I am performing laser drilling experiments and want to measure the diameter of laser drilled holes. Some of the holes are non-circular and i am confused how to measure the diameter of irregular shaped (noon-circular) holes. Could anyone please guide. Some of the examples of (non-circular) holes are attached.
From my point of view you can measure the perimeter (p) of the hole and calculate a diameter (d) by p = 3,14*d.
Another way is to export the contour to a CAD, and aproximate a center. Then you can draw a minimum and maximum diameter circle, both tangent to the closest and farthest points respectively.
Excuse me Sirs, but if the diameter of the hole have 500 micrometers mm, is possible to apply the CMM?
Many thanks to all of you. I think Daniel Martinez Krahmer is right CMM will not work as the diameter is round 500 micrometers. Regarding the accuracy which method is best the perimeter one or exporting the image into CAD?
The one thing i want to mention that i have to measure the average diameter of hole including the minimum, maximum and mean points.
I think CMM will be the best way.
Another way which I think is the measurement of perimeter and comparing it with the perimeter of the hole intended. Although it is not fool proof but still can work.
For visual analysis, Image fitting of the actual intended hole on the hole obtained after the experiment can also be done.
All the best
Best regards
@
White/ blue light scanner non-contact method is also one of the option alongwith CMM to measure the hole diameter.
Dear Shoaib,
According to my suggestion the perimeter measurement way is easiest and proper way to find diameter (as mentioned above) if you don't have facility of CMM.
Regards
I would propose to use the ratio of area to perimeter (D=4A/P). This is a pretty good measure if the shape is not too complicated (basically it is polygonal approximation). Another way is to fit an ellipse to the edge of your hole. This would also give you a measure for circularity of the hole, and, if you wish, the smoothness of the edge (residuals of the fit).
Dear Shoaib,
First clarify your requirements.
Diameter is used for regular circles / cylindrical shapes, and we don't use diameter for irregular shapes.
You may say, you want to know inscribed circle diameter (of a shaft that can fit in these irregular shapes).
and then one needs to know what precision you are looking for???
with given details, imaging seems best / possible option, either through 3D scanners or 2D imaging and then importing it into CAD software for digitizing.
Many thanks to all. Actually some of the holes are irregular and i want to measure the average diameter of holes. I think i should go for circularity measurement also.
Many thanks @yu Huang. Could you please give any example form my images attached.
try optimal scopes and customize software to measure the hole diameter. Shoaib Sarfraz
Can't you just count the high-contrast pixels to find an area, and then take the square-root of 4A/pi? If all of the images are obtained with the same focal length and pixel density, that should work.
So then you could have 3 answers - the inscribed circle, the area, and the circumscribed circle. The relationships between the 3 would also provide a measure of the roundness.
I found this paper discussing just that: http://www.measurement.sk/M2009/proceedings/352_Petrik.pdf
Basic Geometry Area of Irregular Shapes ...
https://www.shmoop.com › basic-geometry
Many thanks Douglas Nuttall Vadim S. Gorshkov
Nirmala S.V.S.G Dhakshna Moorthy for your kind guidance.- Badges
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