Extrusion Nozzle Cleaning via Preform Deflection
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Solution Overview
Problem
In continuous extrusion of thermoplastics, particularly polyolefins like HDPE, deposits form on the extrusion nozzle due to low-molecular components and additives, which become brittle, crumble, and contaminate the product, leading to defects and contamination of the filling material, and existing cleaning methods require process interruption.
Innovation Solution
A method and device using part-circular strip-shaped pressure elements to deflect the tubular preform during extrusion, allowing it to act as a cleaning element by wiping off and transporting away deposits from the nozzle area without interrupting the process, utilizing actuators to form a circular ring that compresses and redirects the exiting melt tube to remove adhering material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical cleaning devices (scrapers, scrapers) are used to remove deposits from the extrusion nozzle, then the deposits are effectively removed, but the extrusion process must be stopped resulting in production loss
Solution Approach 1:
The patent applies preliminary action by deflecting the tubular preform before it solidifies completely, while it is still in a plastic state. This timing allows the preform to effectively wipe off deposits from the nozzle outlet area before the extrusion process continues, preventing deposit accumulation without stopping production
Solution Approach 2:
The tubular preform itself is used as the cleaning element - it serves dual purposes: as the material to be extruded and as the cleaning tool. The preform's own movement and deflection enable it to remove deposits from the nozzle, eliminating the need for separate cleaning mechanisms and maintaining continuous operation
2Ease of operation
If the extrusion process is stopped for manual mechanical cleaning of the nozzle core, then deposits can be removed, but production time is lost and process restart requires experienced personnel
Solution Approach 1:
The patent replaces manual mechanical cleaning with an automated mechanical system. The deflection mechanism with pressure elements automatically deflects the preform to clean the nozzle outlet area, eliminating the need for manual intervention and process stoppage while maintaining effective deposit removal
3Productivity
If ring-shaped ejection nozzles are used for continuous extrusion, then production efficiency is improved, but deposits cannot be seen on the inside core making cleaning difficult
Solution Approach 1:
The tubular preform acts as an intermediary cleaning tool that can access the inner core area of the ring-shaped nozzle. By deflecting the preform, it physically contacts and wipes off deposits from the inner core surface that would otherwise be inaccessible and invisible, enabling cleaning of the hidden areas without changing the nozzle design
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous cleaning of extrusion nozzles without stopping production, effectively removing deposits and preventing contamination, ensuring product quality and reducing production losses.
Implementation Method 1
the tubular preform itself acting as a cleaning element during its deflection
Implementation Method 2
deposits adhering to the outside in the vicinity of the exit gap of the annular extrusion nozzle being wiped off
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method and device for cleaning extrusion heads (10) in the extrusion of thermoplastics, which are ejected or extruded from an extrusion nozzle (14) as a tubular preform (12). According to the invention, in order to remove interfering deposits and baked-on residues (20) on the outlet nozzle (14), the tubular preform (12) is briefly turned around and upset, wherein the deposits (20) adhering in the vicinity of the outlet nozzle (14) are wiped off and transported away by the tubular preform (12). In an advantageous way, the tubular preform (12) itself is used as a cleaning element while the tubular preform is being turned around, while the cleaning automatically occurs during the ongoing operation of the continuous extrusion without interruption of the production process.