Thick Plastic Sheet Stress Relief via Controlled Bending
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Solution Overview
Problem
Existing methods for producing thick plastic sheet materials, such as floor and wall panels, often result in internal stresses that can lead to hairline cracks or deformations due to the extrusion process, and existing solutions are only suitable for materials less than 1 mm thick and require sufficient elasticity for rolling.
Innovation Solution
A method involving the extrusion of a polymer mass into a plate-shaped strand, followed by processing between rollers to form a plate of at least 2 mm thickness, which is then subjected to a controlled bending operation before being sawn to length, using a control device to minimize internal stress and ensure sufficient stiffness by maintaining a low force and using suspension PVC with minimal plasticizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polymer mass is extruded and cooled between rollers to form thick sheet material, then the material achieves the required thickness and structural integrity, but internal stresses are produced that can lead to hairline cracks or deformations
Solution Approach 1:
The patent applies a preliminary bending operation to the sheet material before it is completely cooled. This bending action, performed while the material is still warm and more pliable, pre-compresses the material in a controlled manner to counteract the internal stresses that will develop during cooling. The bending is applied at a specific stage in the cooling process, before the material reaches its final cooled state, allowing stress relief without compromising the final dimensional stability.
2Reliability
If a bending operation is applied to remove internal stresses, then internal stresses are reduced, but the material must be sufficiently elastic (low modulus of elasticity) to allow rolling
Solution Approach 1:
The patent exploits the temperature-dependent changes in material properties. While the sheet material is warm from the extrusion process and before complete cooling, its modulus of elasticity is lower, allowing the bending operation to be effectively applied. As the material cools further, its modulus of elasticity increases, providing the required structural integrity and dimensional stability in the final product. This temporal separation allows stress relief during a phase when the material is more compliant.
3Manufacturing precision
If thick sheet material (at least 2 mm) is produced, then the material is suitable for floor and wall panels requiring stiffness, but existing bending solutions are only suitable for materials less than 1 mm thick
Solution Approach 1:
The patent employs dynamic control of the bending operation, adjusting the degree and timing of bending based on the specific thickness and properties of the sheet material. For thicker materials (2 mm and above), the bending is applied with controlled force and duration to achieve sufficient stress relief without causing deformation. The system dynamically adapts the bending parameters to match the material thickness, making the process versatile for different product specifications while maintaining effectiveness for thick panels.
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 method effectively reduces internal stresses to virtually zero in the sheet material, achieving a modulus of elasticity of at least 1.5 GPa, suitable for thick, stiff panels without additional stress during cooling or handling, suitable for wall, floor, and façade applications.
Implementation Method 1
a polymer mass is melted under pressure
Implementation Method 2
pulled from this extruder head in the form of a plate-shaped plastic strand, which is then cooled down between two or more rollers of a rolling device
Implementation Method 3
the resulting plate has a thickness of at least 2 mm when leaving the rolling device and is subjected to a bending operation in order to lower the internal material stress of the plate
Implementation Method 4
During removal, the sheet material moves in the direction of the sawing device as a result of its own weight
Data Source
AI summary
The present invention relates, on the one hand, to a method for forming a plastic sheet material (1). On the other hand, the present invention relates to a device (5) which is adapted to carry out such a method.