heated bed upgrade: aluminum plate tab at back touching frame

[fluxline 0]

while waiting for support to get back to me about a few issues with the hbu, i took another look at one of them myself, bed does not move smoothly. at the back right of the aluminum plate, there is a tab with an unused tapped bolt hole. it is close enough to the back of the UM frame that I cannot get a .05 mm feeler gauge between them, very tight and rubbing. any body else have the same issue and found a solution?

thx

 

 

[fluxline 0]

For anybody looking to solve the same issue in the future, the tolerance is tight and probably dependent on variance on the plates and assembly.

I loosened all the frame screws, set screws on the log belts, rod fixation on the sliding blocks, and mounting bolts on the linear bearings holding them to the alu plate. I then flexed the frame, which made some popping and creaking noises as it loosened up. I then checked with a square that all was aligned as before. Lightly re-tightened the screws on the frame, working from the inside out. There is still not enough space to get a .05 feeler gauge through.

My next step would be to put some .1mm shims between the back plate and the top/bottom plates to make more space there. If anybody can think of why this would be a bad idea, please let me know.

 

[fluxline 0]

final solution, slight shimming with .05 mm and pulling bed towards front of machine when aligning and tightening of linear bearings. gives a tight .1 mm between tab and back of frame.

 

[IRobertI 520]

If it were me I would've just used a file to take a wee bit of material off the tab. I didn't have that issue with my printer though (but it's a tight fit).

And for those curious what the purpose of it is, it's for the UM2. On the UM2 an M3 screw is put there to hit the limit switch at the bottom of the printer.

 

[fluxline 0]

ya, me too at the beginning, without it already installed. but i went down the path of making sure the frame and z rods were square. might still do that if over time with humidity and flexing it starts to run again.

 

[rob 0]

It's very close on my pinter as well but I've just lived with it as it hasn't seemed to cause any issues yet. Given that the tab is useless I'd be tempted to follow IRobertI suggestion of just hacking it off with a file.

 

[metalman1661 0]

I have the same problem with my UM 1 (UM Beta) and the HBK.

I will probably just take a file to that tab since it is not used.

One other thing that is happening is the left side of the wooden bed cover (side with the tab that hits the upper Z stage limit switch) rides a bit against the back wall just like the metal tab. I took some sand paper to the wood. It reduced it a little bit but I will have to sand it some more since it is still rubbing a bit.

Also, my printer has the lower Z-stage limit switch under the bottom wooden plate (previously pressed by a long wooden piece on the old acrylic bed). This new bed design does not have this long wooden piece to press it so my lower Z-stage limit switch cannot be pressed.

Did you have the same issue?

I will provide pictures once I get home.

 

[fluxline 0]

so, i took a few mm off the tab. if you've not gotten an answer about the lower limit switch, it can be ignored. it is done in software now.

i'm still trying to figure out how the stage is binding around 13mm down, causing a jump in the bed. the tab was not the problem. you can hear it as well as the movement gets quieter, like the things are tightening up. i have play in the lead screw nut as well, wobbles around the screw and can be moved up and down on the screw about 1.5mm.