casting and machining on seperate drawing
casting and machining on seperate drawing
(OP)
Hello,
In the company I work, we have separate casting and machining drawing. On the casting drawings, we use phantom lines on the view to show the machining outlines. One thing I have doubt is we attach datum feature symbols to some of these phantom lines to specify them as datum features. I'm wondering if this is legal because they are non-exist features on casting. Per para 4.24.13 in '09 std, "The datum feature symbol should be attached only to identifiable datum features.". '94 std has same statement. Any thoughts?
In the company I work, we have separate casting and machining drawing. On the casting drawings, we use phantom lines on the view to show the machining outlines. One thing I have doubt is we attach datum feature symbols to some of these phantom lines to specify them as datum features. I'm wondering if this is legal because they are non-exist features on casting. Per para 4.24.13 in '09 std, "The datum feature symbol should be attached only to identifiable datum features.". '94 std has same statement. Any thoughts?





RE: casting and machining on seperate drawing
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: casting and machining on seperate drawing
The subsequent machined surfaces may be indicated by phantom lines on the casting drawing as you do, I just don't believe it's appropriate to indicated them as datums.
(Mech North, I thought the casting datums were meant to remain on the machined part see ASME Y14.38-1996 4.3.1d.. Plus a quick look at 14.38 & I'm not sure I see phantom lines showing as cast surfaces on machined part drawings.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: casting and machining on seperate drawing
The casting drawing should not indicate machining data. One reason is if the machined part changes, the casting drawing may change.
If the part is cast at another company, they don't care about the machined data.
The machine drawing can call out cast surfaces if they are not machined.
Chris
SolidWorks 11
ctopher's home
SolidWorks Legion
RE: casting and machining on seperate drawing
RE: casting and machining on seperate drawing
RE: casting and machining on seperate drawing
RE: casting and machining on seperate drawing
My basic understanding is that the machined datums should be related to the cast datums - hence the cast datums need to be shown in the machining drawing section 4.4 of the 96 edition. Set the datum targets up in such a way that the machined datums are easily derived from them - ideally opposite. You still try and capture some logical function - such as a minimum wall thickness or some such - but it may not be as clear/simple as in a typical machined part.
Sorry Ctopher but the foundry may indeed care about what surfaces are machined for several reasons, including where to put gates & risers etc. (if not explicitly stated on the drawing) and where to do the usual cast lot marking etc. Yes making sure the cast drawing gets kept up to date with the machining drawing can by tricky but there is justification in some cases.
Fsincox, if a full machined reference frame is set up then what you say is I believe correct, however if you have a casting with minimal machining can it not make sense to reference at least some or all of the cast datums? I had a part recently with minimal post casting machining - just a few holes and little 'trimming' and I just kept the cast datums. Arguably I could have established machined datums using selected holes but I think it would have been
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: casting and machining on seperate drawing
Some considerations for cast datums are;
1) machine-off or leave on
2) surface conditions (roughness, form, shape, etc.)
3) stability of workpiece
4) stability of cast datum feature (a thin section may not be ideal as it may shift more during cooling)
5) proximity of machined datum features to the cast datum features
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: casting and machining on seperate drawing
"Datum targets should be located as follows... ...(d) on features no subsequently altered or removed"
Of course it's a 'should' so you can argue just how strong of a 'suggestion' that is but there are very few "shall" statements in any of the standards any more so I generally take a 'should' as a 'shall' unless there's a really good reason to do otherwise.
As to the phantom lines showing the cast surface, I only see this for combined views. This is not the situation the OP says they are in since they explicitly mention separate casting and machining drawings - am I missing something?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: casting and machining on seperate drawing
As for the last comment, I just posted an appropriate use...it's something we tend to do in this forum ;~}
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: casting and machining on seperate drawing
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: casting and machining on seperate drawing
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: casting and machining on seperate drawing
Understood, I am talking of much more complicated parts where I see people reuse cast datums in entirely new frameworks. Not parts setup on cast datums and machine complete in one setting. I still prefer a functional definition of features if at all possible, though.
RE: casting and machining on seperate drawing
The casting house needs to know which surfaces are not machined if the cast lot is to be on a surface that is not machined away.
The machine shop needs to know which surfaces are not machined and also the amount of stock on the machined surfaces.
There may be the need for multiple views on the casting drawing if one casting is used to produce multiple finished parts.
Datums should be defined for each state of the process and only carried through if it is the same surface.
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
RE: casting and machining on seperate drawing
I guess if you tolerance your Rm drawing and machining drawing to leave a min cleanup of .01 why do you need to show the machining features on the RM drawing. We produce two different drawings and or models which have their own respective drawings. The only thing copied from one to the other is showing the RM datums on the Machining drawings. Single source of truth.
Thanks
RE: casting and machining on seperate drawing
Did serve a year - 18 months under a really good checker and learned a lot from him and from various other older, more experienced folks however very limited formal training.
In the 'finer things of life' like casting drawings I'm mostly self taught from referencing the standards.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: casting and machining on seperate drawing
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com