Infill Problem

[StarkFlyer 0]

I designed a holder (Shelf type of design) in Fusion 360.  Cura told me around 25 hours to print it. For a possible fit problem I decided to scale it to 101%.  Now print time is 15 hours.  Set back to 100% scale and 25 hours. Set it to 99% and 15 hours.  Tried many different settings (infill, layer height, etc.) and rebooted computer with no change.  Since I am new to Fusion 360 I went back to A123D and designed the part with it.  Same results.  I am using Cura 3.6.20 Lulzbot Edition (have their mini printer), then switched to Ultimaker 4.4.1 (use for Creality CR10-S). Totality surprised, had same symptoms.  After inspecting with layer view I found at 100% scaling it was doing 100% infill.  At 99% or 101% settings the infill is as expected.  It also took a very long time to process the layer view at 100% setting.  I included two pictures showing the differences.  I also included the part file and one of the profiles I used.

 

For now I am going to print at 101% to in order to complete the job.

 

Just wandering if anyone has stumbled across this problem before or knows how to correct it.

 

Thanks,

Dick

Mini 175 STD pt4Nozzle PLA.curaprofile Pad Holder.stl

[burtoogle 508]

It's because the model's walls are not close to an even number of wall line widths wide. If you want a quick print that should look fine just use a wall line width of 0.5mm. BTW, I use that a lot with a 0.4 nozzle with no problems at all.

[StarkFlyer 0]

Thanks burtoogle.  I used the .5 wall line width to make the print and all was well.  You made me think more about line width settings, nozzle size, etc.  Found other settings that also worked.  Somewhere along the way I saw a "rule," more than once, the line width should be = to nozzle size.  It made sense to me so I always followed it.

[nitro2k01 2]

In this case, Cura sees that the gap between the walls is exactly 1 nozzle width, and reckons it might as well fill that in with a straight line. This gives a slightly higher material use, but a stronger part. However, it also comes at the price of printing those walls at a fairly slow speed.

 

My recommendation in this case would be to set the wall thickness to 3 (which will indeed print like your top picture with the equivalent of 100% infill). Then change the inner wall speed to 100% of the main print speed. (You may need to show the inner wall setting since it's hidden by default.) The higher inner wall speed should work ok in this case since your walls are just straight lines, and with this change, this should print at a speed comparable to or faster than the low infill version. It's easy to see why logically, since the nozzle has to travel the same distance whether printing infill or a straight line of plastic, except now it doesn't have to start and stop periodically to fill in the infill segments.

[Dmitrijs 0]

Did you try setting Extra Infill Wall Count to 1?

[StarkFlyer 0]

I don't think I tried that.  I will keep that in mind the if I have to print this again or run into the problem.  Thanks for the suggestion.

[mkoic 2]

On 6/10/2020 at 5:57 PM, StarkFlyer said:

Thanks burtoogle.  I used the .5 wall line width to make the print and all was well.  You made me think more about line width settings, nozzle size, etc.  Found other settings that also worked.  Somewhere along the way I saw a "rule," more than once, the line width should be = to nozzle size.  It made sense to me so I always followed it.

I had seen a different rule many places, that line width should be 125% to 140% of nozzle dia and have also read that other slicers automatically do this.  I was wondering why Cura defaults to line width = nozzle dia?

[burtoogle 508]

3 hours ago, mkoic said:

I was wondering why Cura defaults to line width = nozzle dia?

 

For at least some of the UM printers, the default is 0.875 * the nozzle dia, so for a 0.4 nozzle, they use a line width of 0.35. I guess they must have evaluated different line widths and decided that is what works best for them. On my non-UM printers I still use a line width of 0.5m (with a 0.4mm nozzle) unless I really need a thinner line for some specific model.

[StarkFlyer 0]

My Lulzbot Mini had a .5 nozzle and Cura was set to .5 line width.  I changed over to a .4 nozzle but Cura kept the .5 line, even after changing it in the printer config.  My CR10-S has a .4 nozzle and Cura defaulted to .4 line width.  I measured the extruded diameter on both printers with .4 nozzles and got .52mm.  Put on a new nozzle and still measured .52mm.  Cura was set for .4mm line width when I did those measurements.  Most of this is over my head but I keep trying to figure it out.