MK4 Warping seperation  

RE: MK4 Warping seperation

I used to see this on my old Neptune 3 printer. I always put it down to draughty printing location (printer lived in my garage) so when I bought my mk4 kit, I also opted to get the enclosure bundle too. Printed something today and the temperature in my garage was 8deg, printed fine. 

so check to see if you are printing in a draughty area, it could be that your printed layers are cooling faster than the one you are laying down which causes it to lift. 

RE:

That is a very large flat model with sharp corners, which creates the most likely warping outcome.  There are a few things that you can do to help since it sounds like you have covered the basics of cleaning the build plate. Just make sure you don't touch the surface after cleaning.  

If this is a design of your own, and the design allows, you could round off the corners so that the corners aren't sharp.  If you need the corners to be sharp, you can model on some mouse-ears to the corners and give them a thickness of .2mm (or whatever layer thickness you are slicing at) and 5-10mm radius from the corners.  This will greatly increase the hold down force at the corners and then you can trim it off with razor when it is done printing.

If this is not your design, and you are not familiar with modifying models in Fusion360 or OnShape, you can simply add a brim of 5-10mm in the slicer, which will have the same affect as the mouse-ears but will surround the entire perimeter of the print.  This takes a bit longer to clean up and includes more waste, but it can be effective.

You can also slow down the first layer print speed.  I've gotten in the habit of printing the first layer at 30mm/s (slower than stock), which increases the adhesion as well.  This along with mouse-ears or brim should help quite a bit.

This does not replace the above advice to try and keep the print area warmer during the print.  If you can print at a time when ambient temps are higher, or after parking a hot car in the garage nearby to heat up the garage bit.  Each of these ideas can nudge your success rate a bit, and hopefully combined you can get it to stick perfectly.

p.s. Do yourself a favor and let the print bed cool off entirely before removing the final print from it.  If you pull it off warm the flat bottom of this print might warp the opposite way, lifting the middle into a slight dome shape.  This is especially true with large flat prints that are also thin.

-J

RE:

Also...you mention that you are only a quarter of the way through the print, but the photo shows solid fill over the entire surface.  Are you printing with 100% infill?  If so, that is also contributing to the warping forces. In most cases it is advised (for many reasons) to use infill percentages much lower than that (I use 10-20% on my larger flat prints) and then rely on the perimeter, top, and bottom layers to provide the strength.

*edit -  I just looked more closely and saw the areas of lower fill in your pics, so the solid fill must be part of your top layers.

-J

RE:

I want to thank you both for your feedback. I re-designed my part reducing the footprint by 60% thinking that would do the trick. In the end it was the brim that saved the day. Even with the brim you can see where it pulled up and even cracked the outer layer. I still have 2 more of these to print but I'm going to just move forward as is.

My lesson here is that it REALLY does not like sharp edges. When I look at the parts on my Prusa printer I see they have rounded or beveled all the edges. In my future designs I will do the same.

RE: MK4 Warping seperation

Sorry the cracking picture dident really come thru

RE: MK4 Warping seperation

Thank you for the follow-up and photos.  It looks like there might be some other tweaks that you can make to your slicing settings and possibly to the hardware as well.  The rippling and irregularity of that back wall of your part makes me think the hardware itself might need some attention as well.  On my kit Mk4, straight and consistently curved walls are much smoother than your photo.  I would check the grub screws and belt tension on your X and Y .

-J

RE: MK4 Warping seperation

Thank you TeamD3dp. Its a newly assembled kit and I tuned the belts using the app but I will re-check and make sure the grub screws (set screws here in USA) are good and tight.

RE: MK4 Warping seperation

I am so glad I found this thread. I though I was the only one suffering from that.

I got my mk4 just a two weeks before winter break. I put it together and run some prints. No issues at all. After I came back from the break I wanted to PLA-print a small piece I designed which is just 32x65 mm. The first layer looks ok. Plastic is well squished and looks just nice. However when the print is like 55% through (10mm high) the warping starts and the front part of the model deattachs from the build plate. No idea why.

I contacted Prusa support chat and we spend some time together trying various things, focusing mainly as if it was a 1st layer problem. After all suggestions I saw no improvement. These are things I tried:

• Another PLA. Nothing.
• Move the model to another spot on the surface. Nothing.
• I moved the printer to my home office (basement is colder). Nothing
• Tried a 3rd party build plate. Nothing.

Needles to say, I clean the build plate with IPA before each print.

Then I printed the model on another printer, a DIY printed powered by a Duet3 board. Printed at once, no issues whatsoever. In nearly 10 years and 11 3d Printers, I've never seen this warping with PLA.

Today I will run my last test before I contact Prusa support chat again. I will print with the same conditions except the build plate temperature, which I will raise from the Prusa-defined-profile of 60°C to 65 or 70°C. Let's see how it turns out.

I have the strong conviction that the bed thermistor must be somehow defective and the the reported temperature is wrong and the build plate is not warm enough. After much testing and thinking is the only explanation I have left, and that's what I want to test today by setting the temperature warmer.

I hope I can get it working. Otherwise I am thinking of sending the printer back and asking for a refund due to defective goods. After many years with DIY printers in which I always had to tinker with something, I was really looking forward to a printer that "just works". Unfortunately it has been everything but

I will report back, if anyone is interested

RE: MK4 Warping seperation

You mention using ipa to clean your bed.  It is generally understood here that ipa is not as effective as a full sink scrub with warm water and dish soap.  IPA will dissolve many things, but doesn't necessarily remove the oils.  Dish soap and warm water will.  Then, obviously don't touch the surface even a little before printing.

Did you slow down the first layer already? Have you tried glue stick or some other adhesion aid yet?

-J

RE: MK4 Warping seperation

Hi, looks very similar to the problems i have on my printer, in the end i realized that real temp. for the heatbed is 15-20 degrees lower than i set in the printer menu. For example i had a lot of failing big surface PETG prints, since i learned that i set the heatbed to 100 degrees (still in real it reach around 80+) and now i can print without issues... Trying to clarify the issue with support. So maybe try to test the temp. with thermocouple (from the bottom of the heatbed) or some pyrometer (i had thermo camera to confirm that my unit has failed thermistor/s).

RE: MK4 Warping seperation

You see, the mk4 is not the first printer I own. I really enjoy building printers and right now I have 9 on my basement. Some waiting to be sold. The thing is, I have been using IPA as a cleaning agent for many years and I've hardy had any issue. Contrary to Methanol, IPA has some capacity to clean a small amount of oils. Not much, but a fingerprint should be no problem.

For the last couple of days I have been trying to troubleshoot the issue as well, also together with the support agents, all of whom have shown incredible patience and willingness to help.

I also noticed that the temperature of the bed is significantly lower than the indicated in the display. Mind you, I've used a IR thermometer to compare, which is not the best thing. But just for kicks, here is what I found. On my mk, as the temperature was set to 60, the IR thermometer showed between 47 and 52. When set to 65, it showed around 55. In comparison, on the DIY printer I have sitting nearby, which uses an Aliexpress-found Prusa-like bed and build surface, when setting the temperature at 60, I read 65 with the IR thermometer. With that printer I can print without issues.

I did try to print on my mk4 with 65 and 70. Although it helped a little bit, I still experienced warping. Just for the sake of completion, I will follow @mixer3d footsteps and raise the bed temperature to 70 or 75 with PLA.

Meanwhile, I was told from Anabella from support that she would review my case internally and notify me per email.

I have until January the 30th to decide if I want a refund or not. If a solution is not found, I will sadly do so. I just want a printer I don't have to tinker with and so far, tinkering is the only thing I've been doing.

Posted by: @teamd3dp

You mention using ipa to clean your bed.  It is generally understood here that ipa is not as effective as a full sink scrub with warm water and dish soap.  IPA will dissolve many things, but doesn't necessarily remove the oils.  Dish soap and warm water will.  Then, obviously don't touch the surface even a little before printing.

Did you slow down the first layer already? Have you tried glue stick or some other adhesion aid yet?

-J

RE: MK4 Warping seperation

After reading your post I checked my heat bed. I used a laser IR reader and I know Prusa frowns on that but I took a reading in 20 different locations (I followed a grid) and averaged the temp of those 20 readings. I did this from 40c to 100c in 10 degree increments. I discovered 2 things. First the actual temperature is about 10 degrees cooler at 60c. Second the problem is linear, that its the greater the temperature the greater the difference. Its as if there is a mathematical error during the Analog to Digital conversion. 

I compensated for the difference in the settings of the Slicer program and printed again. This time there was still a tiny bit of separation but a vast improvement from what I started with.

If would be really nice if Prusa allowed us to calibrate the head bed / thermistor manually using external temperature readings. Maybe in the next firmware release?

RE:

Man, as a scientist myself, I do like and enjoy when one problem of this matter is analyzed so systematically. Well done on your analytical skills and thank you for the update. I am curious though if the problem is linear as you said (could be exponential??) or the actual temperature is always 10°C below the set temperature?. Anyway, not important and not for us to figure it out.

I have some updates on my own, which are as follows:

Seeing that raising the bed temperature was  improving the warping, I kept trying prints with the problematic part with different bed temperatures. Each print with a temperature 5°C above the previous print. I had to raise the bed temperature (set on the slicer) up to 80°C to have a satisfactory adhesion of the parts. Comparable to all my other printers and what I expected from the mk4 from the beginning. It did upset me I could not use the printer/slicer as a "no worries" printer, but at least it was usable and the print quality was top notch. I was printing good part of Saturday with this trick: just raising the bed temperature of the bed to the profiles embedded  with the slicer to 80°C.

Now, along comes a friend of mine with a mk3s+. For the first time since he owns the printer he flipped the steel sheet and voilà, warping. He washed both sides of the sheet with dish soap and water. No scrubbing with a scourer, just with the hand. He was able to print with a set temperature of 60°C. Following his advice, I also washed my build plate with dish soap and warm water. I tried a print at 60°C and I saw just minimal warping, but still some. Later on, comparing pictures, I could see the warping was equivalent to that I saw when I tried another build surface on the mk4. Then, today I tried a 4 hour print (including the problematic part) with the bed temperature set at 70°C instead of the known working 80°C. The print just finished a few minutes ago and I am happy to report that it looks awesome and, although some parts have a relatively large surface, no warping has happened. At all.

So to sum it up, as I have observed there seem to be two problems here: On the one hand, apparently the build plates need some rinsing with soap water before use and, on the other hand, some thermistors are reporting a lower temperature than it should be.

I still haven't heard from Prusa support, by the way.

I am looking forward to your follow ups!

RE: MK4 Warping seperation

So, I am not a scientist. I'm a controls engineer. What I observed with my readings was that the difference in temperature between actual and displayed when plotted out is a straight line (no curve). I attached the spread sheet if your interested.

RE: MK4 Warping seperation

Hi, just in case i did some documentation here: https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-general-discussion-announcements-and-releases/squashing-multiple-mk4-2-71-5-1-2-issues-and-horrible-top-layers/#post-692593

where i compared the thermistor from hotend, and the broken one had similar resistance 'in idle' room temp., and then i put it in a stream of hot air, and the resistance dropped quickly, the new one i got as a replacement was loosing the resistance slower, besides i did not observe anything else (picture of them is attached)

and here is a photo from my hotbed and some other fellow printer was kind to took the photo also, so you can check for comporision, i did the tests with pyrometer, termocouple and thermal vision camera. Support wanted me to check set and read for 50/80/100 degrees and in my case i had drift -15/-20 real temp. than on the display.

https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-hardware-firmware-and-software-help/heatbreak-calibration-failing/#post-693886

and empirical tests confirm my findings, i just set bed +20 and can print PETG without issues, this week i should get spare thermistor for the heatbad, so i will do some comparison also.

ah, one more thing, i had for comparision mini+ and there readings were +/-2 C degrees, (on mk4 -/+ 15-20). And changing the setinng solved all problems with detaching print from plate.

cheers

RE: MK4 Warping seperation

A short update on my part.

3 days ago the support agent sent me an email asking me to perform a temperature tower test and sent pictures from the results. I did so on the double and I added all the info I shared on my last post on the email. The temperature tower was flawless.

Today, 3 days after, I got a response. They thank me very much for the information, which will be very useful. The agent has forwarded the info to the "Quality Team" and they will contact me.

Now, I am upset and disappointed on equal amounts. First of all, why am I asked to do a temperature tower test for that? I have already found out that most probably the issue is how the temperature is read. That's about it. They are going around with tests here and tests there before they decide to send me a replacement thermistor which is 9 euros?? really? all the go and back of emails and chats just to be sure I don't want to get a free 9 eur thermistor? I've spent more than that with all the tests I've done and doing R&D and QA for them.

Anyway, since the deadline for returning the printer and get a refund is approaching (the 3oth of January) and the communications rate is 1 email every 3 days, I have decided to ask for a refund. Very sad, as I was really looking forward to having and using an original Prusa. I can understand how a bad thermistor can find its way to a printer, but I can't understand why that is so difficult to acknowledge and find a solution quickly.

RE: MK4 Warping seperation

have you tried, online chat? instead of email?

regards Joan

RE: MK4 Warping seperation

Of course I did try the online chat. As a matter of fact I believe I did 3 or 4 sessions which were a couple of hours each, which is no problem because if they want me to try something, print takes time, so all is good. At one point one of the agents told me "try this and this and if it fails, we will deem the bed thermistor out of spec and send you another one", and I thought "finally!". It was late at night, so I did what he asked the next day. The test failed and I contacted the chat again. The lady who took me reviewed the case case and started suggesting other things mainly related to the hotend temperature (??). At the end of the chat and after doing some more tests, she told me she would review the case internally and get back to me via email. So there is that.

RE:

The thermistor might actually be intact but have no good contact with the heatbed. Have you tried to press the tape fixing the thermistor?

Unlike some printers may do, I still favor the more honest approach in temperature control. It depends on the whole thermal model including the enviroment (cold walls around?) of how big the difference between measured temperature in the thermistor core and the print surface actually is. There is e.g. a tiny air gap between heating bed and magnetic sheet with higher thermal resistance. If e.g. you observe that your print surface is usually 5 or 10 degrees cooler, then please feel free to increase the temp in the slicer and you are good to go.

As observed, the build plates are at their best when cleaned with dish soap and rinsed with hot water. Once you have done that you can make many dozens of print without intermediate cleaning. That is, unless you touch the bed with your fingers.

As for the temp tower: It seems that they misunderstood you.