the print occasionally stops at the layers and there are small gaps (see picture). This is probably also because in CAD the wall width is 0.6mm and the nozzle also has 0.6mm, but as you described the model is translated into triangles and therefore is probably partly below the 0.6mm and then the print stops. For me this makes no sense because the function "print thin walls" is active. 

I also find it interesting that the flow decreases in the upper part even though there is no script and the flow is constant at 110%. (See picture 2)

Do you know here maybe also know a workaround?

Edited April 7, 2022 by joki1

[gr5 2,173]

flow

 

You are misinterpreting the colors.  If you read the key carefully it is showing mm^3/second.  The amount isn't changing, the speed is slowing down.

 

The default in cura I think is minimum layer time 5 seconds.  Those thin walls can print very quickly (not much to print) so it slows down (as it should) to give the layer below more time to cool.

 

gaps

 

Regarding the gaps - ug - there are over 500 parameters now in cura.  You mention nozzle width but that has no meaning in cura - line width is what matters.  Type line width into the search parameters and try 0.5mm - the gaps will go away which is good but will it now make 2 passes?  I don't know.

 

0.6mm walls

 

I recommend 0.8mm walls.  I'm really not an expert so I could easily be wrong, but if I remember right, the last cookie cutters I made, I used 0.8mm walls and 0.4 (or maybe 0.37?) line width and that was a good thickness to the cutter.  You don't want it too flimsy.  And the dough I was cutting was easy to cut with 0.8mm walls.  I did double height cutters - it was some kind of dog.  Let me see if I can find pictures...

[gr5 2,173]

Oops.  Nope.  I did 2mm walls!!

 

[gr5 2,173]

 

These were fun - I did the cutter in tinkercad for a class I was teaching.  Normally I never use tinkercad.