Tweaking for perfect jerk/accel/pressure advance blob removal.

GeckoBox3D · 2 Apr 2017, 16:24

It is happening every 3 layers, as it retracts on a different corner each time. This is 'optimize start points' feature in S3D. I can confirm that every blob is a retraction point in the slicer simulation. The edge without retractions is completely smooth. The reason its set this way is so that every blob can be seen, rather then having a merged edge of blobs. Normal prints I will choose a hidden place for these. I've uploaded a picture of an edge with no retractions (left side) so you can see what good layer alignment should look like without a blob caused by travel movements or retractions.

deckingman · 4 Feb 2017, 16:41

Sorry I'm getting a bit confused because you said a few posts back that it's not completely a retraction issue. However you now say that every blob is a retraction point which would indicate that it is. The other thing is that you also said that at the temperature you like to print, you do get some stringing which is really why we use retraction. You don't have to put up with stringing just to get good layer adhesion. So, it seems to me that maybe you should increase the retraction amount to prevent the stringing, which will probably cure the blobs.

GeckoBox3D · 2 Apr 2017, 17:07

Sorry, I'll try to be more clear.

These cubes all have blobs created by retraction. I know this as I've set retraction to take place when it moves from perimeter to infill. However, If I turn this retraction off a blob is still created by the travel move. Initially I thought it was solely a retraction issue.

What confuses me is, why does having retraction have such little effect on the blobs? If this was solely a retraction issue, then surely even bad retraction settings should have an effect.

Temperature may have some affect on blob size, but I doubt it will remove the issue entirely. I will however do some tests just so it is another removed variable.

DjDemonD · 4 Feb 2017, 17:37

Do you print external perimeters first or the other way around. This is a very odd problem, I wonder if you print internal perimeters first whether you will still get these artefacts but you wont care as you wont see them?

StephenRC · 4 Feb 2017, 18:45

Increase the E jerk setting. I had been getting that since I boosted the acceleration for the x & y, and never did change the jerk settings. I originally had it at a really low value of 20, and changing it to 200 practically got rid of it. I'm using Titan bowden setup to a 1.75mm e3vd6 with a pressure advance of 0.03.

DjDemonD · 4 Feb 2017, 20:50

I restored my extruder to my old settings, the hardcore settings worked but it did distinctly give off the impression that the gears might be ground away reasonably quickly.

deckingman · 2 Apr 2017, 21:05

If you read the OP's posts you'll see that He's set the jerk to 1200 (was 300 in any case).

The OP said he was getting stringing as well, so I just think it's simply a matter of too little retraction. Maybe 1.8mm isn't enough - we don't know what length the Bowden tubes are. Maybe S3D is using it's own retraction speed with is overriding the firmware speeds.

Edit. Sorry DJ, we must have been typing at the same time. Thanks for the feedback on the "hardcore" settings - I suspected they might be a bit harsh so it's saved me from trying them.

GeckoBox3D · 4 Feb 2017, 22:25

There is no Bowden tube, so 1.8mm is a decent amount recommended by E3D for there hot end. Upping this any higher will likely give jams. My retraction speed is 55m/s set by the slicer.

@ DJDemonD - Internal perimeter first, then external, then infill. S3D doesn't give much choice for which is printed first. That and printing external perimeter first can cause overhang issues so it's not the greatest solution either.

If you look above StephenRC, the tests have been done with a few variants of E jerk at both 300 and 1200.

My next tests are going to be upping the extrusion rate in order to 'smooth' out the pressure differences, although this is just a theory. I'll also try temp tests and stringing tests, and possibly higher retraction speeds/distance.

Whitewolf · 25 Jun 2017, 04:38

I am running a Bowden direct drive extruder and my results might surprise some people but I can attest these settings work very very well.

So Gecko have you changed your slicer settings as well? I do not have a part cooling blower and have successfully completed several benches like this one with PLA: https://www.thingiverse.com/thing:1619976 and 3dbenchy…. I do not have any stringing, oozing or blobbing like when I started.

Warning, I need to tame some of these back as some of them cause my printer to bang around depending on what is being printed but the prints come out amazing

M566 X9000 Y9000 Z12 E9000 ; Set maximum instantaneous speed changes (mm/min)
M203 X12000 Y12000 Z375 E12000 ; Set maximum speeds (mm/min)
M201 X9000 Y9000 Z150 E6000 ; Set accelerations (mm/s^2)
M906 X850 Y950 Z950 E950 I30 ; Set motor currents (mA) and motor idle factor in per cent
M572 D0 S0.1

My Slicer is simplify3D and the bridging in it sucks, most overhangs in these models never get bridge mode enabled but I was still able to get amazing results none the less.

Slicer settings:

62mm/s print speed
115mm/s retraction speed
1.85mm retraction
0z hop
Outline direction: Outside in
Outline overlap: 10% (too much overlap on a well tuned printer will cause bulging like you see I found 10% to be ideal for well tuned estep and filament temp)
Only retract when crossing open spaces is unchecked
force retraction between layers is checked
perform retraction during wipe movement is checked

You might also try (if you have S3d) putting a negative number in extra restart distance if you find blobbing just after a retraction such as -0.02… this will keep less filament from being primed after the retraction. (personally I do not like to solve issues with the slicer and would hunt down the issue causing what you are facing but if all else fails try this setting.

My kids ran off with my benches but the results with snappy XY and snappy extruder completely eliminated any stringing and successfully connected non bridge parameter outlines (S3D bug, they should be treated as bridges) and it did so without the assistance of cooling and a 205c temp on PLA.

Now I just need to find the best jerk settings so my printer does not sound like its banging with every movement of the axis.... I am finding fast moves are the best way, it makes for ultra sooth quality prints with no defects but I need to find the sweet spot for jerk settings to make it maintain the quality that the high speed is giving

deckingman · 25 Jun 2017, 08:37

@Whitewolf:

…...............................
Now I just need to find the best jerk settings so my printer does not sound like its banging with every movement of the axis.... I am finding fast moves are the best way, it makes for ultra sooth quality prints with no defects but I need to find the sweet spot for jerk settings to make it maintain the quality that the high speed is giving

For info, (DC has recently confirmed this), jerk is only used when doing short segmented moves such as circles. So you might have better luck by reducing your acceleration settings.
HTH

Whitewolf · 25 Jun 2017, 09:03

Jerk is the setting i did read his post on that but where the banging occurs with current setting is on the first couple layers of 3d benchy. other prints seem to handle fine but i did reduce the accell to get rid of some ringing at the start of each vase corner.

Currently rerunnung benchy, i might take jerk down a little more.

Something interesting is on benchy one corner of the hull gets over extruded… this does not happen on cubes, i get perfect extrusion and sharp corners kind of scratching my head on that one because extrusion seems to be dialed in as well as retraction

Whitewolf · 25 Jun 2017, 09:49

Here is at 62mm/s and .2 layer height with .4 nozzle PLA 205c

notice there is not stringing and great bridging without a cooling fan.

dc42 · 25 Jun 2017, 10:14

That's very impressive without a print cooling fan. Is any of the air from the heatsink cooling fan deflected downwards?

Whitewolf · 25 Jun 2017, 10:32

@dc42:

That's very impressive without a print cooling fan. Is any of the air from the heatsink cooling fan deflected downwards?

No its not, air is directed away. I believe it has to do with my retraction settings (115mms) and my jerk settings for the extruder (8000), I did several iterations of the retraction and bridging test until I nailed it (https://www.thingiverse.com/thing:1619976) but speed of non print moves and extruder and retract speeds seem to be the key. I figure by dialing it in without a fan, once I add a fan then my bridging abilities will be all that much better.

I am going to do another benchy tomorrow with 90mm/s retraction and 5400 jerk (slower settings) and 2.5mm retraction distance(slight increase) and see if I can't get some better results with artifacts

pogo1213 · 21 Jul 2018, 01:58

Has anyone figured this out, Im having the same issues