Extrusion Pressure Control
In many tubing and extrusion applications , maintaining dimensions is critical and difficult. This challenge is critical if the extruded material has little hot strength or is prone to sticking to itself. To increase control, air can be introduced into center space (lumen), but the pressure must be closely controlled and must self adjust to downstream perturbations such as caused by cutoff machines or saws and variations in windup processes.
The installation of an Equilibar® low pressure control system to control the pressure of the air inside the extrudate gives precise control of the dimensions and allows more repeatable process startups.
As the schematic below illustrates, a controlled air flow is introduced into the extrusion die from a source such as a rotameter or needle valve. The optimum flow rate is just greater than the maximum flow anticipated by the application. The Equilibar precision back pressure regulator controls the die pressure explicitly by venting all excess gas not needed by the extrusion process. The back pressure regulator opens up just enough to maintain tight pressure control at the die. The high flow capacity and lightning fast response of the Equilibar prevents momentary disruptions in pressure that could cause wall thickness variation.
The Equilibar back pressure regulator is dome-loaded, meaning that it gets its set-point signal from a remote air signal. This schematic shows a computer automated process with an electronic pressure regulator supplying the set-point signal to the Equilibar. However, this pressure can easily be supplied by a manual air pressure regulator such as the Equilibar LPR2.
Ease of set up
In a typical operation, the operator would establish the correct vacuum level empirically on the first run of that product, and record that value on a setup sheet for the product. On subsequent runs of that product, the operator simply dials the value into the pressure input on the control panel and the Equilibar regulator maintains that level for the entire run.
Learn more about Equilibar's back pressure regulator technology .
Learn more about low pressure solutions from Equilibar
See also Extrusion with Vacuum Sizing Box application.
