– Surfaces of sufficient sizes to allow repeatable measurementsĭatums are important and care must be taken when selecting them. When selecting Datums, designers should consider the following characteristics: You will usually wind up choosing those Datum featues that determine orientation, location, and functional relationships of part features and their mating parts. Datum Features (and their corresponding Datums) are selected on the basis of design requirements and functional relationships. It’s easiest to think in terms of Datum Features on your parts when deciding which Datums to select. Machine Table, Surface Plate, Angle Plate, etc. Whatever setup you will use is going to include appropriate Datum Feature Simulators. Okay, one more way to think of a Datum Feature Simulator–think about how you would inspect a dimension or tolerance called out by GD&T. These physical devices can all have Datum Feature Simulators that are relevant to our discussions and knowledge of GD&T.Īnother way to think of a Datum Feature Simulator is that they are inverses of Datum Features. We might be talking about some metrology or measuring equipment–for example a granite surface plate or a Go-NoGo Gage. We might be talking about a feature on the CNC machine, such as the table on a VMC or spindle axis on a CNC Lathe. Let’s make this easy–a Datum Feature Simulator is a real physical feature of the machinery that comes in contact with the part. When I first came across the term, my reaction was, “What an odd term–Datum Feature Simulators?” In fact, the term that was used before Datum Feature Simulator was added to the standard in 2009 was, “True Geometric Counterpart,” which is only slightly less odd.Ī granite surface plate is a typical Datum Feature Simulator for planes… Now it’s time to talk about Datum Feature Simulators. We learned that a Datum is an abstract geometric concept and that a Datum Feature is an actual feature on a part that corresponds. In the previous article, we looked at Datums–basic definitions, how they’re shown on drawings, and so on. Please be sure to include what version of the PTC product you are using so another community member knowledgeable about your version may be able to assist.CNCCookbook Beginner’s Guide to GD&T: Datum Feature Simulators and You may also use "Start a topic" button to ask a new question. If you would like to provide a reply and re-open this thread, please notify the moderator and reference the thread. This thread is inactive and closed by the PTC Community Management Team. My estimation is maybe creo remember the B and C datum in its memory because I used to define it in drawing. It just stay there.Īnd also, I went through the tree of drawing, I delete all the feature with name datum B. I check the 3D, there is an axis I built with a name B, in the last position of the tree. Now I want to re-add datum B but it does not allow it saying " same datum name exist". For some reason, I deleted mark of datum B and C from the drawing. One plane, and two cylinder holes as datum feature. On a drawing, I used to define datum, A, B, C. Someone say, it's better to build the datum first in 3D. I like to define datum with the toolbar in the drawing. I just start to use Creo recently, and I've got an issue when I try to set the datum for detailing a drawing.ġ) What is the best way to define datum in drawing?
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