Bed Levelling



  • I have 5 point Leveling setup on my 12x12 bed.
    using a 1/4" Alum Bed with a 1/8 Glass + 1/32" PEI Surface
    its hard mounted to my Printer frame. with no Physical leveling currently possible.
    So i rely on Auto leveling to take care of it

    I cant wait for Grid leveling to be released hopefully this month. (Beta tester here LOL!)

    I find with 5 point i cant really print stuff much larger then 4" x 4" before the leveling gets out of whack. and first layer suffers



  • Looking at your spec, your bed should be reasonably flat - have you checked it with a straight edge? If it is, then grid levelling isn't going to do anything for you. Maybe you just need to pay a bit more attention to that first layer?



  • My wife is jealous how much attention that damn first layer gets LOL

    I have checked it with a straight edge and its not as flat as It should be.



  • That's odd. 1/8" (3mm) glass is usually pretty flat over 12" (300mm) and your aluminium plate would have to be serious deformed to make it bend. I'd be more inclined to try another piece of glass. Out of interest, has it been toughened? I found from recent experience that the toughening process can make the glass distort and went back to "normal" float glass.

    Oh and if you can, take a serious look at your print bed and see if you can't come up with some way of instigating a 3 point levelling system. I appreciate it may not be possible but it's always better to get the mechanics right rather than to rely of the electronics to compensate for any defects.

    HTH



  • 3mm glass is usually Greenhouse glass (According to my Glass suppliers) and can be very variable whereas 4mm is usually Float glass and is better suited to our use.

    Doug



  • Yes, it needs to be float glass (should have pointed that out) or some people use mirror glass which is also flat (unless you visit one of those fairground places). Thanks Doug.


  • administrators

    @Dougal1957:

    3mm glass is usually Greenhouse glass (According to my Glass suppliers) and can be very variable whereas 4mm is usually Float glass and is better suited to our use.

    Doug

    Interesting. I have had several pieces of 3mm and 4mm glass cut for me by a local glass supplier. The only problem I had was that one of three 330mm diameter x 4mm thick pieces wasn't flat. My understanding is that all sheet glass is manufactured by the float glass process these days.



  • @dc42:

    My understanding is that all sheet glass is manufactured by the float glass process these days.

    Not necessarily David. It could be rolled glass. Instead of floating the glass on bed of molten tin, the liquid glass is poured between 2 water cooled rollers. I believe it is cheaper to produce but prone to all sorts of defects which is why it's usually only any good for horticultural purposes.



  • I dont think the glass is the issue.. I have applied a PEI plastic surface that is adhered with 3M Adhesive..applying this adhesive is a bit tricky. I think the PEI tolerance and the Adhesive are whats causing an irregular surface

    I also have a 1/4" boro Glass with PEI and its the same issue.



  • I had been struggling with bed flatness on 310mm round Rostock MV2 bed. I have ended up removing the PCB Onyx heater, the melamine support, and mounting a flat 1/4 inch Al plate directly (with spacers and heat shield under the heater) to the base at 3 points. My previous (stock) setup was warped, and it was making the boro glass to warp too. However, it seems that the boro glass has become flat again after sitting free for a couple of days. Currently, I am using PEI over the boro glass on the top of 1/4inch Mic6 Al. Although my bed may not be absolutely flat, it is a great improvement over what was going on before. After 13-point calibration with the mini IR, the bed leveling reports error of around 0.005mm vs over 0.1mm before. Applying the adhesive to the glass was certainly tricky, and I had to start over several times. Applying 0.8mm PEI was easy.

    In my experience a 3 to 6 mm thick glass will conform, at least to a degree, to a surface under it, so if the bed has a dome in the middle, the glass will warp in the center


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