Casting vs. Machining Drawing
Casting vs. Machining Drawing
(OP)
Hello,
I am looking for some information regardng the differences between casting drawings and machining drawings. Specfically, what kind of tolerances are associated with various casting processes versus a machining process? Also, if I have a part that needs a casting and machining drawing made for it, how would I reflect this difference in Solidworks? Any help would be greatly appreciated.
Thank you
I am looking for some information regardng the differences between casting drawings and machining drawings. Specfically, what kind of tolerances are associated with various casting processes versus a machining process? Also, if I have a part that needs a casting and machining drawing made for it, how would I reflect this difference in Solidworks? Any help would be greatly appreciated.
Thank you





RE: Casting vs. Machining Drawing
And besides, since you're asking this question in what appears to be the context of Solidworks, you may get better answers if you were to post this question in the Eng-Tips Forum dedicated to Solidworks.
BTW, you wouldn't by any chance be a student now would you?
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
http://www.siemens.com/plm
UG/NX Museum: http://www.plmworld.org/p/cm/ld/fid=209
To an Engineer, the glass is twice as big as it needs to be.
RE: Casting vs. Machining Drawing
_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year
RE: Casting vs. Machining Drawing
Processes have capability.
A population of parts has variation and distribution.
It's important for engineers to understand the difference, and use the right word.
RE: Casting vs. Machining Drawing
RE: Casting vs. Machining Drawing
We have a forum559: SolidWorks 3D CAD products. Ask your SolidWorks questions there.
Foundries usually quote tolerances of something like ±0.005"/". If your design requires tighter tolerances you need either to machine, or change your design.
RE: Casting vs. Machining Drawing
http:/
This will give you some guidelines on how to create drawings for cast parts, including the subsequent machining drawing.
It will not give you information on tolerance values, this is derived per Mint.
However, if you want process capability type tolerance information you may have to talk to individual vendors. Sometimes industry associations have guidelines (maybe the source Arunmmrao mentions) or sometimes reference books but they'll typically be fairly general and you'll often get more specific answers from actual foundries. Also as you hint, there are many different casting processes and each has it's own strengths and weaknesses when it comes to tolerance capabilities and related issues.
Some places have design guides on line that you can look at. For instance I've used A.L. Johnson for Rubber Plaster Mold Aluminum castings they have some info online http://www.aljcast.com/prod.html and I was able to get much more information from their free casting design kit.
(This is the wrong place for the Solid Works part of the question, however I'll have to disagree with John about the entire question belonging there - this is a reasonable place for the non CAD part of the question. There are also dedicated drafting & casting forums for those aspects.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Casting vs. Machining Drawing
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Casting vs. Machining Drawing
RE: Casting vs. Machining Drawing
In some eras and in some industries the foundry was given the drawing of the finished part and they create a drawing of what the finished casting should look like, and of course the pattern needed to create the cast part.
RE: Casting vs. Machining Drawing
If their process suits your volume, size, material (etc.) requirements then I'd contact them to get the full guide - there's a lot in it - I spent a couple of evenings going over it last year when I was designing a part.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Casting vs. Machining Drawing
The company I used to work at in the UK had a foundry attached. we would give them a drawing of the finished part. The pattern makers would then create molds for the finished part using an expansion rule. This device was a rule calibrated for the expected shrinkage of that metal as it cooled.
A common nasty practical joke was to lend that rule to a machinist.
B.E.
The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor
RE: Casting vs. Machining Drawing
Well and good, when the foundry understands the design constraints of the finished part.
RE: Casting vs. Machining Drawing
Besides the excellent guidance provided in some of the previous posts, I'd offer this perspective on engineering drawings in general. An engineering drawing, such as those for your cast part and machined part, is a set of requirements for a finished part condition. The drawing should define those requirements as completely and specifically as possible, since anything not defined on the drawing is left open to your supplier's discretion. Castings usually have a separate part number from the finish machined part, because raw castings are commonly supplied by outside vendors.
In the current digital age, it is common to use a 3D CAD model as the basis for the physical definition of the part. Thus, ideally the CAD model of the casting would include all of the relevant features in the cast part as delivered. This means draft, fillets, core supports, tooling points, parting lines, etc. The foundry will add features like risers, gates, etc. to your model, and they will also scale the model with the appropriate shrinkage factor to produce the pattern or mold tooling.
Hope that helps.
Terry
RE: Casting vs. Machining Drawing
It is just a first iterative step towards developing a solid product from a drawing. Handbook on casting will be a good place to start in my opinion.
_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year
RE: Casting vs. Machining Drawing
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?