Hello, everyone. First post here. Looking for an opinion on something I’m thinking about doing. I have had the parts to make my MPCNC for almost 2 years now and FINALLY got together and starting to make things. I have it attached to the bottom ~8U of a server rack and have an interchangeable bed that I’m currently using MDF for. I have a pane of glass attached to one of the sheets of MDF to use for 3D printing, but I’m thinking I would like to add a heated bed to it. I’m thinking that I could elevate it off the MDF a good half inch or so with some 3D printed feet screwed into the MDF (think stationary Taz 6) but I’m not sure if that’s far enough away from the MDF. I also don’t want to raise the bed TOO high as I only have around 3 or 4 inches of Z space to start with. Thoughts? Should I just bite the bullet and find a piece of metal the size of my MDF boards to use instead? Thanks in advance.
1/2 is fine, if you can insulate it a bit even better. I have a mdf plate holder on a printer that runs 24/7 with thin layer of cork and all is well. I have seen cardboard recommended but that seems to be pushing it to me, too dangerous. On that note I rarely go above 63C on the bed, maybe 75C no higher.
Thanks, Ryan! I’m very happy with your MPCNC and am glad to finally have time to finish it. 
I’ll take your recommendation and add a layer of cork to it. Is the heated bed touching the cork which is touching the MDF or is there space in between the layers? I never go above 60C on my other two printers, so I seriously doubt I’d go above 60C on this one.
My heated bed is in direct contact with the melamine the printer is made of. The temps we print at and the temps the heated beds are capable of are hundreds of degrees lower than the ignition point of mdf, which is around 220C to 240C if you were wondering. The heated plates can warp when heated, and I’ve seen them warp the glass above them if it’s not thick enough.
On my 3D-printer an Ordbot Hadron, the heating plate stands on four long M3 bolts. To minimize heat losses and to achieve a more even heat distribution on the building plate by avoiding convection on its underside, I put a 5mm layer of cork directly under the heating plate. The cork is held up and in place by a sufficiently thick layer of padding material, I think polyester quilting cotton, like upholsterers use it, or like the material you use to stuff loudspeaker boxes. No more heat losses.
Cheers,
Ulli.