[Ri...] Posted January 5, 2021 Share Posted January 5, 2021 Anyone have some input on how they might measure this? The Arc Length equation itself is rather simplistic: radius x angle (in radians). Any and all input is greatly appreciated. Thank you. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/ Share on other sites More sharing options...
[SH...] Posted January 5, 2021 Share Posted January 5, 2021 Sorry to say that ,I can't see any photos. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70858 Share on other sites More sharing options...
[Ri...] Posted January 5, 2021 Author Share Posted January 5, 2021 Hmm. Shows up for me. I've attached the PDF for viewing as well.Arc Length Test.pdf Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70860 Share on other sites More sharing options...
[Cl...] Posted January 5, 2021 Share Posted January 5, 2021 Couldn't you get that using a 2d curve and curve length? Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70862 Share on other sites More sharing options...
[Ri...] Posted January 5, 2021 Author Share Posted January 5, 2021 I thought about that, but I would assume that I would have to start and stop exactly at both ends. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70864 Share on other sites More sharing options...
[SH...] Posted January 5, 2021 Share Posted January 5, 2021 I think contour tracer or VMS can do better than CMM in this scenario. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70866 Share on other sites More sharing options...
[Ri...] Posted January 5, 2021 Author Share Posted January 5, 2021 Please sign in to view this quote. Yeah. Contour Tracer would be nice, but that's a huge Contour Tracer to trace that long of a length. As for VMS, same boat as some of the parts get up to 29" long. My initial thought is to turn the CMM into an expensive Contour Tracer. Going to be some trial and error, just thought I'd let some other people take a look at it, and throw their two cents in. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70868 Share on other sites More sharing options...
[Er...] Posted January 5, 2021 Share Posted January 5, 2021 Is a optical comparator with a digital readout an option? My thought was finding the angle between the tangent and the end, and then measuring the radius and doing the math. I guess it depends on how much tolerance you have. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70870 Share on other sites More sharing options...
[Ri...] Posted January 5, 2021 Author Share Posted January 5, 2021 Please sign in to view this quote. CMM is pretty much the only option due to the size. Tolerance is pretty liberal. Finding the tangent is going to be the most difficult part. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70872 Share on other sites More sharing options...
[Ma...] Posted January 5, 2021 Share Posted January 5, 2021 Could you construct the chordal length at the end and where the radius meets the plane and then convert to arc? Hmm does that make sense? Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70874 Share on other sites More sharing options...
[Me...] Posted January 5, 2021 Share Posted January 5, 2021 Please sign in to view this quote. If you had a model of the part, could you constrain the location/radius and use formulas to come up with the arc length? Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70876 Share on other sites More sharing options...
[Er...] Posted January 5, 2021 Share Posted January 5, 2021 I have had pretty good success using projection to locate a tangent like this. Project the Circle to the plane and make sure to scan as close to the edge on both surfaces to create the tangent. This would be the Center of the radius in the X, but to me, the most difficult would be accurately measuring the radius size and location of center in Y. You would have to constrain both the location and size, adjusting until they both gave you close to the same numbers. Meaning constraining the Radius gives you the Y value, that when used and constrained, gives you the same radius, or close to it Once found, I would use the center to create the lines to measure the angle, and use the size to calculate your measurement with a result element. If you had a big enough CMM with optics you could ink the whole part and put it on paper to measure the overall 21.03" working length as a sanity check. 🤣 Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70878 Share on other sites More sharing options...
[Cl...] Posted January 5, 2021 Share Posted January 5, 2021 Maybe I'm overthinking this. Scan (2d curve, high point density) the outside surface up to the end of the arc, starting a little within the 18.15 surface. Where the curve points at the beginning of the arc start to drop off will be the tangent (beginning) of the arc to the flat. Recall the curve points on the arc into a circle and constrain location. Probe a point on the right side flat end of the arc. Recall that point into a theoretical plane rotated at 55 degrees. Intersect the curve at the arc end with that plane, (end) Construct a line from the beginning and end points for a chord length. Now you have three knowns. angle segment, radius and chord length and can calculate the arc length from them? Make sense? Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70880 Share on other sites More sharing options...
[Mi...] Posted January 6, 2021 Share Posted January 6, 2021 Please sign in to view this quote. The issue with this is that it assumes the 55° dimension is correct. If that's out, it'll report the wrong length. Of course, I don't have any better ideas. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70882 Share on other sites More sharing options...
[Ch...] Posted January 6, 2021 Share Posted January 6, 2021 The 18.15 surface defines a line. Construct perpendicular to this line through the tangent ("transition") point, then find the arc's center on this line by measuring the radius (by probing the arc). Construct a line from this centerpoint to the end of this arc and you will have a measurement for the angle. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70884 Share on other sites More sharing options...
[Ri...] Posted January 7, 2021 Author Share Posted January 7, 2021 A lot of good information here. I think I have an idea on how I want to approach it. I will update everyone on what worked best. Thank you for the input, it is greatly appreciated. Link to comment https://qualityforum.zeiss.com/topic/13768-arc-length/#findComment-70886 Share on other sites More sharing options...
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