Runner Film Gate IMD Injection Molding Shear Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In injection molding processes for in-mold decoration or in-mold labeling, high shear forces and shear rates near the sprue area lead to insufficient adhesion of decorative layers due to the adhesion promoter being washed out, and conventional gating systems result in early solidification of plastic, causing streaks and marks on thin-walled components, which impair optical quality.
Innovation Solution
A melt control system with a storage chamber having an asymmetrical, widened cross-section transverse to the melt flow direction, which slows down the melt flow, reduces shear rates and forces, and ensures even distribution, preventing early solidification and surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high shear rates are used near the sprue area for efficient material flow, then injection speed is improved, but adhesion promoter is washed out leading to insufficient adhesion between plastic component and film
Solution Approach 1:
The melt control system segments the flow path into distinct zones: a first region with larger cross-section for high-speed injection, and a second region with reduced cross-section that controls shear rates. This segmentation allows different flow conditions in different zones, maintaining both high injection speed and adequate adhesion promoter protection.
Solution Approach 2:
The invention applies local quality by creating specific flow conditions in different regions. The first region has optimized dimensions for speed, while the second region has controlled cross-section for shear rate management. The adhesion promoter concentration is specifically maintained in the second region where film contact occurs, ensuring local adhesion quality without compromising overall injection efficiency.
2Loss of substance
If narrow runners are used to reduce material loss, then material efficiency is improved, but frictional heat increases causing early solidification and surface defects on thin-walled parts
Solution Approach 1:
The melt control system dynamically adjusts flow characteristics through its geometry. The varying cross-section along the flow path creates changing flow velocity and shear rate profiles, allowing the system to adapt to different filling stages and prevent premature solidification while maintaining material efficiency.
Solution Approach 2:
The invention changes physical parameters along the flow path - specifically cross-sectional area, flow velocity, and shear rate. The first region has larger dimensions for efficient material transport, while the second region optimizes parameters for controlled filling of thin-walled parts, preventing frictional heating and surface defects.
3Manufacturing precision
If wide runners are used to reduce frictional heat, then optical quality is improved, but cycle time and material loss increase
Solution Approach 1:
The runner system is segmented into zones with different cross-sectional dimensions. The first region uses larger dimensions to minimize frictional heat and maintain optical quality, while the second region reduces dimensions to control material loss and cycle time. This segmentation allows optimization of both quality and productivity parameters simultaneously.
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 solution enhances the adhesion of decorative layers, reduces surface defects, and maintains a stable melt flow, ensuring improved optical quality and functional reliability of thin-walled components like touch-sensitive display panels.
Implementation Method 1
Shear forces and shear rates arise when the plastic melt flows through a tool. This generates heat, which is the result of the shearing.
Implementation Method 2
The adhesion of the foil or the decorative layers to the substrate/plastic component is realized by adhesion promoters.
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A melt conducting system (128) for in-mould decoration (IMD) or in-mould labelling (IML) processes for injection moulding flat plastic parts (110), comprising at least one film gate (130) and a runner (136), has between the gate (130) and the runner (136) an accumulation chamber (140) with a cross section that is extended transversely in relation to the direction of flow of the injected material in comparison with the runner (136). An in-mould decoration (IMD) or in-mould labelling (IML) injection-moulding process in which a melt conducting system (128) according to one of the preceding claims is used is suitable for producing a touch-sensitive display panel, in particular for producing a display panel for domestic appliances.