RE: Any way to change the Z Offset?
Why they won't give you a Z-offset calibration on the machine really is baffling.
I found, now that I have 4 MK4 machines, that one of them was really far off, but at some point I loosened all of the screws that attached to the load cell, and all of a sudden it worked much better. It may be worth removing the front fan, loosening up all of the screws, and tightening things down again, maybe not quite as tight, and see if that helps.
I also had one unit that just wouldn't level correctly, even after trying this. I ordered a new load cell part and replaced it, which solved the issue.
RE: Any way to change the Z Offset?
Why they won't give you a Z-offset calibration on the machine really is baffling.
I found, now that I have 4 MK4 machines, that one of them was really far off, but at some point I loosened all of the screws that attached to the load cell, and all of a sudden it worked much better. It may be worth removing the front fan, loosening up all of the screws, and tightening things down again, maybe not quite as tight, and see if that helps.
I also had one unit that just wouldn't level correctly, even after trying this. I ordered a new load cell part and replaced it, which solved the issue.
The weird part is I have to adjust the Z-height up (so the nozzle is further from the bed) and I would have thought a malfunctioning load cell would be the opposite. Next time I need to do maintenance I'll try the screw trick, thanks for the tip! At present, it's beautifully consistent with that 0.035 offset which is why I'm apprehensive about Prusa saying it's an issue with the load cell (which I've already replaced once). If there's just variance in the load cells, that seems like an even bigger reason to be able to adjust the z offset.
I haven't used RTOS outside of some basic examples from the main FreeRTOS tutorials, but I might just grab the firmware and see if I can sort out what it would take to save and load the z-offset setting. In Arduino that would have been pretty easy so maybe it won't be so bad with the MK4 firmware/RTOS. If it's workable then I can maintain a forked version and at least if I can save the value I can use the fork on my printers and then just have to maintain it. And I can submit an actual PR to the main firmware, though it seems unlikely Prusa's ultra-stubbornness would cause it to be accepted.
RE: Any way to change the Z Offset?
Self update fail but I forked the firmware and started digging around and found some interesting things:
https://github.com/prusa3d/Prusa-Firmware-Buddy/blob/8a788ae4e23d0fc79cf15c4c2dde05168b95b6bb/src/gui/dialogs/liveadjust_z.cpp#L88
https://github.com/prusa3d/Prusa-Firmware-Buddy/blob/8a788ae4e23d0fc79cf15c4c2dde05168b95b6bb/src/common/SteelSheets.cpp#L50
If I'm reading all that right, it looks like Z-offset might be getting saved in cases where there are multiple sheet profiles. Sheet profiles exist for the MK3.5 it looks like but not the MK4 (at least it's not enabled on mine and I believe I have the latest firmware). I'm gonna keep poking around to see what I can find.
RE: Any way to change the Z Offset?
Still digging but after poking around the firmware it sounds like Prusa isn't being all that transparent in my opinion. I found some static_assert lines which causes the build to stop, such as:
#if (HAS_SHEET_SUPPORT())
static_assert(!HAS_LOADCELL(), "This caused major issues on XL.");
// Sheet[0] is used both as default sheet and as storage for z offset set by LiveAdjust Z. XL have had and issue that caused the tool offset calibration to fail due to aforementioned z offset. Uncalibrated value being float:max caused z offset to be set to 2 mm which lead to printer missing the calibration pin by almost 2 whole mm. This happens to all XLs that do not have a LiveAdjust Z value set and therefore use the default value.
That mentions the XL but it still bails when trying to build the MK4 firmware. Less important is that it fails and more important is the message above. It implies at least at one point they *were* storing live adjust Z values, just doing so via sheet profiles. This matches what I'm seeing in the firmware.
I'm trying to see if I can get the sheets feature working because all the load/save value stuff already works there instead of trying dig through all the abstraction layers for loading/storing for the EEPROM.
RE: Any way to change the Z Offset?
That was an adventure. While I haven't tested this yet (doing so requires breaking the warranty/custom firmware bridge on the mainboard and I'm not sure if I want to do that yet), I cobbled together I think what would work. It would probably need to get wrapped in ifdef for the appropriate printer configs which I haven't done but for the curious:
https://github.com/prusa3d/Prusa-Firmware-Buddy/pull/4269
Of note too, issue 3306 has been assigned to an active Prusa dev (CZDanol) and they mentioned discussing this in a dev meeting today. So here's hoping!
RE: Any way to change the Z Offset?
Wow, this is yet another huge downgrade with the MK4 (coming from the MK3). The notion that the Z-offset would be linked to a specific print rather than the machine is conceptually incoherent. There are good reasons every major 3D printer I'm aware of allows you to adjust this at the firmware level. As others pointed out, there are differences based upon the print sheet being used, and many other cases where re-slicing makes no sense. For example, I just switched to a 0.25mm nozzle and cannot for the life of me get a clean print. The big problem is that without any way to live-adjust the Z axis, the best we can do is guess what the correct setting is. What previously took a couple seconds to figure out now takes hours and hours of trial and error.
RE: Any way to change the Z Offset?
Wow, this is yet another huge downgrade with the MK4 (coming from the MK3). The notion that the Z-offset would be linked to a specific print rather than the machine is conceptually incoherent. There are good reasons every major 3D printer I'm aware of allows you to adjust this at the firmware level. As others pointed out, there are differences based upon the print sheet being used, and many other cases where re-slicing makes no sense. For example, I just switched to a 0.25mm nozzle and cannot for the life of me get a clean print. The big problem is that without any way to live-adjust the Z axis, the best we can do is guess what the correct setting is. What previously took a couple seconds to figure out now takes hours and hours of trial and error.
A new bed mesh is created at the beginning of each print at the machine, it's not associated with the gcode file. It doesn't matter which sheet you have installed because it's going to probe it before the print.
Most issues people have with the first layer are because they don't keep the nozzle clean. Any buildup or residue on the nozzle will make the bed mesh off.
Between my different machines I've found the bed mesh consistent. The only time I've had to make adjustments was with higher temp stuff like ASA and pccf. With those I've found the nozzle is usually too close. By setting a z offset in the slicer you can compensate.
So as I see it you have 2 options, you can set a offset in the slicer, or you can press and hold the control knob during the first layer. This will allow you to change the live Z for that particular print. This value is temporary as when the printer recreates the bed mesh on the next print it will be overwritten.
RE: Any way to change the Z Offset?
inzania is right, if hyperbolic. I don't view it as a huge downgrade since overall the MK4s is quite a bit better than my MK3s. This is one exception (as-is TPU printing which I do find is a bit of a step backwards compared to the MK3s). I still use MK4s and MK3s in my print farm. I'd maybe consider these trade-offs, though the stubbornness of Prusa of the live-adjust is rather annoying.
I solved it by putting my offsets in the slicer. This does work, and has been consistent across multiple MK4s and my XL, though I have like 600+ combinations of models I need to make which has me nervous I'll end to end up rexporting a bunch if the behavior changes. This is why I want Live-Z to be configurable.
I see your points Brian but I disagree with that being the acceptable solution. Those are workarounds. It's all we got at present but they do have caveats. Whether they impact you is immaterial - they impact some of us and I just don't see any downside to adding Live-Z saving into the firmware as we had it for the MK3 and as do basically all other printers I can think of offhand.
RE: Any way to change the Z Offset?
inzania is right, if hyperbolic. I don't view it as a huge downgrade since overall the MK4s is quite a bit better than my MK3s. This is one exception (as-is TPU printing which I do find is a bit of a step backwards compared to the MK3s). I still use MK4s and MK3s in my print farm. I'd maybe consider these trade-offs, though the stubbornness of Prusa of the live-adjust is rather annoying.
I solved it by putting my offsets in the slicer. This does work, and has been consistent across multiple MK4s and my XL, though I have like 600+ combinations of models I need to make which has me nervous I'll end to end up rexporting a bunch if the behavior changes. This is why I want Live-Z to be configurable.
I see your points Brian but I disagree with that being the acceptable solution. Those are workarounds. It's all we got at present but they do have caveats. Whether they impact you is immaterial - they impact some of us and I just don't see any downside to adding Live-Z saving into the firmware as we had it for the MK3 and as do basically all other printers I can think of offhand.
I think the issue with storing the live Z is temperature related. Even on my MK3S I have to create separate sheet profiles for printing higher temp stuff for the same reasons. The higher temps make the nozzle and bed thermally grow more and thus the need for change in offset. So for example I have multiple satin sheet profiles, one for ASA and another for PLA/PETG, although PETG is borderline being too close as well for sharing the same offset as PLA.
What would be nice if to be able to set different offsets for different temperatures. That in combination with the nozzle probing seems like it would work well.
I'm not sure what the challenges would be involved with implementing that.
Put in a GitHub request, although I'm willing to bet one already exists.
RE: Any way to change the Z Offset?
There is a GH request (see above).
RE: Any way to change the Z Offset?
I now have 6 mk4s machines. All of them print too close with PLA settings, and all of them are slightly different. I have a 0.02mm offset in the slicer, which gets them all close, but I really wish we could just adjust each machine individually. One is always about 0.05 too close, and I can reliably adjust by that amount to make it perfect, every time. The problem isn't always the nozzle (and with recent firmware updates, I haven't found dirty nozzles to impact it at all). I actually replaced the part with the force sensor on one machine because it was reliably off by a lot, every time.
It's not an unreasonable ask for a z offset for each machine, to adjust for the quirks of the individual sensors in that specific unit.
RE: Any way to change the Z Offset?
I have 2 (with a Core One hopefully getting here eventually...) and an XL. The MK4s and XL all seem to work better with a Z offset set in PrusaSlicer of 0.035. I don't use this all the time - only when I'm printing something where the bottom layer is visible.
The fact that they are all the same tells me we should have access to tune this without having to run custom firmware or set slicer params.
I hadn't looked at the bug report in a while ( https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/3306) so I pulled it up and, interestingly, 0.035 is what another user found too. Might be a coincidence. I arrived at that value after printing first layer tests, but is interesting nonetheless!
RE:
So as I see it you have 2 options, you can set a offset in the slicer, or you can press and hold the control knob during the first layer. This will allow you to change the live Z for that particular print. This value is temporary as when the printer recreates the bed mesh on the next print it will be overwritten.
Hmm... I had read that this was possible online but I cannot seem to get it to activate during my prints (I hear a beep when I hold it down, but the screen does not change). I'll try again.
FWIW, I'm very familiar with the other debugging you've described. I've been 3D printing for 5+ years and have built my own printers from spare parts, as well as contributed to code to firmware repositories and gcode interpreter software repositories. I'm frustrated because the MK4S was supposed to be my "splurge" printer that "just works," yet it's currently the least reliable of any of them.
Posted by: @m00dawg
inzania is right, if hyperbolic. I don't view it as a huge downgrade since overall the MK4s is quite a bit better than my MK3s.
If I seemed hyperbolic, it's because my MK4S was mostly unusable for about 5 months after I bought it due to an acknowledged firmware bug with the MMU (overcurrent error), which was only corrected by Prusa support a couple weeks ago (I was emailing back and forth with them and root-caused the issue for them).
The reason I find the lack of a firmware Z adjustment odious is because I am constantly using different filaments (I rarely use any kind of basic PLA), and live-adjusting the Z offset is a daily part of my workflow with all of my various printers (I rarely print the same thing twice). In my experience, it is very normal to need slightly different offsets for different filaments. Even when using the same basic material, different brands sometimes require fine-tuning that is much easier to do in real time than going back-and-forth with the slicer. And a smooth vs. textured sheet behaves differently as well (I understand it recreates the profile, but again I find that the two require different offsets to achieve good results).
RE:
Sorry, old post in this thread, but... see below
Hi Vladimir, I sliced an object twice. One with an offset of -0.03 (left in screenshot) and one with an offset of 0.3 (right). The first G1 movement is changed by this offset - the left is G1 Z.017 and the right one is G1 Z.5. And the printed objects behaved as expected: With positive z offset there a gaps between the lines.
Interestingly, the purge line is not modified by this - it's in both cases Z0.2.
The the offset is working - so the question for me remains, of this will be the same for all mk4 or should it be a feature for an individual printer.
Prusa Support told that this z-offset setting does not matter on mk4. My delta is around 0.05. Cleaning the nozzle before printing is not easy on mk4, since the nozzle is not hot enough for this when its steady, and it start moving to the home position when it is hot
It's good to see some empirical evidence of how the z-offset in PrusaSlicer works. I'm going to assume for the moment that the "the left is G1 Z.017" is a typo and should be G1 Z0.17 (0.2 - 0.03 = 0.17)...
I remember on my MK3(S+) there was a firmware enforced minimum first layer height of 0.15mm. If the g-code had a first layer height of less than 0.15mm the first layer would still be printed at 0.15mm and be under extruded for the actual printed layer thickness because PrusaSlicer calculated the extrusion amount based on less than 0.15mm layer height. It makes sense that this limitation is enforced before the live-z offset was applied on MK3 series, but I don't have confirmation. I know the Buddy-based firmware (MINI, MK4 series, C1, XL) is a completely different codebase to the Rambo firmware (MK3 series), but until I know for a fact otherwise I'm conservatively expecting the same 0.15mm first layer thickness to have been carried over. I've never done a firmware dive before so I'm not sure where (in either codebase) to look.
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RE: Any way to change the Z Offset?
Yep, the ideal option is to have multiple build-plate options as we had on the MK3 with different live-Z's. There's some references to this in the firmware so Prusa was working on this at one point.
Since my last post, my One did arrive and I noticed the stock settings seem to work well for PETG and a textured build plate. This makes some sense since I recall using a lower Z height with textured build plates on the MK3. Since there are no concept of build plates on the 32-bit platform currently, this makes sense why I find it's too low when printing with smooth/PLA.
Solving this in the slicer "works" but if that value ever changes, having to re-export hundreds of models sucks and is the main reason why I'm a vocal advocate of having a way to save live-Z settings.