[solved] PreloadVE tuning - secondary seam??

McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21
[solved] PreloadVE tuning - secondary seam??

Post by McNugget6750 » 30 Jan 2021, 14:59

EDIT: The secondary seam was caused by extruder skipping due to too high PreloadVE speed. I needed to get at low as 6mm/s to have my extruder do this properly. See explanation and pictures in thread to understand this.


Hey guys,

I'm slowly getting the hang of Preload tuning. I also learned certain restrictions like when I preload too much, my extruder starts skipping steps during preload (testing 0 - 1 using the wizard).
photo_2021-01-30_11-57-40.jpg
What I'm confused about is the following:
photo_2021-01-30_11-57-50.jpg
I'm getting this secondary seam I can't explain. I get this on a lot of my prints and it makes no sense since it doesn't seem to appear in the gcode. Any idea what this is?
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Last edited by McNugget6750 on 31 Jan 2021, 00:51, edited 1 time in total.

McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: PreloadVE tuning - secondary seam??

Post by McNugget6750 » 30 Jan 2021, 16:01

After the first rough print, I printed again with values between 0.3 and 0.5 and landed on 0.45 for my PreloadVE number.
photo_2021-01-30_12-59-56.jpg
But here also, very reproducible, a secondary seam! The print itself looks great, though!
photo_2021-01-30_13-00-01.jpg
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McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: PreloadVE tuning - secondary seam??

Post by McNugget6750 » 30 Jan 2021, 21:24

I'm at a point where the prints come out really looking great. I still have an effect, though, where the perimeters come out thin first and then (basically after the secondary seam I'm experiencing) slowly creep back up to normal thickness. Is this an issue with not enough or too much Preload? Also, it seems like more preload overloads my extruder. That raises the question if I'm preloading too quickly. I'll try a halfing my preload speed and go though the wizard again and report back.
photo_2021-01-30_18-18-36.jpg
btw: PreloadVE tuning also mostly solved a large chunk of my stringing issues.
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McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: PreloadVE tuning - secondary seam??

Post by McNugget6750 » 30 Jan 2021, 21:46

I have to take a few things back I said in my last post:
The wizard calibration looks great on the calibration block but terrible on a real life 3D print. Not sure why this is such a problem, still...

The backside looks great but the front is a disaster.
photo_2021-01-30_18-43-49.jpg
photo_2021-01-30_18-43-52.jpg
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McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: PreloadVE tuning - secondary seam??

Post by McNugget6750 » 30 Jan 2021, 22:43

This is an incredibly interesting tuning session!
At 5mm/s for PreloadVE my extruder is able to keep up for values between 0 and 1. It looks like this:
photo_2021-01-30_19-40-15.jpg
The cool thing is, that also eliminated the secondary seam I was seeing on a lot of my objects.
photo_2021-01-30_19-40-18.jpg
I'm now tuning for max PreloadVR speed first (which doesn't seem to be part of any wizard) and then take the value I find to restart PreloadVE tuning.
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McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: PreloadVE tuning - secondary seam??

Post by McNugget6750 » 30 Jan 2021, 23:19

At 7.5mm/s for PreloadVE speed, I get some extruder skipping in the last 8mm or so. I assume, that's too fast then and before deciding on a PreloadVE value, I should reduce the speed a little again.
photo_2021-01-30_20-19-00.jpg
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McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: PreloadVE tuning - secondary seam??

Post by McNugget6750 » 31 Jan 2021, 00:13

Here, another tuning session from 0.3 to 0.5 PreloadVE.
I'd call that (on the test object) near perfect. No extruder skipping at 6mm/s preload speed.
photo_2021-01-30_21-10-40.jpg
Next, I need to dial in the seam gap and depth and understand how both of these interact with each other.
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McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: [solved] PreloadVE tuning - secondary seam??

Post by McNugget6750 » 31 Jan 2021, 02:04

I noticed, that with a well tuned PreloadVE value, the settings for seam gap and seam depth just make the seam appear ever so slightly wider but not nicer to look at or nicer to the touch.
When a seam reaches this quality it's really hard to photograph. I think recessing the entire seam a little into the part would make it less visible but this is so much better than where I started last week, it's almost hard to believe it's the same printer.
photo_2021-01-30_23-03-19.jpg
photo_2021-01-30_23-06-21.jpg
photo_2021-01-30_23-06-23.jpg
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McNugget6750
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Joined:28 Jun 2017, 16:21

Re: [solved] PreloadVE tuning - secondary seam??

Post by McNugget6750 » 31 Jan 2021, 12:29

But then again: The real life part looks like crap. This is a rather thin structure. I read a couple times that thin structures need a different PreloadVE value than normal, thick objects.
photo_2021-01-31_09-22-35.jpg
I believe the underlying issue is that Kisslicer retracts within layers, within the same object / perimeter. I see my extruder retracting the preload (not destring, which is set to 0 right now) before every single move. At least my extruder doesn't like that and whenever other people have posted their PreloadVE tuning results and showed some thin walled examples, it looked less then optimal. This is especially bad when extruding small amounts like in this example. For some reason, there are hundreds of small travel moves within this skin layer and each one results in the use of the PreloadVE function in my case. The part then becomes unprintable.
PreloadVE going wild 1.JPG
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McNugget6750
Posts:32
Joined:28 Jun 2017, 16:21

Re: [solved] PreloadVE tuning - secondary seam??

Post by McNugget6750 » 31 Jan 2021, 14:54

I'm printing the thin structure game controller grip again with a PreloadVE set to 0.2 (down from 0.348), preload speed of 5mm/s and, and this seams like cheating to me but it looks great right now, "Loop1 > Perimeter". That solves my ripped seam on the perimeter entirely but it seems a bit like hiding the issue instead of solving it. Photo follows when the print it done in 2h...

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