Deep Drawing Mold with Stretching Assistant for Uniform Wall Thickness
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Solution Overview
Problem
Existing methods for deep-drawing containers from thermoplastic film often result in uneven wall thickness, damage to the container surface, and inability to produce containers with steep side walls and undercuts due to heat transfer and improper material distribution during the molding process.
Innovation Solution
A mold design that clamps the plastic film outside the container edge area, allowing it to bulge against the deep-drawing direction and utilize differential pressure with a stretching assistant after the deep-drawing process, preventing premature contact with mold components and ensuring even stretching for uniform wall thickness and edge thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If compressed air is supplied to form an annular air cushion between the container moldings and the plastic film, then the plastic film can expand uniformly without contact with the mold, but the air cushion becomes difficult to balance and the plastic film may still contact the hold-down device or guide sleeve
Solution Approach 1:
The plastic film is pre-stretched by the stretching assistant before the deep-drawing process begins. This preliminary stretching action prepares the film to expand more uniformly during subsequent pneumatic forming, reducing the difficulty of maintaining a stable air cushion and preventing premature contact with mold components.
Solution Approach 2:
The stretching assistant acts as an intermediary element between the plastic film and the mold components. It provides mechanical support and controlled stretching during the forming process, mediating the interaction between the expanding film and the mold structure to maintain uniform wall thickness without requiring perfect air cushion balance.
2Manufacturing precision
If the plastic film is clamped between sealing edges of the upper and lower parts of the mold during deep-drawing, then the film is secured for forming, but heat is transferred locally from the film to the hold-down device or guide sleeve causing uneven wall thickness
Solution Approach 1:
The stretching assistant is extracted from the mold structure as a separate, movable component that provides stretching functionality without being part of the fixed hold-down device or guide sleeve. This separation allows the stretching function to be performed without the heat transfer problems associated with fixed clamping components.
Solution Approach 2:
The stretching assistant performs preliminary stretching of the plastic film before the deep-drawing process begins. By pre-stretching the film, the subsequent forming process requires less contact pressure, reducing heat transfer to clamping components and maintaining more uniform wall thickness distribution.
3Ease of manufacture
If the plastic film is mechanically stretched by the stretching assistant during deep-drawing, then the film can be pre-formed, but the film may contact the hold-down device or guide sleeve causing surface damage
Solution Approach 1:
The stretching assistant is designed as a dynamic, movable component that can adjust its position and contact pressure during the forming process. This dynamic capability allows it to provide necessary stretching while avoiding excessive contact that would damage the plastic film surface, unlike fixed clamping components.
Solution Approach 2:
The stretching assistant enables controlled changes in stretching parameters during the forming process. By adjusting the stretching force and position dynamically, the system achieves effective pre-forming while maintaining contact pressures below the threshold that would cause surface damage to the plastic film.
4Reliability
If the edge of the container is clamped during deep-drawing to secure the film, then the film is held in place, but the edge becomes thick or forms a bulge making uniform wall thickness difficult to achieve
Solution Approach 1:
The stretching assistant applies localized stretching action specifically to the plastic film material, creating a bulge in the clamped section that redistributes material away from the edge area. This local quality change ensures the edge maintains uniform thickness while the film remains securely positioned during forming.
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
Enables the production of deep and undercut containers with uniform wall thickness and a thin, evenly thickened edge, preventing surface damage and ensuring efficient cooling and sealing capabilities.
Implementation Method 1
a section of heated plastic film (1) is arranged between the upper part (2) and the lower part (3)
Implementation Method 2
utilize differential pressure with a stretching assistant after the deep-drawing process
Data Source
Figure 1
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AI summary
A method for deep-drawing a thermoplastic film container involves (a) clamping a film section, spaced from the container edge-forming region, in a mold, (b) pre-curving the clamped section using a pressure difference, (c) introducing a stretching auxiliary (17) opposite to the pre-curvature, (d) applying an opposite pressure difference, (e) applying pressure by lowering a lower holder (24) and (f) demolding. A method for deep-drawing a container from heated thermoplastic film (1) in a mold involves (a) clamping around a film section, spaced from the region forming the container edge, by closing the mold, (b) pre-curving the clamped section using a pressure difference opposite to the deep-drawing direction, (c) introducing a stretching auxiliary (17) into the clamped section, opposite to the pre-curvature, while maintaining the pressure difference, (d) applying an opposite pressure difference to the clamped section, on or shortly before reaching the final position of the auxiliary, (e) lowering a lower holder (24) onto the clamped section and applying pressure with its lower edge (33) and (f) demolding the container from the mold parts (25, 26) by opening the mold. An independent claim is included for a mold for carrying out the process, having an upper part (2) with a cooling block (5), a lower holder (24) and a stretching auxiliary (17) and a lower part (3) with mold parts (25, 26), where (i) the cooling block has free space (30) with a height (C) and (ii) the lower edge (33) of the lower holder in the inserted position has a spacing (D) from the lower edge (32) of the cooling block less than the spacing (E) between the underside of the stretching auxiliary and the lower edge of the cooling block.