Machining a forging

Hello,

I just completed modeling a forging. Now I need to create the maching
for this part.

How can I start modeling the machining from this forging? I need to
update the machined model when the forging is revised.

Thank you.

 

"base part" is one method...
putting the forging into an assembly and then making cuts in the assembly is
another

 

How about using configurations: one configuration of the forged part with
the machined features suppressed, and a configuration of the machined part
with all features unsupressed.

Mike

 

Crossposted to alt.machines.cnc

 

This all seems a bit backwards to me.
The finished part should control the forging to a large degree,
usually.
Start with the finished, add stock & draft, etc. == > forging
design.
Then it should be mostly associative, right?

 

Cliff,

Yea, it does seem backwards, but from a modelling (construction) angle, it's
more straight forward. Having the forging as a base allows you to go from
simple to complex. The other way (which makes much more sense from an
engineering perspective), is more complex to model. It could be done that
way in many cases though.

Both methods can be associative. Whether or not changes in the driving
parameters result in desired behaviour depends on how well things were
defined.


Mark

 

That's what I usualy do. Never had to regret it.

 

Mark,
It's easier to delete/ignore holes & suchlike in the finished part
than to try to guess where they are from a forging or casting.
So I'd think, anyway <G>.
The "design rules" [part ==> forging] should be simple
compared to [forging ==> part] too I'd think.

So ..... why did they do it this way (or try to)? Now, for each part
they have to design BOTH part & forging 100% I'd guess ...... instead
of just the part (or it's family) and do some tweaking from there.

Probably I'm just to lazy .....

 

I disagree--all question of SW methodology aside, using the forging as the
base part corresponds to physical reality.

You can hold the forged part in your hand before machining. I've never yet
seen anybody weld additional material onto a machined part to create a
forging.

 

Products are not designed as collections of forgings. They are designed as a
collestion of assembled finished parts.
Forgings, and die catsings for that matter, are derived from finished
product designs. Why would you reinvent the wheel?

 

Ever see a CAD or CAD/CAM system or a pattern/model shop?

 

Mark,

Cliff,

In Solidworks you'd use a function called configurations. The base
configuration is the forging, the other would be the machined forging. This
is just a simple case. One part could concievably have dozens of variations.

It's just easier, from a parametric "housekeeping" point of view, to model
the forging and cut away all of the machining. This is also the most natural
workflow for the software. It's also true for Pro-E and other similar
systems.

Mark

 

Mark,
There you go with a 3 X 4 X 10 forging and end up
finding out that the part is 4 X 4 X 11 after machining .....
and piles of reverse engineering time on that forging.

 

Cliff,

When you design piece parts, forged or otherwise, in the context of an
assembly, it's pretty hard to make those kinds of mistakes. You can also tie
key features, between one part and another, with equations so the
proportions remain constant. Not very hard to do really.


Mark

 

Hmmm... that statement seems odd:

Working in UG, one loads the finished part model into a new part file
for the toolpath work. Next, one would load the forging model (as an
assembly: lives in a separate part file)into this file. The forging
model is then "mated" to the part (ie, centered about the part for best
fit). Then, fixtures are either created or brought in (assembly) and
mated to the forging surfaces for location. As the part nears
completion, other fixtures may be brought in (other layers) and mated
to some of the machined surfaces of the part.

The point is (IMHO): the finished model should be the root part. If
your concerned about inprocess machined features, one can save an
inprocess model (created by the toolpath) to be used as stock for
subsequent operations. This can be done via UG's own inprocess stock
feature or imported from say Vericut.

Designers design parts. Not forgings. They are a result of the finished
part.

 

Just to update: I see this was a crosspost from comp.cad.solidworks
(darn Google). I wouldn't have made the reference to UG.

 

Bill,

Why not ? Nothing wrong with hearing about how things are done in other
systems by other people.

Mark

 

Bill,

Sounds kind of open ended. Does the forging update when changes are made to
the base part using this method ??

Don't know if I like the idea of using a mesh model as a production
reference.

This is both a yes and a no,, depends. Often, a machined part is very
different from a forged/machined version. You usually have alot of rough,
drafted features with only the "working" surfaces and features machined. I
think it's important to have this accurately represented in the master
assembly. I don't do many forgings, but I do castings. The results are more
important than the steps or methods.

Regards

Mark

 

Mark,
But then you are going part ==> forging/casting <VBG>.
As I asked about ......

 

Bill,
There are a few in alt.machines.cnc that worked in the
pattern/casting/model/forging fields and might be quite
expert at it ....

Do they start with a forging and then design the part?