Thermoforming Device Uniform Film Heating
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Solution Overview
Problem
Current thermoforming devices for plastic films used in optical and ophthalmic applications suffer from non-uniform heating, leading to defects such as stretching, folds, tears, and scratches due to the placement of the heating system outside the chamber, which interferes with precise sag measurements and results in uneven film deformation, particularly on spherical substrates.
Innovation Solution
The hot air blowing unit is adapted to flow parallel to the plastic film between two lateral sides of the chamber opening, allowing for a stable and uniform laminar flow, reducing space outside the chamber and enabling precise sag measurements, with additional improvements using a slanted ring and deflector to guide the air flow and prevent turbulence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the heating system is placed outside the chamber next to the film sag measurement system, then the measurement system can be positioned for precise sag measurements, but the heating system interferes with the film heating process and causes non-uniform temperature distribution
Solution Approach 1:
The hot air blowing unit is repositioned from a location outside the chamber to a location inside the chamber, changing the spatial dimension of the heating process. This allows the heating to occur in the same space as the measurement, eliminating the interference between the two systems while maintaining both measurement precision and heating effectiveness.
Solution Approach 2:
The heating process and measurement process are merged into the same spatial location (inside the chamber). The hot air blowing unit is positioned to blow hot air across the film from one side, while the measurement system is positioned to measure sag from the opposite side, allowing both functions to operate simultaneously without interference.
2Device complexity
If the hot air blowing unit is positioned outside the chamber, then the chamber interior is not occupied by heating equipment, but the space outside the chamber in front of the opening is occupied, interfering with the heating of the film
Solution Approach 1:
The heating process is moved from the external dimension (outside the chamber) to the internal dimension (inside the chamber). The hot air blowing unit is positioned inside the chamber to blow hot air across the film, utilizing the available space within the chamber interior rather than outside, thereby eliminating the spatial conflict.
3Volume of stationary object
If the film is heated by a system located outside the chamber, then the heating system does not occupy chamber space, but the temperature distribution on the film becomes non-uniform, causing defective deformation
Solution Approach 1:
The heating process is repositioned from external to internal, changing the spatial dimension. The hot air blowing unit inside the chamber can direct hot air flow across the film surface, providing uniform heating from within the chamber space without compromising the availability of chamber volume for other operations.
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 configuration ensures uniform film deformation and prevents defects in the final product, meeting the high quality requirements for optical and ophthalmic applications by maintaining consistent temperature and isotropic deformation around the central axis.
Implementation Method 1
a system for heating the film, adapted to heat the film held by the attachment system, and comprising a hot air blowing unit arranged to produce a stream of hot air flowing externally to the chamber and in contact with the film
Data Source
AI summary
A thermoforming device heats a plastic film to a substantially uniform temperature, in order to impart a curved shape to said film. The device includes a chamber, the internal pressure of which is variable and which is closed by the film, a system for measuring a sag in the film arranged outside the chamber and opposite said film, and a system for heating the film. The heating system includes a hot air blowing unit which is suitable for producing a hot airflow flowing parallel to the film between two opposite edges of said film.