Preload artifact?

Hutch
Posts: 13
Joined: 16 Oct 2018, 18:26

Preload artifact?

Post by Hutch »

IMG_20181016_183038342.jpg
Hi I'm having trouble figuring out what to do next. This printer is a linear rail delta 300x500mm and 700mm bowden and duet for brains. I'm new to kisslicer (love it!) and have been going through calibrations in order for the last few days. I can't seem to be able to effect this little bump that happens at the beginning of preload (black sharpie lines to try to show the bumps). I have tried adjusting every setting/combo speed one at a time even firmware accell jerk settings but I can't effect the bump -only move it with increased speed. I have about a half kilo of testing cubes.. To me it seems like backlash or a lag and possibly it's always there just hidden in the z seam. I don't get the artifact when I use firmware linear advance (and it is off for these tests). I'm hoping someone will know what it is. I feel like I have exausted what I can do with settings and am starting to repeat tests. Going in circles my next thing to try will be to get rid of the bowden and try swinging extruder. I see the same bump in another post picture but they didn't use preload.? Am I lost o-0

viewtopic.php?f=12&t=2133#p6097
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Last edited by Hutch on 16 Oct 2018, 23:54, edited 2 times in total.
Hutch
Posts: 13
Joined: 16 Oct 2018, 18:26

Re: Preload artifact?

Post by Hutch »

Pla is the filament heres the latest cube and code
ks_wizard(58).zip
gco
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PLA.jpg
PLA.jpg (81.8 KiB) Viewed 1644 times
hacker
Posts: 149
Joined: 20 Aug 2016, 18:25

Re: Preload artifact?

Post by hacker »

Unfortunately, I didn't keep my collection of test cubes, but at some point I started to get the same results, though never had time to figure it out. By the fact that there was that time when I happily calibrated preload I guess I've done something wrong to the settings, though I have zero idea what could it be… Since I still don't have the time to even try figuring it out I'll listen in here :)
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pjr
Posts: 692
Joined: 05 May 2015, 10:27
Location: Kamnik, Slovenia

Re: Preload artifact?

Post by pjr »

hacker wrote:Unfortunately, I didn't keep my collection of test cubes, but at some point I started to get the same results, though never had time to figure it out.
Ditto.

My advice: If LA works well for you then use it with KISS. Put the K value into the material G-code and insert that into "Select new extruder and Warm". If LA has been properly coded into the firmware it should work better than preload. Preload is only effective at the start and end of paths; it does not "know" how the hardware works (acceleration/jerk/etc). LA should (theoretically) perform better at corners and anywhere else acceleration/jerk/etc come into play, and should work equally as well at the start and end of paths.

The big problem is that LA on a 8-bit MCU running at 16 MHz can produce poor results, especially when its implementation is questionable.

Peter
Hutch
Posts: 13
Joined: 16 Oct 2018, 18:26

Re: Preload artifact?

Post by Hutch »

IMG_20181017_105609310.jpg
Throwing in the towel on this one for now but here are results from changing preload speed. vP mm/s left 5, mid 25 and right 35 - best I can tell observing the artifact happens when Pl first starts it's retraction but my extruder train 3to1 geared was at it's limit or at least sounded like it.
hacker
Posts: 149
Joined: 20 Aug 2016, 18:25

Re: Preload artifact?

Post by hacker »

Admittedly, I actually never played with preload speed, except for randomly changing it once in a while and not looking at the results. Maybe I should pay attention.

As for pressure advance (like Hutch I have duet with reprapfirmware, so no K, no LA here, but there is pressure advance) I couldn't get any noticeable improvement from that either. I even tried to run it through wizard, even with straight corners to see it in all its glory, but either things weren't bad from the beginning or refused to improve noticeably up to the point where things started to get worse. Maybe I should get back to the experiments again.

But at the beginning preload seemed to do some magic. Maybe I should see if I have interesting settings to compare with in my KISS 1.6 setup. Or maybe it's just KISS 2 when it happened — I don't remember.
Hutch
Posts: 13
Joined: 16 Oct 2018, 18:26

Re: Preload artifact?

Post by Hutch »

Here's what happens when you try Duets pressure advanced (0.08) with preload test :o. I was running through extruder jerk Accel testing and kicked in PA at the top it got wild e stepper was screaming and with no hop knocked down the towers 8-) . I may have seen some progress just before I wrecked it really limiting E jerk to 5mm/s and E accell to 1000 but will have to try the proper model again. Probably sitting squarely in the insanity camp now - I am starting to think it's just the nature of remote bowden extruding.
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frozen.rabbit
Posts: 132
Joined: 17 Nov 2014, 09:20

Re: Preload artifact?

Post by frozen.rabbit »

I've never used preload with direct drive extruder on my printer, never had print artifacts like that.

What are your prints like with 0 preload?
Hutch
Posts: 13
Joined: 16 Oct 2018, 18:26

Re: Preload artifact?

Post by Hutch »

nopl.jpg
No preload or retraction. I think its still there just hiding right at the seam so think Kisslicer just revealed the defect not caused it. Im not totally sure if I don't have a mechanical issue - manufacturer is replacing aluminum balls they are undersized and swing freely. I'm pretty new on a delta so half confused on chasing down problems. Though it seems that this artifact is caused by the extruder. I guess I will know more when I get bigger balls. :mrgreen:
hacker
Posts: 149
Joined: 20 Aug 2016, 18:25

Re: Preload artifact?

Post by hacker »

Given I experience pretty much the same and so does Peter who uses cartesian printers (maybe not only, not sure), I wouldn't blame your delta mechanics. Yesterday tried a wizard print with pressure advance (M572) going from 0 to 0.3 (I think) and seen pretty much no difference. But I'm not sure it was a good idea to use carbon fiber filament for that, something more traditional would probably make a better test material…
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