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Beginner questions  

Active Member
Beginner questions

Hey Guys! 🙂

I'm completely new to 3D printing so I have some questions maybe you can help me with:

1. Filament is kinda extruding while preheating. Sometimes the pieces stick to the
PEI while doing the 9 point calibration before the print. Sometimes it sticks to the first layers ruining the print.
Is this normal? Any tipps how to handle this kinda "passive extrusion"?

2. Prints take significantly longer than predicted. For example my first Print the presliced whistle took about 45min. in normal mode at 100% speed. The file itself contains a 25M in it's name and also on the website it is written to be a 20 minutes print.
Do you experience the same?

3. I have printed with clear PETG and the were some burnt looking brown spots in the print along with some printing irregularities. They were brownish artefacts with some copper-looking things in it. Maybe some dirt in the Filament itself? Or burnt PETG? Printed at 230C sliced with prusacontrol with the PET stock settings.

4. I got "blobs" at the top layer of multiple prints so far, always at the spot where it finishes the print. There are often some little strings coming out the blob making this particular area looking not as clean as the rest of the top layer (wich is georgeous by the way). I also noticed these kinda knobs and little strings while printing everytime it stops an extrusion before traveling to the next spot. They normally lay done beautiful as the extruder covers them up with the next layer.
Has it to do with the retractions?

5. X-Axis Idler pulley (that thing on the other side than the motor) is rubbing against the plastic part even if I push the belt all the way back in the X-Carriage in opposite direction of where the pulley is rubbing. At least for now the belt doesn't "wobble" anymore by x-movements. But is there a fix for the rubbing by now?

6. Yesterday my extruder gears were "squeeking" while extruding. Just at that one particular print. Any Ideas what was going on?

7. What are normal speeds for good nice looking perimeters? I thought the MK3 should be ridiculous fast compared to others. So my question: Are the default settings for PLA in Slicer PE "fast" compared to what other printers need to print good quality?
Because I'm having good looking results with it 🙂

Sorry guys maybe I'm just a bit too curious but I like questioning stuff so... 😀

Posted : 27/03/2018 5:53 pm
Estimable Member
Re: Beginner questions

Whew that is a lot! Since no one else has jumped in yet, I figured I would offer what LITTLE help I could.

1. This is normal. PIA, but normal. Always watch the first layer and clear the junk away as it levels.

2. Print time estimates are way off in my experience also.

3. No clue here...

4. It could be retractions, It could be over extrusion. It could be the filament. Takes a bit of experimentation to fix this issue.

5. A lot of people experience this and it is a bit annoying. It can be ignored if you can manage to do so.

6. no idea here

7. Not sure here either...

Posted : 28/03/2018 3:45 am
Trusted Member
Re: Beginner questions

1. This will very by filament. Some are worse than others. Keep an eye on it, and yank out any stray pieces if possible.

2. Print estimates can be all over the place, so many variables. However, I have found the estimates in the newest Slic3r PE, and Octoprint to be pretty realistic.

3. PETG is notorious for blobbing, retractions help, but if the design has lots of small areas or gaps, it will be worse. Clear/natural PETG will discolor as it blobs up on the nozzle. Usually it is pretty easy to remove. One of those things you just learn how to handle with experience. You will learn what prints will work great with PETG, and what parts will struggle.

4. Retractions, and linear advance or coasting will help with this. Retractions can be adjusted, linear advance is currently disabled, but supposed to be coming back very soon. I think CURA has support for coasting?

5. Haven't had this issue. Do you have the most current printed parts? There were some updated parts to address some alignment issues.

6. Double check the tension on the Bontech gears.

7. The defaults in Slic3r PE are fairly conservative for many situations. I have been able to ramp them up considerably on larger, blocky parts, that have large areas to fill. On of those things you just play with and get a feel for. In my experience, the MK3 is much faster than my previous printer adventures.

FYI - I would recommend breaking up questions in smaller chunks for better interaction.

Posted : 28/03/2018 5:41 am
Honorable Member
Re: Beginner questions

1. I had this issue when I first got my Mk3. I solved it two ways.
1.A) I first lowered the PINDA probe a touch lower. This prevents the print nozzle from getting as close to the print bed, which MASSIVLY lowers the temp of the "extruded blob". This solved the problem for me... but... I'm OCD. (PS: BE VERY CAREFUL DOING THIS. YOU CAN CRASH YOUR NOZZLE)
1.B) I decided to modify my print-start script. I will preheat the nozzle to 160c, then wait for print-bed to reach temp. Once the print bed reaches temp, I turn the cooling fan on MAX, and pre-heat the nozzle the rest of the way. (The cooling fan cools the "extruded blob, and soft plastic don't stick, only molten). Once the nozzle is pre-heated, I perform the 9 point calibration. I have re-adjusted my PINDA (messing with extruder assembly) and it is now higher than after I adjusted it. I believe it would be leaving blobs again, if not for this solution.

2. I actually have experienced this. I'm not really sure why.

3. I know nothing of PETG. I would guess it's "junk" that was on the nozzle that "fell off".

4. Coasting would help. Linear Advance does help. Hopefully it comes soon. Just gotta wait a few more days/weeks... Retraction can make it better worse, but not truly fix it.

5. I am unsure of this. If it's making an annoying noise, I would put a touch of any of the approved oils for the rods on the side of the pulley... But most people would scream at me for doing that... 😀

6. I had a filament that "clicked" rather loudly on another printer. Could have been something funky with the the filament?

7. I am running around 60mm/s for inside perimeter, 40mm/s for outside, 25mm/s for small, although your results WILL vary. I advise you to speed it up to what feels "That's crazy!!!" And print. If it's a giant DISASTER... Stop the print, and slow it down. Once it prints, did it print good enough? Slow it down some more? Speed it up a bit more, maybe it's still fine? As much the "same" as these printers are, they are each VERY unique.

Keep asking, keep questioning. Every time you ask a question to someone who knows more than you, you are admitting you have more to learn. Every time someone who knows one of the answers, replies, maybe someone else who thought they knew the answer but didn't might learn, or learn there is another way, another option. Maybe the "grey" will become apparent, and a greater understanding of a concept will come.

EG: I have use Windex to print PLA. Everyone says it's crazy. But I can NOT print with my cheap PLA without it.

Hi, I'm Sean. I used to work on CNC machines.
I try to not make mistakes, but the decision is YOURS.
Please feel free to donate to my filament/maintance fund.

Posted : 28/03/2018 6:11 am
Trusted Member
Re: Beginner questions

One trick you can do to get a feel for speed is start turning up the speed on the controller. Many times I can crank it up to 200%! However, that can have unexpected consequences. For example, we ran a vase and were able to go up to 250%, and the print looked great. However there was considerable lose in layer adhesion once we started handling it. 150% proved to be fine though.

Posted : 28/03/2018 6:36 am