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gd&t - perpendicularity
- Thread starter Eins73
- Start date
pmarc
Mechanical
- Sep 2, 2008
- 3,247
Actual perpendicularity error is the minimum possible distance between two parallel planes perfectly perpendicular to datum plane A within which all points of measured surface lie. The minimum distance must be smaller than the specified value of perpendicularity tolerance (in your case 0.05).
That means you do not search for any tangent plane - you check how far apart the two parallel planes, as described above, are.
That means you do not search for any tangent plane - you check how far apart the two parallel planes, as described above, are.
- Thread starter
- #4
pmarc
Mechanical
- Sep 2, 2008
- 3,247
Like I already said, forget about tangent plane (green line on the sketch).
1. Probe the surface (you will get a cloud of points).
2. Take two imaginary planes that are parallel to each other and perpendicular to datum plane A and try to close them as much as possible (so that all inspected points are in between the planes).
3. Measure distance between the imaginary planes.
4. If the distance is smaller than or equal to 0.05, geometry meets the print. Otherwise it does not.
1. Probe the surface (you will get a cloud of points).
2. Take two imaginary planes that are parallel to each other and perpendicular to datum plane A and try to close them as much as possible (so that all inspected points are in between the planes).
3. Measure distance between the imaginary planes.
4. If the distance is smaller than or equal to 0.05, geometry meets the print. Otherwise it does not.
CheckerHater
Mechanical
"Measure distance between the imaginary planes" - brilliant!
- Thread starter
- #8
the green line refering to the part plane (X1), and the plane cross the datum plane at which another plane (Y1) of the perpendicular to datum is set. the distance of the plane Y1 to the maximum slant of the part along the datum is measured as the perpendiculrity ?
pmarc
Mechanical
- Sep 2, 2008
- 3,247
Eins73,
Allow me to doubt that the green plane is the part surface. Perfect surfaces (in this case perfectly flat) do not exist, so the green perfect plane cannot represent actual surface. It is an approximation at best.
On your initial sketch MEASUREMENT B is the correct method of perpendicularity error verification. Two horizontal lines define extent of measured surface and two vertical extension lines spaced 0.03 apart exactly represent two planes I have been talking about in my previous posts. Since the distance between the two vertical lines is not greater than 0.05, actual measured surface meets print specification.
Allow me to doubt that the green plane is the part surface. Perfect surfaces (in this case perfectly flat) do not exist, so the green perfect plane cannot represent actual surface. It is an approximation at best.
On your initial sketch MEASUREMENT B is the correct method of perpendicularity error verification. Two horizontal lines define extent of measured surface and two vertical extension lines spaced 0.03 apart exactly represent two planes I have been talking about in my previous posts. Since the distance between the two vertical lines is not greater than 0.05, actual measured surface meets print specification.
CheckerHater
Mechanical
Eins73,
Please try to imagine the following:
Perpendicularity is NOT relation between two planes.
Perpendicularity is a requirement that all points of one surface lay within the tolerance zone, perpendicular to the plane (called “datum plane”) derived from another surface.
Please try to imagine the following:
Perpendicularity is NOT relation between two planes.
Perpendicularity is a requirement that all points of one surface lay within the tolerance zone, perpendicular to the plane (called “datum plane”) derived from another surface.
powerhound
Mechanical
It looks like measurement B in your OP is how you should be checking perpendicularity.
John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
CheckerHater
Mechanical
pmarc,
I was not trying to correct your post, I was trying to give OP different prspective, different view at the problem.
In fact, I was so confident that your post is correct, I didn't even look at it.
I was not trying to correct your post, I was trying to give OP different prspective, different view at the problem.
In fact, I was so confident that your post is correct, I didn't even look at it.
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