Started to print the cover for the K8200.
After a few layers the four corners (all four) starts to raise.
Why is this happening???
After e few more layers the extruder hits the corner and the print is destroyed.
Any clues appreciated.
Deformation by temperature difference. Because the corner is minus of material, it cannot loose its heat by material around. So it deforms the most by releasing heat by air. You see this afinnitys also in the steel-welding. If they come in a corner, the corner gets the problem to melt away, because it doesn’t loose the heat anymore on the less surrounding steel. Steel and filament are opposites with isolating.
So I think its very good to make the heat as low as possible to make the temperature difference smaller. And if possible Dont use the ventilator. The ventilator is good with very small pieces that get to hot if the nozzles comes there a lot. But its bad when it cools a layer too much and it takes a while before the nozzle comes back.
And if the first layer is nog good stucked on the botton, the cornes are the first ones that comes loose by deformation. Again, the temperature difference as small as possible. So the bed temp. very high, and the nozzle as low.
With ABS this gives a BIG difference. If the bed is 50 degrees and the nozzle 235, it goes definiteley wrong, but if the bed is 70 degrees and the nozzle 190/195 degrees, it stucks much better. And if the first (3-5) Layers are correct, the rest will follow also correct with higher temperatures.
So this are my tips. Unfortunately you must also seek the solution by yourself because every machine, filament and speeds are different.
Succes,
Jeroen
Ps: I’m also still seeking for the best configurations, so you can walk away during the printing 
You could try printing with a 6mm brim
This will secure the print to bed a little better it will also clear the extruder of air bubbles and make sure it is primed.
Thanks for the tips
Raised the bed temp to 60. This did have a positive influence, however at layer 33, the extruder hit the print and wiped off the bed.
I would expect that I should sander the bed, but what else can I do? Raise the bed temp again?
I have not tried the 6mm brim, but that will be in the plan for the next few days
Check the distance between the extruder and bed (the middle) while the bed is heated about 60
I did mine with a piece of paper folded in half so it would drag just a little
Also make sure you go around the bed to make sure the extruder doesn’t dig in to the bed
I hope this helps
If your are printing with PLA:
It is paramount that the bed is grease free, Use Isopropyl alcohol or something similar to thoroughly degrease the bed. The difference between a greasy bed and a bone dry bed is enormous. Also rough up the bed surface with a bit of sandpaper (grit 200 - 400).
If your are printing with ABS:
Put an even layer of clear packing tape on the bed and use the supplied (downloads) abs config profile. The packing tape will ensure a good adhesion with ABS. If you want to print with PLA again you will have to remove the packing tape, this is best done when the bed has cooled down so it does not leave any residue. Degrease the bed again to be sure.
I had bad adhesion with PLA to start, and I found that scuffing the surface of the PCB with 200 grit sandpaper gave a little tooth for the PLA to adhere to. At 200 grit, you will see surface marks in the print, but they are smaller and less noticeable than all of the other surface effects you see from 3D printing in general. I also found that a bit more heat would help with adhesion.
I have been printing a multi-layer skirt fairly close to the print, and this helps to keep the heat in. I do about 20 layers about 5mm away from the print. It helped in my situation. I found this idea on another forum.
Also, I found that my prints were going fine for a while, but later started to lift. I found that the air vent in the ceiling was directing airflow close enough to the printer to cause cooling at the edges, causing them to raise. I found that turning off the air conditioner during the print helped. In fact, I stopped printing taller skirts and it seems that the primary issue was airflow. Even a small airflow in the right place can cause a print to deform. As a result, I am going to enclose my printer.
Sanded and degreased the bed. also recalibrated the distance from the extruder to the bed.
Better but still raised corners, but now I was able to print the entire K8200-cover without the print being wiped off the bed.
Still raised corners (3 out of 4)…
I noticed that the bed is bend (curved, so the middle is approx 1-1.5mm higher than the corners. I plan to disconnect the bed and drill new (wider) wholes, in order to make the bed plane and level.
But before that I would like to have an opinion on that operation.
I had the same issue - warped PCB. This was magnified by the holes in the PCB being slightly ‘off’ from the underlying frame. This resulted in torsion / cupping of the PCB. I took it apart and filed the holes a bit to get the interference out of the fit. This definitely helped.
I originally shimmed the PCB to get the cup out of the middle, but I found in use the cup went away and I removed the shims. The cup probably was caused by the tight fit. I think the design is such that you can accommodate a slightly out-of-flat PCB by compromising on the gap at the corners to find the best setting to reduce the gap in the middle. I adjusted so that the middle was good, and a couple edges are a tad too tight or loose.
Some people convert to a three-point mount, but I would rather use it as-is. Works for me. The biggest factor I found on lifting corners is geometry that leads to it combined with airflow. Once I limited airflow with skirts and shutting off the heating/AC, everything got a lot better. I also take great pains to make sure the first layer goes down thick and hot. An iffy first layer is just a nonstarter.
Just a follow up.
I removed the heat bed. Dilled the existing wholes in the metal frame from 3mm to 3.5mm metal, remounted the heat bed and recalibrated.
The heat bed is not 100% plane, but much more than before.
And the best: I have no more raised corners.
What also helps is to rise the skirt and brim setting of the slicer. With the skirt and brim, you enlarge the surroundings of the product. The enlargement will be the first part that will rise in the corners but will be removed afterwards. I noticed that this work very good with the ABS material (enlarged the skirt and brim setting big and coupled the skirt against the brim and enlarged the thickness of the skirt to 2 layers).
So this will work even better with PLA. If I can flatten the ABS with this, PLA will be a piece of cake!
Ps: This work only if the first layer is “pushed” against the bottom of the bed. So the nozzle must be almost against the bed in the first layer. If you see a mark following the nozzle and a very thin layer, the better! The second layer must be visible and sometimes this will be a very precise calibration, but if it works, the product will stick to the bed for sure. If the first layer is very loose, everything will go loose.
Further it is very important to keep the bed in heating. So I turn off the notice of the bed temperature in the G-codes, so I can heat it maximum without waiting on the bed reaching the max. temperature. The temperature itself is NOT important because the Sensor is manipulated by the nozzle/filament temperature. Just keep the bed heating without stopping. If it stops too long, the product will crack (you hear this) and get loose. (because the temperature is shrinking the bed and material). In the metal world they use this shrinking and expanding with temperature a lot for mounting strong assembly’s with for instance a metal pen.
Succes!
Jeroen Huijsen
otherwise use a mirror with or without blue tape