Quote:
Originally Posted by Garyh
Interesting concept but how does epoxy hold its shape and does it have a good expansion coefficient. How does one polish out epoxy?
Keep us posted on your experiment!
cheers
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It's mixed with the hardner, and gradually sets over a day or two.
The resulting mess was so hard it wouldn't come out of the tin - which also shows there's no shrinkage...
Speed control's an easy fix next time: PicAXE counting pulses from the tacho on a small motor (courtesy of an old 5.25" floppy drive), and PWM drive back to the motor for power adjustment.
Was just thinking - to stop a meniscus forming between the liquid epoxy and the container, I might wind the speed over the planned setting RPM (the one that sets the focal length), so that the epoxy runs up the sides a little, essentially to 'wet the sides', and emilinate the bulge a meniscus might form...
A gross example would be the letter 'M', compared to the letter 'U'
With the M, the parabola forms in the middle, but the epoxy sticks to the sides a little, preventing it lifting high enough to make nice clean edges.
Spin it faster to wet the sides, the slow down, which makes the epoxy fall back down a little, hopefully, theoretically, maybe.. forming a cleaner parabola...
...and who knows, if the air's clean enough, the aluminium coating might fill perfections enough to not need final finishing(high hopes. very, Very high...). Where in/near Tassie can I get silvering / aluminising done though!
...back to Supercheap for more parts!