Adhesive Dispensing Nozzle Boundary Layer Interruption
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Solution Overview
Problem
The dispensing of adhesives often results in undesirable strings or teardrops due to defects in the dispensing process, leading to contamination, cosmetic issues, and increased costs associated with rework and maintenance.
Innovation Solution
A method involving a flow control valve system that introduces a non-adhesive fluid, such as air or a liquid, into the adhesive extrudate upstream of the application nozzle to interrupt the boundary layer, preventing string or teardrop formation by creating a non-contact cut, with valve timing and volume adjustments based on adhesive properties and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adhesive is dispensed continuously through the application nozzle, then productivity is improved, but stringing and teardrop defects increase due to boundary layer accumulation
Solution Approach 1:
A non-adhesive fluid (inert gas or liquid) is introduced as an intermediary substance into the adhesive extrudate. This intermediary fluid interrupts the boundary layer of the adhesive, preventing stringing and teardrop formation while allowing continuous dispensing operation
Solution Approach 2:
The rheological parameters of the adhesive flow are modified by introducing the non-adhesive fluid, which changes the flow characteristics and boundary layer properties of the adhesive extrudate, thereby eliminating defects without stopping dispensing
2Object-generated harmful factors
If the flow control valve closes completely to stop adhesive flow, then stringing is prevented, but productivity decreases due to stop-start operation
Solution Approach 1:
Instead of completely closing the valve to prevent stringing, a non-adhesive fluid is introduced as an intermediary that interrupts the boundary layer, allowing the valve to remain open and dispensing to continue without stop-start operations
Solution Approach 2:
The mechanical action of completely closing the valve is replaced by a fluid dynamic solution where the non-adhesive fluid interrupts the adhesive boundary layer, achieving stringing prevention without mechanical stop-start operation
3Object-generated harmful factors
If adhesive viscosity is increased to reduce stringing, then defect formation decreases, but dispensing precision and control become more difficult
Solution Approach 1:
A non-adhesive fluid is introduced as an intermediary that interrupts the adhesive boundary layer, reducing stringing without requiring changes to adhesive viscosity, thereby maintaining dispensing precision and control
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 approach ensures clean, string-free and teardrop-free dispensing of adhesives, reducing contamination and cosmetic defects, and minimizing rework and maintenance costs by providing a precise control over the dispensing process.
Implementation Method 1
introducing a non-adhesive fluid into the extrudate within the flow control valve upstream from a distal end of the application nozzle such that the non-adhesive fluid interrupts a boundary layer of the extrudate
Data Source
AI summary
A method of dispensing an adhesive on a substrate includes flowing an extrudate of the adhesive through a flow control valve and an application nozzle, and introducing a non-adhesive fluid into the extrudate within the flow control valve upstream from a distal end of the application nozzle such that the non-adhesive fluid interrupts a boundary layer of the extrudate and a non-contact cut of the extrudate is provided. The non-adhesive fluid can be air that forms a bubble in the extrudate of the adhesive flowing through the application nozzle and adhesive dispensed onto the substrate is free of a string and/or a teardrop.