Ultrasonic Joining of Thermoplastic-to-Metal Sheets Without Molded Bosses
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Solution Overview
Problem
Traditional ultrasonic welding techniques face challenges in accurately and efficiently joining dissimilar materials like thermoplastic and metal, particularly due to high labor and costs associated with molding complex thermoplastic pieces with bosses, and the difficulty in forming strong joints without melting or deforming the materials.
Innovation Solution
Applying ultrasonic energy to a thermoplastic sheet to fill holes in a dissimilar metal sheet, creating a weld point that provides mechanical interlock without the need for fasteners or complex molds, thereby simplifying the joining process and reducing production time and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional heat staking process is used to join thermoplastic piece with metal piece, then mechanical interlock is achieved through mushroom cap formation, but production cost and time increase due to complex molding of boss-bearing thermoplastic pieces
Solution Approach 1:
Instead of forming a protruding boss on the thermoplastic piece that requires complex molding, the invention inverts the approach by creating a recess or hole in the metal piece that receives the thermoplastic material. This simplifies the thermoplastic molding process while achieving the same mechanical interlock function through the complementary geometry in the metal component.
Solution Approach 2:
The metal piece is prepared in advance with a pre-formed recess or hole structure before the joining process. This preliminary action eliminates the need for complex real-time molding of the thermoplastic boss, allowing for faster production while maintaining the mechanical interlock strength through the pre-configured receiving geometry.
2Strength
If complex thermoplastic pieces with bosses are molded to achieve proper fit with metal pieces, then mechanical interlock is formed, but manufacturing complexity and cost increase due to specialized molds
Solution Approach 1:
The invention transfers the geometric complexity from the thermoplastic component to the metal component. Instead of molding complex boss features in the thermoplastic piece, a recess or hole is formed in the metal piece, which can be achieved through simpler processes like punching, drilling, or stamping, thereby reducing mold complexity while maintaining mechanical interlock capability.
Solution Approach 2:
The complex boss feature is extracted from the thermoplastic piece design and relocated to the metal piece as a recess or hole. This extraction simplifies the thermoplastic molding requirements and reduces the complexity of the molding process while preserving the essential mechanical interlock function through the complementary geometry in the metal component.
3Manufacturing precision
If traditional ultrasonic welding is applied to dissimilar materials, then joining is achieved, but accurate and quick joining at target interface is difficult without melting or deforming workpieces
Solution Approach 1:
The invention modifies the ultrasonic welding parameters and interface geometry to suit dissimilar materials. By adjusting factors such as ultrasonic frequency, amplitude, and duration, along with optimizing the recess geometry in the metal piece, the process achieves accurate and quick joining while controlling heat input to prevent melting or deformation of the thermoplastic material.
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 reduces production time and costs by eliminating the need for special molds and complex thermoplastic piece molding, enabling efficient joining of dissimilar materials with improved mechanical interlock and reduced material deformation.
Implementation Method 1
applying ultrasonic energy to thermoplastic polymer in a sheet material to fill existing hole(s) in a dissimilar sheet material
Data Source
AI summary
A ultrasonic welding method of joining dissimilar-material workpieces, such as sheet materials, and the joined components formed thereby. The method includes applying ultrasonic energy to a thermoplastic piece to fill a hole of a dissimilar piece to form a weld point that is made up with polymer from the thermoplastic piece. In general, the geometry of the thermoplastic piece is not altered during the process. The dissimilar piece generally has a higher melting temperate and can be metal, thermoset polymers, or other thermoplastic material. The welded pieces can be arranged in a lap, laminate, or double lap configuration. In some embodiments, the hole of the dissimilar sheet material includes undercut features that improve the mechanical interlock between the dissimilar pieces. In some embodiments, the weld point has a mushroom cap to improve mechanical interlock.