Gear cutting groove in filament when printing "flat" terrain models

Snapmaker 2.0
1

Situation:
I’ve been trying to print some terrain type files, with no success so far.
I’ve been using the free Touch Terrain website to generate the files (https://touchterrain.geol.iastate.edu/), but I’ve encountered the same problems when using Terrain2STL (http://jthatch.com/Terrain2STL/).
As you’d expect, these models have a very low Z aspect ratio, so overall dimensions are something like 250 x 250 x 5-10 mm.

Problem:
Fairly quickly into the print job, maybe 5-15 min in, no filament is being extruded any longer.
The reason for this is clearly that the extruder gear is cutting a groove into the filament; this damage is very obvious.

My thoughts:
First, I should note that I don’t encounter such problems when printing “normal” models, say a 3D Benchy.
So I would exclude things like filament quality, printing temperature, or tension in the line.
I also doubt that the Z offset is an issue.
I’ve already adjusted my retraction settings to make them “less aggressive”, so I’m using 2 mm retraction distance at a speed of 30 mm/s.
Finally, I also think the gear itself seems OK, see attached image.

IMG_20201010_142446
IMG_20201010_1424463480×4640 3.07 MB

Questions:
I assume these issues are related to the printer having to print these fairly wide, flat layers; but maybe I’m wrong…
Has anyone else encountered similar problems?
Any suggestions on how to proceed?
Should I for example try a “smarter” slicer or should I further reduce my retraction settings?

Any suggestions are very much appreciated, as I’ve been struggling with this for a while…

2

Have you done an e-steps calibration, or other basic checks to make sure it’s not overextruding?

I’m not sure how much experience you’ve had with this new machine, but out of the box it’s not calibrated, and will need a few basic things checked. Many people have threads on it, mine is here: Snapmaker 2.0 Initial Calibration Settings / Experiences

Just this morning I had stripped filament because of an overextrusion issue, maybe that’s on my mind and your issue is something else.

Regardless, your nozzle is now likely clogged, try doing a cold pull(https://all3dp.com/2/3d-printer-clogged-nozzle-how-to-perform-a-cold-atomic-pull/). If that doesn’t work you may need to change hot ends while you can clean out the blockage.

3

I don’t quite follow how overextrusion would be linked to the gear cutting a groove into the filament?!
Also, as mentioned, printing other models has worked very well recently.
It’s just these large, flat terrain models that have been problematic.

4

It’s somewhat of an indirect cause.

So, obviously the gear is trying to bite into the soft filament and direct it downwards.
Normally, the filament then flows into the hot end, melts, and the pressure of the above solid filament forces hot plastic through the nozzle.

If something were to block the exit of the nozzle, the viscous plastic will require extra pressure to achieve the same flow.

The motor driving the gear has, for all practical purposes, infinite available torque, and will drive the filament and whatever speed is being commanded. However, the filament, being soft, can only withstand a certain amount of pressure being applied.

An overextrusion situation can lead to there being too much plastic at the exit of the nozzle, causing backpressure. The end result, is the stepper is applying too much force to the filament and it strips out.

In the short term, you need to check the filament is not being obstructed by anything in the path through the hot end and nozzle. You can gently press on the filament with the feed door open, and it should freely flow out, almost under it’s own gravity with little force.

If you’re having to force it, the nozzle is clogged, and the gear will continue to strip filament until the clog is removed. Even partial clogs will cause extra force to be applied, stripping the filament.

In the long term, you should inspect the print as it’s printing and make sure you don’t have an overextrusion situation.

Apologies, if this is overly basic, maybe someone else will find it useful. If you’ve had other successful prints and they weren’t overextruded, there may be something with the geometry specific to what you’re printing that is causing issues with the specific slicer settings you’re using. At that point, I’d need to see the model that worked, what settings you used, and the new model, and what settings you’re using to be able to make any further comments.

EDIT: Also check that the filament on the spool isn’t binding during the print.

1 Like
5

Dear @brent113, sorry if I sounded brash in my reply, that was not my intention.

I purposely used a “brand new” hot-end on one of my recent attempts and the failure / the groove in the filament occurred nonetheless after around 5-15 minutes of printing.
A nozzle blockage as the underlying reason for failure makes sense to me based on your explanation; but if it so, then this blockage must be building up right from the start of the print job.

This then raises the questions:
Is the wide and flat terrain geometry I’m trying to print conducive for a blockage to occur?
Or to put it in another way, why would the blockage occur for this job and not for others?

6

so a wide flat print is more prone to clogs due to over extrusion because they tend to be solid. so if you print a benchy and your over extruding the extra plastic oozes out in all directions and only causes a minor increase in pressure. when you print something solid the extra filament cant just ooze out because there is already plastic in around the nozzle and results in a larger pressure buildup.

my question is, how soon does it grind the filament? is it happening on the first layer? if so then it is likely a Z offset issue. even if your not having the issue on normal prints, because of the increased surface area of the first layer you can have more issues with z offset on wide flat prints, for similar reasons as i stated above.

hope that helps,
-Atom

7

It doesn’t always happen in the first layer, but sometimes it does.
Does this mean my Z offset is actually too low?
I’ve been calibrating my Z offset as suggested by Snapmaker;
But perhaps I should somewhat increase the distance in this case?

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8

Some people have had better luck setting the final z height at the end of the calibration where it barely touches the card. Check this out from Atom:

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9

Though if it happens outside of the first layer @brent113 is probably correct and it is an over extrusion issue. What is your esters currently set at?

10

I’ll definitely give the z height adjustment a try, thanks for the tip.

I’m not sure what you meant by “esters”, I assume something related to the extrusion rate?
I’ve been using the standard settings for PLA, so kept it at 100%.
But perhaps I could give 90% a try and see if that helps with reducing/removing over-extrusion issues.

11

You’ve done the e steps check and when you command 100mm of filament exactly 100mm is fed? That will be a lot faster than randomly tweaking values and seeing if it fixes it.

Also check your filament diameter with a micrometer. Mine is 1.72mm, on average, sampled in at least 5 or 10 places. Compared to a true 1.75mm that will underextrude at 96% of what it should.

Correcting both e steps and filament diameter gave me perfect results at 100% extrusion multiplier. If you’re having to change that, something else is wrong, in my opinion.

The standard check is to print a 20mm or 25mm cube in vase mode, at a known width, for instance .5mm. Measure that with a micrometer, and if it’s pretty close, say between .48 and .52, that’s perfect.

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12

Very useful tips, many thanks!
I’m still doing some laser-stuff, so I will start looking into the extrusion situation next week.

But as a short answer:
No, I haven’t properly checked the filament feed or the filament diameter thus far.
As a newbie to 3DP, I assumed the standard settings would be OK…
I have encountered the same extrusion problems with 2 different filament brands.
So if the diameter is indeed an issue, it must be skewed in the same way for both brands.

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13

I also had another thought: I have seen several people mention dust causing partial nozzle clogs. Would you double check that at 200C or so, with the filament door open you can easily feed filament manually by gently pushing filament into the top? With just my hand’s weight alone, and not pushing down with any force, I can feed filament rather quickly. I had a partial clog, and when I tried that I found I had to push a bit to get any to feed. Additionally, when there was no clog filament will drip out the bottom a bit, just under its own gravity. With the partial clog that did not happen.

If you have a partial clog I think you will be unable to properly check e steps, as it will definitely underextrude vs an unclogged nozzle.

Please update! I’m curious if you think you may still have a partial clog, or if you’re quite positive you don’t. You could also try swapping hot end and seeing if there’s any noticeable difference.

Also, would you mind posting a picture of a print during the first layer, I think it would be helpful to look at the extrusion pattern. Sometimes there’s obvious signs of z height issues from that.

1 Like
14

I doubt that dust-related clogs or hardware in general are causing my issue.
I am also able to easily push down the filament and, as you mention, I can also see filament dripping out a bit under its own gravity.
Also, my issue continued even after I switch to a brand-new hot end.

So overall, I think looking into the z height adjustment and into the extrusion settings is a good next step.
I’ll get back to the 3DP module around the middle of next week and will report back, also with some photos.

15

One of the main things to learn is that there’s really no such thing as a ‘standard setting’. Everything is a starting point. From there you have to adjust for different filament brands and types and even colors. White often times needs to be printed a few degrees hotter than black. Different filament types work with a different offset. I’ve found with PLA I do .05 or .10, with PETG .15 and with TPU it needs to be squished and I use no offset.
Your environment, temperature and humidity will be different than someone who lives in a different part of the world. Your machine will be different.
-S

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16

I was having the same problems with my machine, I re-calibrated, but raised the last point just a bit. This solved the problem of the fliament being “chewed up” inside the gears. I knew I didn’t have a clogged nozzle, because I could push the filament through the hot end easily once it was heated up. The nozzle was too close to the printing surface and nothing was coming out.

17

Watch the temperature readout on your display. The times that I have seen the gear chew up the filament like you describe, I found that something had caused the extruder to turn off and drop below the temperature needed to continue melting the filament. Could be something in the gcode being generated that’s turning it off or something else is happening that’s overriding your first layer temperature settings