0199b// Angularity, Parallelism or Perpendicularity with Implied Flatness
We to knowing that, orientation control ( Angularity, Perpendicularity and Parallelism) always come with implied flatness. We will shown you some of the example how orientation control's tolerance zone shape give this control come with implied flatness.
Case 1: Tolerance zone defined by two parallel planes for surface features
The slope for this part is control by Angularity 0.5 related to Datum A. Therefore, this surface must fit between two parallel planes which orientated with 30 degree related to datum A with 0.5 spacing. So, before we orientate the surface to 30 degree, we must able to fit the surface into 0.5 spacing. That is right! This is the implied flatness. If you unable to fit this into the 0.5 spacing. There are no chance to meet Angularity requirement.
Case 2: Tolerance zone defined by two parallel planes for feature axis
In this example, we need to the hole parallel 0.1 to the Datum A. The tolerance zone will be two parallel planes with 0.1 spacing and parallel to datum A. Features axis for the hole establish by unrelated actual mating envelope. This means features axis is a perfect straight line. This straight line never "carry" any Straightness information regarding to the hole. Therefore, NO implied Straightness here.
Case 3: Tolerance zone defined by cylindrical tolerance zone for features axis
In this example, a slanted hole is control by an 60 degree Angularity control with 0.05 cylindrical tolerance zone.
Similar to the example in case 2, feature axis is a perfect straight line and never "carry" any Straightness information regarding to the hole. Therefore, NO implied Straightness here.
Case 4: Tolerance zone defined by two parallel lines for line elements (Radial line elements)
In this example, this concave cup required a 0.1 Perpendicularity control for each of its radial elements.
The tolerance zone shape will look like the diagram above. Two parallel planes with 0.1 spacing and Perpendicular to the Datum axis A. Then, each of the radial elements must fit between two parallel planes.
In order to fit the radial elements between parallel planes. These, elements must meet the 0.1 flatness. This know as is implied flatness. Not for entire surface, but only for each of the radial elements.
Any implied Straightness by orientation control?
By the end of this post, I can't find any scenarios can observe implied Straightness by orientation control. If you identify any, feel free to contact me. Gbwonggbwong@gmail.com
Authur: WONG GUAN BOON
Publish: 22nd Mar 2019
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