Print Head Maintenance Unit for Contact Lens Ink Clogging
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Solution Overview
Problem
Conventional maintenance stations are not suitable for fast drying inks and UV curable inks used in the manufacture of silicone hydrogel contact lenses, as they often lead to clogging of print head nozzles due to fully or partly cured and dried ink residues.
Innovation Solution
A maintenance unit comprising a drum with a covering and a roller that applies and wrings out a cleaning liquid to maintain the print head in a damp state, preventing clogging by dissolving and removing dried ink residues without entering the print head's cavities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional maintenance stations are used with fast drying inks and UV curable inks, then printing productivity is maintained, but print head nozzles become clogged due to dried ink residues
Solution Approach 1:
The maintenance station performs preliminary cleaning actions on the print head nozzles by applying cleaning liquid through a roller before clogging occurs. The roller continuously contacts the nozzles and applies cleaning liquid to dissolve and remove dried ink residues, preventing blockages before they affect printing operations.
Solution Approach 2:
A cleaning liquid is introduced as an intermediary substance between the dried ink residues and the nozzles. The cleaning liquid penetrates the nozzle openings, dissolves the dried ink residues, and facilitates their removal, enabling the nozzles to function properly without direct mechanical intervention that could damage them.
2Reliability
If cleaning liquid is applied to remove dried ink residues, then nozzle clogging is prevented, but cleaning liquid may enter and damage print head cavities
Solution Approach 1:
The cleaning liquid is applied locally and selectively to the nozzle surfaces that require cleaning, rather than flooding the entire print head. The roller design ensures that cleaning liquid is deposited only on the external nozzle surfaces where dried ink residues accumulate, avoiding penetration into the internal cavities and sensitive components.
Solution Approach 2:
The roller creates a controlled transfer or 'copying' of cleaning liquid onto the nozzle surfaces in a regulated manner. This controlled application ensures sufficient cleaning liquid is present to remove residues while limiting the amount that could potentially enter the cavities, balancing cleaning effectiveness with component protection.
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
Effectively prevents clogging of print head nozzles by keeping them sufficiently wet and cleaning dried ink residues, ensuring continuous operation in the manufacture of contact lenses, particularly silicone hydrogel lenses with printed images.
Implementation Method 1
a roller which is so arranged that it presses against the covering on the drum to wring excessive cleaning liquid out of the covering
Implementation Method 2
cleaning dried ink residues without entering the print head's cavities
Data Source
AI summary
The present invention generally relates to a printing apparatus including one or more print heads for depositing printing fluid onto a substrate, wherein the apparatus comprises a maintenance unit for the one or more print heads. The present invention further relates to a method for cleaning one or more print heads from adhering printing fluid. The present invention also relates to the use of the apparatus in the automated manufacture of a contact lens, in particular a silicone hydrogel contact lens.