Avoiding early Prusa Mini Issues + Common Issues  

RE: Avoiding early Prusa Mini Issues + Common Issues

Would you say the Mini+ has some of the issues ironed out? just ordered my first Prusa (mini+) yesterday and missed this thread... now a bit scared. 😮 My current printer I've used for a year solid (monoprice) and not once had jam or any issues, the only maintenance I've done is lubricate the moving parts and its been good.

RE: Avoiding early Prusa Mini Issues + Common Issues

I received my first Mini+ about two weeks ago and haven't had any problems so far. (knock on wood)

RE: Avoiding early Prusa Mini Issues + Common Issues

Posted by: @avh

I received my first Mini+ about two weeks ago and haven't had any problems so far. (knock on wood)

Thats good to hear 😀 

RE: Avoiding early Prusa Mini Issues + Common Issues

Last week I spoke with a representative from Prusa and he told me that the distance between the block (stock) and the heatsink should be 4.7mm. The nozzle with a distance of 0.5mm with the block and check that the PTFE tube is firmly in the connectors without any movement. But even following these steps, the 3 MINIs that I have are covered at the beginning of the printing, that is, I think there is a problem between the loading of the filament and the beginning of the printing, when the temperature drops to 170 for the calibration of the mesh and then go back up to 215 to start printing. Somewhere in the hotend the filament expands and plugs. The strangest thing about all this is that there are three MINI printers and I assembled them without touching anything in the extruder and hotend and all three failed in the same, I mean that I suspect there is something wrong in the factory assembly or some problem in the parts.

RE: Avoiding early Prusa Mini Issues + Common Issues

@markiz87-2

Keep contacting support and they will get it right.  

RE: Avoiding early Prusa Mini Issues + Common Issues

@markiz87-2

mine had a screw missing in the minda-bracket and I had similar problems but I rebuilt the hotend according to the guide and used a fair share of arctic silver 5 and now it works like a charm.

RE: Avoiding early Prusa Mini Issues + Common Issues

I've been having the same issues, I have a MINI+ which was ordered in mid October and delivered mid December.

I had several prints with the Prusament sample pack which were fine, but I switched to Filamentive rPLA and had a couple of OK prints before I kept getting jams.  A few of the jams caused the filament to snap in the bowden tube.  I spoke to support and was guided through clearing the jam, but didn't get as far as preventing it from happening again.  My heater block is definitely lower than expected, so it's looking quite possible this is the issue. 

I also get the clicking when it does a retraction (which I think was determined to be the gears not being fully meshed together in the extruder?).

Also, I've noticed that the jams tend to only happen when making fast extrusion/retractions - which seems to happen a lot when printing infill.  I wonder why? Something about molten plastic being pulled up too far and pushed back down again and smooshing out into the void?

RE: Avoiding early Prusa Mini Issues + Common Issues

I can definitely confirm, after doing a cold pull without the PTFE tube in the heatbreak, a plug had been formed around the bottom of the PTFE tube. I suspect that when the nozzle was heated, the plug eventually partially melted and flowed into the path of the nozzle opening restricting the flow - all consistent with the original problem at the top of this thread. I guess quick retractions just churned the semi-melted  plastic into the path of the nozzle more easily?

I have pushed the heatbreak right up into the heatsink with the bowden fitting removed, tightened the grub screws again and reinstalled the PTFE tube and reattached the lower fitting according to the replacing the hotend - Installing the PTFE tube instructions. 

Since doing that, I've had no problem printing for at least 4 hours - no clicking (other than the normal clicking when retracting), or underextrusion.

One slightly weird thing is that after performing this maintainence that running a self test resulted in a failure - apparently because the nozzle didn't cool down fast enough (at least, the test terminated after "waiting for cooldown").  This happened twice, leaving 20 minutes between tests, both failed.  Then I tried again after running a test print, and it passed, twice. 🤥 Can't explain that one.

It is a little concerning that dispite this thread existing, and even an upgrade to the MINI+ being released, it's still happening to kits shipped a year later.  I guess since the problem takes a few hours of printing (and the plug accumulating) it's not easily tested for or reproducible during QA, apart from checking dimensions with a gauge to check the heater block is high up enough into the heatsink (which would need to be done by hand).

RE: Avoiding early Prusa Mini Issues + Common Issues

@naxxfish

Is it normal for Mini+ to 'click' during retractions? Driving me nuts with the noise (printer is pretty silent apart from this).

So far i've had one filament break inside extruder. Have just moved the heatbreak as far as it will go and doing a test benchy. I was hoping this would also reduce clicking, but perhaps this is just a design flaw of the extruder? Very disappointing compared to the silent Mk3s extruder.

RE: Avoiding early Prusa Mini Issues + Common Issues

Posted by: @colin-3

@naxxfish

Is it normal for Mini+ to 'click' during retractions? Driving me nuts with the noise (printer is pretty silent apart from this).

My MINI+ does click when retracting, yes - and I video'd it and confirmed with support that this is normal behaviour. It's not obvious as to why, and it doesn't sound purely like backlash (there's a kind of springy ping to it as well?).

The Mk3s's extruder is direct drive, so possibly a bit unfair to compare it with the bowden tube in the mini. But it is the loudest thing that the mini does, it seems!

RE: Avoiding early Prusa Mini Issues + Common Issues

@naxxfish

Thanks for that. I did notice when i had the extruder apart that manually moving the large gear showed some play in the gears, and that did make a similar noise, i guess amplified when the motor is used. A shame the meshing isnt better.

Appreciate the reply.

RE: Avoiding early Prusa Mini Issues + Common Issues

I've had my Mini+ for 2 weeks now.  It printed perfectly for 5 days and then an hour after finishing a perfect print I told it to print it again.  That's when the clog/under extrusion happened.  Searching the Knowledgebase I did the cold pull and cleaned the extruder gears.  That fixed it for 7 days and then it happened again.  After trying everything for 2 days I was pointed to this thread.  So far raising the hotend seems to have fixed it.  My test Benchy looks great and I haven't heard a single click.  It's so nice to be printing again.

RE: Avoiding early Prusa Mini Issues + Common Issues

Posted by: @schnoidz

I've had my Mini+ for 2 weeks now.  It printed perfectly for 5 days and then an hour after finishing a perfect print I told it to print it again.  That's when the clog/under extrusion happened.  Searching the Knowledgebase I did the cold pull and cleaned the extruder gears.  That fixed it for 7 days and then it happened again.  After trying everything for 2 days I was pointed to this thread.  So far raising the hotend seems to have fixed it.  My test Benchy looks great and I haven't heard a single click.  It's so nice to be printing again.

That was the same for me, after spending some time on chat with support it was solved, like you have lift up the hot end but the trick is to do a 3/4 turn not 1/4 turn, the tech told me to do that and its been good now for a month. They said the 1/4 in the manual needs updating, I looked today it still says online to do 1/4/ so I guess they didn't update the manual yet.