How To Measure Profile Of A Surface Without Cmm
Profile tolerance in GD & T is the amount of divergence a surface or a line is allowed to have. When used with a datum, profile tolerance can command form, size, orientation, and even position. Let'south learn more than about Profile tolerance, the definition, type of profile tolerances with uses and examples in this commodity.
What is profile tolerance?
Profile tolerance is the corporeality of deviation of a profile of a line or a surface. No surface tin be made admittedly perfect. Due to machine or measurement variations, engineers should allow a deviation in the line elements or surfaces called profile tolerance.
Please brand a note that, Profile tolerance tin be used with or without a datum.
Types Of Profile Tolerance
There are two types of contour tolerances.
- Profile of a line
- Profile of a surface
Profile Of A Line
The profile of a line is the amount of deviation a curve can have. Information technology is the allowable variation in the curvature of a curve. The profile of a line is the 2D version of profile tolerance.
When you mention profile tolerance of a line, what that means is that every cross-section of that surface should have the same corporeality of deviation of the curvature of the curve.
The profile of a line is closely related to Straightness and circularity. The reason being, all these three types of tolerance defines how much divergence is immune in a profile.
If it is a straight line, Straightness tolerance is specified. If the profile is circular, circular tolerance is immune. If the contour is neither a straight line nor a circle, a profile tolerance of the line is used.
Profile Of A Surface
The profile of a surface is the 3D version of the profile tolerance. Dissimilar the profile of a line that controls the curve, the contour of a surface controls the complete surface.
When measured at any point on the surface, all points on that measured surface should exist in betwixt the surface tolerance zone mentioned .
Types Of Profile Of A Surface Tolerance
The types of profile of a surface can be categorized based on the direction of variation and applicability of surfaces,
These are types of profile of a surface tolerance based on the direction of contour tolerance
- Unilateral Profile Tolerance
- Bilateral Profile Tolerance
Bilateral Contour tolerance can exist further categorized as below
- The bilateral equal profile tolerance
- The bilateral unequal profile tolerance
These are the types of profile of a surface tolerance based on applicability of surfaces.
- Profile tolerance on a surface
- Profile tolerance in between two points of a surface
- Contour tolerance all around
- Contour tolerance all over
Unilateral Contour Tolerance
When the tolerance zone of a profile is in ane direction, it is called Unilateral profile tolerance. Come across the below instance where the contour tolerance is just in i management. It tin besides be in the opposite direction, only it tin not be in both directions.
Bilateral Profile Tolerance
When the tolerance zone of a contour is spread beyond both sides of the true profile, it is called bilateral profile tolerance. In the feature control frame, nosotros need to use a " U " modifier symbol which shows how much deviation is allowable outside of the truthful profile. The " U " symbol is only required when there is diff bilateral tolerance.
Bilateral equal profile tolerance
When the profile tolerance zone is equally distributed on the both sides, and so it is called bilateral equal profile tolerance.
Bilateral unequal profile tolerance
When the profile tolerance is unequally distributed on both sides, it is chosen bilateral unequal contour tolerance. In the beneath picture, what the contour tolerance means is that the total profile tolerance is .003. Out of that, .002 is on the outside of the truthful profile. Whatever is showing after the " U" modifier is the get-go of the outside surface.
Profile tolerance on a surface
This is how a profile tolerance on a surface is shown in the drawing. In the beneath example, only one surface volition take the profile tolerance until it reaches a point where there is no tangency.
Profile Tolerance in betwixt two points on a surface
If the profile tolerance is not applicable on the whole surface, simply only on the surface between two points, then this is how information technology is shown on the drawing.
Profile tolerance all effectually
if the contour tolerance is all around the connecting surfaces and then this is how information technology is shown on the drawing. The surfaces practise not necessarily need to run into the tangency.
Profile Tolerance all over
When the profile tolerance is applicable on all surfaces of the part then is called profile tolerance all over. Beneath is the notation for that. So in the below image, all surfaces of the part will have .002 profile tolerance.
Profile tolerance and datum
Profile tolerance can be used with a datum or without a datum. When used without a datum, it only controls the shape of the line or surface.
When profile tolerance is used with datums, it can control the form, size, orientation and position of the surface.
What is a profile tolerance zone
The virtual envelope that gets created by the profile tolerances is called the profile tolerance zone. In the beneath example, the envelope formed past the blue surfaces is called the profile tolerance zone.
Every point of all true surfaces should be in between that tolerance zone. In the case of a line, every point of that line should be in betwixt that tolerance zone.
How to measure profile tolerances
If it'south a very uncomplicated surface, then a meridian gauge can be used to measure profile tolerance. But if the surface is complex, and then CMM ( Coordinate measuring machines) is used. The CMM can scan the information points and match them with what is shown in the cartoon.
Nowadays, all designs are fabricated in CAD software. And so CMM data points are compared with the CAD data to check whatever deviations. There is a software chosen PolyWorks which is very adept to do this kind of job.
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Conclusion: GD&T profile tolerance
Profile tolerance is beneficial in industries similar automobiles and aerospace as these industries employ complex shape parts. But that does not mean that only these two industry uses profile tolerance. Now a day profile tolerance is used in almost every industry.
Delight note that profile tolerance increases part price every bit suppliers need special machines like CMM to measure profile tolerance. Unless information technology is essential, we should refrain from using profile tolerance.
When profile tolerance is used, no other dimensions are shown for that profile, became if there are datums, you may apply bones dimensions.
I promise I could able to give enough ideas on contour tolerance. If you withal have questions, please write in the comment section, and I will be happy to help.
Frequently Asked Questions ( FAQ)
What Is a Contour Tolerance
Profile tolerance specifies a uniform boundary and the true profile inside which the elements of the surface must lie.
How to measure out profile tolerance?
Simple contour tolerance can exist measured using tiptop gauge. Complex profile uses CMM to measure
What does letters a, b and c ways in a contour tolerance?
Those letters are datum names. When profile tolerance is used with datum'south, it controls form, shape, orientation, and position.
Source: https://www.riansclub.com/profile-tolerance/
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