General principle
This process is often called « in-line » thermoforming. It is thermoforming, but in the present case the thermoforming unit is attached to the extrusion unit, and all is done in one-step. The thermoforming unit is fed by the sheets coming directly from the die, without any winding.
Animation - Extrusion Thermoforming Processing Technique
Advantages of this in-line process are:
- energy savings: the heating section of the thermoforming unit is reduced, or absent when the heat of the sheet coming from the extruder is still enough to allow its deformation
- yield of the machines is optimum, homogeneous sheet temperature
- less storage, compact lines
- immediate feed-back : quality problems can be quick detected and solved.
But, this process has some drawbacks: it is much more difficult to operate, and transitions from one production campaign to one another are long and need time. This process thus must be dedicated to very long series (e.g. disposable cups).
In-line thermoforming lines don’t offer the same outputs than off-line extrusion and thermoforming lines. In fact, thermoforming throughputs are always low compared to extrusion throughputs. In the off-line process, one extrusion line can be used to produce sheets for 3 or 4 thermoforming lines. In the in-line extrusion-thermoforming, each line needs one extruder for one thermoforming machine.
From the application point of view, there is no difference between objects produced by in-line or off-line machines. Markets are roughly the same.