Introduction to the Conventional Inner Container Process of Stainless Steel Cups

30-03-2026 / By Aijunware

As a part of our daily life, stainless steel cups are inseparable from our daily lives. Have you ever known that different cups actually have different processes? This article will talk about the conventional stainless steel cup liner process.

The conventional inner liner process is divided into two types: one is a stretched inner liner, and the other is a water-swollen inner liner. The main difference is whether there is a weld seam. The inner liner with welded seams is a water swelling liner, while the inner liner without welded seams is a stretching liner. This is the obvious technological difference between the two. The principle of stretching is that a thick stainless steel sheet is stretched through multiple rounds of molds to form an inner liner. The principle of water swelling is that a stainless steel tube is formed by water swelling once in the machine, forming the required cup body. Both have their own advantages and disadvantages, which will be discussed in detail below.

The stretched inner liner has the advantages of strong plasticity and a seamless inner liner. For some irregular cups, the water swelling mold is usually difficult to achieve the required shape, so the stretching process is generally used. The products processed by this process have the characteristic of a seamless inner liner; therefore, compared to a water-swollen inner liner, the product has stronger unity and aesthetics. However, stretching molds also have drawbacks, such as some cups with relatively high heights requiring multiple stretches or even vacuum tempering to achieve the desired stretching height, which greatly increases product costs. Therefore, it is generally recommended to use this technique for cups with relatively low heights, such as beer glasses and irregularly shaped cups, which require strong aesthetic and integration requirements.

Another type of water-swelling inner liner is more common in the daily production of insulated cups, because it can be formed in one go and is naturally much more efficient than stretching processes. Therefore, we recommend using water swelling technology to make cup shapes such as conventional straight tube insulated cups and car cups, which have completely consistent insulation performance, lower cost, and shorter time for mass production. Some people may worry that the insulation performance of the inner liner may not be as good as that of the stretched inner liner due to the welding seams caused by water swelling.

As a professional stainless steel manufacturer, we can responsibly inform you of this and will not do it at all! Because a cup undergoes at least three vacuum insulation performance tests during our factory production process:

1. The one round of testing will be conducted after the vacuum is completed

2. The second round of testing will be conducted after the product is polished, and

3. The third round of testing will be conducted during the product packaging stage.

Therefore, regardless of the cups' stretching or water-swelling process, our factory can guarantee a vacuum insulation performance of 99% or higher. If you are truly concerned about the impact of the weld seam on aesthetics, you can refer to the previous recommendation and use internal ceramic spraying technology, which can effectively cover the water swelling weld seam and enhance the integrity of the cup. If you are a purchaser of end products, it is recommended that you prioritize water-swelling inner liners in your future product purchases. This can bring you better profits and also deliver bulk goods to you faster.

I hope the above description is helpful in your purchase. If you pursue higher-end products and have strong requirements for product integration, you can choose stretching technology. Pursuing product cost-effectiveness and hoping for prompt delivery, water swelling technology may be a better choice. If you have any further questions, please leave them, and we will respond promptly!