Advantages and disadvantages of downblown film blowing machines

Down-blowing film blowing machines have several advantages：

1. Low equipment height: The membrane bubble is pulled downward from the die head, eliminating the need for tall factory buildings. It is suitable for production environments with limited space. The overall structure of the equipment is compact, resulting in low infrastructure and installation costs.

2. Simple film traction control: The traction system is located below the equipment, making it easy to operate and re-traction the film after breakage. It is suitable for small-batch production with frequent changes in film specifications.

3. Suitable for heat shrink film production: When the film bubble moves downward, it is naturally stretched by gravity. After cooling, the film has a high longitudinal shrinkage rate, which is especially suitable for the production of heat shrink films such as PVC and POF.

However, down-blowing film blowing machines also have the following disadvantages：

1. Poor cooling effect: The membrane bubble moves in the same direction as the hot air (co-current cooling), resulting in low cooling efficiency, slow production speed, and uneven cooling of the film, which can easily lead to thickness deviation. It is not suitable for producing thin and wide films.

2. Poor membrane bubble stability: Under the influence of gravity, the membrane bubble is prone to sagging. It is necessary to strictly control the traction speed and cooling air volume, otherwise "neck shrinkage" will easily occur, affecting the flatness of the membrane.