(Summary for the busy - plastic primer does not help ABS adhesion to glass heatbeds!, for those interested in more detail -read on)
I have been using "ABS juice" applied to glass sheets on top of a heated bed for a long time now as the only reliable method I have found to get parts to stick well. The one thing that continues to annoy me is having to reapply the coating between prints. The issue is that the film of ABS does not stay stuck to the glass when it's cool, rather it stays stuck to the part printed on it (which makes perfect sense). What I have been looking for is something that will stick really well to the glass and ABS when hot but only to glass when cold.
This is a quick report on Plastic Primer, designed to get "Plastic" style paints to stick to anything, including glass.
It's the best thing I have found so far but it still does not work that well! The problem is the primer sticks really well at low temperatures <50C but becomes tackier the warmer it gets and by the time it's up to ABS bed temperature it does not stick to the glass very well.
The best results I got were after repeated applications of a thin coat of primer, followed by a wipe with ABS juice. The acetone dissolves the primer, making an ABS and primer mixture. This mixture sticks to the bed better than pure ABS Juice and sticks to the object better than pure primer.
Setting the heated bed to the right temperature is also key: too hot and the primer/juice mixture lifts off with the part, too cold and the abs warps and lifts off the bed. In the picture below the marks towards the centre are from when the bed was too hot (100C) - almost clean glass left. The marks towards the front are with the bed too cold (60C).
The parts I was printing are not normally a problem for warping: the Y bearing mounts for a Mendel90. They have rounded corners which helps to reduce warping as well. An example of the warped parts:
Setting the bed to 80C, no fan and first layer 200% extrusion, I managed to get non-warped prints that stuck to the bed:
That said, this method was far from ideal, and appears to only work with parts that are not very prone to warping.
So..... if anyone knows of an adhesive/primer/something else that sticks really well to glass at 20C to >100C, sticks really well to ABS at >100C but does not stick to ABS at room temperature then let me know!