Hi,
the epoxy may make up only 1/6 of the volume of the mix but you will have roughly 10l mixes, that's still a lot of epoxy.
I have used epoxies in boat building, model aircraft making and potting high voltage electronics. All epoxies exotherm to a certain
extent, its a question of the thermal properties of the mix and the volume of the mold relative to the surface area.
I'm sorry but I think you are going overboard here, epoxy granite with embedded cast iron for mountings......is a very extensive/expensive
and time consuming project, rather more than is required to mill 'easy metals' as is your goal.
A welded structure of hollow rectangular section steel suitably stress relieved will be more than adequate. If you wish to fill the sections
for vibration damping afterwards so much the better. The material is cheap and readily available and very quick to fabricate compared to
epoxy granite.
I bought some el-cheapo aluminum couplers with a spiral cut slot. They are inclined to flex somewhat under torsion, rather more than I thought.- couplings between the ball screws and the steppers (specific words to search for? Something to take into consideration?) Would you say that there is anything in particular to look out for here ... Or can I just use any coupling?
They account for more 'lost motion' than the backlash of the gearboxes. As it turns out I've had two decent crashes with my machine, in both cases
me doing something dumb, and in each case the coupler 'twisted up like a carrot'. Because of the gearboxes the steppers can generate over 20Nm
stall torque, enough to do real damage. The aluminum couplers are a bit like a mechanical fuse, they shear off before anything really expensive gets
broken.
Bellows type couplers are much torsionally stiffer but way WAY more expensive too. The lost motion I get from the flexure of the cheap couplers I use is
about 4um....I live with it! Theres all sorts of things I can spend money on without getting hung up on couplers. Good microswitces for home switches are
a much better use of my money.
Craig