Ophthalmic Lens Production Line With Mold Buffering for Lot Changes
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Solution Overview
Problem
Existing production lines using plastic lens molds are limited to producing only one type of contact lens at a time, require large stockpiles of molds with different geometries, are inflexible, and must stop production for interruptions, leading to inefficient use and cumbersome lot changes.
Innovation Solution
A production line and method that allows concurrent production of multiple lots of ophthalmic lenses by using injection-molding machines with integrated buffer modules to ensure consistent environmental exposure of plastic lens molds, multiple ovens for continuous curing, and self-driving shuttles for inspection module buffering, enabling quick lot changes and continuous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plastic lens molds are produced using injection-molding machines and stored for later use, then the molds can be kept ready for production, but the environmental conditions (temperature, humidity) during storage differ from production conditions, causing geometric deviations
Solution Approach 1:
The buffer module pre-acclimatizes plastic lens molds to production environmental conditions before they are used. Molds are transferred from storage to the buffer module where they are exposed to controlled temperature and humidity conditions matching production conditions, eliminating geometric deviations caused by environmental differences.
Solution Approach 2:
The buffer module acts as an intermediary between storage and production environments. It provides a transition zone with controlled environmental conditions that gradually acclimatize molds, preventing direct exposure to production conditions and thus avoiding geometric instability.
2Ease of manufacture
If production lines use plastic lens molds that are produced separately and supplied to the line, then the molds can be manufactured cost-effectively, but the production line must stop for lot changes and mold replacements
Solution Approach 1:
Multiple plastic lens molds for different lots are pre-produced and pre-acclimatized in the buffer module before production needs them. When a lot change is required, pre-prepared molds are already available in the buffer module, allowing immediate replacement without stopping production.
Solution Approach 2:
The buffer module maintains a continuous supply of acclimatized molds ready for use. While one set of molds is being used in production, another set is being prepared in the buffer module, ensuring uninterrupted production flow during lot changes.
3Device complexity
If the production line produces only one lot of contact lenses at a time, then the process is simple and manageable, but the line is inflexible and cannot respond to changing production requirements
Solution Approach 1:
The production system is segmented into independent modules: production modules that can work with different mold sets, and a buffer module that manages mold inventory. This segmentation allows different lots to be prepared independently and switched between without affecting the entire production line.
Solution Approach 2:
The production line becomes dynamic through the buffer module, which enables flexible switching between different mold sets and lots. The system can adapt to changing production requirements by selecting from pre-prepared molds in the buffer, transforming a static single-lot process into a dynamic multi-lot capability.
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 efficient production of diverse ophthalmic lenses with reduced downtime, flexible lot changes, and continuous operation by ensuring consistent mold exposure and using buffering mechanisms to decouple modules from interruptions.
Implementation Method 1
a flowable hot thermoplastic material is injected at high pressure into casting dies through so-called hot runners
Implementation Method 2
After the flowable hot thermoplastic material has cooled down to form the plastic lens molds
Implementation Method 3
curing of the lens-forming material may be effected with the aid of UV-light and UV-photoinitiators contained in the lens-forming material, these UV-photoinitiators triggering photopolymerization and/or crosslinking of the lens-forming material (which may be a monomer or a prepolymer) upon being exposed to UV-light
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An automated production line for the production of ophthalmic lenses comprises: - a production line front end (1) comprising: - a first and a second injection-molding machine (10, 12), - a casting module (14), - a filling station (144) and a capping station (145), - a stacking module (15) and a curing module (16), - a destacking module (17) and a demolding and delensing module - a production line back end (2) comprising: - a treatment module (20), - an inspection module (21), wherein self-driving shuttles in the inspection module can form a queue and act as a buffer for the primary packaging module if an interruption of the primary packaging module and variations of the cycle time in the primary packaging module are buffered so that the extraction module is able to operate largely independently from the upstream and downstream components of the manufacturing line.