MK3S experience leads to MK4 questions
I owned a MK3S for over three years and was very satisfied with its performance. After the Christmas rush of 3D printing I sold it, with the intention of buying an MK4.
I've been doing my research, and have some concerns about the automatic first layer feature. I never had much of an issue setting my first layer height, but sure, I can see it as a nice feature.
I tend to print with PETG on the textured sheet, and once the nozzle gets to temperature, filament slowly drips from the nozzle. I'm not sure if everyone has this problem, but I did. I learned to live with it. I would move the extruder up to about 160 mm after a print. As the next print started and the extruder slowly moved down to do the bed leveling I would pluck off the filament that was hanging from the nozzle. Sometimes I only had to wipe the end of the nozzle with a balled up Kimwipe. On rare occasions enough filament dripped out during bed leveling to leave anything on the sheet. If it did, I would quickly wipe any tiny blobs off the sheet with my Kimwipe. The end result was always a perfectly clean sheet when the print started. I knew from experience that even a small blob could result in a blemish on the bottom of the print, which many times was the surface that I wanted to look perfect.
My primary concern is that if PETG drips out of the heated nozzle on the MK4, and I don't get the tip of the nozzle clean enough, how will the Z-height get set correctly?
I also read with the MK4 that small filament blobs can end up on the sheet during bed leveling. Some have commented that it's no big deal, but I disagree if they end up under my print. On the KM3 the entire bed was probed, so you had a chance to quickly give it a wipe if necessary while the print head was moving around the large area. WIth the MK4, it's only probing under the print, so there isn't going to be a chance to do that.
A secondary concern is that the load cell sensor reading will be affected by the tension in the filament source. I keep my filament in a dry box which has a PTFE Teflon tube. On my MK3S I load the filament and the PTFE tube just barely goes into the top of the extruder. The tube (with the filament inside) is stiffer than just filament. The MK3S seems to handle this additional load without a problem, but it doesn't have a load cell sensor.
Finally, I've read about filament getting twisted as it goes through the extruder. That could be a bigger problem when the filament is inside of a PTFE tube.
So, are any of these real concerns, or am I just being silly? Worrywart is my middle name.
RE: MK3S experience leads to MK4 questions
It cleans it's nozzle prior to the bed sensing and again prior to starting the print, it has never caused me a problem with the occasional dots after leveling, if the print goes over them you don't see them on the print as they are so small, if they are left there until the next levelling then the process will detect an anomaly and remeasure a tiny amount away.
I have done a number of prints from a drybox sitting on the enclosure via a ptfe tube and it has never been a problem.
RE: MK3S experience leads to MK4 questions
I tend to print with PETG on the textured sheet
This has not been the seamless experience I was hoping for. I found that on my two Mk4s I need to manually adjust the z level by about -0.02 once the print starts to get good adhesion. PLA seems to be fine.
I didn't find oozing to be much of a problem. You can still clean the nozzle (if you want to, you can add end gcode to raise the nozzle higher than default), and you can still use a wipe to remove filament from the bed while the bed is heating up after leveling. (I have very rarely actually had any dots on the bed). I'm not sure what to think about the initial nozzle cleaning procedure the printer is going through. It works with PLA and PETG and fails routinely with PC-CF, unless you quickly pull off any oozing filament (so it makes it a manual cleaning).
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: MK3S experience leads to MK4 questions
@jp-guitars, I would be interested in some more detail regarding the nozzle cleaning. The Bambu printers have a rubber nozzle cleaning station, the MK4 doesn't. Can you link to a video that shows how this works?
@fuchsr, That's disappointing about the PETG Z-height being off. I assume that there is no way to do a manual Z-height like we did on the MK3S. No setting to turn off the automatic feature. In terms of the oozing, as long as there is an opportunity to manually wipe the nozzle, I guess that is acceptable.
Thank you both for your responses.
RE: MK3S experience leads to MK4 questions
It basically prints a line on the front left of the bed so that any ooze gets deposited there. I will try and make a video in the morning.
By the way, most of my prints are PETG on the satin sheet and I have had zero problems with Z height or adhesion, only issues I've had are with TPU which seems to decide at random to stop extruding. I'm not experienced at all with TPU so need to learn a bit more to figure out how to resolve that.
RE: MK3S experience leads to MK4 questions
@jp-guitars, Thank you. I look forward to seeing that video. I have a satin sheet and can use that when I print PETG. How well does the PLA adhere? I've had a bear of a time getting it to stick to the smooth sheet with my MK3S. Lots of cleaning was necessary unless I had lots of surface area on the bed. That's why I went to PETG with the testured sheet. Perfect every time.
RE: MK3S experience leads to MK4 questions
I will echo the above comment that any (very few in reality) tiny dots left from probing can easily be found and cleared after probing while the nozzle is heating up. I also mostly print PETG, primarily small designed parts and jigs for work that require fairly accurate dimensions. I do check and clean the nozzle before each print simply on principle and to minimize any chance of problem. I'm not doing 'production' printing though, so taking an extra few seconds for a quick check/clean is not a bother at all.
Regarding the filament twisting...I did have a problem with it initially on our kit built Mk4. My 11 yr. old son did almost the entire assembly and may not have gotten everything perfectly straight. Just to be certain though (since I was getting perfect print quality otherwise) I reprinted the parts that hold the rollers against the extruder gears (following the advice of this forum), and swapped them out myself, being sure they all went together as straight as possible. I've since been printing without any twisting whatsoever. It seems that very few people have this problem, and if you do end up with it, the printed parts are small and the replacement takes very little time.
This is my first printer, and although I tend to be detail oriented, I didn't bring much previous experience with me when I got started with the Mk4. So far I've been very happy with the print quality, dimensional accuracy, first layer perfection etc.. Failure rate is almost zero other than my own silly learning curve slicing mistakes.
With the continued frequent releases of new BL printers, I've revisited my decision to buy a prusa, and in my particular use-case I continue to be happy with my choice. Philosophically I cannot get comfortable with the seemingly underpriced releases from BL, and their unwillingness to provide clear answers to the data privacy question when they know that's the main reason folks are still avoiding them. That silence speaks volumes to me, as did their X1E product that hints at the $ value they place on the data that they are collecting in comparison to the 'non-commercial' X1C. It all feels like the difference between the Ad and Ad-free Amazon kindle pricing. You can save a buck and you and your data become the product, or pay the actual price of the product up front. Clearly they have the technical capability to offer a truly offline option including FW updates and no chance of mystery log file uploads etc., and they are willing to lose customers to keep from offering it. If they change that stance, I and likely many others would reconsider them when the next printer purchase comes along.
As for now, I have very little reason not to be quite happy with the Mk4.
-J
RE: MK3S experience leads to MK4 questions
@jp-guitars, How well does the PLA adhere?
I think in the early days I had one problem caused by being lazy with cleaning, since then I run a scraper over the surface after removing the print, which normally does nothing, and then if there is a significant shadow from an earlier print or noticeable finger prints give it a wipe down with IPA which is probably every fourth or fifth print. For me it has been so reliable for both PLA and PETG that I am having to make a conscious effort to actually keep it clean
RE: MK3S experience leads to MK4 questions
This is all good information. Thank you.
On another note, I used OctoPrint 100% of the time with my MK3S. How do you all send jobs to the MK4?
RE: MK3S experience leads to MK4 questions
Prusa Connect. I actually prefer its UI over Octoprint, and for me it has the functionality I need for my small farm. Transfer speeds have become totally acceptable since the last few updates to firmware and slicer. Some features could be better, such as file management, but as I said, I'm pretty happy with it.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: MK3S experience leads to MK4 questions
Note to anyone reading in the future. I will zap the video in a couple of weeks to save space on my google drive
My very rough and ready video of cleaning : https://drive.google.com/file/d/1bMiETcshWLRdEokk1TuRNku8tZVNgP1J/view?usp=drive_link
- Up to 22 seconds is the first clean, note it removes the bit hanging from the nozzle
- Then there is a jump whilst it heats everything up, I would normally remove the bit that it wiped whilst this was happening but as I was trying to capture a standard start I left it
- Up to 45 it is probing the bed in the wipe area
- Up to 1:01 it is doing the wipe. It does pickup the hang from the first step at this point which is why I would have removed it but normally it wipes slightly away so misses it
- Last couple of seconds is starting the print
Hope this helps
RE: MK3S experience leads to MK4 questions
@jp-guitars, Thank you for posting that. It was very interesting. It doesn't make me feel great, I have to admit. The big blob that was hanging off the tip at the start was knocked off, but ended up getting picked up at the end and moved into the print area. I also saw a bunch of gray debris on the print bed. From previous prints I guess.All that being said, I saw opportunities to get in there and manually wipe. I was having to do that on my MK3.I wonder if Prusa will ever go down the route of adding a cleaning pad like the Bambu has. That seems to work very well from the videos I've seen.
RE: MK3S experience leads to MK4 questions
I too print primarily PETG, but on the textured sheet. PLA always works, give me a great squished first layer and prints very well, but PETG is a different story. I haven't tried the satin sheet on this printer yet, but the amount of effort I have to put into getting great PETG results on the textured is a little frustrating. But even with that hassle, the joy of not having to adjust the Z-off set when changing nozzles or build surfaces, can't be understated. I do manage to get the print quality I want even if I have to do more work that I was expecting.
I find Prusa link adequate for me needs, most of the time, but having interface like the Klipper UI would be much nicer.
RE: MK3S experience leads to MK4 questions
@lynn, Did you read what @fuchsr wrote above about printing PETG "I need to manually adjust the z level by about -0.02 once the print starts to get good adhesion"?
RE: MK3S experience leads to MK4 questions
I did, and his method works. Actually, I think his method may be the only way currently available for us to get a consistently filled in first layer with PETG on the textured sheet. I've been doing it myself and an exact-0.02 offset works some of the, but not always. There is just too much variation in surface height of the textured sheet, especially since the bed mesh routines are done at 170C and any amount of PETG left on the nozzle tip is going to cause an additional offset error. On the smoother sheets the total offset error is minimized because the sheets variations are small. I also agree with @fuchsr about the nozzle cleaning routing. If the plastic is not hot enough be smashed completely flat during that routine it does nothing useful.
This is an important issue for me because I print primarily with PETG and in many of my prints the textured surface is the presentation face, and having obvious lines showing on that face is not appealing to me.
So, my current process is to clean the nozzle for each print, stand at the printer to ensure nothing oozes out before the nozzle cools down, and keep my trigger finger ready to adjust the z offset. In order to get the offset adjusted without before your part starts to print, I recommend adding a skirt to each print jobs and adjusting the z-offset while it is printing. It's worth noting that the oozing problem is worse with PETG because of its inherent moisture vulnerability.
I plan on experimenting with over extrusion on the first layer to see if I can fill in the surface a little better when printing with PETG/ASA/ABS, on the textured sheets. But that will cause problems of its own.
Good luck to all of us.
RE: MK3S experience leads to MK4 questions
after thinking about for a few minutes, I have to recant the idea of playing with over extrusion on the first layer. It will not really work.
RE: MK3S experience leads to MK4 questions
@lynn, PETG on the textured sheet was always perfect with my MK3S (when I wiped the nozzle manually of course). I also use the textured surface as my presentation face. When I started printing I was using PLA, but getting it to stick on the smooth sheet (sticking to the textured sheet was a complete no go) required tedious cleaning with dawn. I switched to PETG on the textured sheet and never looked back. Except for the few times I needed PLA because of a specific color requirement.
I don't know how much moisture affects PETG oozing. I keep my filament in a dry box at all times and never let the humidity go above 20%.
You mention that the bed leveling is done at 170C. I guess that's to reduce oozing during that procedure. It probably also means that there is a delay waiting for the nozzle to cool down to 170C. Not an improvement over the MK3S that doesn't have that delay.
I started this thread to see if my suspicions about the MK4 were true. Mainly being that a nozzle that oozes filament is going to be an issue. Feedback I'm getting is confirming those suspicions.
Assuming that some of the Prusa people look at these postings, I would ask if we can get an option to do a manual z-offset like we had on the MK3S, at least until they are able to better address an oozing nozzle.
RE: MK3S experience leads to MK4 questions
For me printing PETG on the satin sheet on the MK4 is totally painless. No corrections needed. Load and print. The only time I had some oozing was when I had left the spool on the printer overnight. Keeping it in the bag together with a 'car' humidity absorber solved that.
RE: MK3S experience leads to MK4 questions
Yep, me too.
When you watched my video, I think you might have missed my comment about normally removing any ooze, there is a ton of time to do that if required. In reality it is a non event. You mentioned my bed was dirty, that was because it had not been cleaned for about five prints, but the print still came out fine.
PETG on the statin sheet just works
RE: MK3S experience leads to MK4 questions
When I printed PETG on the smooth sheet, it stuck a little too well. But more importantly, I like the textured look on my prints.
@jp-guitars, I did comment on your video: "All that being said, I saw opportunities to get in there and manually wipe".
@efvee, I always wondered if PETG oozing can be prevented. Any chance you know what humidity level you have in the bag?