Concavity of a Closure (Plastic Bottle Cap)

[[An...]]

We have an issue with trying to measure out concavity of a plastic bottle cap. Not sure how to go about doing this? It may be really simple, but I am new to this and it is driving me crazy. How would you go about measuring the top of the cap for concavity? This is a 38mm cap, if you want a picture for reference, just go to Corvaglia website.

[[Ke...]]

This would depend somewhat on what tool(s) you have available. Tactile CMM, O-Inspect, optical scanning probehead, etc. Personally I would start by trying scanning to lines 90degrees apart, and getting the max and min points of each, then doing some subtraction with them to give 2 height change values, one for each line. From there you could potentially change the strategy by adding more lines, doing a grid scan, or other ways of acquiring more data for the evaluation. Compare to another measurement value to make sure it seems reasonable, and then check that it is repeatable.

[[An...]]

We are using the probing technique on an O inspect, we are using a 3mm ball probe also. Basically just very simple probing points for our measurements. Our caps are on a plate (face down) and attached using strong magnets to hold them in the center. I understand we can't get a concavity measurement that way at all. Was just curious, thanks for the input. We know that when we try to take the top panel thickness of the cap, the concavity makes the measurement a bit off slightly to what we typically would expect when we probe a point on the inside of the panel in the cap and then probe the surface plate point and take the height difference. We are doing pretty well here otherwise.

[[Cl...]]

Scan two curves 90° apart across the cap. Then use minimum, or maximum coordinate in
whichever axis you want with the curves to get the deepest (or highest) points in the cap.

[[DW...]]

Kevin Harold - Why was my comment about potentially sending the part out to a CT scanning facility deleted? And your comment responding to my comment that Zeiss offers this service is also deleted?

[[Je...]]

Great question. I will look to see if I can locate the admin who deleted the responses but I am not aware of any communicated reasoning.

I don't have the previous comments made to see if they violated any terms of use.

[[DW...]]

I was just trying to be helpful by letting the OP know there are other ways to get what he wants, and Harold chimed in with Zeiss' ability to perform CT scans for customers. I guess no soliciting even for Zeiss services 🤣