Material conditions in GD&T - What are they ?

An important concept in GD&T based on which the tolerance value changes . What are material conditions in terms of size of Features ?

Material conditions refer to the different ways that a feature or part can be manufactured and the resulting implications for the tolerance requirements. There are three main material conditions defined in GD&T:

Maximum Material Condition (MMC): The maximum material condition is used to define the maximum amount of material that a feature or part can have. It is often used for mating parts to ensure that they fit together properly, and it typically results in a tighter tolerance.
Least Material Condition (LMC): The least material condition is used to define the minimum amount of material that a feature or part can have. It is often used to ensure that a part will still function properly even if it is at the lower end of the acceptable material range, and it typically results in a looser tolerance.
Regardless of Feature Size (RFS): The regardless of feature size condition is used to eliminate the effect of feature size on tolerance requirements. It is used when the size of the feature is not critical to the function of the part, and it typically results in a tighter tolerance.

By specifying a material condition, the designer can communicate the allowable deviation from nominal dimensions and help ensure that the part or feature will function properly in the final product. It is important to note that the selection of material conditions should be based on the intended function and manufacturing process of the part, and that different material conditions may result in different tolerances and costs.

For External features of size , Maximum Material condition is largest value of size dimension.

For Internal feature of size, Maximum Material condition is the smallest value of size dimension.

IN the below drawing , The Feature control frame has a M symbol beside the value of 0.1 for perpendicularity of the feature of size which has a basic size of 92.

This means that when the width of the component is at its maximum size the variation in Perpendicularity will be default 0.1 but as it moves away from its maximum material condition the value 0.1 will increase in proportion to the decrease in size of the width (92 dim)

Categories: GD & Tolerancing