#1. Cooling – water (8 –20 degrees C) is circulating in the entrance and exit blocks. This creates a pressure tight Polymer Plug or seal at both the screen Entry port – keeping the polymer in and air out and at the Exit port. At the Screen Exit the water-cooling maintains a sold Polymer Plug (seal) that contains the filter screen.
#2. Heating – When a screen change is needed the two cartridge heaters at the exit, heats the tip of the Polymer Plug permitting it to move. Four high quality cartridge heaters maintain temperature levels in the main section of the AutoScreen.
#3. Screen Advances - The Polymer Plug (containing the screen and impurities) that is under pressure moves out of the exit for a predetermined length determined by the timer or pressure regulator or manual operation. This also moves the contaminated screen across the flow of plastic and a fresh sreen section enters.
#4. Polymer Plug Solidifies – the exit heater is shut-off and the soften Polymer Plug again hardens, sealing the exit. Ready for the next screen change…1,2,3,4.
Controls
AutoScreen has a choice of screen replacement rate controls. We offer a simple timer-based controller for lightly contaminated materials where constant speed is required and a controller based on pressure differential which uses two melt pressure transducers. The latter is for applications with heavier and variable contamination which require screen replacement adjustments to maintain constant pressure and output. This control provides outstanding pressure with +/- 15 psi accuracy, automatically.
There is also a manual screen advance button for fast color and material changes.
The compact AutoScreen is mounted between the end flange of the extruder and the die. Up-stream and down-stream adapters will have been machined either by you or by AutoScreen, if requested.
The screen change can be triggered by: A timer which is preset Change in pressure, Manually
Which process is used generally depends on the resin, levels of contamination, pressure related issues, and processing requirements.
Timer-based controller for lightly contaminated materials where constant speed is required
Pressure differential controller which uses two melt pressure transducers. This is used for applications with heavier and variable contamination that requires screen replacement adjustments to maintain constant pressure and output. This control provides outstanding pressure control with ± 15 psi accuracy, automatically and with maximum screen usage economy.
Basic Operation
Once the AutoScreen has been physically installed. the water lines connected, heaters connected to the controller, and when required the pressure transducer is fitted and connected to the controller, you are ready to follow the simple Start Up.
The AutoScreen screen filter material enters the main body of the ScreenChanger from its storage canister holding either 66’ or 125 ‘ of rolled screen filter material. It passes across the flow channel and then exits the ScreenChanger body carrying with it any contaminates.
When the extruder is running, the AutoScreen unique design uses an integrated process relying on cooling and heating of the melt and pressure to control the change of the screen.
Controls
A timer which is preset
