Re: [CAD_CAM_EDM_DRO] Plexiglass / Clear Polystyrene / Clear Plastics & Prototyping

Hi Abby:
Were you implying that you're using all three of these materials??
Your post is unclear...it seems to suggest that PVC, polystyrene and
Plexiglas are all the same material; they're not, of course.
May I recommend Acetal (Delrin) as an alternative for machined
prototypes...it's a very strong polymer, that machines beautifully.
It's only downside is that it cannot be easily glued.
PVC is also a good material for prototypes, but it has the drawback that it
releases corrosive gases when it is heated. (even the heat of machining is
enough to create "that smell")
The odour is quite distinctive, and in reasonable concentrations, it will
rust your equipment. (in high concentrations it will injure you!!!)
It machines quite freely, however, and in contrast to Delrin, it glues
readily.
Styrene is the material that is used in the clear components of most plastic
airplane and car models.
It is quite brittle, and does not have very good physical properties...I
don't recommend it.
Plexiglas is acrylic...it is also somewhat brittle, but is very commonly
used for fabricated items that are clear.
I personally prefer polycarbonate for those applications...it is clear as
well, handles similarly to Plexiglas, but has far better impact resistance.
It can be glued and solvent welded as readily as Plexiglas, and machines a
little better.
Hope this helps.
Cheers

Marcus

----- Original Message -----
From: "Abby Katt" <abbylynx@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, June 08, 2003 10:00 AM
Subject: [CAD_CAM_EDM_DRO] Plexiglass / Clear Polystyrene / Clear Plastics &
Prototyping


> A while back I remember some discussion upon the subject of
> prototyping materials.
>
> I remember relating my stories on the horrors of prototyping with
> wood - the fine powdery dust getting into leadscrews and gears,
> mopping up the oil and lubricatant and making a black mushy sticky
> goo! Still, wood is a lot faster to cut than metal and you're less
> likely to break small end-mills on it. But for all the inconveniance.
>
> I recently started using clear-PVC/(polystyrene sheet as it's called
> in the UK or Plexiglass as it's called in the States). This stuff is
> great! Sure, there are a few things you should know about it - like
> clamping it between two pieces of wood so it doesn't vibrate and
> crack when you're sawing it, but it mills just fantastic, to a great
> finish and at a very high cutting rate. The only thing, of course, it
> to keep spindle speed somewhat low, so as to not MELT it and thus
> cause it to stick up your cutting tool. I've not found that problem
> yet - and spray it with a little WD40 as it's getting cut. The swarf
> is a flakey white heap like coconut and cleans up really easily with
> a vavuum cleaner (it's a lot easier if you've used WD40, since it all
> sticks together in a neat clump).
>
> Also, it's dead easy to super-glue sheets together if you need to
> prototype on something slightly thicker than what sheeting is
> available.
>
> And, as a bonus, you can boast to your friends that your prototype
> was made on a StereoLithography machine. :P
>
> Just a 2p tip.