The Sheet Extrusion Process
Courtesy of Battenfeld
The Plastic Sheet Extrusion Process
Definitions, Roll Stack Functions, Roll Stack Configuration Figures
One of the most mystifying things one must
What criteria will guide you in making sense of all the different roll arrangements available, when you have a specific type of sheet to produce, as well as a desired production rate to achieve?
With this in mind, I set out searching for a definitive summarization of pros and cons for as many of the known roll configurations, either in the field or depicted
From what I’ve been able to determine, there does not seem to be anything published that can be conveniently accessed. I decided I would try to do my best to put one together for use as a reference.
This article is an attempt to unravel the whys and what-for’s that need to be understood, when properly selecting a particular type of roll stack configuration, especially, if the product quality and production rate is specific. It will be presented in three parts over the near future weeks.
Definitions, Roll Stack Functions, Roll Stack Configuration Figures,
Product and Production Requirements, Process Control Points in the Roll Stack
Types of Roll Stacks and their Advantages and Disadvantages.
Although many factors need to be considered when specifying a roll
On occasion I’ve read an interesting article and have not been completely sure of how the author is using a particular term. In order to avoid confusion and spare
Roll nip:this is the pinch point between two parallel rolls. There is a primary nip between the kiss and the master roll and a secondary nip between the master and the exit roll.
Bank (also referred to as the bead):
Roll Stack Function
When attempting to select the proper stack for a given product at a desired rate and to the required specifications, there are factors that must be clearly understood.
Imparting of surface finish:
Sets final sheet thickness:
There are situations in which a processor will occasionally use the stack to function as a calendar. I have witnessed banks, three to four times the size of
For example, a processor will tend to run a large bank to compensate for when the extruder is not totally stable and surging is occurring. The large bank prevents a loss in sheet gauge, at the expenses of producing a sheet higher in stress and possibly with an inferior sheet surface quality.
Controls the line speed
The roll speed is adjusted to maintain a balance between the output of the extruder and the takeaway of the roll stack to ensure the smallest bank, in the roll nip. Additionally the stack works with the pull rolls to transport the web to the line’s end.
Controls Residual Sheet Stress:
Stress from thermal gradients and chain orientation should always to be kept to a minimum to ensure the highest quality of sheet.
Roll Stack Configuration Figures
2. Vertical Up Stack
3. Vertical Down Stack with small Kiss Roll
4. Vertical Up Stack with small Kiss Roll
5. Offset Up Stack
6. J Stack
7. Incline Up stack
8. Incline Down stack
10. Three Roll
11. Four Roll Horizontal Stack
12. Vertical Down Stack with Post cooling
13. Vertical Down Stack with Air knife
14. Variable Position third roll (Pivoting Roll or Swiveling Roll Stand)
15. Variable Position first roll with a pivoting third
Roll Stack Configurations
Learn about the many others, with the pros and cons that each styles has to offer.