3D Printing in a straight line without using vase mode

[twan_peeters]

Happy holidays everyone 🙂 I'm looking to 3D print the following object. Aware that the solution may lie in PrusaSlicer settings, but there might also be some Fusion 360 advice involved so that's why I'm posting here as well.

The challenge is that I want to print this more or less like vase mode, without using actual vase mode. I want the printhead to follow a straight line and create a 1-perimeter wall. When I select vase mode the printhead follows the correct path, but when I deselect vase mode the path the print head follows is a bit messy and I suspect will result in less strength and constant unnecessary retractions. 

Vase mode creates a smooth one-line path without retractions.

Without vase mode the print head first draws little lines, and then starts doing the blades.

I tried creating a small cut in the inside of the structure to see if that would guide the slicer software in the right direction, but unfortunately it does not really work.

I tried creating a small cut in the inside of the structure to see if that would guide the slicer software in the right direction, but unfortunately it does not make the slicer software calculate the path in a straight line either. Originally this step is not there and the model looks clean inside without cuts(picture 2). Does anyone have an idea of how I can achieve a straight printing line for the perimeters? I attached the .STL file.

[davebYYPCU]

Huh?  Vase mode is doing what you want.

Why would you turn it off?

[twan_peeters]

I cannot use vase mode, the top needs to be closed and vase mode cannot draw bridges. Also in vase mode you are forced to use a single base layer. I am going to add a 5mm base to the model, because it needs to be sturdier than that!

What I'm looking for is a solution to guide the printhead into choosing the right path through PrusaSlicer or Fusion, more or less choosing the a similar path as vase mode would to limit retractions. 

[GRSnyder · Accepted solution]

If you're using the Arachne perimeter engine (which is in both Cura and PrusaSlicer; you might have to explicitly enable it in PS), it seems to produce better results when the interior frame is thicker than one extrusion. The exact width of "two perimeters" will vary with your settings, but PS will tell you what's optimal in the Layers and Perimeters panel.

 

And of course, the same goes for the fins: you want them to consistently be a clean two traces wide. In the STL above, it looks like the fins were swept perpendicular to the wave, so the cross-sectional width varies throughout the form and the slicing behavior does as well. You can use the Parallel option in F360's Sweep to keep the fins locked to the original width. 

Attached is a quick and dirty mockup of the body portion of the original design. This one slices nicely for me, but again, you might need to tweak either your settings or the model parameters.

 

[twan_peeters]

Just wanted to take a moment and thank you for taking the time to think about this, and working out a little example in Fusion of how to improve. I wasn't aware my cross-section width was varying, and this has fixed a problem I didn't even know I had! Thanks @GRSnyder 😄

In my model I used the thin-extrude tool to make the fins, but the sweep method is much better in this instance. 

I also posted this thread at the Prusa Forum and learned there that in PrusaSlicer it also semi-solves the problem when you select 'Close Holes' as slicer mode instead of 'Regular' (Print Settings -> Advanced -> Slicing). The combination of this PrusaSlicer change and your Fusion suggestions is perfect!  

Going to celebrate the end of year now, but excited to rebuild my model and try again. Looks like it should work without issues. Thank you! 🙌🏻