Method of manufacturing a liner, liner, and appliance
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Solution Overview
Problem
Current manufacturing processes for refrigerator liners, particularly those using semi-crystalline polymers, face limitations due to the need for vacuum forming and deep thermoforming steps, which are costly and inefficient, and restrict the use of materials like polypropylene due to high stretching requirements.
Innovation Solution
A method that omits vacuum forming by pre-shaping extruded sheets through perimeter trimming and folding, allowing immediate processing without cooling delays, enabling the use of semi-crystalline materials like polypropylene and reducing production costs and time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If vacuum forming and deep thermoforming steps are used for manufacturing liners from semi-crystalline polymers, then the liners can be formed with complex shapes, but the production cost increases and the process becomes less efficient
Solution Approach 1:
The manufacturing process is segmented into distinct operations: extrusion of sheets, perimeter trimming to create flaps, folding along hinge lines, and joining adjacent edges. This segmentation allows each operation to be optimized independently and eliminates the need for complex vacuum forming and deep thermoforming steps, thereby improving manufacturing efficiency while maintaining the ability to produce complex liner shapes
Solution Approach 2:
Instead of forming the liner shape by stretching and molding the sheet material in traditional vacuum forming, the invention inverts the approach by creating the shape through folding pre-trimmed sheets. The perimeter trimming creates flaps that are then folded and joined, inverting the conventional sequence of forming operations and eliminating the need for high stretching ratios that limit material selection
2Shape
If high stretching ratios are applied during thermoforming to achieve desired liner shapes, then the liners can be formed properly, but the sheet material must be amorphous (like polystyrene) and cannot use semi-crystalline polymers (like polypropylene)
Solution Approach 1:
The invention inverts the conventional forming approach by eliminating high stretching ratio thermoforming. Instead, it uses perimeter trimming to create flaps that are folded and joined to form the liner shape. This inversion removes the constraint that requires amorphous materials, enabling the use of semi-crystalline polymers like polypropylene which offer cost advantages and improved performance characteristics
Solution Approach 2:
The invention changes the key process parameter from high stretching ratio thermoforming to low stretching ratio folding and joining. This parameter change fundamentally alters the material requirements, allowing semi-crystalline polymers to be used instead of being restricted to amorphous materials, thereby expanding material selection flexibility
3Manufacturing precision
If sheets are cooled down for several days before thermoforming to achieve homogeneous temperature, then the thermoforming can be performed properly, but the production time increases significantly
Solution Approach 1:
The invention extracts and eliminates the lengthy cooling down step from the manufacturing process. By using perimeter trimming and folding instead of high stretching ratio thermoforming, the process no longer requires several days of cooling to achieve temperature homogeneity. This extraction of the cooling step dramatically reduces production time and increases productivity while maintaining manufacturing precision through the alternative forming method
4Ease of manufacture
If multiple forming methods (solid phase vacuum, stretch and pressure forming) are employed for manufacturing liners from polypropylene, then the liners can be produced, but the operating expenses increase
Solution Approach 1:
The invention merges multiple separate forming operations into a simplified integrated process. Instead of employing distinct solid phase vacuum forming, stretch forming, and pressure forming steps, the invention combines perimeter trimming, folding, and joining into a unified manufacturing approach. This merging eliminates redundant operations and reduces operating expenses while maintaining the ability to produce liners from polypropylene
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 efficient production of lightweight, compact liners with reduced material thickness and faster cycle times, allowing the use of polypropylene and polypropylene compounds, thereby lowering costs and optimizing factory layout.
Implementation Method 1
a) extruding a sheet
Implementation Method 2
c) folding the sheet and joining adjacent edges
Data Source
AI summary
A method for manufacturing a liner, in particular for the cabinet of a refrigerator, allowing to leave out a deep thermoforming step. The method includes extruding a sheet, trimming the sheet, folding the sheet and joining adjacent edges of the sheet.