Modelling Cast parts

I am working for a company who are just implementing Wildfire 2 for the
first time after using autocad. A lot of the models are cast parts and
so require a casting drawing and a machined part drawing. Currently in
AutoCAD they draw the profile of the machined part in a dashed line on
the section of the part in the cast drawing.

Is there a way of doing this in pro without using sketches on the
drawing or datum sketches in the part, as it would be good to have the
detail associated with the machined model itself.

Also the raw casting sometimes are used in different machined parts to
create different parts.

I noticed a few posts mentioning Pro/CAST... would this help them
achieve what they are after? I am having trouble finding anything about
it though so any help on that would be appreciated too.

I look forward to your suggestions!

 

I know kind of a cool way to see this; I'm not sure how it would work out on a
drawing. But, for what a casting or forging designer needs to see (the extra, the
material "allowance"), this is ideal:
create either your cast or machined part, then, either cut away the extra, as
would be done in machining, or design your machined part and add the material
allowance to arrive at the casting. The first is CASTING-01, the second is
CASTING-02. Make an assembly and put the two together, superimposed, one on top of
the other. Do the casting as translucent with a lighter color ('View>Color and
Appearances') so you can see the machined part 'inside'. Maybe, in a drawing, with
one on top of the other, the inner model will give you a hidden line outline.
Also, could this be done with a instances of a family table? or with views based
on rolling back the part to show the earlier condition?

Sorry, don't know anything about Pro/CASTING but it does sound suggestive, doesn't
it!?! Wouldn't surprise me a bit if it encompassed exactly the functionality you
need. Although, if you go online to the PTC website, Pro/CASTING is an illusion.
You get instead, TOOL design, but no specific module. Once again, PTC thinks it's
being clever by creating a mystery, but will likely (if we can tell by thier
history) shoot themselves in the foot. Good Luck, PTC! Hey, go with what you know.

 

I'd suggest you make & detail separate casting & machining models. If
you model the casting, then use Insert - shared data - merge from other
model to place it's geometry in the machined model as a single feature,
you can re-use the same casting in numerous machined final parts.

Be sure to match absolute accuracy between casting & machining. (Use
0.02 as a starting value, it works for pretty well everything)

When creating machining features, only reference datums etc in the
machining model, so you can chop & change the casting without the
machining going wrong.

Where are you based? I may be able to help you out further.

 

..02 mm or equiv?

 

Better yet, model the machined part first and then use it as an
Inheritance and basis for the casting. Changing a feature in the
machined part will automatically alter the cast shape.

Who can model the casting first anyway? When you think about, the
machined part drives the casting, not the other way around. You need
to know what the final part looks like before you can determine the
casting geometry.

Regards

 

Which came first; the chicken or the egg?

The few casting models I've done began with a customer's furnished part. I
copied machined faces, created over lay quilts (cast condition) and merged. New
family table instance cut the machined faces using the copied surfs as a basis.

I `think' I'd go thru the same process starting from scratch. It fits the way
my head works and I'm not sure I'd always know if a casting will be used during
initial design. If I did a lot of that kind of stuff I might re-think. Knowing
I'm looking for a casting and modeling from the get go as such would be more
efficient, or so one would think.

http://www.mcadcentral.com/proe/forum/forum_posts.asp?TID=28795&TPN=3
(look for dsergison's stuff, scroll back to the first or second page for a cool
pic Cat engine mockup) outlines a cast then cut process.

 

Thank you very much to everyone who has posted. I'll need to see how my
company want to do things - cast first then machined or vice versa.
I'll certainly try out all of your suggestions and see which suits
best.

I had thought about using the inheritance feature but wasn't too sure
what this would do. What is the difference between inheritance and the
merge option from shared data?


As for the Pro/CASTING, I found that we do have it installed - its
Pro/MOLD / Pro/CASTING extension, seems to be mainly for setting up the
die but I have still to investigate this further. As David Janes
pointed out above, there doesn't seem to be anything on PTC's website
about this. I'll just have to go through the help files some more.

Thanks again for all your help.

 

The way we do it is to:
1. Create the casting.
2. Add machining features.
3. Group the machining features (call it "machining" or something like that)
4. Create one drawing for the casting and one for machining using the same
model.
5. On the casting drawing just use VIEWS>REPRESENT>SIMPLIFY (and select your
machining group which will now dissappear on the drawing.)

NOTE: The only way to get the views menu (it was shown in previous
releases of Pro/E but hidden for some reason in Wildfire) is to create a
mapkey for it:

Use a text editor to open your config.pro file and add the following: (then
save it).
mapkey Representation @MAPKEY_NAMEDrawing View Representation;\
mapkey(continued) @MAPKEY_LABELRepresent;#VIEWS;#REPRESENT;
Or use syntax for a typed mapkey like:
mapkey vrv #VIEWS; #REPRESENT;

Restart ProE Wildfire and open a drawing. You can customize your screen to
include the mapkey as an icon on the tool bar, or use the keystrokes vrv as
in the example above.

See this webpage for reference: http://www.synthx.com/tom/sy_tip_0502.htm

Good Luck!

 

"Who can model the casting first anyway? When you think about, the
machined part drives the casting, not the other way around. You need
to know what the final part looks like before you can determine the
casting geometry."

Bye and large the two evolve in step with each other through the design
process. Keeping the models separate has the advantage of letting you
take multiple finished parts from one casting without having lots of
suppressed groups of machined features at the end of the model tree
which you need to drive with a family table and your pdm system
probably won't support properly.

If you're lucky enought to have an IT department who thought about
family tables when they configured your plm, can I come & work for you?

 

John,

I think you're doubling your work by maintaining to two distinct and
un-related models. I've never known enough at the start of a design
process to determine the casting's geometry before that of the finished
part - it is just counterintuitive.

With Inheritance, you create the cast model, insert the Inheritance
feature, suppress the machined bits that you can (holes, etc). Then
add offsets to the surfaces that will be machined.

You would not use this part as the basis for another machined part.
Instead, you would either family-table the original machined part or
make another Inheritance-based part for your machined iteration. That
way, a change to the original (which is changing the casting), would
propigate.

Regards

 

I can't speak from personal experience of inheritance, all I can do is
say I have a process which works for me. I'm not following the creation
process you outline, do you have pointers to any documentation?

 

Well, we always hope we help. Often, it's a shot in the dark. This one stirred up
some process discussion, not that it directly pertained to your technical
questions on representing, old style, cast and machined features in a single
drawing. Well, easy in ACAD, not so easy in Pro/e, that's about all I got out of
this discussion.

That, and the fact that most people don't seem to appreciate what a casting is.
Well, think brass bell (Liberty comes to mind), think cannon, think trivet or
potbelly stove or automobile frame or lathe bed or axle. Now we're starting to get
into cast parts that actually require machining. But, please, one and all, the
charm, the wonder, the economy of casting is that 95-100% of the finished product
is captured in the rough casting. Even today, when modern products demand greater
accuracy, some type of casting will fit the bill:
http://www.key-to-metals.com/Article59.htm

In light of this and, contrary to prevailing opinion, this doesn't call for
building the casting around "the final, machined product". First, a part that
required heavy machining would have been built from a forging, cold or hot drawn
billet, extruded shape, cold drawn or rolled sheet or plate. People make castings,
in the first place, because they require MINIMAL machining. The machining is
effectively, as far as the casting is concerned, an after thought, a refinement, a
frill, an affectation. The casting, its essence, its basic form, is given and
unaffected by later machining. Its utility and stuctural properties are taken
account of and built into the rough form of the casting. These are not altered, in
the slightest, by later machining. Such things, for example, as minimum wall
hickness, can influence the nearness of two valve ports to each other, but will,
in no way, influence the overall shape, proportions or weight of the basic
casting. This could happen only if more than about 5-10% of the weight of the
rough casting would need to be removed to produce the machined product. If your
manufacturing process is routinely doing this, you need to consider starting from
a rough material other than one that's founded.

 

David,

People usually make castings for cost and, most importantly, because it
is next to impossible to machine some shapes. And you don't put rough
castings or forgings in a finished product, so the machined part is
hardly an 'afterthought' - it is the primary focus.

Forget the liberty bell for a moment and let me give you a 'real world'
(not Old World) example:

You are working on an engine. You want a bracket to mount the
alternator to it; odds are pretty good you already have the alternator
AND the engine (who would make the engine around the bracket?). So,
you open the engine assembly and insert the alternator into it. You
position the alternator assy where you want it in space; now you start
making a bracket that fits.

Do you mean to tell me that, at this particular point in your design
process, you think you can start modelling a CASTING? Of course not,
you are going to make a finished part. You're going to put in hard
points, mounting holes, screws, etc. You're going to make sure you can
get a socket wrench in to the screw heads. You're going to be
finessing the location so that you have good wrap angles on the belt
and the center distance works out to a standard belt size while the
tensioner is mid-range in it's motion. There are dozens of little
corrections to fit and usability, none of which you can make with a
casting model. If you're worth your salt as a designer, you already
know if you're going for sand, investment, lost foam, or die casting
and you're considering constant wall thickness and draft angles and
other peculiarities to each process.

Now you find yourself with a finished, machined part - not a rough
casting. In order for you to finish your bracket project, you then -
downstream - need a casting model. Your first 10 parts you're probably
going to make from solid or SLA while you're waiting on your foundry's
tooling and samples anyway.

Meanwhile, your buddy Tom has decided that where you put the alternator
is just IDEAL for the power steering pump - and he wants to know if
you'd mind sharing your bracket with his pump? C'mon, all it needs are
three holes and an ear, you can do that right? 'Course you can. So do
you add it to your casting to see if it too fits? Of course you don't
- you add the holes to your finished part - and the ear too. You want
to see how the power steering pump looks alongside the alternator.
Now you need to get a three cylindrical bosses and an ear on your
casting too.

Meanwhile, Fred needs to do something about the fact that you've just
put a mounting pad onto the side of his engine block for your bracket -
and you weren't working with the raw casting either; were you -how
could you have been?

That's why you just cannot know in advance what your casting is
supposed to look like until you've modelled the finished part. You
cannot design an assembly like that working with raw material any more
than you would put a piece of 4340 round stock in place of shaft in a
gearbox - which is essentially what you're advocating when you get
right down to it. Finished parts come first.

John Wade:

I'm sorry if I was a bit unclear in my description of the use of
Inheritance for castings, so here it is again:

-Model your finished part

- Make a new empty part - File>New

-Insert an Inheritance of the finished part as the first feature -
Insert>Shared Data>Inheritance from Other Model. Assemble it to
Default.

- Expand the model tree of the Inheritance feature so you see the model
structure of the finished part

- Working from the bottom of the model tree and going up, highlight
each feature that would NOT exist in the casting (tapped holes for
example) and suppress it. This will NOT propigate back to the original
part. Be careful at this point to make sure that parent/child
relationships are not causing the uninteded suppression of features
further down the tree. If they do, you may need to alter the original
(machined) model's design intent or find another way to deal with the
feature.

-Once you've suppressed the machined features that you can, add offsets
(Edit>Offset) to the surfaces requiring cast stock for finish machining
or fill in with Extrudes areas that you want material on for fixturing,
etc. Obviously, you're probably not going to be adding any cuts.

Offsets are just one way of adding material - there are also Variable
Dimensions and plain old Extrudes.

Now that you've made your casting and made it parametric to the
finished part, if you decide later on that you need to add something -
or remove something - from the finished part, all you need to do is add
it and then open the casting model and RMB on the Inheritance feature
and do Update Inheritance for your changes to propigate.

Regards
Peter Brown

 

Peter, it's unfortunate that you didn't trouble yourself to quote my presentation
on this subject of castings. It was historical and fairly broad reaching. But, I
thought, when I wrote it that it captured the essentials of castings, the main
reasons for founded parts, then as well as now. What has changed is only that more
is expected of founded parts, possibly more than ought to be expected of them. You
seem to jump over them as something dirty and inconsequential. The fact is, that
people continue to design castings which contain all the main elements (stuctural,
mechanical, esthetic) of the functional part that they need. You have difficulty
with the idea that machining is an "afterthought". I understand because the
machined part is also essential, one might even say, the whole point of the part,
the thing which makes it actually useable. On machined castings, I'll agree. The
last castings I worked on were hydraulic valve bodies. Probably 25-30% of their
surface area was machined. Beyond that, one begins to wonder why bother with
castings. True enough, coring (which hasn't been mentioned so far, in this
discussion) pre-removes material so that there is less to remove with machining.
In the case of valve bodies, cores, which are essential to casting design, make
passages through the valve body to facilitate the machining of valves and ports.
As to the design of valves and ports, the essential design criteria are the final,
machined feature. Only this decides such things as minimal wall thickness and how
to space/mount hydraulic or electrical throws on valve stems.

You live in denial (ignorance?): fully 95% of all castings require NO FURTHER
MACHINING. (By number, not gross tonnage). Most of the rest require a little (one
or two machined features) modification. But that's the essential point of
castings: you design the casting: all the functional, mechanical and esthetic
features are included. All that is sometimes required is to smooth its interface
witht he rest of the world. So, machined features are required to construct this
interface. Generally, if designed properly, the casting will undergo little or no
change because of such modification. When you reach the point where you are simply
taking a finished, machined part and adding a little 'extra' everywhere, you've
pretty much lost the POINT of a casting: MOST features could be used, AS CAST ~
that was the TRUE cost savings. When 90-100% of surfaces are machined, the
advantages of the casting are lost. Might as well take a saw cut billet and cut
everything out of it, especially if it's a more free machining, less abrasive,
stronger material.

I do the bell and trivet, purely cast, no machined features and you do the engine
block, extreme opposite, nearly 100% machined, the place at which manufacturers
start to envision other technology because the raw material price (casting, saw
cut block, etc.) is far outweighed by the cost of machining ~ 10 to 1. The more
machined features you put on a casting, the less reason there is to use one, the
less savings, the smaller the machining advantage from coring (see previous point
on grey iron abrasiveness, increase in tooling costs.)

Again, bear with us here. If you are modelling a finshed part, you are modelling a
finished part. The casting is almost incidental. I repeat: 95% of casting design
is NOT like this. Functional castings are designed every day, they are not
machined, but cast, parts. Zero, or minimal, machining is required. And the
machining is because of interface, not structural/mechanical, requirements. The
structual/mechanical stuff is already taken care of in the basic, cast part. So is
the basic geometry.
So are the esthetics. Somebody wants the bell to rock more smoothly, not wobble
around; they machine the hole and normal sides of the tang. It rocks smoother, the
sound is cleaner. Small modification, big effect.

Thanks for this nice description and introduction to the use of an inheritance
feature: with this, I might actually try one now.

One of the best discussions we've had in this NG. Thanks, Peter, for taking the
time and sharing your experience.

 

David,

Forgetting the historical perspective, what I completely disagree with
is that you can model your casting before your machined part. I've had
a few engineer pull that stunt when moving parts from 2D to 3D ( where
the geometry was predetermined) and it is a pain in the ass. Why?
Because parts change over time (the old PTC lifecycle mantra). And
when we decide that we need more thread engagement on a part and a wall
or flange has to be thicker, do you know how tedious it is to try to
infer from a casting which dimension you need to change to achieve the
desired result, without causing other geometry to move? And - AGAIN -
I don't care what is going on with the casting really, I want more
threads - a machined feature. I should change it at the machined part
level, and then the casting should catch up with it.

And again, I'm sorry - but I have to take exception to your statement
that "95% of all castings require NO FURTHER MACHINING"..? You
generally make well-reasoned and rational arguments, but don't tell me
that I am in denial - or that I'm ignorant. How can you come up with
such an unsupported figure? I've spent 21 years in industry and I've
never seen a casting that we just turned around and shipped out again
as finished. 95% bears no relationship to reality, unless you are
discussing a tape measure case or similar die casting. All that
stuff's going injection molded anyway. I mean, c'mon, who is making
BELLS? Look at all the products PTC touts - Harley V-Rods, John Deere,
Caterpillar......not a bellmaker among them. Probably not a finished
cast part either.

To put your 95% claim to rest, I challenge you to go in your garage and
find a SINGLE - just ONE - cast part on your car, lawnmower, chain saw,
iron rake, or bicycle that has NO MACHINING. Sintering doesn't count,
molding doesn't count. Open the hood and find one, get out your
creeper and find one. Cranks, cylinder heads, intake and exhaust
manifolds, u-joints, steering forks, mower decks, control arms,
differential housings, throttle bodies, aluminum rims, brackets,
housings, brake rotors for God's sake.........ANYTHING. When you find
one, let me know.

Until then, castings are the downstream BYPRODUCT of machined parts.
Remember, virtually any cast part can be machined from solid, with
enough effort....and hardly any part as a casting can substitute for
the machined one, I don't care how much you try.

Regards,
The Ignorant Peter Brown