Filling machine forming tubes : overview

1. Introduction

What is a film forming tube ?

The 1^st part of the filling process for a vertical form fill and seal machine (VFFS) consists in unwinding the film, tensioning it and aligning it. However, at the end of this process, the film is still flat. It is thus necessary to fold the film in a way that it can take the shape of the final packaging, be filled and sealed properly. This is the function of the forming tube to convert the film to a tubular shape.

The forming tube is actually composed of 2 parts : a specifically shaped shoulder that allows to change the direction of the film and converting it to a tunnel shape, and a tube that will allow to adjust the form taken by the film and perform operations such as vertical sealing.

2. Film forming

2.1 Film forming components

The forming section is made of the following components :

• Forming shoulder (or forming collar)
• Forming tube

Figure 1 : Components of a film forming section (forming set)

2.2 Film forming principle of operation

STEP 1 : Film conversion through forming collar

Forming collars have very specific shapes. They allow to convert the packaging shape from a flat to a tube like shape.

STEP 2 : Bag shape forming on forming tube

Once the film shape has been radically changed thanks to the forming collar, the film is around the forming tube. Both sides of the film web must then be overlapping after forming so that a seal can be made to close the pouch on the side. The size of the seal and its shape can be controlled thanks to a forming plate positioned just before creating the 1st seal of the pouch.

The film formed is then transferred to the next process steps such as sealing (bottom of the pouch 1st) and filling with material.