Prusa Slicing problem with accuracy  

RE: Prusa Slicing problem with accuracy

Hi mpirringer
can you save the slicer details in a Project file (.3mf file) then Zip the file into compressed format and add the Zip file in your next post, we can have a look at your issues... 

the correct place to offer suggestions to Prusa Developers, is the Prusa Git Hub page for the product in question... Prusa Slicer, in this case. 

regards Joan

RE: Prusa Slicing problem with accuracy

I hope this works testbox.3mf was sliced with an outside perimeter of .88 and testbox_2 was sliced with an outside perimeter of 1. On the 2 mm wall in the first case you get a .24 mm or so gap between the 2 perimeters so you have no perimeter adhesion in the x and y axis in the 2nd case that fills in but the 4mm post is hollow which is filled correctly in the first case. This probably does not matter if you print a model to look at but has a negative impact as outlined in the OP when printing mechanically accurate parts.TestBox

RE: Prusa Slicing problem with accuracy

That's an odd extrusion width, with a 0.4mm nozzle you can expect two perimeters and an infill making 5 strands in all:  Check your nozzle size setting [ Printer Settings > Extruder n > Nozzle diameter. ]

Cheerio,

RE: Prusa Slicing problem with accuracy

Looking at your first Test box, your perimeter  'extrusion width' was set to 1.5mm  and you ended up with a gap between the walls in the inner wall around the post. 
If you reduce your perimeter extrusion width to  between 0.88 and 1.23  the space between the external perimeters is filled, as expected.   

In your second Test box, you have increased your external perimeter extrusion width to 1.0mm, leaving less space for perimeters between the walls, 
in this model you need to reduce the perimeter extrusion width to 0.9mm to cause the gap between the walls to be filled. 

regards Joan

RE: Prusa Slicing problem with accuracy

@diem

I am printing with a .8 nozzle

RE: Prusa Slicing problem with accuracy

@joantabb Sorry if I did not make the point clear - I can "fix" one of the problems at a time with playing with settings. But not all of them. This testbox is to illustrate the problem. It becomes more evident on more complicated parts. I am hoping for some changes. I tried Superslicer which is also based on SLIC3r. it behaves a little bit "less wonky" 

See we do not print Models we print actual mechanical parts. The above issues became apparent when printing a compound planetary that will (hopefully) lift reliably 600+lb (300+kg) repeatedly. It uses over 5kg of plastics. We print a lot of projects that involve 10kg+ of material . So we are not your run of the mill cosplay or model printer here is a link to one of those projects that consumed 14kg+ of hips https://pirringers.com/3dp/?p=36 and yes all files are available on grabcad. So that "playing with settings" sometimes takes longer than designing the part and it often requires the part to be redesigned to accomodate the slicer "wonkiness" and yes PS and now SuperSliccer (and originally SLIC3R) are less problematic than any other slicer I know. But we print what we call "solid" That means parts with enough perimeters to not need infill and get a part as close as possible to injection molding 3dP. So we love the "max Vol E" feature as we mostly print with a .8 on a volcano. Which gives us a happy medium between accuracy and speed. A bigger nozzle would not give us more speed as plastic only melts so fast - hence the Max Vol E "happiness". So my hope is to get you guys to get PS to the point that ideally I click "make solid part" and my part does not have any holes or gaps. It would avoid to have to go layer by layer through a stack of double helical gears pieces with cut outs and bolt and bearing holes etc to look for "wonkiness" If you are interested you can read about the current project here https://www.chiefdelphi.com/t/testing-plastics/392752 All printed on some Anycubic Chirons

RE: Prusa Slicing problem with accuracy

Posted by: @mpirringer

I am printing with a .8 nozzle

A 2mm wall with a 0.8mm nozzle - default extrusion width 0.9mm, is not going to be an easy fit.  You can tweak the extrusion if that doesn't impinge on the rest of the part, or change the nozzle.  The narrowest accurate wall with a 0.8mm nozzle will be in the region of 3.5mm but it will be close from 2.7mm.

Quite a few of the regulars here print working parts; you are not talking to Prusa but to a group of Prusa users. 

Generally 100% fill is a mistake, more perimeters is always better so you are looking in the right direction but even so, depending on the plastic used, you might profitably incorporate a few voids.  If you are stressing the parts close to failure, and one does go you are likely to to have shards everywhere.  A few voids act as crack-stoppers and failures are less dramatic.

Your "make solid part" feature request might be addressed by setting a high number of perimeters in:

Print Settings > Layers and perimeters

Hth, Cheerio,

RE: Prusa Slicing problem with accuracy

@diem We design voids in and also use them to make the parts stronger and lighter by directing the layers  here is an example Like on those gears we cut holes to make "spokes" Which then are solid sometimes with 10 or 15 perimeters whatever it takes As for material we use a lot of HIPS and Some PETG and Nylon. Those materials tear more than shatter - you still have pieces of plastic though. 

Yeah I found the Github thing and left a message there - FWIW superslicer which is a fork has it kinda fixed so I hope in the near future PS will too.