New to the Process: Calibrating the Machine

Howdy, folks. I purchased a SM 2.0 for my classroom, and am currently in the process of learning how to use it so I can teach my students about rapid prototyping.

Currently, I’m using Luban on a W10 machine. I’m using the latest firmware build (upgraded it, this week). I have am organizing my sample builds, starting with temperature variants, and these are my results so far:

As you can see, I’ve got a lot of very solid strings going. One of the first things I did was change the default retraction speed (after the first print model was a tangled mess), but I was wondering what I should start modifying from here, to get a better result?

I’m certainly no expert on getting beautiful prints with the SM2, but I have found that reducing speed and temperature greatly reduce stringing. 190 is generally the temp, and speed 35-45. Though even with those, I get some hiccups. Really need to get back to debugging the extrusion on my SM2 when I get the time.

untergeek recently posted a link to a retraction calibration tool. It will generate a tower with various retraction parameters in a single print. There are 3 different parameters you can change (temp, retraction speed, or fan speed), but I would recommend only changing one at a time.

There’s also some pre-sliced temperature towers in the 3D Print Guide, section 4.1, along with other suggested test objects.

As for your actual question… I don’t know either. My retraction test looks a lot like your test.

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What filament do you use?
I would suggest to set your retraction distance to 1mm @ 60mm/s.
Less distance prevents backed filament in the nozzle.
I would start with a temp tower.

I have read about the sm filament of the 2.0 several times, from time to time the quality is poor…

I’m certainly no expert on getting beautiful prints with the SM2, but I have found that reducing speed and temperature greatly reduce stringing. 190 is generally the temp, and speed 35-45. Though even with those, I get some hiccups. Really need to get back to debugging the extrusion on my SM2 when I get the time.

190 is the bottom range of the PLA filament I’m using. I’ve been going from there to 205, which is the default SM2 setting.

untergeek recently posted a link to a retraction calibration tool. It will generate a tower with various retraction parameters in a single print. There are 3 different parameters you can change (temp, retraction speed, or fan speed), but I would recommend only changing one at a time.

I just looked at that site. I’ll have a go with that and see what I get out of it. I have a lot of ‘test’ builds, but I didn’t realize you could modify the temp and retraction rates ‘on the fly,’ as it were, inside the GCode.

What filament do you use?
I would suggest to set your retraction distance to 1mm @ 60mm/s.
Less distance prevents backed filament in the nozzle.
I would start with a temp tower.

I have read about the sm filament of the 2.0 several times, from time to time the quality is poor…

I’m using the default spool of PLA that came with the machine. I’ll definitely back off my 3mm retraction distance. As for the PLA, I got a single good print of several objects at once, but after I updated the firmware, everything went higgledy piggledy, again. I’m guessing due to the extraction error correction in the latest build, which is why I’m starting from scratch.

Luban won’t let you do that, which is why it’s a separate tool.

Fundamentally, GCode is a series of commands to “move this motor this distance”. If you can do something once it, you can do it multiple times. For example, the Temp Tower in xchris’ 3D Print Guide were manually editted to have the temperature change added at the correct location. Which is why the GCode is available for download, rather than instructions for how to slice and hand edit the files.

Enable retraction

You can use the default settings in Snapmaker Luban. And the work speed should be low so that the dwelling time is long enough to retract the filament.

Edwin

Good to know. Looks like I have a little reading to do on GCode.

Edwin, that was one of the first things I did after my first print.

Clewis, I used untergeek’s tower, and along with a 30 minute job cleaning the bed after the print because the initial layer was so thin it would not come up, this is what came out:

I’m not sure I’m reading it correctly though. Following the large loops up and around, and looking for the best print area, I seem to need a full 6mm retraction, and (counting the loops up, starting with the default 10mm, and going up by 10 per increment), it needs to retract at 200mm/s. That can’t be right, can it?

I think I might need to try another test (but with something else, because I don’t want to have to scrape my bed for another half hour).

I wouldn’t give that test any credence, as it is not a proper test. Retraction tests are rather tricky, and the majority of the ones that I’ve seen are fairly useless. For the direct drive extruder on the Snapmaker 2.0, something in the range of 0.4-1.0mm is what you should use. Different filaments may need different retraction, like PETG. It will work better with a 0.8-1.0mm retraction, while a good PLA (not Snapmaker) will work great with 0.4mm.

The better tests only test stringing, and don’t use paper thin walls or needle point towers. As a teacher, this might even be a good exercise for your students.

BEST OF LUCK!

Could you please send me the STL file and G-code file so that we can try to reproduce this issue at our end.

As @WilliamBosacker wrote, the retraction test is rather tricky and we need to analyze this problem with certain models.

Cheers
Edwin

Since I started to use a dehumidifier, I no longer get ANY strings at all.
Could be that is contributing to the issue…

I’ve been sharing the test results with the students, and we’ve been talking about them in relationship to what we known about the process. We’re also printing out a small 15mm miniature, for comparison purposes, with each tower we’ve printed (see below). What test would you recommend for just retraction issues?

Here are the GCode Files for the various tests I’ve been running. Test_01_01 and Test 03_01 are retraction test towers, and the 01_02 and 03_02 are small game figures. I’ve run them both at 190, 195, 200, and 205 degree, using:

  • 60mm/s travel speed
  • 1mm Retraction distance
  • 60mm/s Retraction speed.

The best result I’ve gotten at this point, using the Snapmaker PLA included with the machine is below. As you can see, I’ve moved from solid threads to a few smaller threads and lots of fine webbing, so I guess that’s a bit of improvement:

Test_01_01.gcode (407.6 KB) Test_01_02.gcode (1.5 MB) Test_03_01.gcode (380.2 KB) Test_03_02.gcode (1.5 MB)

It’s pretty dry in here, but I can give that a shot.

I use this one: https://teachingtechyt.github.io/calibration.html#retraction

My settings are:

  • Retraction: 1mm @ 60mm/s
  • Z hop of 0.5mm

I believe @WilliamBosacker uses 0.4mm retraction

I thought it was dry here in Denver, but I bought a hygrometer and found out the RH was up in the 80s and 90s in the last couple weeks! I’m running a Sunlu dryer box at 55C (for ABS) on top of the enclosure, feeding through PTFE tube to a Thordsen inline dryer at 90C, and from there through a hole in the top of the enclosure, right over the middle of the X rail, to the printhead in PTFE tube. The roll now turns with no jerking on the X rail, and I can definitely see the difference between dried filament and not dried!

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@NTorson while none of the current tests are perfect, the one that @brent113 as provided a link for, covers half of the test. A full and complete test should use retraction, detraction and Z-hop. With PLA the Z-hop can be fairly minimal, if not removed entirely. However, with PETG you definitely should use a Z-hop. Also, different brands of filament act differently, so you need to take that into account as well.

I haven’t had the time to do any Z-hop tests, but I have dialed in my retraction and detraction settings pretty well. Here is what I am currently using:

 BRAND   | Type |   Retraction   | Detraction
OVERTURE | PLA  | 0.4mm @ 65mm/s | 40mm/s
OVERTURE | PETG | 0.8mm @ 65mm/s | 40mm/s
OVERTURE | TPU  | 1.2mm @ 40mm/s | 25mm/s

These are good starting points, and once I have time to do some Z-hop tests, I’m sure that things will even get better. I have pretty much been using PETG exclusively, as I like it’s characteristics better than those of PLA. I’ve started using ABS-like resins and my Elegoo Mars Pro, for printing functional parts that are almost exactly like extruded plastic parts. They also have extremely high temperature resistances, which I need for the headed enclosure of my Ender 5 Plus.

I hope this helps you and your students. Who knows, but your students might even be able to write a program that builds the GCode to test this. :wink:

P.S. I looks like Teaching Tech added “Prime (unretract) speed (mm/sec)” (detraction) and Z-hop to the test, so you have everything together now.

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I’m did some tests of this one this morning. I ran them at 190, 195, 200, and 205, with the Snapmaker PLA (unfortunately, that’s all I have, at the moment, having shot my budget on the machine and enclosure). I’ve set the retraction parameters for:

1mm Retraction
60mm/s Retraction Speed
0 Extra Restart
40mm Prime Speed
0.5 Z-Hop

All the resulting temps had ‘hairy legs,’ to some degree, but really, there was little real difference between the various temperature ranges. Pretty much all of them came out looking like this:

So it’s clear from this particular test (thanks, Brent) that retraction isn’t really my issue. So I’m kind of stuck at why I can’t get a relatively clean print on my other models (like the ones below) using the same retraction settings. Is there something else in this GCode that I’m missing?

I will say that I don’t believe the 4 spiral test is a particularly valid test, and it definitely should not be used on a printer that hasn’t been dialed in. Think of it this way, we know that FDM printing is not particularly good at printing that type of pointed peak, and it is extremely unlikely that anyone is going to use it for that purpose. So, is it a valid test?

The other model looks melted, like the nozzle temp is 215°C or higher. It also looks like the layer height is very large. Was this printed using the Fast profile in Luban? Tests should always be performed at Normal, or slower settings. When I zoom in, the layer height of the print on the right is more than twice that of the print on the left.

For the 2 prints with stringing, what did you use to slice them? Is it Luban, as you describe in your first post? If so, that may be the issue. Try using either Ultimaker Cura, or PrusaSlicer. Ultimaker Cura version 4.9.0 and later, now have a Snapmaker profile that is built-in, which was created by a community member. PrusaSlicer seems to work slightly better for me, but you will need to create a profile yourself from scratch. PrusaSlicer only accepts profiles from the manufacturer, and Snapmaker hasn’t provided one as of yet.

While Luban does use a very old version of Ultimaker Cura, approximately 80%+ of the settings are hidden and can’t be changed. Also, my experiences with the Snapmaker filament were that prints would look great when printed at ~205°C, but the layer adhesion was terrible. At 215°C the layer adhesion would be close to what it should be, but the appearance would be bad, and stringing would begin at that temperature as well. However, the filament that you have may be rebranded from a different vendor.

Since the latest retraction test came out very well, I have a feeling that changing the slicer may address your issues. If it doesn’t, then we need to eliminate the filament as being a possible cause of the issues, by using a filament that is known to be good. A 1kg spool of a good filament will run you around $23 from Amazon. For these tests, you should only need a maximum of ~250g. There may be some 1kg spools available in the $16 range, but they could also be pretty bad, so it’s hit and miss with them. Also, I would recommend using a neutral color like gray for testing, as it is much easier to see the problems, and dramatically easier to photograph.

Because of the retraction results, I don’t believe that the filament is our current issue.

Thanks for the feedback. I ran the test, and the results where counter intuitive to me. I wasn’t sure how useful it was, but it seemed to be useful. I’ll stop linking back to it.