It serves two purposes.
It is a stacking lug that keeps the cups from sliding inside of each other doing packing and shipping.
It also makes the rim diameter the same size as other cups (whether they are paper, plastic or styrene injected with a nucleating agent that makes the foam) made by the company allowing the same cups to use several different style lids that the company offers.
I don’t think so. For a given design and manufacturer, volume is handled by changing depth. I’ve never seen a small size cup with a small diamter, but a freakishly thick rim so that it could handle a larger lid.
Neither have you. The female portion of the lid has both an outer and inner diameter that snaps on to the cup top, and if you flip over a bunch of these lids, you will find that the width of this ring doesn’t change.
Volume can be changed using depth and/or diameter hence a “squat” product.
The rim diameter and/or thickness can be changed to meet the sealing ring I.D. of any lid or the the outsert of the of the lid tooling can be changed to meet the rim O.D of the cup.
I don’t have to flip the lid over to see the sealing ring I.D. I can measure it.
Please don’t presume what I have or haven’t seen after my 24 years in R&D thermoplastics at now the country’s largest manufacturer of disposable food service products.
Logic tends to impress me more than credentials. Volume can be changed any number of ways. Depth can be changed, diameter, slope angle of the wall, etc. So if you want lid size ‘L’ to fit two cup sizes, what makes the most sense? Hold diameter constant.
You suggest diameter doesn’t need to be held constant, the thickness of the ring can make up the difference. Observe some cups. Is this how it is done? If you view the cup from the top down, the rim has more than one diameter. If you vary the ring to control OD, the distance from OD to ID, the wall thickness at the rim, is not constant. Now go look at the top again. Does it fit just the OD, or is there a 2nd contact made with the ID. At least with the cups I’ve got here, that’s how it works. So how would this help make tops universal?
No, he doesn’t. Go back and reread his initial post. He was basically saying, “it’s useful to give a polystyrene cup a rim that matches the thickness of the corresponding paper/plastic/whatever cup, because then you can use a variety of lid styles (e.g. soda type, coffee type, etc) that were designed for the other types of cups.” Nowhere did he mention trying to vary the volume of the cup while keeping the lid the same. You brought that idea up, not him.