Bed material

I did some research yesterday regarding bed material.  The only safety glass available locally is 6.35mm laminated, which is no good for a heated bed.  The plate glass I had cut at ZAR10 a piece, can be tempered / armourplated at a cost of around R200 each.  Tempered glass can NOT be cut, it is cut to size before tempering.  Pyrex glass is not available locally in the size I'm interested in.

So, plate glass it will be.  Plate glass can crack if heated non-uniformly.  My plate glass sheets are 200 x 200, smaller than the heated area on the PCB.  Let's hope for the best (I'll probably only run at around 80 degrees initially), and if plate glass does not work out, I'll move to an aluminium plate.

I did, however, heat the plate glass in the oven to 150 degrees C without problems (slowly). 

The plate glass was Kapton-taped using soapy water, similar to window tinting films.  It is not perfect, but will do for the first round of tests.

I also found that my hot-end is slightly high, the bed does not elevate quite high enough.  Currently the HBP is about 1 inch above the aluminium platform plate (40mm long bolts and nuts with springs to adjust for level).  I had to lift the entire platform by inserting M8 washers between the aluminium plate and plastic brackets, now it can touch (with the build plate as far up as it can go).  If not enough, I can add more washers or even an extra washer on the arm joints (to lower the hot-end another mm or two).