How do you temper your Plexi?? Heat it up the area with a hot air gun or ??
Dave
On 8/3/2018 12:22 PM, Bengt Sjölund wrote:
You always have to temper the PLEXI after using cutting tools to get
rid of 'tensions' built up by the cutting! This is a MUST DO !!!
Have been doing domes for underwater photography 30-40 years back and
for sure all my domes where fixed with screws and appropriate washers.
/Bengt
Den 2018-08-03 kl. 18:01, skrev Dave Cole:
>>screws are forbidden
You just have to be careful. Don't over tighten the screws. Use
washers, etc.
They make drills specifically for plexiglass. The tip angles are
different than standard drills.
You must drill plexiglass with a backer board. If not the backside
will breakout and fracture the edges which will leak to cracks.
However, gluing it is easier than screwing it together. So unless it
needs to be able to come apart, why not glue it.
At one time, plexiglass was a lot cheaper than lexan. But I don't
think there is much of a cost difference now. Maybe 25% or so.
Lexan is much more impact resistant, so why not use that... Unless
you have sheets of Plexiglass lying around. :-)
Dave
On 8/2/2018 11:58 PM, Peter Blodow wrote:
Gentlemen, treating transparent plastic material is tricky, but not
hard to do. For instance, in my company's shop we sometimes had to
make covers (hoods) for scientific laboratory equipment.
Polycarbonate, whatever its trade name may be (Macrolon in Germany),
can be bent cold like sheet metal if not too thick.
Plexiglass (PMMA, polymethyl methacrylate) can be bent warm and
glued with pure acetone or acetone with a little PMMA dissolved in
it. Straighten the sheet sides with a mill, no slits or chinks are
allowed. Screws are forbidden. We made ourselves thin heating rods
in different lenghts which were placed beneath the bending line for
several minutes, then bended by hand. Fixing the angle until cold is
necessary. If more covers of same type are to be produced, deep
drawing might be useful. Make a plywood fixture consisting of a flat
plate and a second plate lying on top of it with a hole of the
desired shape cut out, all inside covered with velvet foil to avoid
scratches. Then hang the PMMA sheet in a 200° C heating cabinet
until soft enough, quickly clamp it between the plywood plates and
blow the sheet up with compressed air. We once made bowler hats this
way for the public at an exhibition.
Peter
Am 02.08.2018 um 20:28 schrieb Gene Heskett:
On Thursday 02 August 2018 13:55:54 Dave Cole wrote:
On 8/2/2018 1:32 PM, Gene Heskett wrote:
On Thursday 02 August 2018 12:37:36 Dave Cole wrote:
Why not put a standard keyboard into a plexiglass box with an open
side towards the operator?
You can still see the keys if needed if you make it out of clear
plexi. A sheet of 1/4" plexi, a table saw, and some plexi glue is
all you need.
When it gets scratched up, make another one, or buff it out.
Dave
Thats a thought. But I'd probably use the bullet proof stuff. I'll
see if theres glue for it next time I get to Lowes.
Thanks Dave.
Are you thinking of Lexan/Polycarbonate?
I know that Menards sells plastic glue but its in small quantities. I
suppose one could be screwed together if the plastic was thick
enough.
I know that drilling Plexiglass can be tricky as it tends to
fracture/shatter if you are not careful.
I think that Lexan is more forgiving but more costly.
Thats the stuff, but couldn't recall the name, (oldtimers?) what I do
know is that it drills a lot like stainless. Perfectly sharp drills
and
lots of pressure on them. I can't recall ever shattering it though.
It can be bent but takes a surprising amount of heat to soften it
enough
to bend.
thanks Dave.
Dave
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