TAZ 5 Bed adhesion

Hello all,

I have had my TAZ 5 for about 2 months now and it has been working great. I have had it going pretty much 24/7 since I got it and over the last few weeks I have been noticing a change in the surface of the glass bed.

Almost all of my prints have been printed in the exact center of the bed. I have noticed in this area where almost all of my prints are done the bed looks different when the light reflects off it. It appears the edges around the bed (about from the edge to 2-3 inches in from the edge) look kinda dull when you look at it at an angle with with light. However the center of the bed in 3-4 inch area looks very shiny and prints are very difficult to remove even when letting it cool down entirely. I tested printing things on the edges more with no other change in temps or any sort of height adjustment for the Z-axis and prints remove off these spots with little to no effort once cooled.

I have already tried moving my z-axis up some without much success. I do not believe this is the issue since when prints are more toward the corners or edges of the bed they come off effortlessly. I am wondering if perhaps by printing in the same spot constantly or perhaps being too aggressive in getting my prints off the bed I damaged the surface somehow. Perhaps I damaged the PEI surface? Honestly I know very little about how the bed is assembled or what makes it special. I normally let the bed cool down to 20-24 degrees before attempting to remove a print.

I have been printing with PLA at 60 degree bed temp and 205 nozzle temps. I have tried several brands of PLA and that has not solved my problem. My parts look very smooth on the bottom regardless of where on the bed I print them.

Any help would be appreciated.

Thanks,
Justin

The Taz 5 has an apperent “hump” in the middle. The bed itself is actually perfectly flat, but the 10mm rods on the X axis and the Y axis allow for a 0.01 to 0.05 deflection in the middle, which shows up as the nozzle being closer to the bed. The stock glass bed also heats better in the middle which leads to better adhesion. As you use PEI, the top surface ablates away a tiny (microscopic) amount every time you use it, exposing new surface material that may work better than the edge material that isn’t used as frequently. The Taz 6 prototype has 12mm rods mainly for the deflection reason.

You can adjust for height as needed when printing different locations, or explore some of the printer modifications to take care of those issues you identify.

I was worried I may have damaged the PEI or something. Hopefully what you are saying is the case. I do not really want to adjust my z axis up anymore since it is pretty much perfect where it is at.

As piercet mention the head sags in the middle, bringing it closer to the bed. Once you start measuring the bed levelness with a dial indicator this becomes very apparent.

You actually would what to move the nozzle lower closer to the bed if you are doing a print that uses the edge. Honestly don’t be afraid to turn that endstop… The more you do it the more comfortable you will be with it. I will sometimes turn that thing on the fly at the start of each print just to adjust for what I am printing. I just go off of how I want that first layer to visibly look (I do Z height visually now).

And don’t worry about damaging your bed. Unless you deeply dig into it with a knife… Or poor acetone all over it… The only way I damage mine anymore is when the prints stick overly well… Which I need them to do for long prints. Which then causes bubbling… Which is a catch 22… I hate PEI, not so much the material I self but rather the inadequate adhesion to the glass plat.

Anyways if you think it is the bed. Buy some 2000 grit sand paper and go to town on it. They will say “lightly” sand. But that’s wrong. Get some elbow grease in there.

Post a picture of the bed.

Your PEI is most likely okay.

If the center has a yellow or silver hue on top of the red, then it could be bubbling from removal of parts. Lulzbot may replace the bed, but I think they’ve changed their policy recently. Their recent recommendations is to try and roll the area out…

If the prints are easier to remove around outside of the bed, then you’ll need to lower the nozzle a bit to the bed. Alternatively, use the Z-offset gcode value in your slicer software to better control the nozzle height. If the center is adhering well, and you’re worried the size of the print may cause adhesion problems close to edge of the bed, set a Z-offset value of -.1 to -.2 to lower the nozzle.

Yeah, my first bed bubbled due to a fatty PEI layer. The print would literally pull it up print.

My 2nd bed is now bubbling due to part removal. Which is sad considering I go slow and I am very careful. Unfortunately for long prints, it’s necessary to get stuff to stick overly well otherwise corners warp and peel.

Thus my conclusion is - PEI is good stuff but the problem lies with adhesion to the glass bed. I’m currently in the process of searching for better alternatives or fixes.

Love the PEI… A thicker sheet of PEI with the same adhesive could spread out lifting load. Could extend the life of the PEI to glass adhesion…

I think I’m ready to move onto a removable plate. PrintinZ Zebra plate on a glass only heated bed from i-t-w… I’ll lose a few millimeters of print height, but should be compensated by the dual extruder v2’s shorter hotend profile.

So I do not have a good way to post a pic of the bed. There is no bubbling or discoloration that I can see. It is kind of a shiny-ness to the center of the bed that outside of the bed does not have.

My problem is not that the edge parts of the print are not sticking. My problem is the center is sticking way too well. Would lowering the nozzle help with that? The parts I print toward the edges of bed are coming off perfectly and sticking well during printing. Center is sticking well during printing but quite difficult to remove post print.

You’ll want to raise the nozzle if the prints are sticking too well.

You can try to remove the sheen with a fine sandpaper… but if the ABS still sticks, I wouldn’t worry too much about the color…