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MJA Research
(@mja-research)
Active Member
MINDA problem

Hi. I have 3 Mk3s machines in a small but growing farm and just taken delivery of a Mini to see if this will work for us. There is definitely something wrong with this design because the live Z offset is impossible to set and keep correct. When starting a print from cold the mini heats up to 170c to do the mesh leveling.  Then parks the hot end raised to approx 3.06mm, in my case, whilst it heats up to the 215c required for the PLA material being printed. However, this proves to be far too high and the print fails on the first layer.  If I stop the print and restart it after the next and subsequent 170c mesh level processes the parking height changes to a higher point.  After 4 or 5 retries it settles at about 3.13mm and when this happens the print completes without fault with a perfect fist layer height as set in the initial calibration.
My calibration for the fist layer Z was fallowed as per the manual and was fine. My result was a -1.495 ( this will be different with each machine depending on where the factory set the MINDA sensor height) I think the fault is a combination of software and hardware.  The MINDA sensor seems to be providing different results each time until finally settles on the last reading. If I do multiple prints immediately after each other and before the bed and hot end have cooled much, it will print again without issue.  I notice that the sensor in the Mini called MINDA does not have a thermistor in it and so the new 32bit board with all its extra speed and processing power is not being asked to compensate for the MINDA reading changes as it heats up.  Please PRUSA can you get something sorted for this as this machine is not really workable and a good deal frustrating.  I may have a faulty MINDA but then there is no test that can check this because it does actually give readings.

Posted : 30/09/2020 6:08 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: MINDA problem

You have tried everything I would suggest - consider a chat with support.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 30/09/2020 6:29 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINDA problem
Posted by: @john-j20

Hi. I have 3 Mk3s machines in a small but growing farm and just taken delivery of a Mini to see if this will work for us. There is definitely something wrong with this design because the live Z offset is impossible to set and keep correct. When starting a print from cold the mini heats up to 170c to do the mesh leveling.  Then parks the hot end raised to approx 3.06mm, in my case, whilst it heats up to the 215c required for the PLA material being printed. However, this proves to be far too high and the print fails on the first layer.  If I stop the print and restart it after the next and subsequent 170c mesh level processes the parking height changes to a higher point.  After 4 or 5 retries it settles at about 3.13mm and when this happens the print completes without fault with a perfect fist layer height as set in the initial calibration.
My calibration for the fist layer Z was fallowed as per the manual and was fine. My result was a -1.495 ( this will be different with each machine depending on where the factory set the MINDA sensor height) I think the fault is a combination of software and hardware.  The MINDA sensor seems to be providing different results each time until finally settles on the last reading. If I do multiple prints immediately after each other and before the bed and hot end have cooled much, it will print again without issue.  I notice that the sensor in the Mini called MINDA does not have a thermistor in it and so the new 32bit board with all its extra speed and processing power is not being asked to compensate for the MINDA reading changes as it heats up.  Please PRUSA can you get something sorted for this as this machine is not really workable and a good deal frustrating.  I may have a faulty MINDA but then there is no test that can check this because it does actually give readings.

The Prusa Mini is in principle not yet fully developed. It runs, but is still expandable. There seem to be many problems with the sensor and as far as I know Prusa is working on a solution. The filament sensor does not work proper, although there is not much that can be connected wrong. My Mini filamentsensor doesn't work either, because the signal is inverted (tested with several and the original Mini sensor). The firmware itself is also very upgradeable. And then there is the M500 story - yes/no/perhaps....
Be patient and wait is the motto.

 
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 30/09/2020 7:17 pm
MJA Research
(@mja-research)
Active Member
Topic starter answered:
RE: MINDA problem

Actually, I will take you to task on that point of accepting the Mini is under development and does not work.  I don't recall being advised that this is the case when I purchased it.  I also don't recall seeing any comments by Joseph that this is the case.  When a product is released it should work.  The fundamental issue of the MINDA sensors not working was reported in the forum and to Prusa Research back before March.

I feel that perhaps they should have recognized this as being an issue and then stopped taking orders until it was resolved.  Selling products that do not even do the initial first layer correctly and make no mention of it in the manual and the web site sales page is simply wrong.

I am a full supporter of Prusa and that can be seen by my investment in the brand's products. IMO your suggestion to wait is not acceptable and after waiting for several weeks for my order to arrive I would have thought this issue would have been fixed.  let us get to the point that really matters.  the sensor is inferior to the Mk3 PINDA as it does not have a thermistor wire.  this could be an easy change for Prusa.  put the price up by the difference or at least allow us to buy the PINDA and change it over.  the software is well within Prusa capability to sort out as they have many very capable programmers on the staff.

we should not have to wait months for a fix that is quite simple to implement.  I for one would be happy to pay for the changes. 

Posted : 30/09/2020 7:49 pm
bobc
 bobc
(@bobc)
Reputable Member
RE: MINDA problem

Tbh, at this stage the only thing that will get Prusa's attention is a public "exposé" by some respected 3d maker describing the issues with the Mini and the apparent lack of action from Prusa. Users reporting issues in forums or on github are easily brushed under the carpet. While people are still placing orders for the Mini, there is no real need for Prusa to do anything.

I have never owned a Prusa before, I thought with their commitment to Open Source etc they would be better than this, but sadly I don't find it the case. I think they have really dropped the ball with the Mini. It doesn't make me inclined to buy another printer from Prusa. Do Prusa really not care about their reputation any more?

BTW, it's a simple job to put a PINDA on the Mini, there is an example in this thread https://forum.prusaprinters.org/forum/user-mods-octoprint-enclosures-nozzles/printing-abs-on-the-mini-with-pinda-and-110-bed/. The drawback is you have to void your warranty with custom firmware. This is really something Prusa should be doing officially.

Posted : 30/09/2020 8:31 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINDA problem

@john-j20

This is certainly annoying for many, but the user, like me, unfortunately can't change anything about it. I think there are many products on the market that could be improved. As far as I know, Prusa works on the problems reported with high priority and you just wait until the time comes or you give the product back. I usually return products that I am not satisfied with.
I solve it for myself by looking for solutions within my own capabilities, but that's not everyone's cup of tea and that's not the original thought when buying a 3D printer.
We in the forum can only contribute in the sense that we directly report the shortcomings to Prusa. The more people do this, the more likely it is that something will change.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 30/09/2020 8:35 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: MINDA problem
Posted by: @john-j20

Actually, I will take you to task on that point of accepting the Mini is under development and does not work. 

I am not so sure that is correct.  Except for an occasional jam (every 1-2 weeks), it works perfectly for me.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 30/09/2020 8:40 pm
mafredri
(@mafredri)
Active Member
RE: MINDA problem
Posted by: @bobcousins

BTW, it's a simple job to put a PINDA on the Mini, there is an example in this thread https://forum.prusaprinters.org/forum/user-mods-octoprint-enclosures-nozzles/printing-abs-on-the-mini-with-pinda-and-110-bed/. The drawback is you have to void your warranty with custom firmware. This is really something Prusa should be doing officially.

Why would you do this? To my knowledge there is no difference between PINDA and MINDA, other than name and color. It's simply a way to differentiate between the two. IIRC Josef Prusa himself mentioned this on one of the Prusa Live episodes.

Posted : 02/10/2020 10:28 am
mafredri
(@mafredri)
Active Member
RE: MINDA problem
Posted by: @mafredri

Why would you do this? To my knowledge there is no difference between PINDA and MINDA, other than name and color. It's simply a way to differentiate between the two. IIRC Josef Prusa himself mentioned this on one of the Prusa Live episodes.

Never mind, just looked at some MINDA pictures and saw it's only 3 wires, so I suppose JP was referring to it being the same as PINDA V1, not V2.

Posted : 02/10/2020 10:36 am
MJA Research
(@mja-research)
Active Member
Topic starter answered:
RE: MINDA problem

So to follow up.  I reported this by sending an email to Prusa directly.  I received a reply just now as follows below:

………………………………………………………….

sorry to hear about this the reason for this is that the MINDA itself doesn't have the temp thermistor as the PINDA2 has. Unfortunately, replacing the MINDA doesn’t seem to be a solution in this case. This issue was already reported and is discussed on Github as well.
 
 
First possible solution:
  • move the MINDA around 10 cm from the heatbed
  • perform the FLC with the PLA or another filament
  • now before each print, make sure that the MINDA is at least around 10 cm away from the heatbed 
 
Second possible solution
  • remove the spring steel sheet (Also make sure there is no filament rests under)
  • preheat the heat bed up to 90°C and wait at least for around 10 minutes (Settings - Temperature - Heatbed) 
 
Third possible solution is discussed on our FORUM where the MINDA is kept away from the heatbed, so there is as less as possible temp impact on it(similar to the first possible solution)

Please let me know if this helps.
………………………………………………………….
 
I think this kind of supports my disappointment really.  the work round will most likely work as long as the MINDA sensor is at the same temp as it was at the time the FLC is completed it will be repeatable.  So adding a delay whilst parked between 170c and the filament printing temp rise will, in principle, work.  however if you FLC at PLA temps and them wish to use PETG or ASA the issue will happen again.
it is utterly unacceptable that the issue has not been fixed despite being aware of it since release.  I posted this topic before i had checked the forums for similar issues.  (MY BAD!) sorry to all who have seen this before but finally it is official that the manufacturer knows the MINDA does not work in this design and it is not a faulty one.  It is simply an oversight in design through cost saving IMO.
 
I hope they make a change soon because their untarnished reputation is likely to take damage if not and i would not like to see that as i really think Joseph and his ethos is brilliant! 
This post was modified 1 year ago by MJA Research
Posted : 02/10/2020 1:35 pm
Tracy
(@tracy)
Trusted Member
RE: MINDA problem

I have stopped recommending the Mini to my friends because of this issue. Prusa saved, what, maybe $10 by using a Minda instead of a Pinda? It's very disappointing. At this point I'm more likely to recommend an Ender 3 to my friends who can't afford an mk3s.

Posted : 02/10/2020 5:21 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: MINDA problem

@tracy

If you turned to me and suggested the Ender-3 over the Mini, I would laugh and think you are foolish.  The Ender-3 is garbage compared the the Mini.  I have two years of experience with Enders and would never recommend this to an enemy much more a friend.  I have been successfully using a Mini for 9 months.  It works fine for most.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 02/10/2020 5:26 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: MINDA problem

I am rereading this thread.  Why is this only occurring with some printers and not all.  It just does not make sense.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 02/10/2020 5:38 pm
Tracy
(@tracy)
Trusted Member
RE: MINDA problem
Posted by: @charles-h13

I am rereading this thread.  Why is this only occurring with some printers and not all.  It just does not make sense.  

It must be due to differing print habits. It's a fact that the Minda doesn't have a temperature sensor and that temperature affects its readings.

This post was modified 1 year ago by Tracy
Posted : 02/10/2020 5:40 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: MINDA problem

@tracy

Maybe it is different environments.  I am in Georgia and it is very humid.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 02/10/2020 5:44 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINDA problem

@tracy

I think that you can gain functionality by some adjustment work and levelling of the printing bed. The printer is mostly made of printed plastic and you have to improvise if something doesn't work as it should. For example, I have made adjustable the printing bed and level it to a range of 0.1mm. Since then I have had no problems at all. The print results are similar to those of the MK3.

Room temperature 27 degrees C., rel. Humidity 43%

I can't say anything about the ender, but I think that with a $150 printer you certainly have to deal with other problems.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 02/10/2020 6:26 pm
mafredri
(@mafredri)
Active Member
RE: MINDA problem

By the way, I have had similar issues on my MK3S with a PINDA V2. So I wouldn’t be too hasty to believe that a temperature sensor in the MINDA would fix all problems. It’s quite likely related to print environments and individual differences in the *INDAs. For instance at my home the temperatures are around 22C and 40-50% rel. humidity. That’s a pretty low starting temp for the PINDA, combine that with rapid heating from the print bed during BML, the PINDA temperature could easily go from 25C to 30C between first and last measuring point. Add to that, the MK3S does not calibrate for PINDA temperatures <35. This leads me to believe that a stable *INDA temp is key for good results. How well a probe handles a throw off 5C between measurements could be due to individuality, giving one possible explanation as to why some people have problems whereas many don’t.

Posted : 02/10/2020 6:46 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: MINDA problem
Posted by: @karl-herbert

I can't say anything about the ender, but I think that with a $150 printer you certainly have to deal with other problems.

Other problems is right.  Second print: I developed under extrusion so I contact Creality.  They tried for 2 weeks to help me.  I got a replacement.  Within 6 prints, I experienced user extrusion and jams.  

For the first two years, problem after problem.  I finally upgraded to a Pinda Probe, Dual Z, Titan Aero extruder, and new 32 bit board from BIQU.  About $300 and have it running like and I stress “like” a Prusa.  The “Like” is a stretch.  

I am eager to see what the problem is with the Mini.  I have tied to help at least a dozen folks get this to work like mine does.  I just don’t get it.  I don’t think it is the user.  It has to something else.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 02/10/2020 6:55 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINDA problem

@charles-h13

The Prusa Mini uses relatively inexpensive components and also printed plastic parts, which are subject to certain tolerance fluctuations. If the assembly is not very precise, various malfunctions can occur.
For this reason I have completely disassembled the printer, changed some parts, rebuilt and reassembled it.
As far as the firmware is concerned, I can only make limited changes, since I am not a specialist in this area.

 
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 02/10/2020 8:19 pm
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