Spiralize!

[walterwoj 0]

I am trying to print solid cylinders (100% infill)  in polycarbonate on a 36" Cartesian printer with a 3mm nozzle.  It is important to minimize voids in the material for later machining.  My main problem is voids in the layers between the rings where the head stops or slows to go to the next ring...

 

What I want to do is print the whole layer as a single long spiral without any stops.  I'm not concerned about the surface finish of the inner and outer surfaces as they will be machined to size. 

 

What options or set of options will give me this spiral?

[Slashee_the_Cow 429]

Depends if it has to be a spiral pattern or if you just want the whole thing done with no travels. You can get a circular pattern but it does each line separately, with a travel, which isn't exactly what you want with the following settings:

• Walls > Wall Line Count to 0
• Top/Bottom > Top/Bottom Thickness to at least half the height of your object so that all of it is considered top or bottom
• Top/Bottom > Top/Bottom Pattern to Concentric

That will give you this (with the non-retracting travels in blue):

 

But if it doesn't have to be a spiral pattern, just one continuous line without travels, and you don't care about how it looks, with the settings above turn on Top/Bottom > Connect Top/Bottom Polygons:

No travels (displaying them is still turned on). Don't ask me why it chooses to do it that way. Like most things to do with slicers, accept it for what it is and move on.

[walterwoj 0]

I think the travels are the issue with my current setup, I'm getting voids in some spots (travels) and over extrusions on the last line of a layer b/c it's in the middle, on one layer it's ok but over 10-20 layers it gets bad enough to strip the part from the build plate.  I really think a true spiral pattern would solve the problems for me.

[Slashee_the_Cow 429]

9 hours ago, walterwoj said:

I think the travels are the issue with my current setup, I'm getting voids in some spots (travels) and over extrusions on the last line of a layer b/c it's in the middle, on one layer it's ok but over 10-20 layers it gets bad enough to strip the part from the build plate.  I really think a true spiral pattern would solve the problems for me.

The problem with trying to print a proper spiral pattern is that the line has to get thinner at the end and eventually come to a point, which seriously disrupts flow, and by the sounds of it a consistent flow is exactly what you need.

 

The concentric pattern with connected polygons has no travels and is a giant loop so no movement (other than up) is required at a layer change, so the flow is consistent (except at layer change, where it will stop extruding), but if you have Travel > Retract at Layer Change turned off then it doesn't really interrupt the flow, just pause it for a fraction of a second as the print head moves up. It also changes the path it takes every layer so no voids will form.

[GregValiant 1,351]

Cura cannot give you a spiral pattern for the Top/Bottom Skins or infill.  It would be nice if you could:

• Spiral a layer outward
• Move up
• Spiral back to the center
• Move up
• etc, etc, etc.

That's a fair sized nozzle - are you running a pellet feeder?

 

In addition to Slashee's suggestions, you could set Cura up so the print is all walls (Wall Count = 1000) and a Random Z seam.  The travel moves would change on each layer so they wouldn't "stack".

Another thing to try would be ZigZag pattern for the Top and Bottom Skins and for the Infill with the Infill at 100%.  The nozzle keeps extruding for the little connector line that connects each long extrusion.  With ZigZag the setting "Randomize Infill Start" is available so the nozzle wouldn't be returning to the same spot all the time.

 

[Slashee_the_Cow 429]

7 minutes ago, GregValiant said:

In addition to Slashee's suggestions, you could set Cura up so the print is all walls (Wall Count = 1000) and a Random Z seam.  The travel moves would change on each layer so they wouldn't "stack".

Another thing to try would be ZigZag pattern for the Top and Bottom Skins and for the Infill with the Infill at 100%.  The nozzle keeps extruding for the little connector line that connects each long extrusion.  With ZigZag the setting "Randomize Infill Start" is available so the nozzle wouldn't be returning to the same spot all the time.

Even if the travel moves aren't stacked right on top of each other the odds they'd cross another travel get ever higher so you still run the risk of developing lumps where that happens.