"Bob La Londe" wrote in message
...
I finally decided to make a vacuum formed polystyrene cover for the
encoder on the front of the big mill. Seems pretty straight forward.
I've got my first vacuum box finished except for the port to put the
vacuum hose in. I noticed a lot of the DIY guys make a hole for the
smaller vacuum hose even though they have a full size shop vac with the
big hose. Is there some reason for that? Seems to me that the larger
port for the larger hose would evacuate the box faster and form the
plastic quicker before it cools. Am I missing something obvious?

(I have some PETG on the way to play with in case I don't like the way
polystyrene forms or holds up)

If this goes well, I have all kinds of ideas for vacuum forming...


Finally got around to the first attempt this evening using Plaskolite
polystyrene.

1st attempt I didn't get the plastic hot enough and let it sag far enough.

2nd attempt was not bad over all. There was just a little too much radius
at the junction between the mold and the table.

3rd attempt we spaced up from the table with popsicle sticks. It formed
very well with the radius below the mold. I had an issue with webbing
because I took the sheet down too fast, and let it vacuum down too quickly,
but I have a feel for it now.

There will be no forth attempt with polystyrene for this project. The
polystyrene is more than hard enough when formed, but its way to brittle. I
have some PETG ordered that should arrive sometimes this week, so I'll give
it a shot when it does.

I do have some ideas for the use of the polystyrene in the future though. I
need to look into its chemical reaction a little more and find out what it
reacts to, and what its stable with.