Shrinkage for Chemill

I am creating a forging that will be chemically milled, which means
that .010 will be taken off of all surfaces, I need to expand my model
to allow for this reduction. I know that I can scale the model, for
thermal shrinkage and what not, when I use the scaling feature and
type in .01 not all of the surfaces changed correctly, it expands the
entire model by 10% not .01, does anyone know how to accomplish this?

 

: it expands the
: entire model by 10% not .01, does anyone know how to accomplish this?

Select all the surfaces/quilt and offset by .01 (or -.01?), but how to do this
(button pushes) depends on the rev of Pro/e you are using.

David Janes

 

Thanks alot David, that was a good idea I already tried it and it
didn't work, what happened is the geometry was to complex and when all
sides were offset .01 some geometry overlapped and blew up. It isn't a
bid deal. What I am going to do to fix it is when I cut the die on the
CNC in my tool path parameters I am going to set the stock allowance
to a negative .005, which will be a total of .01 after both sides of
the die are made.

Shaun

 

: > : it expands the
: > : entire model by 10% not .01, does anyone know how to accomplish this?
: >
: > Select all the surfaces/quilt and offset by .01 (or -.01?), but how to do this
: > (button pushes) depends on the rev of Pro/e you are using.
: >
: > David Janes
:
:
: Thanks alot David, that was a good idea I already tried it and it
: didn't work, what happened is the geometry was to complex and when all
: sides were offset .01 some geometry overlapped and blew up. It isn't a
: bid deal.
It actually is a big deal. One of the things that offsetting surfaces helps with
is precisely the kind of part anomalies that you found. And it is an anomaly when
surfaces intersect and thus fail. It means that there are walls on protrusions
that are so thin that they will disappear when this much stock is removed. Unless
you mean to put holes where none are designed or turned flats (say, at the top of
a rib) into sharps, this should tell you that the model exceeds minimum wall
thickness somewhere. Something that should be checked on, don't you think.

: What I am going to do to fix it is when I cut the die on the
: CNC in my tool path parameters I am going to set the stock allowance
: to a negative .005, which will be a total of .01 after both sides of
: the die are made.
:
Horrible, awful idea, resist the temptation to take this foot-shooting, "easy" way
out. You are only making trouble for yourself down the road. If anyone else is
trying to work with your programs, this is a good way to yourself marked as a ....
well, there are so many unpleasant names, I can't think where to start. So, my
advice: stick with the surface offset method. It has the advantage of being widely
used and recommended so you look like a pretty sharp and sophisticated user if you
practice this; it is a recommended way of checking the manufacturability of
models -- it's a free byproduct so why not take advantage. And you won't make any
enemies by faking out your fellow programmers.

One other possibility for error in offsetting surfaces needs mentioning: model
accuracy. If set too low, offsetting can challenge Pro/e's ability of correctly
offset surfaces, especially when small patches are formed. Move the relative
accuracy setting one more decimal place to the left and try it again.

David Janes

 

Chris,
I do have the mold mod so it is really easy to add or minus
shrinkage. If you do not have the mold mod it is still really easy to
add shrink, all that you have to do is have your .prt open, then click
on modify and scale model, when i use this i scale it 1.009 because we
have found for the type of Ti and the temps we are running at we get
..009 inches of shrink per inch. The scall model makes every thing
larger by .009inch per inch. This is the same as in the mold mod but
the mold mod allows you to pick 1/(1-s) or 1+s and it also allows you
to use different values for different directions.