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inverse elephant foot issue..  

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JasonG
(@jasong)
Active Member
inverse elephant foot issue..

I am trying to use prusa slicer for my other printer as well, which is a folgertech FT-5.  I am runnign the latest 2.2.0.  This other printer has a .6 nozzle on it.  This is the first time I am playing with a nozzle of this size, and my heater block can handle the extra flow.

I am having a very hard time getting the first few layers to print straight vertical shells or walls.  My first layer height is .2 and subsequent layers are at .4 height.

If I print a 40mm X 40 mm cube with a 20mm square hole in the center, the first layer is not wide enough to meet 40mm and the inside hole is larger than 20mm.  A few layers up the outside dimension of the cube is 41mm and the inside hole is now 18.5mm.  So I cant use a simple XY scale.  I feel that the permiter lay down is not calculated correctly, and is placed on the edge.

 

I have attached my latest config.  I have been trying to get this to work for 2 days now, doing many test prints, and i cant seem to get this to stablize.  I have checked my esteps on my extruder many times.  The printer has an SKR 1.1 pro, with tmc2130 drivers, and all connected to octoprint.

 

I try changing some settings like the extrusion width in advanced print settings, and they dont always seem to change anything.  Like an obvious one is external perimeters, if I set that to .3 .6 or even .8 no change happens on my prints.

 

Any help or guidance would be appreciated.

Posted : 08/04/2020 12:17 am
bobstro
(@bobstro)
Illustrious Member
RE: inverse elephant foot issue..

Did not find a config attached. You have to zip up any files to upload and attach them here.

There is a setting under Print Settings->Advanced->Slicing->Elephant foot compensation, but it won't take negative values. It sounds like your 1st layer(s) is under-extruding. If you print a shape with a shelf on it (I've attached a sample) how do the walls look. Is the distortion only where solid layers transition to hollow walls or vice versa?

 

Attachment removed
My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 08/04/2020 4:06 am
JasonG
(@jasong)
Active Member
Topic starter answered:
RE: inverse elephant foot issue..

sorry that the files didnt post.  I have elephant now set to zero, but the bigger problem that the rest of the layers were over extruding.  I did change one setting which helped me a lot, and that is to lay down the external perimeters first.  Once I made that setting, the walls are very vertical and the inside dimension is much closer, but not perfect.  Its still a tiny bit small.  I will do some tests with large and small objects with holes and see how i can adjust the xy size compensation slightly larger.  thanks for your help @bobstro.

 

Jason

Posted : 08/04/2020 5:23 am
Neophyl
(@neophyl)
Illustrious Member
RE: inverse elephant foot issue..

If your normal layers are over extruding have you calibrated your extruder steps per mm ?  Or checked your actual filament width using calipers and altered the filament settings to match ?

If you look in Bobs signature above you will see a link to his notes website.  Its full of good stuff that should be read 🙂

Posted : 08/04/2020 5:51 am
JasonG
(@jasong)
Active Member
Topic starter answered:
RE: inverse elephant foot issue..

thanks for the info..i have checked my esteps many times today, did a full half meter extrude and it measured out perfectly.  I will check out his site, but turning on perimeters first really helped me out.  I also think i had my z accel waaay too high at 100, its a lead screw setup.  I set that back to 10.  Maybe it was skipping steps.

Posted : 08/04/2020 5:57 am
Neophyl
(@neophyl)
Illustrious Member
RE: inverse elephant foot issue..

Just had a look at what the MK3 uses for machine limits on Z, Max feedrate =12, Max Accel=1000, Max Jerk 0.4

My Cr10 profile has 100 for max Z accel though

Posted : 08/04/2020 6:21 am
JasonG
(@jasong)
Active Member
Topic starter answered:
RE: inverse elephant foot issue..

yea my FT-5 the original marlin 8 bit config file showed 10 as the max accell.. its a dual leadscrew system, im sure it can do more, but i think its fine at 10.

Posted : 08/04/2020 4:46 pm
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