Up to 50% Plaster of Paris. Not to be used above 1450C. At what temperature do the jewelry silver alloys melt?
John
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Bill in OKC too via groups.io
Sent: May-05-20 3:39 PM
To: [email protected]
Subject: Investment casting, was Re: Workshop Practice Series, was Re: [digitalhobbyist] Thickness reduction
is the Safety Data Sheet for Fogor's Premium Blend Investment. Among
other things, it lists the ingredients, and approximate percentages. A 10.5# bag is about $20, which ain't that bad if you're doing
one small casting. This stuff is for high temperature white metals. But if you need to do a bunch of stuff, it gets expensive fast!
Bill in OKC
William R. Meyers, MSgt, USAF(Ret.)
A human being should be able to change a diaper, plan an invasion,
butcher a hog, conn a ship, design a building, write a sonnet, balance
accounts, build a wall, set a bone, comfort the dying, take orders,
give orders, cooperate, act alone, solve equations, analyze a new
problem, pitch manure, program a computer, cook a tasty meal, fight
efficiently, die gallantly. Specialization is for insects.
LAZARUS LONG (Robert A. Heinlein)
On Tuesday, May 5, 2020, 05:20:36 PM UTC, John Dammeyer <johnd@...> wrote:
From: [email protected] [mailto:[email protected]] On Behalf Of Bruce J
On May 4, 2020, at 6:40 PM, John Dammeyer <johnd@...> wrote:
One of these days I'll get around to casting this mount for my harmonic drive. It pulls from the sand nicely. ?Drawn with Alibre
CAM. Fitted to the motor. ?Then tapers and draft added and expanded by 3% for shrinkage. ?Sectioned into 4 parts and printed as
4 pieces.
Glued together, body filler, primer and paint.
Absolutely no interest in stinking up my sand with lost PLA process nor lost foam.
Lost PLA is cast like lost wax?in a plaster mold, not sand; at least every description of it I've seen has been done that way.
--
Bruce Johnson
Yes.? And in fact with lost PLA you can use wax to smooth out fillets and rough spots before adding the plaster and sand layers to
create the shell to burn out the PLA. ?And for complex forms that might require multiple split patterns there is no doubt that this
approach will make something more complex.? You could design a carburetor this way.? And perhaps the hours of printing time,
lost PLA pattern prep time with plaster and sand is worth it.
But generally sand casting patterns is often for more than one.? Most of what I've cast for the mill conversion can be done with
plate and spacers.? The need for castings really isn't there for a one-of project.
But the photo shows the LH side of the X axis with DC Servo motor and bearing holder.? ?The next photo shows the same bearing
holder and flange now repurposed and mounted to the RH side of the X axis.? And that casting photo I posted in the last email was
for a smaller Bergerda AC servo in place of the DC servo.? So I made a second motor mount for it.
A friend has a G3617 mill (longer X axis and horizontal mill feature).? If he decides to go CNC the patterns are done.? Of course
he's big into 3D printing too so he could print the plates etc. and plaster/sand coat them and pour them.? But that would take him
a lot more time compared to borrowing my patterns.
Eventually someone with a G3616 mill may want to follow my eventual documentation on how to convert one.? And will want a
set of castings.? These are all big prints and not all would even fit on my 200mm square 3D printing bed.
John
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