"CAD is Master" note
"CAD is Master" note
(OP)
Hello,
I deal with thin metal stampings and have a customer that is insisting that I have our parts 3D laser scanned because he interprets the note "CAD is master" on the print to mean; Whatever dimension is not listed on the print must be checked to the Math Model.
I have always interpreted "CAD is master" to mean; if there is a discrepancy between the Model and the Print, the Model supersedes the Print.
We do a point cloud CMM layout at PPAP and annuals, and we check parts to an attribute gauge. We feel this is more than adequate to check thin metal stampings to the print and/or CAD.
Also since our materials are thin we check the parts in a constrained state. I don't even know how you could scan parts on a fixture.
Your thoughts?
I deal with thin metal stampings and have a customer that is insisting that I have our parts 3D laser scanned because he interprets the note "CAD is master" on the print to mean; Whatever dimension is not listed on the print must be checked to the Math Model.
I have always interpreted "CAD is master" to mean; if there is a discrepancy between the Model and the Print, the Model supersedes the Print.
We do a point cloud CMM layout at PPAP and annuals, and we check parts to an attribute gauge. We feel this is more than adequate to check thin metal stampings to the print and/or CAD.
Also since our materials are thin we check the parts in a constrained state. I don't even know how you could scan parts on a fixture.
Your thoughts?





RE: "CAD is Master" note
If you have missing dimensions on your print, and reference the model, then your customer has a point about wanting the part verified against the model.
However, dictating the process is questionable - especially if as you say the proposed process may not be appropriate.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: "CAD is Master" note
In the real world, anything you place on your drawing may and will bu used against you like charging extra for every FCF.
RE: "CAD is Master" note
We are implemented Model Based Definition (MBD) here. I object to terms like "limited dimension drawing" and "CAD is Master" because they have no meaning. I have updated our title blocks to state that if the feature is not dimensioned, the dimension is whatever is on the 3D CAD model.
In a narrow technical sense, you need to prove that your part meetings their drawing and model. How accurate is a laser scanner compared to a CMM?
On the other hand, this is not really a problem. If your customer wants parts laser scanned, laser scan them, and adjust your prices accordingly. Warning them that you are about to do this is possibly an even better idea.
--
JHG
RE: "CAD is Master" note
"CAD is Master" tells me that the CAD model describes the ideal geometry from which certain deviations are tolerated. If the part requires constraint to be inspected, those constraints should be on the drawing or somehow represented in the model.
If you can perform a CMM check with the part in the inspection fixture, there's no reason using a laser is any different.
RE: "CAD is Master" note
Tunalover
RE: "CAD is Master" note
It seems to me that using "CAD is Master", there is no point of having a dimensional drawing.
In today's over-sensitive world, it would seem "CAD is Master" would be not PC.
Chris, CSWA
SolidWorks 14
SolidWorks Legion
RE: "CAD is Master" note
It's your drawing. It's your note. You define the interpretation, not him.
Hopefully you have the meaning actually documented somewhere in your company standards.
RE: "CAD is Master" note
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
RE: "CAD is Master" note
Not to mention that "D" may be interpreted as "design".
Your "cad data" represent theoretically exact (basic) sizes and shapes. You still need to apply GD&T to something which may be "flat" 2D drawing.
RE: "CAD is Master" note
Both drawing and model contain data.
Board drawings are also "designs".
I stand by my statement that "CAD(D) DATA IS MASTER" is meaningless without further definition as to which data is indeed the master.
But then, in my experience I have only seen similar statements declaring that "CAD MODEL TAKES PRECEDENCE OVER DRAWING."
“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV
RE: "CAD is Master" note
1. DIGITAL PRODUCT DEFINITION PREPARED IN ACCORDANCE WITH ASME Y 14.41-2003.
2. THIS DRAWING SHALL BE USED WITH MODEL (INSERT PART NUMBER) (REVISION PER THIS DRAWING) FOR COMPLETE PRODUCT DEFINITION. MODEL GEOMETRY IS BASIC.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: "CAD is Master" note