The reason why the bottle cap cannot be opened easily: source of resistance

Popular Science | Why is it difficult to unscrew beverage bottle caps?

According to calculations, it takes about 2-6N.m to manually unscrew the cap of a beverage bottle.

Even though the entire bottle cap industry chain is so complete and mature, there is still a bug that cannot be easily unscrewed, which violates the most basic function. Have we done something wrong? Is there anything we should do to solve this problem? Will the next development of bottle caps solve this BUG?

First of all, it is not a common phenomenon that bottle caps cannot be easily unscrewed. At present, I have not seen any company’s beverage products that are generally difficult to open. Therefore, this should be caused by an abnormality in the sealing process of the drink. Of course, consumer subjective factors such as girls deliberately acting coquettishly cannot be ruled out…

Popular Science | Why is it difficult to unscrew beverage bottle caps?

01 The reason why the bottle cap cannot be opened easily: source of resistance

We usually use this posture to open a bottle of drink——

Touch the side of the bottle cap with your finger and rotate it counterclockwise. During this process, the finger is subjected to resistance in the opposite direction. If the resistance is too large, it will appear that it cannot be opened easily. There is a special indicator called cracking torque to measure this performance. The formula of torque is M=F*L, F is the resistance, and L is physically called the moment arm. Let’s talk about it in detail below.

1.1 Source of resistance F (friction between bottle cap and bottle mouth)

Another source of resistance is the resistance of the connecting bridge when the cover body is separated from the anti-theft ring.

Okay, having said that, there are two aspects. One is to make it more difficult for you to twist it, and the other is to make it more difficult for you to unscrew the bottle cap from the bottle head.