Plastic-Metal Positive-Locking Connection via Heated Insert
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Solution Overview
Problem
Current methods for connecting plastics and metals in multi-material structures, such as mechanical, adhesive, and welding techniques, face issues like stress concentrations, long cycle times, low reliability, and environmental concerns, and existing hybrid techniques are either time-consuming or prone to failure under load.
Innovation Solution
A method involving a plastic workpiece with a connecting element on its surface, where a recess is created in a second workpiece, and the connecting element is heated to be plasticized and pressed into the recess, forming a positive-locking connection without significant stress or external projections, allowing for easy automation and reduced apparatus outlay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mechanical connections (riveted or clinch connections) are used to connect plastics and metals, then the connection provides structural strength, but high stress concentrations occur in the workpieces and subsequent slackening may occur due to creep, moisture and relaxation
Solution Approach 1:
The invention changes the physical state of the connecting element by heating it to its melting point, transforming it from a solid mechanical connector to a molten material that can be injected into the recess. This phase change eliminates stress concentrations and creep issues associated with traditional mechanical connections, as the molten material flows and bonds without creating rigid stress points.
Solution Approach 2:
The invention replaces the mechanical connection system (rivets or clinch connections) with a thermal-fluid system. Instead of using solid mechanical fasteners that create stress concentrations, the patent uses heated connecting element material that is injected in molten state into a recess, allowing the material to flow and bond without mechanical stress concentrations.
2Ease of manufacture
If adhesive connections are used to connect plastics and metals, then the connection can be made without mechanical fasteners, but the cycle times are comparatively long due to the curing time of the adhesive
Solution Approach 1:
The invention dramatically reduces the curing time by changing the temperature parameter of the connecting element. By heating the material to its melting point and injecting it in molten state, the bonding process occurs almost immediately upon cooling and solidification, eliminating the long curing times associated with adhesive connections while maintaining ease of manufacture.
3Strength
If welding processes (ultrasonic welding, resistance welding, vibration welding, induction welding and infrared welding) are used to connect plastics and metals, then the connection can be made directly between materials, but the energy consumption is relatively high on account of the comparatively low efficiency
Solution Approach 1:
The invention extracts the high-energy welding step from the process by pre-heating the connecting element material separately before injection. Instead of applying high-energy welding directly to the workpieces, the patent heats the connecting material in advance to its melting point, then injects it in molten state, significantly reducing the energy required during the actual connection process.
4Reliability
If hybrid joining techniques (metal-collar joining or injection moulding with cavities) are used to improve connection properties, then the connection reliability can be enhanced, but the methods are either time-consuming or require complicated preliminary processing
Solution Approach 1:
The invention performs preliminary heating of the connecting element material to its melting point before the actual connection process. This pre-action allows the material to be injected in a fluid state that easily fills the recess and adapts to the geometry, simplifying the overall process while ensuring reliable bonding without complicated preliminary processing of the workpieces themselves.
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 method enables a reliable, stress-reduced, and efficient positive-locking connection between plastic and metal workpieces, eliminating the need for additional processing and reducing environmental impact, with the potential for high loading capacity and easy automation.
Implementation Method 1
heating the connecting element, so that the material of the connecting element is plasticized
Implementation Method 2
pressing plasticized material into the recess
Data Source
AI summary
A method of connecting a plastic workpiece to a further workpiece and a device for carrying out the method are shown and described. The object of providing a method with which a positive-locking connection between a plastic workpiece and a further workpiece can be produced in a short time and without considerable outlay in terms of apparatus is achieved by a method comprising the following steps: providing a plastic workpiece and a further workpiece, placing the further workpiece against the plastic workpiece, providing a connecting element on a surface of the plastic workpiece, this surface being opposite the surface against which the further workpiece bears, producing a recess in the further workpiece, this recess being provided on the surface bearing against the plastic workpiece, heating the connecting element, so that the material of the connecting element is plasticized, and pressing plasticized material into the recess.