Prints are very brittle on the Z axis
I've been careful not to call this a layer adhesion problem because when I search for layer adhesion I find lots of people talking about problems with the first layer adhering to the bed!
I have an MK3 that is a little over a year old. I primarily print in black PLA, and just recently the prints on the MK3 have taken on a very matte appearance, whereas the same parts with the same PLA appear glossy when printed on my newer (less than 6 months) MK3S. The matte/glossiness of the parts alone wouldn't bother me, but the matte parts printed on the MK3 are also very brittle. Thin walls on parts printed on the MK3S are difficult to break by hand, whereas on the MK3 they break with very little force applied. I've done multiple cold pulls, and I'm pretty sure the hot end on the MK3 is about as clean as it's going to get. It's the same PLA (I've opened up a new spool as well, thinking maybe it was moisture content related), the same printed objects, and in some cases, the exact same gcode. I have upgraded the nozzle on the MK3 to the E3D to the nozzle X. I've ordered a new pre-assembled hot end from E3D (I want to do the MK3S upgrade anyway), but is there anything else I should be trying short of changing out nozzles, heat breaks, etc.? I'll admit I'm taking the easy way out because of the impending MK3S upgrade, but it's something I'd like to be able to troubleshoot and fix going forward, so looking for suggestions to try between now and when the new hot end arrives! Thanks!
Best Answer by rmm200:
Maybe your thermistor in the MK3 is off? Which profile are you using?
I would try raising the nozzle temperature ten degrees at a time and see how it does. Maybe turn the print fan down - or off.
Stop on or before you get stringing - and don't go crazy with this. Fires not allowed.
You might have to back off the Nozzle X and try it with standard brass.
RE: Prints are very brittle on the Z axis
Definitely do a PID tune at your print temperature.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
RE: Prints are very brittle on the Z axis
Maybe your thermistor in the MK3 is off? Which profile are you using?
I would try raising the nozzle temperature ten degrees at a time and see how it does. Maybe turn the print fan down - or off.
Stop on or before you get stringing - and don't go crazy with this. Fires not allowed.
You might have to back off the Nozzle X and try it with standard brass.
RE: Prints are very brittle on the Z axis
@bobstro
That's a really good call. I've done this before with my CR-10 (wasn't the issue, different story), but the MK3/MK3S have been so bullet proof for me I had totally forgotten about that kind of troubleshooting! I'll do that and report back. Thank you for the suggestion!
RE: Prints are very brittle on the Z axis
@robert-rmm200
I'm really hesitant to compensate with slicer settings unless I absolutely have to. I'm producing structural parts for sale, so a lot of the gcode is "tuned" and I'd hate to have to maintain different settings for different printers. I do change the profile in PrusaSlicer from "MK3" to "MK3S" for new gcode files, but this is more to keep the MK3S from beeping at me about using gcode meant for an MK3 than because of any noticeable difference in prints.
I don't want to be one of those guys who says "But I haven't changed anything so it can't be that!", but I would like to make sure I've exhausted the list of potential causes related to the MK3 specifically rather the compensating in software.
Thank you for the suggestion, and definitely something I'll look at if it comes to it!
EDIT: I appreciate you're probably not suggesting I stick with whatever changes I make in the slicer, that it's probably just a way of figuring out if it's the thermistor or not!
RE: Prints are very brittle on the Z axis
Between any two printers how accurate or matched are the thermistors of the two. If they vary in age buy a significant amount the thermistor are unlikely to be reading the same values. My first thermistor in my Mark 3 began giving lower Temps until it failed after about a year and 6 months.
RE: Prints are very brittle on the Z axis
So the PID tune doesn't seem to have made a difference. So if I'm reading these other suggestions right, it's a possibility that the thermistor in the hot end has degraded and is showing a lower temperature than the block actually is?
I guess the only way to test this is to set the nozzle to 210 (as per the thermistor) and measure it with another tool (my infrared thermometer doesn't seem up to this task)?
Or I could raise the nozzle temperature in the slicer, knowing that the thermistor is actually reading a lower temperature than the nozzle actually is, thereby setting the nozzle to the desired 210?
My MK3 is showing 581 days of total print time (which isn't actually possible unless Prusa is burning them in for months). So based on Jerry's comment about a failure after 1 year and 6 months, the thermistor could be on it's way out. Does it make sense to try a new thermistor at this point? At £7, it's a lot cheaper than a new hot end!
RE: Prints are very brittle on the Z axis
You have two printers. Use your digital thermometer on both.
Actual reading does not matter - but they should read the same if both are set to 210.
RE: Prints are very brittle on the Z axis
@robert-rmm200
I know what you mean, but this infrared thermometer (a cheap Amazon point and shoot one) isn't accurate enough spatially to measure a relatively small hotspot like the nozzle or block. It's fine for a nice big area like the heated beds (which is what I got it for). There is too much variation to compare the two hot ends (readings from 21 all the way to 127, but no where near the 210 it should be). If I had a temperature probe (the kind with a contact tip), I could measure the temperature across the two hot ends to gauge whether they were getting to the same temperature or not. I might pick one up anyway, I could always use another tool!
RE: Prints are very brittle on the Z axis
@robert-rmm200
I've just completed a print of the same part where I raised the temperatures by 10 degrees in the slicer as per your reccomendation. Aesthetically the parts are much closer to the MK3S prints (but still not quite as glossy, maybe half way there), but they are MUCH, MUCH, stronger than they were (I can no longer break them by hand).
I can stand to have this printer down for a while (this is why I got the second printer anyway, and I'd be surprised if the new thermistor isn't here by the weekend or early next week anyway), so I'm not planning on slicing new all gcode for this printer yet, but is there anything else I should be looking at between now and when the thermistor gets here?
I found this little "experiment" very promising, and makes me think I'm on the right track, so thank you very much for that!
RE: Prints are very brittle on the Z axis
So I've just finished swapping out the thermistor and ran the PID Calibration. The print seems incrementally better, but still not as strong or as glossy as the MK3S prints. It's better than earlier prints from the same printer with the original thermistor, but not as good as the test print where I raised the print temp by 10 degrees.
Ill try more test prints tomorrow at higher temperatures just to see if there is further improvement, but if the thermistor isn't the problem, then what else could it be?
RE: Prints are very brittle on the Z axis
My experience with nozzle x is that you need to increase temperature by around 10 degrees, sometimes even 15 degrees compared to a regular bras nozzle.
If you part comes out mate then that is most likely due to temperature being too low.
Note that a harder nozzle will have a harder time to transfer enough heat in to the filament as it passes by for it to melt properly in its way out, this is why you almost for sure need to increase temperature by about 10 degrees compared to normal when you use a nozzle x.
On my MK3S i print my Prusament PLA at 225 degrees instead of 215, if i use 215 or lower the print at the start may work but then later depending on the model i may get extruder clicking and under extrusion, and this goes away when i slow down printer a lot (gives filament more time in nozzle to melt) and/or when i increase the temperature a bit.
Also if you haven't already, get one of those blue silicone socks
RE: Prints are very brittle on the Z axis
Also, i forgot to say, too low temperature will cause layer adhesion problems and make it very easy to separate the part along the layers.
This is exactly what happened to me a while back, printed tracks for an rc tank i found on thingiverse.
Printed the tracks and it took probably 2-3 days to get it all printed and it came out looking good, except that once i started to use it parts of the track separated and track got useless (nubs used to move track forward flew off)
After investigating it, i found i could easily pull off the nub along the layer lines, so had to start playing around with temperature and other settings.
All this was with nozzle x and before i realized how much i had to increase temperature to get a good print.
RE: Prints are very brittle on the Z axis
My experience with nozzle x is that you need to increase temperature by around 10 degrees, sometimes even 15 degrees compared to a regular bras nozzle.
If you part comes out mate then that is most likely due to temperature being too low.Note that a harder nozzle will have a harder time to transfer enough heat in to the filament as it passes by for it to melt properly in its way out, this is why you almost for sure need to increase temperature by about 10 degrees compared to normal when you use a nozzle x.
On my MK3S i print my Prusament PLA at 225 degrees instead of 215, if i use 215 or lower the print at the start may work but then later depending on the model i may get extruder clicking and under extrusion, and this goes away when i slow down printer a lot (gives filament more time in nozzle to melt) and/or when i increase the temperature a bit.
Also if you haven't already, get one of those blue silicone socks
This is really helpful, thank you! Since my last post, I've tried the silicone sock, and there was a slight improvement. I've also ordered some brass nozzles to try going back to those. I know it probably seems silly when all I have to do is raise the temperature by 10 degrees, but it's important to me that I isolate the root cause of this. I spent a lot of time with cheaper Chinese printers taking more of a scatter-gun approach to troubleshooting, so I'd like to be more comfortable with the MK3/MK3S then I was with my CR-10, especially if I'm planning on increasing my printing capacity down the road!
RE: Prints are very brittle on the Z axis
Just finished a test print after installing a new brass nozzle, and all is right with the world again. I marked the answer from @robert-rmm200 as "Best" because it was the first mention of the nozzle, but thank you very much to @torbjorn-j3 and everyone else who helped out! I'm going to feedback to E3D, as they should probably mention this regarding the Nozzle X.