How do you interpret the flatness tolerance of a part with multiple datum features?

Datum features are the physical features associated with a datum symbol or datum target as specified on a blueprint or CAD model. Things to consider. -Datum features lock down the 6 degrees of freedom of the part with the use of physical or theoretical datum simulators and should be sufficient size to accomplish the task. - The order of precedence is established by the datum references in the feature control frame. -Datum features should represent the functional requirements of the part and the relationship to the assembly as applicable to the design intent.

Datum Features are actual features of a part and those features are used to establish the Datum. -Datum features are chosen from real physical features on the part. -Datum features are either permanent or temporary. -Datum features should be a) functional b) Representative of mating or seating features. c) accessible to those in manufacturing & inspection.

Per ASME Y14.5, datum features can be planar surfaces, which establishes a datum plane. They can also be features of size (e.g. cylinders, spheres, and others) which establish centers (axes or a point, or a combination thereof). They can be conical surfaces, or irregular surfaces, which can establish combinations of datum planes axes, and a point. Datum feature identifier symbols must contain an uppercase letter (except I, O, Q), and datum target identifiers must contain an uppercase letter (exceptions as previously noted), followed immediately by a sequential number series starting with "1".

Flatness is the deviation of a Feature to itself, regardless of Datum's. No matter where a Plane is in space, the deviation from the part being checked to a perfect plane is the result.

Hello, and thanks for your question. GD&T Flatness is a characteristic that evaluates the form of a feature(s) independent of any datum reference frame. This task is best accomplished on a Coordinate Measuring Machine using either tactile or non-contact sensors. The non-datum related state of the flatness characteristic makes it useful for controlling the form of a surface without needing to tighten tolerances on other print dimensions.

This statement yields an incorrect implication. Flatness, when applied to multiple nominally planar surfaces, limits the form deviation of each surface independently of every other surface. Each surface may be adequately flat, but they are not coplanar, which most people assume for a flatness control. Coplanarity (i.e co-flatness) is instead achieved (Y14.5) by applying a single profile of a surface control to all appropriate surface simultaneously. Also, the flatness control symbol is essentially a leaning parallelogram.

Flatness is surface form control. A perfectly flat surface is defined as having all its elements in the same plane. To apply flatness tolerance - First, we have to understand the requirements. -once the requirements are met, by using FCF int he drawing to specify flatness control symbol and tolerance value. - Flatness is independent of Datum so kindly refrain using Datums in FCF. -Make sure that Flatness tolerance value must be less than the size tolerances.

You don't measure tolerance, you measure deviation. You measure a nominally flat surface and determine if it is within or outside of the flatness tolerance.

From the perspective of measuring flatness by using universal coordinate measuring machine (CMM). Sampling strategy is crucial in determining whether our flatness measurement is valid or not. Also, sampling strategy of CMM is a dominant uncertainty contributors. The basic idea is that, we want to capture or probe surface points as small as possible but capture the extreme feature deviation on the flat surface me are measuring. For sampling strategy, grid sampling points seems the reference approach since it captures points in a grid formation covering the whole surface. Another option is by using adaptive sampling strategy that can estimate where the most deviation area of the surface to measure and ignored the others areas to save time.

MMC is the condition of a feature wherein the feature contains the most material. -It is often thought of as a heaviest feature. -it is the smallest hole or largest shaft. -MMC symbol is usually used to preserve a mating boundary, a constant boundary of VC

LMC is the condition of a feature wherein the feature contains the least material. -It is often thought of as a lightest feature. -It is the largest hole or smallest shaft. -LMC concept is usually used for features when the preservation of material is of great importance.