Re: [CAD_CAM_EDM_DRO] Machineable wax problem

Hi Bill:
I was a dentist in a former life, and I did a lot of dental implant
work.
Much of it involved precision casting (lost wax).
I can recommend two materials and one product you may have never heard of
before.

Polycarbonate will give the best burnout of any plastic I know.
It is machinable but you need razor sharp cutters and you can't run up the
spindle speed too high.
3000 RPM is about the limit for a 1/4 " cutter.
Any higher and you will likely end up with a melted blob on the cutter.

Delrin is beautiful to machine but the burnout releases toxic gases and is
not as clean as polycarbonate.
Delrin also has lousy wettability, so the castings are rougher because the
investment won't flow as well when the pattern is invested.

The product I have found a billion uses for is called "Relate"
It is a burnout acrylic used to lute bar patterns for dental implant bars.
It burns out super clean; it can be waxed to, carved, milled, ground
polished etc,etc.
It is a 2 part mixable material (powder and monomer) with a set time of
about 5 to 10 minutes depending on the mix and the cross sectional area.
It handles about like molasses on a cold day when it is first mixed, and
will stick to polycarbonate but not to Delrin.
It can be shot into a rubber mold.
Its shrinkage is negligible.
It is also rigid enough to be handled easily in very skinny cross sections.
This makes it ideal for tiny clasps, bezels and other fragile features on a
pattern.
For any kind of jewellery work, it is absolutely wonderful.
I know it is made by Parkell; I don't have an address for them because I get
one of my dental lab buddies to order for me.
I can try to find out for you though.
Cheers

Marcus


-----Original Message-----
From: William Reidsema <wreidsema@...>
To: CAD_CAM_EDM_DRO@yahoogroups.com <CAD_CAM_EDM_DRO@yahoogroups.com>
Date: Sunday, April 08, 2001 3:34 AM
Subject: [CAD_CAM_EDM_DRO] Machineable wax problem

>Hello All,
> I read this group every day and it is amazing how
>erudite some of the contributors are! I have a simple
>problem that, perhaps, cannot be solved. On the other
>hand, maybe someone has a solution.
> I do a lot of jewelry prototyping in machineable
>wax
>which is then burned out of a mold and cast in
>precious
>metal. The problem is this: I spend as much time
>digging wax residue (chips) out of the final wax
>carving as I do milling the piece. If I cut plastic,
>then the milled carvings have almost no residue to dig
>out. Unfortunately, the plastic doesn't burn out as
>well as wax.
> Anybody on the group know of a material that will
>cut cleanly and burn out as well? Any other
>suggestions
>will be appreciated. I've even tried building a dam
>around the wax and cutting in water. Nothing seems to
>work!
>Bill Reidsema