Compression Mold Resilient Element Thin-Wall Precision
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Solution Overview
Problem
Existing compression molds face challenges in forming objects with very thin bottom thickness due to hard contact between mold halves, caused by elastic and thermal deformations, leading to damage and limitations in molding precision and capability, especially when forming caps or containers with thin walls.
Innovation Solution
The design of a compression mold where the closed mold geometry is defined by internal dimensional tolerances of the mold elements, independent of press deformations, ensuring precise distance between mold halves without plastic, and incorporating a compensation assembly to manage plastic volume variations and shrinkage, while preventing hard contact and enabling the formation of objects with thin walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the nominal thickness of the forming cavity is reduced to match very thin bottom thickness requirements, then the molding precision for thin-walled objects is improved, but the risk of hard contact between mold halves increases due to elastic and thermal deformations
Solution Approach 1:
The patent introduces a resilient element (spring) between the actuator element and the first half-mold that beforehand cushions against hard contact. The spring is pre-configured to compress before the mold halves can hard contact, absorbing deformation energy and maintaining a minimum safe distance even when the forming cavity thickness is reduced for thin-walled object molding.
2Productivity
If the press structure is made more complex (e.g., forming carousel), then productivity is improved, but the precision of the distance between mold halves deteriorates due to long chain of dimensional tolerances
Solution Approach 1:
The patent segments the distance control function by introducing the resilient element that independently manages the distance between mold halves. This segmentation isolates the precision-critical distance T2 from the press structure's dimensional tolerance chain, allowing the press to operate with higher productivity through complex mechanisms like forming carousels without compromising molding precision.
3Device complexity
If the closing position is defined by abutment of actuator element with end stop, then the mold structure is simplified, but the distance between mold halves becomes highly sensitive to press deformations
Solution Approach 1:
The resilient element acts as an intermediary between the actuator element and the first half-mold. It mediates the force transmission while maintaining a buffer distance, decoupling the closing position definition from direct abutment with the end stop. This allows the mold structure to remain relatively simple while achieving insensitivity to press deformations through the intermediary's compliance.
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 solution prevents hard contact between mold halves, maintains precision in forming thin-walled objects, and allows for the successful molding of objects with bottom thicknesses as low as 0.2-0.3 millimeters, ensuring reliable and precise compression molding of caps and containers with facilitated fracture areas.
Implementation Method 1
a resilient element 13 being arranged between the axially movable actuator element 5 and the first half-mold 1 in order to compress before a possible hard contact
Data Source
AI summary
A mold is provided for forming caps for closing containers by compression molding doses of plastic material, where a bottom wall of the cap, or at least one portion of the bottom wall is very thin. The mold includes two half-molds axially movable towards each other which assume an end closed position without a dose. A tubular element is slidable around the second half-mold and partially defines the cavity. The tubular element contacts an axial abutment of the first half-mold at one side and an axial end stop of the second half-mold at the other side to prevent hard contact between the half-molds.