missing small sections of layers after a retraction

7

So I am missing small sections of a layer when it prints, after a retraction for a layer change or a move, the extruder stops moving (no it isn't clicking or anything else. Just not moving). Which is fine for a few millimeters because the pressure inside the Bowden setup keeps pushing enough filament through. However, once that isn't enough it starts to make very thin lines with beads of plastic just barely holding things together. Basically this ends up as a good 2 cm or more at times of highly under extruded lines. This happens in the slowdown after the retraction when it is restarting. it simply doesn't move the extruder at all. The reason I know this is because I can see the extruder not moving, in that brief period. I know it is not the extruder clicking or anything else because I can disengage the extruder spring and push filament through manually during this time with no issues.

I am using Ideamaker currently because I like it.

I have looked at this Holes/ missing layers (after retraction) in 3d printed objects which is somewhat similar in appearance, but not in reason. enter image description here

Just a better image from the other side of the print

EDIT: So I figure it is some form of coasting that IdeaMaker has implemented for their Raise printers. I am going to try and reduce the length of the coaster attempt to convert my Bowden to a direct drive with titan extruder. I have the Titan already, but it has been giving me issues with not having enough power to push filament without ripping it to shreds. That's another thing I have to look at at some point when I have the time.

user3779413

Posted 2017-10-04T06:54:47.300

Reputation: 71

Which slicing software you are using ?? and most of the slicing software is extruder or retract material on layer change, tool change. The value of extruding or retract material set in software. Try to change the value of extruding or retract material in slicing set . – Kallz – 2017-10-04T06:59:43.523

Hi. Like I said I'm using Ideamaker and I have fiddled with the retraction settings. raised them to 50mm/s and 7mm retract all the was down to 10mm/s and 2 mm retract. it does this on every retract. regardless of whether it is a new layer. But it is more of a problem when doing the outer shells as i makes it look bad and seriously messes with part strength – user3779413 – 2017-10-04T07:40:17.763

1i'm not quite sure about your issue as i don't see any effects on your pictures but in MatterControl there is param which adds extra extrusion after retraction, so user can say - retract 2mm but then extrude 2+0.2 to compensate any lacks. could it be the solution? – darth pixel – 2017-10-04T11:01:57.120

well I don't use matter control. Okay. picture this. The extruder does a retraction when it shifts to an outer layer. It restarts at a lower speed. Say 20mm/s instead of the usual 50-60mm/s. The printer continues it's movements until the restart is over and continues with the rest of the print. During this restart period where it should be laying down the first part of a line, the extruder motor is not moving at all. The only thing that is being extruded is due to pressure in the bowden. – user3779413 – 2017-10-04T18:10:08.490

(continued) Once the pressure runs out the nozzle is barely extruding any plastic. Basically so little that it only forms a few tiny little beads connected by essentially hairs so thin it would look like stringing. Once the restart is over the extruder kicks in again and starts extruding plastic perfectly. – user3779413 – 2017-10-04T18:10:25.293

This is opposite to grums, to avoid grums the retraction should be 2.00mm and starting at 1.8mm, so for missing feeds should be 2.00 retraction and starting 2.2 or more; depending and how weak is the strenght of your feeder. – Fernando Baltazar – 2017-10-05T17:32:17.907

Grums? not a term I am familiar with. The feeder strength is pretty good. pushes harder than I can with ease. The question is would adding an "extra restart amount" ,as it is called in Ideamaker, push 0.2mm of filament during that period when the extruder is not pushing when it should be pushing?

also 2mm of retraction would be way too little for my Bowden. It would create a stringing fiesta.

but anyway. I'll fiddle with the extra restart later this evening. Don't have much filament on hand because my order is late, but I'll give it a try – user3779413 – 2017-10-05T18:31:09.387

i understand you don't use MC but maybe it's worth to try ;) – darth pixel – 2017-10-05T18:37:34.797

I'll certainly give it a look. Not a super huge fan of always connected printing. If I had another raspberry pi or a really old laptop I would set it or something similar up. However, I don't. My main pc is close enough, but I run into the issue of using it's full performance often when I am rendering or crunching large data sets when I am doing sql or coding work on it. I'll look into it anyway and explore some options. – user3779413 – 2017-10-06T17:07:45.717

Answers

1

I know this might be a bit late, but I have been facing very similar issues with my printer (Anycubic Kossel Linear Plus).

In my case, I have managed to solve this problem by reducing retraction speed and retraction and extrusion max accelerations (if you are using Marlin, go to Control -> Motion and scroll down to A-max extruder and A-max rectract). I went down from 1800 to 1200 for extrusion and from 1400 to 1000 for retraction.

Also, I have played a bit with the stepstick, allowing a bit more of current for the extruder motor (normal XYZ are have a Vref~0.7 and the extruder it's set to 0.9). My understanding of the issue, is that the stepper motor cannot cope with the torque it is asked to deliver at sudden changes (high accelerations) and simply gets blocked until the acceleration is reduced. This can be due as well by too much friction (low printing temperature, clogged nozzle,... but it was not my case). Here there is a lot of information about the drivers.

oscgonfer

Posted 2017-10-04T06:54:47.300

Reputation: 11

1

Try lowering your retraction settings further. I have had this issue before as well, but you need to experiment with your retraction settings in order to get it right. I would suggest placing 2 one cm blocks side by side and starting with a retraction of 2 mm and working your way up from there until you get the lowest stringiness with the least amount of under extrusion.

TECTEC3 Studios

Posted 2017-10-04T06:54:47.300

Reputation: 416

The problem with that is anything less than 4mm retraction at 30mm/s retraction causes pretty bad stringing. The thing is this doesn't happen on smaller prints. Which is to say it doesn't happen when there aren't any retraction restarts. So It wouldn't happen on a calibration cube for example.

I am just puzzled as to why when a retraction restart occurs that the extruder motor doesn't kick in until after the restart is finished.

Oh. also the length of the retraction doesn't matter and still creates the same length of severe under extrusion effect after extrusion restart. – user3779413 – 2017-10-04T18:08:22.147

Try decreasing the speed of retraction from 30mm/s down to 15mm/s. This won't increase your print time by too much but it might produce better results. – TECTEC3 Studios – 2017-10-04T18:12:55.800

That doesn't solve the problem of the extruder not restarting when the retraction has finished and the extrusion needs to restart. Basically it retracts, pushes back the same distance to end the retract and then doesn't move the extruder for a few centimeters. Also I have tried all the way down to 5mm/s retraction speed. Other than increasing blobs and stringing it does nothing to fix the extruder from not restarting after a retraction is complete. I really wish I could video this. but there are too many things in the way of the nozzle to get a good view with a camera. – user3779413 – 2017-10-04T18:20:20.843

I use the dremel ideamaker as well and I have never had this issue before. You probably have a defective machine. You should try sending it back and getting a new machine. – TECTEC3 Studios – 2017-10-04T23:29:49.330

I think you mean the Dremel Idea builder. I am not using that machine. I meant the slicer that I am using is IdeaMaker. From Raise3d.
If it was something to do with the motherboard on my machine that wouldn't be the problem. Because it is an MKS base 1.4 which i bought a spare for as it was on sale and I was planning on actually using it for another project as a test platform (mpcnc). I swapped it in yesterday to see if the same problem existed and of course I updated Marlin. Still the same issue. Sigh. So much wasted plastic.
– user3779413 – 2017-10-05T06:45:18.740

Have you tried using simplify 3d. I know that it is a very good software, and very well worth the price, if getting that high quality software doesn't fix your issue, then I'm not sure what will. – TECTEC3 Studios – 2017-10-05T10:19:36.717

No I haven't. I hear it is good, but I don't really have the money right now to buy it. Not super rich. Saved up for a while to buy my printer. Just going to add another picture that I just took. Since it is clearer and actually taken with a proper camera, not a phone. – user3779413 – 2017-10-05T14:07:55.163