Brand new prusa mini: Z needs to adjust on every new print.  

RE: Brand new prusa mini: Z needs to adjust on every new print.

i also got mine exchanged by prusa. After a few months with the new one i can say that the problems is gone 95% of the time, normally it holds the calibration perfecty for over 20 prints now, but sometimes still a ramdon 0,2mm jump accure, so its a lot better and the old probe clearly was faulty, but the new one is still not perfekt.

RE: Brand new prusa mini: Z needs to adjust on every new print.

@rdanielo

my gcode has this: G1 Z1.5 F50 ;

So pretty close to the bed.

RE: Brand new prusa mini: Z needs to adjust on every new print.

Anyone mind measuring the distance from the bottom of the MINDA mount to the bottom of the probe itself?

RE: Brand new prusa mini: Z needs to adjust on every new print.

idk how relevant it is, because you could install the probe on slightly diffent heights, but mine is installed with exactly 8mm distance.

RE: Brand new prusa mini: Z needs to adjust on every new print.

Important is the correct distance of about 1mm to the nozzle tip:

https://help.prusa3d.com/en/guide/how-to-adjust-the-height-of-the-m-i-n-d-a-sensor-mini_154547

The MINDA is an inductive switch and has a limited switching range of about 1-2mm.

RE: Brand new prusa mini: Z needs to adjust on every new print.

Probe height should be very similar between all machines unless the heatbreak has fallen, in that case there's a bigger issue than the Z being off a little. All things considered, mounting holes have minimal travel, hard length on the heatbreak, PTFE tube, etc. I would suspect that the difference shouldn't be too large. So I've edited the heat shield to match a distance of 8mm. The heatshield itself is reduced to 7mm to ensure it's out of the print path (though it should be safe the same length of the MINDA, I reduced it for safety of the possible tolerance differences). I made a 45 degree angle to help reduce direct heat on the plastic (though considering it's all PETG to begin with, this shouldn't be an issue either, but it's still a little less plastic).

https://www.prusaprinters.org/prints/42167-prusa-mini-minda-heatshield

If anyone wants to try printing this out of PETG, replacing the current mount, adjusting their MINDA and checking results there it is. I figure this and a silicone sock should be about all required to keep the heat from the hotend from infecting the probe and keep it room temp for cold z calibration.

RE: Brand new prusa mini: Z needs to adjust on every new print.

@skreelink

I should mention that I don't use the original hestbreake, instead I use the bondtech upgrade one. One of the many problems I had with the printer as delivered was that I always got jams with the original one, because plastic could escape at the bottom of the internal pfte tub. And that even after I took the whole assembly apart and rebuild it because the heat break wasn't properly installed and fastened. Luckily this issues are gone but maby I installed the Minda differently. Idk if the bondtech hestbreake is exactly the same length, I installed the nozzle tip to Minda height to exactly 0,80mm. After also replacing the Minda and readjusting  all axis for orthogonality and step calibration the printer finally works relaibly 19 out of 20 prints. But I also would love the option to upgrade the Minda to pinda, since it only would take a firmware feature. I even would pay for that in hope to address the remaining 1 out of 20 prints with waaaaay of z offset.

RE: Brand new prusa mini: Z needs to adjust on every new print.

@skreelink

Printed it and installed it. I previously had to preheat the nozzle for a few minutes, and stay close to the printer during the first layer, because I had many issues linked to heat.
After installing it, I've made a few prints, and I didn't get any issues. Whether I make prints after letting it heat for a while, or just after turning it on, it seems to keep a good calibration.

So thanks a lot, it saved me a lot of trouble :3

RE: Brand new prusa mini: Z needs to adjust on every new print.

Posted by: @artemisfowlii

@skreelink

Printed it and installed it. I previously had to preheat the nozzle for a few minutes, and stay close to the printer during the first layer, because I had many issues linked to heat.
After installing it, I've made a few prints, and I didn't get any issues. Whether I make prints after letting it heat for a while, or just after turning it on, it seems to keep a good calibration.

So thanks a lot, it saved me a lot of trouble :3

That's awesome to hear. 🙂

RE: Brand new prusa mini: Z needs to adjust on every new print.

I contacted Prusa support and they told me the Minda actually has a thermistor like the Pinda on the MK3S. The only factor is the MK3S firmware has temperature compensation, and that feature is coming to the Mini next firmware release... Which is odd, considering the Minda is only a 3 wire sensor? Their solution was instead of preheating the Minda, was to keep it cool. I'll quote what live chat told me below.

Support: the issue has to do with the Minda probe, which sometimes is affected by the temperature of the bed, this is being fixed in the next firmware release
in the meantime, the issue can be avoided by raising the extruder 10cm above the bed before each print so the probe is away from the bed during preheat 

Me: A friend of mine is the one that referred me to Prusa and he mentioned something about a thermistor in the Pinda probe Is there a thermistor in the Minda probe?

Support: there is, but the MK3S has the firmware compensation for the temperature, which is the same being implemented in the MINI soon
for now, the best is to avoid heating the probe too close to the bed before printing, so the mesh bed leveling calibration is not affected

My advice is to add this gcode to the start gcode in PrusaSlicer printer settings > custom gcode
G1 Z100 F720
right after the the second line in start gcode

Maybe this, in addition to the heatshield mod I made, would be a solution? I'm going to print one myself, change it out, and calibrate to see if it works. The preheat wait time is a bit annoying. :p

RE: Brand new prusa mini: Z needs to adjust on every new print.

@skreelink

Well the thermistor will  be news to a lot of people here 😀 I'll be positive and say I think the support person must have got something confused (as the only other alternative I can see is that they deliberately mislead you). The good news is that (according to a comment on GitHub) they are hoping to build a release candidate for the next firmware version today, so we shouldn't have too long to wait and find out.

RE: Brand new prusa mini: Z needs to adjust on every new print.

The Mini currently lacks both hardware and firmware temp compensation. I doubt that this can only be solved by adjusting the firmware. Since the MINDA of my Mini was defective, I am currently using the probe (PINDA V2) of the MK3. So the Mini would be ready for the compensation. May I be corrected.

RE: Brand new prusa mini: Z needs to adjust on every new print.

@skreelink

An alternate reading of that message (speculation)- new Minis are coming off the line with a 4-wire temp compensated probe. The firmware isn't done yet, but when it is, they'll activate it. Presumably owners with the old revision Minda could swap theirs.

Does anyone with a newly delivered Mini happen to have a 4-wire Minda?

RE: Brand new prusa mini: Z needs to adjust on every new print.

Posted by: @amd20x6

@skreelink

An alternate reading of that message (speculation)- new Minis are coming off the line with a 4-wire temp compensated probe. The firmware isn't done yet, but when it is, they'll activate it. Presumably owners with the old revision Minda could swap theirs.

Does anyone with a newly delivered Mini happen to have a 4-wire Minda?

That would be a nice thing, but I would prefer to not have to pay for a feature that should have been included since the beginning.

RE: Brand new prusa mini: Z needs to adjust on every new print.

I think we would all prefer not to pay. At this point no one is saying you need to pay, it’s all speculation. 
Texy

RE: Brand new prusa mini: Z needs to adjust on every new print.

@skreelink

An alternate reading of that message (speculation)- new Minis are coming off the line with a 4-wire temp compensated probe. The firmware isn't done yet, but when it is, they'll activate it. Presumably owners with the old revision Minda could swap theirs.

Does anyone with a newly delivered Mini happen to have a 4-wire Minda?

Received the Mini less than a week ago and it shipped with the 3 wire M.I.N.D.A. probe.

RE: Brand new prusa mini: Z needs to adjust on every new print.

Someone posted that they are getting a V2 MINDA here, but now I can’t see the post 🤷🏼‍♂️
Texy

RE: Brand new prusa mini: Z needs to adjust on every new print.

Posted by: @texy

Someone posted that they are getting a V2 MINDA here, but now I can’t see the post 🤷🏼‍♂️
Texy

Yes, it was me but somehow my post disappeared... 

Anyway I have my Mini since July and i also am plagued by the constantly changing z offset depending on the temperature. I decided to talk to the support and they confirmed me that they are rolling a new MINDA v2 right now on all new printers. Support also send me the MINDA v2 probe as a replacement which should arrive tomorrow, so yeah let's see if they finally nailed the issues down!

RE: Brand new prusa mini: Z needs to adjust on every new print.

@wybielacz1

Will you report back your results? I don't want to bother support to send me a new minda if it will have the same problems.

RE: Brand new prusa mini: Z needs to adjust on every new print.

I don’t think it’ll work without new firmware though - did support say anything about that?

Texy