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About ready to give up on the Prusa Mini  

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Rick
 Rick
(@rick)
Trusted Member
About ready to give up on the Prusa Mini

The Mini was working well for a few days but now it has become nearly impossible to work with. Under extrusion and jamming is now the norm. I’ve done multiple rounds of cold pulls and clearing the nozzle with the included needle. I have done a factory reset and rolled back to the firmware that was delivered. What has me stumped now is that after the factory reset and recalibration I was able to print the Benchy successfully.  Now, when I slice something with the settings from the Benchy, I can’t get it to print due to serious under extrusion and jamming. Even unloading filament is a struggle with the filament getting stuck either at the end of the tube at the hotend or at the extruder. I bought this as a second printer to work alongside my MK3S making a product we sell on Etsy. As it stands now I cannot trust it. I’m now seriously considering returning it and ordering a second MK3S. That’s more than I wanted to spend but at least I’ll probably be able to depend on it.

 

I’ll make one last attempt tomorrow after drying the filament for a few hours. I doubt that will help since it was only a few minutes between the successful Benchy and the following failures using the same roll of eSun PLA+.

 

Posted : 19/03/2020 12:36 am
Bubak liked
Frankincell
(@frankincell)
Estimable Member
RE: About ready to give up on the Prusa Mini

If you haven't already, check out this thread...  https://forum.prusaprinters.org/forum/hardware-firmware-and-software-help/hot-end-assembly/

A couple of things I learned were...

1. Don't use a wrench to tighten down the ends of the bowden tube.  Apparently, those brass rings on the inside will compress the plastic tube creating tight-spots. 

2. Be sure the heat-break tube is all the way up against the ptfe tube so that plastic can't leak out around it.

3. Make sure you have the extruder tension set properly.  Little slips in the filament going through the extruder gears will lead to under-extrusion.

All your filament are belong to us!...
Posted : 19/03/2020 2:10 am
Susan and Randy liked
Rick
 Rick
(@rick)
Trusted Member
Topic starter answered:
RE: About ready to give up on the Prusa Mini
Posted by: @frankincell

If you haven't already, check out this thread...  https://forum.prusaprinters.org/forum/hardware-firmware-and-software-help/hot-end-assembly/

A couple of things I learned were...

1. Don't use a wrench to tighten down the ends of the bowden tube.  Apparently, those brass rings on the inside will compress the plastic tube creating tight-spots. 

2. Be sure the heat-break tube is all the way up against the ptfe tube so that plastic can't leak out around it.

3. Make sure you have the extruder tension set properly.  Little slips in the filament going through the extruder gears will lead to under-extrusion.

Thank for the reply.

1. I finger tight the brass fittings then just a very slight snug with the wrench. 

2. I thought about the heat break issue but all three of the grub screw heads are stripped out so I can't back them out.

3. The extruder tension is what I’ve been playing with for most of today. That includes doing what I can to clean out the plastic in the extruder. The only thing I’ve found that will get in there is a round toothpick. So scratch with the toothpick to loosen the plastic, blow it out, advance the extruder, rinse and repeat. Not sure how to set the tension. It was clear with the MK3S but no idea where it should be set on the Mini.

Posted : 19/03/2020 2:54 am
Frankincell
(@frankincell)
Estimable Member
RE: About ready to give up on the Prusa Mini

@rick-m12

Check near the bottom of this page, that tension screw is hard to find.

https://www.prusa3d.com/under-over-extrusion/

All your filament are belong to us!...
Posted : 19/03/2020 3:21 am
Frankincell
(@frankincell)
Estimable Member
RE: About ready to give up on the Prusa Mini

There have been several folks who had an issue with that heat-break being too low.  Perhaps you could put a drop of superglue on the end of the 1.5 mm Allen key and get them out that way.

All your filament are belong to us!...
Posted : 19/03/2020 3:47 am
Rick
 Rick
(@rick)
Trusted Member
Topic starter answered:
RE: About ready to give up on the Prusa Mini
Posted by: @frankincell

@rick-m12

Check near the bottom of this page, that tension screw is hard to find.

https://www.prusa3d.com/under-over-extrusion/

I know where the tension screw is. I’ve been tightening it snd loosening it for most of the day but I can’t find anything like a sweet spot. Tight or loose I still get under extrusion and/or a jam. 

Posted : 19/03/2020 4:06 am
Oxygen
(@oxygen)
Reputable Member
RE: About ready to give up on the Prusa Mini

I have a photo of a spec filament scraping that is in the tube causing trouble

I'll look into the above steps -- my mileage so far with prusament is great -- every other filament is a nightmare

I have some filaments that just break in the extruder gear (and leave specs of filament in the extruder)

I have filaments that I have to heat to 230 degrees to even extrude otherwise it just clogs and stops

but every time I switch back to Prusament is is just fine and produces fine prints

This post was modified 2 years ago by Oxygen
Mini with FW:4.3.1 + SuperPINDA + Bondtech Heatbreak + PC4-M8 couplers + 1 piece boden...
Posted : 19/03/2020 7:17 am
Rick
 Rick
(@rick)
Trusted Member
Topic starter answered:
RE: About ready to give up on the Prusa Mini

@oxygen

I’ve seen other posts here that say the same thing. Prusa filament works fine but other filaments have issues. I suppose I should try some Prusa filament but that’s not an option for me. They don’t have the colors we need for our product and it’s about twice as expensive as the eSun filament we do use. I wonder if they tried any other filaments in their testing.

Posted : 19/03/2020 8:15 am
bobc
 bobc
(@bobc)
Reputable Member
RE: About ready to give up on the Prusa Mini

I had similar issues, and was also nearly ready to give up. I wanted a printer that worked well out of the box, and didn't turn into a another "project".

The hotend issue is absolutely CRITICAL to good operation! I didn't really want to disassemble it, and also had a problem with stripped grub screws. But after stripping down the extruder to clean out the teeth three times, I decided I had to get in there.

After adjusting the hotend, and re-positioning the MINDA, the underextrusion and jamming is now 99% solved. I replaced the grub screws with cap head bolts. The grub screws are a design flaw IMO. I am using cheap AnyCubic and unbranded ebay PLA, and both work well.

So tackle the hotend! I don't like the way the heatbreak is secured, and I think that the hotend works loose due to vibration and continuous pushing of filament. Even if it was OK at factory test, over time it works loose. You can't get an adequate torque on the grub screws without stripping the head.

Also loosen the brass tube fittings, because the olive causes a constriction in the tube (another design flaw IMO). I don't use the wrench, and not even finger tight, more "finger snug". I also removed the PTFE tube into the extruder, and have filament spool underneath the printer, to minimise drag going into the extruder. Note sure if that helps much.

Keep the extruder gear free of filament, that is also crucial. Once the teeth clog up, you get more skipping and more clogging.

Another issue I had I haven't seen mentioned is that my hotend cooling fan was running slow because some cables were rubbing against it. This also causes jams.

It's been a bit of a frustating journey, and if I hadn't experience with other printers I may well have got a refund. But now the Mini is printing better than any printer I've have owned, I just need to do regular maintenance check. My main issue now is inconsistent first layer height, but I can manage that.

Posted : 19/03/2020 10:20 am
xhillb61
(@xhillb61)
Trusted Member
RE: About ready to give up on the Prusa Mini

Rick, on my experience it´s allways al small issue causing problems.

I fought the MMU2 for 3 months, I succeeded.

 

Good luck

Posted : 19/03/2020 4:47 pm
Frankincell
(@frankincell)
Estimable Member
RE: About ready to give up on the Prusa Mini

@rick-m12

Whoops, I mis-understood the last line of your post...  "no idea where it should be set on the Mini."

Now that I re-read it, in context it's obvious that you know where the tension adjuster is.

Clearly I need more coffee...  🙂

And I agree with @bobcousins, you'll have to take apart that Mini HeaterBlock-HeatBreak thing to resolve this.

https://help.prusa3d.com/en/guide/how-to-change-a-heaterblock-heatbreak-mini_122769#123122

Hang in there...  Once you get this one issue fixed you'll love it.

This printer has a larger print area than my Anet-A3s or my MP-Mini-Delta, and is the same size as my Cetus3D, but way better, and that's saying something.

All your filament are belong to us!...
Posted : 19/03/2020 5:30 pm
Sfbrain
(@sfbrain)
Estimable Member
RE: About ready to give up on the Prusa Mini

OK, give up with the Mini ..................

 

Sell it to me !!  😉 🤣 😉 

 

I was lucky enough to order my Mini early and it was delivered between Christmas and New Year, so its a very early, Mk1 machine.

It has been used sucessfully every day since.

The only key to these machines is to read the manuels, take care, be patient and DO NOT beleive everything you read here on this forum.

I have watched numerous people make their small issues into huge problems by following guidance offered on here.

The Mini is a great printer

S

Posted : 19/03/2020 6:10 pm
Matteo Cristini
(@matteo-cristini)
Reputable Member
RE: About ready to give up on the Prusa Mini
Posted by: @steve-4

be patient and DO NOT believe everything you read here on this forum.

I have watched numerous people make their small issues into huge problems by following guidance offered on here.

Could you please expand on that? I have not received my printer yet and I'd like to know what posts you are referring to. 

Thanks!

Posted : 19/03/2020 6:14 pm
Sfbrain
(@sfbrain)
Estimable Member
RE: About ready to give up on the Prusa Mini
Posted by: @matteo-cristini
Posted by: @steve-4

be patient and DO NOT believe everything you read here on this forum.

I have watched numerous people make their small issues into huge problems by following guidance offered on here.

Could you please expand on that? I have not received my printer yet and I'd like to know what posts you are referring to. 

Thanks!

OK, i may have been unfair to many people who are only trying to help others.

But ............ i see issues raised and then 3 different solutions offered as solutions ..... At leased 2 of these solution can not be right !!

When you get your printer .......

1.   Take your time building it, follow the manuel and dont force anything, everything goes together properly if done carefully.

2.  Follow the setup and calibration guidance religiously.

3.  Keep repeating the Z-level process (in the menu) until your results are just like the pictures in the manuel. (The level really is lower than you think)

4. there are two main areas to understand and keep an eye on on your printer ...... the bowden feeder (on the Z tower) and the extruder (on the X axis (where the plastic comes out)).  The bowden feeder has a tension adjuster in it to regulate the pressure on the filament as it is fed to the extruder, The tension is set (without filament in it) by screwing the adjuster screw in until its head is flush with the plastic housing.  The extruder end (or hot end) is a little more sensitive, but once set up will run flawlessly until you change something (like change a nozzel etc). Follow the guidance in the 'Knowledge base' on the Prusa site to the letter !!. The goal here is to have no gaps internaly (in the hot end) between where the fillament enters the extruder (on the top) and where the plastic is forced out (nozzel).

Do all this and you will have no problems

My Mk1 Mini has done abot 500 hours of printing so far

Hope this helps

S

Posted : 19/03/2020 6:35 pm
Rick
 Rick
(@rick)
Trusted Member
Topic starter answered:
RE: About ready to give up on the Prusa Mini

Regarding the tension setting on the extruder, I did set it so the head of the screw is flush with the housing and I get almost constant slipping while running the z height calibration. That leaves me with a potential hotend issue. That’s where I get stuck due to the faulty installation of the three grub screws that all have stripped out heads. So, are the heads stripped out because the quality of the screws isn’t sufficient for the necessary torque? Or, have they been over tightened which may have deformed something inside. That latter one could explain the under extrusion and apparent jamming issues.

Posted : 19/03/2020 7:07 pm
Sfbrain
(@sfbrain)
Estimable Member
RE: About ready to give up on the Prusa Mini
Posted by: @rick-m12

Regarding the tension setting on the extruder, I did set it so the head of the screw is flush with the housing and I get almost constant slipping while running the z height calibration. That leaves me with a potential hotend issue. That’s where I get stuck due to the faulty installation of the three grub screws that all have stripped out heads. So, are the heads stripped out because the quality of the screws isn’t sufficient for the necessary torque? Or, have they been over tightened which may have deformed something inside. That latter one could explain the under extrusion and apparent jamming issues.

Arrhh, the 3 grub screws !! 😉 

They only hold the tube inside the housing still, there are 3 of them for 2 reasons .......

1.   so that the tube can be held firmly

2.  So that overtightening them (to hold tube) is not necessary. If you overtighten any one of them you run the risk of deforming the tube, which will lead to problems inside the tube with the PTFE tube, filament etc etc.

So mildly tighten them all on the tube.

I have replaced mine with M3x5mm Cap head screws, these have a bigger size allen key slot in the top, so easier to use (but dont overtighten them).

In my experience ALL under and over extrusion issues stem from incorrectly assembled hot ends 😉 😉 😉 

S

Posted : 19/03/2020 7:26 pm
Rick
 Rick
(@rick)
Trusted Member
Topic starter answered:
RE: About ready to give up on the Prusa Mini

Here is how I was able to deal with the grub screw issue. I used a T6 bit and pressed it firmly into the grub screw, just enough to get a bite. Then, while putting moderate pressure holding the bit into the screw, I used a wrench on the shaft to loosen the screw. It only takes a tiny rotation to free up the screw. Once the screw moves you don’t need the wrench. Then I could continue to back the screw out using the bit and just my fingers.

This post was modified 2 years ago by Rick
Posted : 19/03/2020 8:10 pm
Rick
 Rick
(@rick)
Trusted Member
Topic starter answered:
RE: About ready to give up on the Prusa Mini

Update...  Now I need to see if I can find some replacement screws locally. Elsewhere in these forums I see that an M3 x 4mm cap screw works.  

Posted : 19/03/2020 8:16 pm
Rick
 Rick
(@rick)
Trusted Member
Topic starter answered:
RE: About ready to give up on the Prusa Mini

I was able to move the hotend up by 3 or 4 mm then retightened the grub screws. Then I reset the Minda height and recalibrated the first layer. That seems to have fixed the issue for now. Resliced mr test using all defaults for 0.2 SPEED and it’s printing now. First layer looks pretty good and best of all no under extrusion or slipping in the extruder. IMG_1092

This post was modified 2 years ago by Rick
Posted : 19/03/2020 9:26 pm
atomleef liked
Sfbrain
(@sfbrain)
Estimable Member
RE: About ready to give up on the Prusa Mini
Posted by: @rick-m12

I was able to move the hotend up by 3 or 4 mm then retightened the grub screws. Then I reset the Minda height and recalibrated the first layer. That seems to have fixed the issue for now. Resliced mr test using all defaults for 0.2 SPEED and it’s printing now. First layer looks pretty good and best of all no under extrusion or slipping in the extruder. IMG_1092

Way to go buddy 👍 👍 👍 

Posted : 19/03/2020 9:46 pm
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