New Mini+ - teething problems and costs  

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Owt From Nowt
(@owt-from-nowt)
Active Member

Hi,

First I've been running an I3 Mk3S for years now so I'm not exactly a newb ...

  • Bought a Mini+ as a second printer to help with my small business. It arrived just before Xmas. 😀 .
  • A week later it wouldn't print, had to strip down the hot end, replace the nozzle and the PTFE tube - ☹️ . (£5.00)
  • Printed great for a while. Then started under extruding wasting lots of filament on prints that just weren't good enough. 😠
  • Bought a bondtech upgrade kit (£66.60).
  • Arrived minus most of the screws, 😡  had to buy some screws to replace the missing ones - bondtech wouldn't send them and told me to go back to the person I bought the upgrade kit from - Who couldn't supply me any screws and told me to get them elsewhere. (£5.49) 😡 
  • Finally fitted the new extruder - printed great for ONE print, then the PTFE Boden tube parted from the bit thats supposed to hold it in the nut ... 🤬
  • Have had to order a replacement from Prusa (£2). 
  • Now have to wait for those to arrive. 😳 

So far my "smart", "affordable", "reliable" second printer has proved almost anything but. Costing me an additional £80 and I still have only a few prints to show for it.

When it was working had to print PLA at 230C and at 90% speed.

So far not that impressed. If I'd have known I'd have all these problems I'd have saved up and just got a second Mk3S!

 

This topic was modified 3 months ago by Owt From Nowt
Posted : 11/02/2021 9:50 am
technogeeky
(@technogeeky)
Eminent Member

For people reading this who are considering buying one, I think it's important to remember there is a strong self-selection bias on this forum: most people will be complaining and seeking help, and it's rare for people like myself to report in who have had almost no problems at all.

I got my on Dec 25th and I have had almost nothing but success. I had a few times when the clicked like a angry dolphin trying to win a debate using castanets - this was due in the two cases to me using a difficult filament (HTLPA) and in another case tightening the idler screw too far.

I have had basically nothing but perfect prints. I've tried maybe 10-15 filaments overall, and already gone through about three rolls. I've had no problems getting things to stick to the bed. I've done detailed models, structural models, etc.

As a person with no 3d printing experience beforehand, I have been thoroughly impressed. I've printed lots of smaller test objects, my calibration/scale objects measure e.g. 39.98 mm for 40. I was able to put down single sheet first layers with no defects at all across the whole first layer.

Did your printer not come with an extra PTFE insert tube (I am assuming this is the one that you quickly replaced). I have heard reports of the existing one warping or not being the correct size.

Why did you have to replace the nozzle so quickly? Most advice seems to suggest several cold pulls repeatedly before that step. Do you (or anyone else) know how likely you are to disturb the PTFE tube fitment by swapping the nozzle?

Anyway, please keep us updated on the difficulties you're having.

Posted : 11/02/2021 3:14 pm
Owt From Nowt
(@owt-from-nowt)
Active Member

@technogeeky

Don't get me wrong, I think Prusa printers are the best on the market, and my MK3S is a true consistent workhorse, and I can't praise it enough. 

I'm happy to believe that my mini+ is probably one of a small number with problems. After all you can't make that many of anything and not have the odd one that has problems.

There was a second hotted PTFE tube, and as others have noted it was a different size to the one already in the hot end. I did perform quite a number of cold pulls before swapping the nozzle, nothing cured the problem so I gave up and bought the bondtech extruder.  

The under extrusion does, however, appear to be a common problem experienced by others, not just me.

Posted : 11/02/2021 3:31 pm
cwbullet
(@cwbullet)
Illustrious Member

@owt-from-nowt

I do not think your experience is shared by all, but there is a small but vocal number of folks with problems.  I would post each problem you are having one by one and let us have an opportunity to assist you.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 11/02/2021 3:37 pm
Dragon1291
(@dragon1291)
Trusted Member
Posted by: @technogeeky

Do you (or anyone else) know how likely you are to disturb the PTFE tube fitment by swapping the nozzle?

 

Looking at the heatbreak drawing: https://github.com/prusa3d/Original-Prusa-MINI/blob/master/DOCUMENTATION/MECHANICAL%20PARTS/mini-heatbreak.pdf

The PTFE tube has 6 mm between it and the heatblock/nozzle interface. So in theory, a nozzle swap done correctly should not affect the PTFE tubing in any meaningful way. 

Posted : 11/02/2021 8:08 pm
technogeeky
(@technogeeky)
Eminent Member
Posted by: @dragon1291
Posted by: @technogeeky

Do you (or anyone else) know how likely you are to disturb the PTFE tube fitment by swapping the nozzle?

 

Looking at the heatbreak drawing: https://github.com/prusa3d/Original-Prusa-MINI/blob/master/DOCUMENTATION/MECHANICAL%20PARTS/mini-heatbreak.pdf

The PTFE tube has 6 mm between it and the heatblock/nozzle interface. So in theory, a nozzle swap done correctly should not affect the PTFE tubing in any meaningful way. 

OK. Thank you.

So my questions about the OP are: why did you have to wait to get a 2nd piece of PTFE tube when the kit was supposed to come with an extra?

Why did you go straight into nozzle swap and/or quickly conclude the need for the Bondtech upgrade based on these problems; or did the OP just want to upgrade something on the printer they saw as usefully upgradable?

 

Thanks!

Posted : 11/02/2021 8:10 pm
Owt From Nowt
(@owt-from-nowt)
Active Member

@technogeeky

Sorry. The bit I’m waiting for is the PTFE tube from the extruded to the hot end, this bit: https://shop.prusa3d.com/en/minimini/1067-extruder-print-head-ptfe-tube-mini.html

I went through everything I could think of before getting the extruder upgrade. I followed all the cold pull advice etc. Then when that didn’t work, I tried the nozzle swap. 

Posted : 11/02/2021 8:52 pm
technogeeky
(@technogeeky)
Eminent Member

If you could also provide pictures of the underextuded prints and let us know of any other mitigating factors, it may help.

A lot of people who have had problems discovered that the PTFE tube inside the heatbreak is just slightly the wrong length (sometimes even from the factory, it seems).

Other things can be involved that you might not think are - retractions caused by e.g. octolapse or stringing avoidance actually making extrusion worse.

I have gotten in the habit of doing extrusion flow calibration (on that teaching tech website) on every single filament. For most of the highest quality filaments, I can always just leave the extrusion multiplier to 1.0, but most of my more mediocre filaments require a setting of something like 1.04 or 1.06 - this may not seem like a huge difference, but the difference in print quality is substantial.

Posted : 11/02/2021 10:07 pm
cwbullet
(@cwbullet)
Illustrious Member

@owt-from-nowt

Like said above.  Pictures are needed.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 12/02/2021 12:39 am
Owt From Nowt
(@owt-from-nowt)
Active Member

@cwbullet

Filament PLA, 240C, 100% speed. If I try to print at 210C to 215C ... filament freezes in the hot end and Pops the boden tube out of its "olive". Luckily I ordered 5 replacements, already had a replacement pop.

Posted : 17/02/2021 1:48 pm
Cashew92ftw
(@cashew92ftw)
Eminent Member

Is it possible to have a badly placed thermister? 

 

Im waiting on my first prusa mini, but 240 to print sounds off to me. Your useing just standard PLA or prusament? 

Orange Juice Please...
Posted : 17/02/2021 2:40 pm
Owt From Nowt
(@owt-from-nowt)
Active Member

@cashew92ftw

yup, filamentum PLA, runs at 210-215 on my mk3s. For a support email in with Prusa ...

Posted : 17/02/2021 2:42 pm
cwbullet
(@cwbullet)
Illustrious Member

poor extrusion !

--------------------
Chuck H
3D Printer Review Blog...
Posted : 17/02/2021 3:57 pm
Owt From Nowt
(@owt-from-nowt)
Active Member

@cwbullet

I think thats what I said right in the original post.

Posted : 18/02/2021 2:02 pm
cwbullet
(@cwbullet)
Illustrious Member

@owt-from-nowt

I was confirming with an exclaimation point.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 18/02/2021 2:05 pm
technogeeky
(@technogeeky)
Eminent Member

@owt-from-nowt

If you can only print very good PLA like that at 240 C, and you don't have tons of stringing, I'd guess the thermistor must be bad. It looks like you're still under temperature (under extruding) even at 240, so hand-waving here I'd guess the hotend is really at something like 180 C?

 

Posted : 18/02/2021 2:08 pm
Owt From Nowt
(@owt-from-nowt)
Active Member

@technogeeky

Thats my thought too, but I don't have a way of measuring the actual temperature that I know of. Any suggestions?

Also, wiggling the wires dosen't  cause the temperature readout to "wobble" ... 

Posted : 18/02/2021 2:13 pm
technogeeky
(@technogeeky)
Eminent Member

@owt-from-nowt

The other day, I used a very accurate thermometer to try and measure the temperature and the problem is getting good and reliable contact. I tried to really jam it in there, and it measured about 30 C lower than the printer thought. I don't think that method can really be reliable without a fixture to hold the new thermometer on there.

I would get replacement thermistor and see if it helps? It's unfortunate to wait for it.

Posted : 18/02/2021 2:15 pm
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