RE: MK3S experience leads to MK4 questions
Hi having similiar issue, i wanted to add that for a while i had to manually offset the Z height, to some -0.050, and after a while i realized that my heatbed is cooler than anticipated, set in the menu. So i did experiment after multimple measurements (with pyrometer, thermocouple and thermal vision camera) and i concluded that heatbed in my printer is 15-20 degrees cooler than it should be. So i change the setting of the heatbed to 100 C degrees, now it has around ~80, and i can print full plate PETG prints, and what is important there is no need to "fix" the load cell value, it works fine.
RE: MK3S experience leads to MK4 questions
@mixer3d, That's interesting. Are you going to contact Prusa about the heatbed temperature?
RE: MK3S experience leads to MK4 questions
Hi, yes i already in email exchange with them, waitin for reply :p
You can see photo from some fellow printer machine, and mine here: https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-hardware-firmware-and-software-help/heatbreak-calibration-failing/#post-693886
cheers
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I have to update with new information. I started to see the print head drive into the build plate on the right side while printing a purge tower. This made me question the flatness of the build plate. Something I was already inclined toward because of my years of MK3 3xperience. I started another tread to discuss the BML routines and further troubleshooting on my part with help from @rainer-2 identified a recurring misalignment between the two z-axis heights. This caused the right side of the x carriage to become gradually closer to the bed. I haven't' found the problem just yet but doing a z-axis calibration before each print mitigates the bed level problem. I'm adding it to this thread because it was likely a factor with my textured sheet squish complaints in this thread, especially when printing towards the right side of the bed. I still make a small -z adjustment for prints where I want the textured surface to be perfect, but with this z-axis calibration it looks pretty good without it. I've attached before and after pics to portray the effect of the z-axis issue. This was an embarrassing mistake for someone whose been making for 7 years, but there you go.
RE: MK3S experience leads to MK4 questions
The Z axis calibration should be done every time the printer is turned on. The reason is simple: the Z-axis screws are not self-locking, and when the printer is turned off, the motors do not hold anything in position and can rotate independently, and this can cause the X-axis to stop being perpendicular to the Z-axis and therefore parallel to the plane of the bed. This shift cannot be compensated by MBL because the inequality can be greater than the limits of MBL and the problem is in the world. So my recommendation is: either do not turn off the printer, or after turning it on, perform a Z calibration to balance everything.
RE: MK3S experience leads to MK4 questions
@miroslav-h4, Wow! Z axis calibration whenever the printer is turned on. Does Prusa recommend this? I never did this with my MK3S and never had any issues (as far as I know).
RE: MK3S experience leads to MK4 questions
Don't think mine has been done since I assembled it. It does regularly check the x and y but not the z.
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I agree with everything you just said and that the Z axis calibration should be done every time the printer initializes, but it doesn't. The MK3, only did it if it decided a z-axis problem existed during the BML routine, The MK4 didn't think anything was wrong even thought the bed mesh data demonstrated a 1.8 mm rise from left to right. I'm still surprised that real world experience hasn't accounted for this reality by mitigating it in the standard printer routines. What they have now only homes the z-axis to the build plate when it starts up.
It makes me wonder why not when I see so many folks seeking advice and showing pics that look just like the ones I posted. In my case the printer stay on all the time, and I've seen the misalignment occur between prints on the same day. What I added to mitigated was GCode tom move the z-axis move to the top after the first G28, and then added a second G28 to keep it happy. This works, but I think it should be part of the the default printer profiles provided by Prusa.
Good luck to us all.
RE: MK3S experience leads to MK4 questions
Check at power-up??? The MK4 automatically checks zero x and zero y and bed level as a standard procedure before it starts any print. Bed level is checked for the area where the print is going to be, in 9 to 30 points. There should be no need for manual intervention. If you need to make corrections nonetheless this can be done in the setup menu. When you think the first layer height is off check this value in setup, and also check first layer settings in the slicer.
The Z-measurement is done at a standard temperature of bed and nozzle. If you just loaded the say ASA filament and the nozzle is on print temperature, you will see nozzle temp is reduced before doing the z-measurement, and then increased again for the print. The nozzle is cleaned (wiped across the surface) just outside the left-forward print area. Do not forget to brush the nozzle from time to time.
The kit build instructions do not tell you to grease the spindles of the z-motion. However I strongly recommend to do this. Also from time to time send the Z-carriage up to max from time to time to spread the lubrication.
Note the printer control has no feedback on the position of the nozzle other than these initial zero's and can live only by the result of steps integration from that point.
RE: MK3S experience leads to MK4 questions
The Z axis calibration should be done every time the printer is turned on.
That sounds extreme and if this was a wide-spread issue, we should hear a lot more about it. I suspect there's something else going on, maybe one of the z motors or the trapezoidal nuts. I'll be curious to know what Prusa support suggests.
RE: MK3S experience leads to MK4 questions
Yep, doing the calibration every time is excessive, but until I find out what's tweaked that's what one must do.
I reworked both z-axes today we'll see what happens. the trapezoidal nuts are brand new and seem perfect. I normally would have lubricated the z-axis threads, but as @efvee notes the Prusa notes say not to. I haven't contacted Prusa yet but may if I can resolve it in the next few days. Testing the motors seems like a bad time, but I'm game, if I have to
To @efvee, I would say everything said is correct, but does not work if the x-carriage is screwed. i.e. not parallel to the bed.
RE: MK3S experience leads to MK4 questions
@fabnavigator i will get new thermistor for the heatbed
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I use the MK4 for about 4 month now. Printing a lot on TXT-sheet with PETG. So far I did not have much trouble except the little dots from the autoleveling. Knowing this I have te be couscous to clean the sheets before starting a new print. Problem was that the autoleveling was leveling on the residu from the previous print. Then the first layer and bed adhesion went wrong. Thorough cleaning with a scraper is the answer for that. The dots never interfered with the prints themselves. They are so smal, you wil not see them in the print.
About X-axis calibration. Never did that after the initial calibration. It is not nessesary, maybe over time. There is something to take good care of, and that is the assembly of the X-axes, especially step 11 in the manual: https://help.prusa3d.com/guide/4-z-axis-assembly_431406#445447. I think when that is done incorrectly it will cause misalignment over the time and calibration is needed.
RE: MK3S experience leads to MK4 questions
well now .... factory assembled mk4 FW 5.1.2, in a prusa enclosure, only addition to the printer is a silicone sock .... I have been printing petg on the textured sheet for 3 months now, zero problems, perfect adhesion using IS and standard setups nothing tricky. the probing dots were more prominent early on but with firmware upgrades I might get a tiny smidge on the first 2 probes, the unit usually probes a much larger area than what is printing so even if it leaves a dot it has not caused any troubles. even with prusa PETG I find dry boxing for a few days before using results in less "drooling and stringing" and generally wait until is down to 15% or less humidity. the slight drool I get while waiting for temps to commence print either can be snatched with a small knife blade, but I generally don't fret over it as it sticks to the prime line, and have only had one print where the drool dropped into the first layer but I let it keep rocking and it turned out fine.
RE: MK3S experience leads to MK4 questions
@Lynn totally agreed. There's some wiggle-room in the x-rails, and you can adjust by hand when the power is off. You can use calipers to ensure the x-rail is parallel with the bed, but a simple block may do also.
BTW I had found I fixed the Z motors too tightly on building the kit. The image @hesbas shows is very relevant, but note that the 'wrong' case in general should be solved by unwinding the right Z-motor screws and not by tightening the ones on the left. The Z motors should hang tight in their screws but not more than that. There's rubber plates above them and they should have room to do their work.
RE: MK3S experience leads to MK4 questions
Hi, @fabnavigator i wanted to update, that i replaced the hotbed thermistor and now temperature difference is around 10 degrees (i tested only with pyrometer, and thermal vision camera) but before was +/- 15-20 ... now at least when i set the bed temp. 90 i have 85, before to have bed temp. 85 i had to set 100... Anyway i can for now, nad still have some range to tweak for other material.
RE: MK3S experience leads to MK4 questions
@mixer3d, that's good news. I received my MK4 kit today and started building it. I'm looking forward to seeing some of this on my printer.
RE: MK3S experience leads to MK4 questions
Just found this thread today. Coming from a MK3S+ to a MK4 with the Textured Steel Sheet and printing only PETG I find it hard to believe that only in this post the PETG issues with the Textured Steel sheet are discussed.
I loved the PETG surface finish of my MK3S+ and the MK4 does not even come close to competing with the results the MK3S+ delivered.
On the MK4 with all prints the first layer lines are always so much apart, that the surface has no uniformity and the individual lines are very noticeable from all directions with a bit of light coming from one side.
In Prusa Slicer under printer settings the Z-Offset can be adjusted for the MK4 somewhat permanently, so that the offset is backed into the Gcode permanently.
With an offset of -0.15 i get a uniform somewhat comparable surface finish on the MK4 to the MK3. With smaller prints 5 to 5 to 5 centimetres this works fine. On bigger prints the nozzle sometimes builds up residue so artefacts and defect rate is a lot higher.
Right now i am testing with a -0.06 offset again, but I am underwhelmed of what Prusa delivered with the MK4. Never wanted but now considering switching to Bambu... - for the MK4 the textured steel sheet should not be sold and also not advertised to be used with PETG.
Also changing the first layer speed to 25 mm/s seems to have improved the first layer.
RE: MK3S experience leads to MK4 questions
I've been printing for about a week, and I am very happy with the MK4 kit I built. Having built an MK3 three years ago I was able to appreciate all of the improvements. Much of it is a similar design, but almost everything has been improved.
I only print in PETG and PLA and so far have only used the satin sheet I bought for my MK3s. Perfect results every time. I was worried about the PETG oozing out of the nozzle like on my MK3S. Zero oozing with the MK4. The MK4 keeps the temperature low during bed leveling and only comes up to temperature right before printing.
The load sensor seems to be doing its job well enough for what I've been printing. I haven't bothered to print out a single layer over the entire bed to see how well it really can do.
I haven't seen any filament debris on the bed so there has been no need to clean the bed after a print finishes.
I keep my filament in a dry box which has a PTFE Teflon tube while I'm printing and it works fine with the MK4. I've had no filament twisting issues.
The only thing I haven't tried is printing PETG on the textured sheet. That's because I sold my textured sheet when I sold my MK3S. I'll probably order one soon because I really like the surface you get. Once I do, I'll write up my results.