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1、,GD&T,Proof that implementing GD&T can save Coloplast money !,Michael Ziade COLOPLAST CORPORATION 4/26/2007,What is GD&T ? Brief description of GD&T Savings Training Implementation Conclusion,What is GD&T ?,GD&T (Geometric Dimensioning and Tolerancing) is a precise mathematical language that describ
2、es the size, form, orientation and location of part features. It is also a design-dimensioning philosophy that encourages designers to define a part based on how it functions on the final product.Through the use of functional dimensioning, tolerances are assigned by the designer based on the parts f
3、unctional requirements, often resulting in a larger tolerance for manufacturing. This eliminates problems that result when a designer assigns arbitrary, or too tight of a tolerance to a part because he/she doesnt know how to determine a reasonable, functional toleranceDrawings do an outstanding job
4、of displaying nominal geometries, but the designer still needs to put in allowable variation, and GD&T symbols are the way those tolerances are expressed on the drawing. Ideally, there is a product team participating in the design process, including those involved in assembly, manufacturing and qual
5、ity. GD&T can provide uniformity in the specification and interpretation of the drawing, thus eliminating guesswork and wrong assumptions and ensuring that design, production and inspection are all working in the same language.,There should be a quality/inspection plan for every CAD design, and insp
6、ection specifics should be included in the drawing.Often a common misconception of GD&T is that it is simply a series of symbols to eliminate words here and there. Sometimes there is an impression that its understanding should be somewhat automatic without much training. GD&T tends to be the “Rodney
7、 Dangerfield of the industrial world: it “gets no respect.” The true power and magnitude of the system is not recognized. Thus, there is a tendency to dismiss it almost entirely as another gimmick to upset our work schedules and cause confusion. However, GD&T is an entire universal language of engin
8、eering statement.Remember that GD&T analysis is the link between Design and Manufacturing.,GD&T Notations:Basic Dimension: Theoretically exact, untoleranced dimensions that specify the perfect location, size, shape, or angle of a feature.Basic dimensions are identified by enclosing the dimension in
9、a box.Basic dimensions specify theoretically exact value from which variations are defined through feature control frames as well as toleranced features and notes.General tolerances do not apply to basic dimensions.,GD&T Notations: (Cont),Geometric tolerances are different from the tolerances allowe
10、d for the size of feature, they specify the allowable variation of the shape of a feature.There are three basic types of geometric tolerances: Form, Orientation and Position tolerances.Geometric tolerances are specified using a control frame consisting of a tolerance symbol, a tolerance value and op
11、tional datum planes.Material condition modifiers define the condition at which the tolerance is to be applied. If the maximum material condition is specified, then there is a “bonus tolerance” associated with a decrease in material.1. The form of a feature is assumed to be perfect at its maximum mat
12、erial condition. 2. If no material condition is specified, then it is regard less of feature size.,Symbols for Geometric Tolerances,GD&T Datum Surfaces and Features,Feature Control Frame,A geometric tolerance is prescribed using a feature control frame. It has three components:1. the tolerance symbo
13、l,2. the tolerance value,3. the datum labels for the reference frame.,Reference Frame,A reference frame is defined by three perpendicular datum planes. The left-to-right sequence of datum planes defines their order of precedence.,Order of Precedence,The part is aligned with the datum planes of a ref
14、erence frame using 3-2-1 contact alignment.3 points of contact align the part to the primary datum plane;2 points of contact align the part to the secondary datum plane;1 point of contact aligns the part with the tertiary datum plane,Using a Feature as a Datum,A feature such as a hole, shaft, or slo
15、t can be used as a datum. In this case, the datum is the theoretical axis, centerline, or center plane of the feature.The “circle M” denotes the datum is defined by the Maximum Material Condition (MMC) given by the tolerance.,Material Conditions,Maximum Material Condition (MMC): The condition in whi
16、ch a feature contains the maximum amount of material within the stated limits. e.g. minimum hole diameter, maximum shaft diameter.Least Material Condition (LMC): The condition in which a feature contains the least amount of material within the stated limits. e.g. maximum hole diameter, minimum shaft diameterRegardless of Feature Size (RFS): This is the default condition for all geometric tolerances. No bonus tolerances are allowed and functional gauges may not be used.,
