Known good part obscures the problem of shrinkage unless you want them
to take your known good and scale it for shrinkage which they will do at
$$/hr. ;-)
Working from their shrink % will allow you to do the sizing and that
make it simple for them.
A foundry 100 mi or so from me and out in the boonies was using house
insulation foam for patterns but that generated a lot of plain carbon
smoke so I don't know if they do that anymore.
Good luck with your part however you do it.
Dave
On 1/23/22 10:56 AM, Chris Albertson wrote:
What you give a foundry is typically the part you want, a pattern. They
can advise on the limits of what they can do. For example there is a
minimum and maxim thickness and overall size.
They can also tell you how much the iron will shrink so you can adjust the
pattern
Then for you own good you would want to make the pattern so as to minimize
the amount of machine work. This also saves you money as you pay the
foundry by the pound. So make the parrn have all the curves and shape you
need.
Wrapping is another issue. if you make it too thin or thick the result
will not match the pattern.
Tranditionally, patterns where made of wood or maybe wood with bondo over
it and sanded and finished sooth. But today you would 3D print the pattern
and give them a plastic copy of the part you want. They pack it in sand
and make a mold from your pattern.
Some can do a process that is like "lost wax" so then you print using a
kind of plastic that the melted metal burns up
But this is for a "*mini*-mill" you do NOT need cast iron parts. The
cutting force is very small. Why not make your adaptor out of plastic?
Platic seems like the wrong material because "real mills" are made of
steel. I have a CNC converted Mini mill and the conversion parts are
printed plastic. It you design, knowing the strength of that material
you can do well. I can not measure flex with a dial indcator
Plastic is like designing a part with glass. It is very strong and rigid
until it shatters. But look at the size of the spindle motor and drive
gears on a mini mill. You would shear the teeth off the drive gears
before generating enough force to break a plastic adaptor shim.
In any case, then after AFTER you know the plastic part works, then you
give the foundry the known-to-work part to use as a pattern and they make
you one in metal.
I've dealt with some manufacturers and while you used to have to ship a
pattern, now days you can email them the design file and they can print the
pattern and do the design check that looks for violation of thier min and
max thickness.
There are also places that can do a 3D print in metals like aluminum of
even stainless steel. But this is not yet cheap.
On Sat, Jan 22, 2022 at 6:26 PM fxkl47BF--- via Emc-users <
emc-users@lists.sourceforge.net> wrote:
Yes, if you are near Windy Hill, then I understand that they do a lot
of one-offs for vehicle restorers etc.
It's certainly worth considering.
OK
So from the photos in the ad what would I want to have made?
A big rectangle?
The only "true" surfaces on the back are the dovetails.
I think that's a bit of a wimpy mount.
If I disassemble it I can tell if the unfinished surfaces beside the
dovetails are thick enough to drill for additional supports.
Or is that a lot of overkill.
Just attach to the dovetails and be done with it.
I have a 3D printer.
This is go'n to to be fun :)
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