Injection Nozzle Shut-Off with Screw Tip Sealing at Lower Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional injection molding systems rely on high pressure to dislodge a cold slug, leading to inefficiencies and non-uniform heating, which results in high energy consumption and part deformation.
Innovation Solution
An extrude-to-fill injection molding system with a nozzle closure apparatus using a screw tip that opens and closes the nozzle, eliminating the need for a cold slug and allowing for lower injection pressures, enabling effective conductive heating and consistent material temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high pressure is used to dislodge the cold slug, then the nozzle can be opened for the next injection cycle, but the injection pressure is largely absorbed by the volume of plastic between the screw tip and the nozzle, resulting in high energy consumption
Solution Approach 1:
The patent removes the cold slug (a harmful element) from the system by using a screw tip design that prevents its formation. The screw tip seals against the nozzle tip to contain molten resin, eliminating the need to form and then dislodge a cold slug, thereby extracting the harmful cold slug formation process from the injection cycle
Solution Approach 2:
The patent changes the pressure parameter from high pressure (20,000-30,000 psi) to low pressure (500-1,500 psi) by modifying the sealing mechanism. Instead of relying on high pressure to dislodge a cold slug, the system uses a sealed containment approach where the screw tip forms a seal against the nozzle tip, allowing pressure to be efficiently transmitted to the mold cavity
2Stress or pressure
If the barrel has a heavy or thick wall section to withstand high pressure, then the barrel can handle the injection pressure, but the heat conduction to the plastic from the band heaters is reduced, resulting in non-uniform heating
Solution Approach 1:
The patent changes the operating pressure parameter from high to low, which allows the barrel wall thickness to be reduced. This thin-walled barrel design improves thermal conduction from the band heaters to the plastic, achieving more uniform heating while still withstanding the injection pressure through the sealed screw tip-nozzle interface
3Reliability
If the cold slug is used to seal the nozzle between shots, then the plastic is contained in the barrel, but very high pressure is required to dislodge the cold slug, leading to energy inefficiency
Solution Approach 1:
The patent converts the harmful cold slug (which causes energy loss) into a beneficial sealed containment system. By using the screw tip to seal against the nozzle tip, the system eliminates the need for cold slug formation and subsequent high-pressure dislodging, transforming the harmful cold slug mechanism into an efficient low-pressure sealed system
Solution Approach 2:
The patent extracts the cold slug from the injection process by implementing a screw tip sealing mechanism. The screw tip seals against the nozzle tip to contain molten resin between shots, eliminating the need to form and dislodge a cold slug, thereby removing the energy-wasting cold slug cycle from the system
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
The system operates at lower pressures, reducing energy consumption and achieving more uniform part density and reduced warping, with improved heat conduction and flexibility for various applications.
Implementation Method 1
inserting a disk-shaped screw tip portion of a screw tip of the extrusion screw that is configured or shaped to match a geometry of the nozzle near the nozzle opening to extend axially into the nozzle and fit inside the nozzle to seal the nozzle and close the nozzle opening
Implementation Method 2
the thickness of the barrel to be reduced, which results in more effective conductive heating that contributes most of the heat needed for melting materials in the barrel
Implementation Method 3
A traditional injection molding system melts a material, such as a plastic, primarily by shear heat that is dynamically generated by rotation of a screw
Data Source
Figure 1
Figure 2~3B
Figure 3C
AI summary
An injection molding apparatus and method of fabricating a molded part are provided. The apparatus may include a barrel, a nozzle enclosing an end of the barrel and defining an opening in fluid communication with an inside of the barrel, and an extrusion screw positioned at least partially inside the barrel and rotatable relative to the barrel. The extrusion screw may include a screw tip. Relative axial movement between the barrel and the extrusion screw may open or close the opening of the nozzle to permit or prevent, respectively, material flow through the opening of the nozzle. The method may include clamping a mold, opening a nozzle, rotating the extrusion screw to pump a molten material into the mold until the mold is filled, closing the nozzle, and unclamping the mold to release a molded part.