Re-sealed bags with yin/yang zippers began in the early 1990s and were originally used to package minced cheese and candy. However, the model usually uses a forming tube that can be rotated 90 degrees to introduce the zipper into the flash seal to form the top of the bag.

In fact, this results in a side loading of the package, and the final width is often greater than the width required for the contents, resulting in unnecessary zipper material usage.

Bosch's Trans-Zip re-sealing machine introduced in 1998 improved this situation. The Trans-Zip device cuts the pre-closed zipper from the reel to a reasonable length, laterally pre-seal the zipper across the film, and then pulls the film across the main forming shoulder and forms the package with a zipper fixed in the transverse seal. Bags, and filling and sealing bags.

Other methods tend to introduce the zipper into the longitudinal seal and then form the flap. Compared with other methods of transverse sealing, the above method has more advantages.

First, because the zipper is attached to the short side of the bag, the amount of zipper needed can be saved. At the same time, due to infusion from the narrow side of the package, leakage loss can be reduced, thereby saving the amount of packaging material for a specific weight product.

Moreover, zip fasteners can also be used to produce hemmed bottom bags, box bottom bags and flat bags.

Bosch also successfully developed an automatic temperature controller for transverse sealing tools. Thus, a peelable laminate can be used to form an easily openable seam on the zipper. When it is not necessary to produce resealable bags, it takes only 10-20 minutes to convert the main bag machine into a regular bag. When converting, different forming shoulders may be required.