Injection Molding of Rigid Plastic and Foam Layer
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Solution Overview
Problem
Existing methods for producing molded parts with a rigid plastic carrier and a flexible foam plastic layer often result in uneven bubble formation and surface imperfections due to the presence of blowing agents, which compromise both mechanical properties and aesthetics, particularly in visible automotive applications.
Innovation Solution
The method involves using one or more overflow channels at the end of the cavity to collect and discard irregular bubbles, and applying a vacuum to remove blowing agents from the melt front, while ensuring high pressure is maintained in hot runners through the use of non-return valves to prevent foaming, thereby achieving uniform bubble distribution and improved surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If blowing agent is used to produce the flexible foam plastic layer, then the foam structure is formed, but uneven bubble formation and surface imperfections occur
Solution Approach 1:
The patent extracts and removes the harmful blowing agent from the system by providing a vacuum connection at the end of the cavity. This allows the blowing agent to be evacuated from the molded part after injection, preventing it from causing surface imperfections and uneven bubble formation while still allowing the foam structure to form.
Solution Approach 2:
The patent applies preliminary action by maintaining high pressure in the hot runners through non-return valves before the blowing agent can cause problems. This prevents premature foaming in the hot runners and ensures uniform bubble distribution in the final product.
2Stability of the object's composition
If blowing agent is present in the plastic melt, then foam formation is enabled, but mechanical properties deteriorate
Solution Approach 1:
The blowing agent is extracted and removed from the molded part through the vacuum connection provided at the end of the cavity. This removal of the blowing agent prevents the deterioration of mechanical properties such as impact strength, brittleness, and fatigue strength while still allowing foam formation to occur.
3Stability of the object's composition
If blowing agent is present in the plastic melt, then foam structure is created, but aesthetic properties deteriorate
Solution Approach 1:
The blowing agent is extracted through the vacuum connection at the end of the cavity, removing the source of aesthetic deterioration. This prevents gas bubbles and surface imperfections while maintaining the desired foam structure inside the molded part.
4Ease of operation
If pressure is not maintained in hot runners, then material flow is improved, but foaming occurs causing non-uniform bubble distribution
Solution Approach 1:
Non-return valves are installed in the hot runners to preliminarily maintain high pressure before the plastic melt is injected. This prevents premature foaming and ensures uniform bubble distribution in the final product while still allowing proper material flow.
Solution Approach 2:
The pressure parameter in the hot runners is changed and maintained at high levels through the use of non-return valves. This parameter change prevents foaming in the hot runners while allowing proper material flow and uniform bubble distribution in the molded part.
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
This approach ensures a fine-celled foamed core with uniform bubble size and distribution, enhancing the mechanical and aesthetic properties of the molded part, including impact strength, brittleness, fatigue strength, and appearance.
Implementation Method 1
a connection to a vacuum pump being provided at the end of the cavity, via which the propellant is removed from the molded part
Implementation Method 2
plastic melt containing a propellant to produce the flexible foam plastic layer
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
The method involves limiting a cavity (5) by two molded halves (1,2). A rigid plastic support is provided, which is supported in the cavity by a heating channel (3) and a feeding channel (4). A driving unit is removed from a mold at an end of a melt front of the plastic melt that has propellant. Independent claims are included for the following: (1) a device for manufacturing a mold part made of a rigid plastic support and a foam plastic layer by injection molding in a tool; and (2) a device for executing a mold part manufacturing method.