Viscous Material Dispenser Calibration via Stroke Distance and Weight Feedback
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Solution Overview
Problem
Existing dispensing systems for viscous materials on substrates, such as printed circuit boards, face challenges in accurately controlling the amount and rate of material dispensed due to variations in viscosity over time and between batches, leading to unpredictable material deposition.
Innovation Solution
A method and apparatus that calibrate the dispenser by moving the actuator over variable stroke distances, weighing the dispensed material, and adjusting the stroke distance based on a function relating weight to stroke distance, allowing for precise control of the desired quantity of viscous material, and optionally using a second actuator with a stroke distance offset to ensure consistent dispensing across multiple dispensing heads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the dispenser uses a fixed stroke distance for dispensing viscous material, then the dispensing process is simple and fast, but the amount of material dispensed becomes unpredictable due to viscosity variations
Solution Approach 1:
The system performs preliminary calibration by dispensing test deposits at multiple known stroke distances and measuring their weights before actual dispensing operations. This preliminary characterization creates a reference dataset that is used to determine the correct stroke distance for achieving the desired deposit weight, thereby ensuring accuracy without requiring complex real-time adjustments during production dispensing.
Solution Approach 2:
The calibration process uses measured weights of test deposits as feedback to identify the relationship between stroke distance and material dispensed. This feedback information is used to select or adjust the stroke distance parameter to compensate for viscosity variations, enabling accurate dispensing control based on actual material behavior rather than theoretical assumptions.
2Manufacturing precision
If the system calibrates each dispensing head individually, then the calibration accuracy for each head is high, but the calibration time increases significantly
Solution Approach 1:
The system combines the calibration processes of multiple dispensing heads by performing reference dispensing operations where multiple heads dispense simultaneously or in sequence during the same calibration cycle. The controller coordinates the calibration of all heads together, using the same reference measurements and viscosity characterizations to determine appropriate stroke distances for each head, thereby reducing total calibration time while maintaining individual head accuracy.
3Productivity
If the dispenser uses a larger actuator stroke distance, then the volumetric flow rate increases, but the precision of controlling the exact amount of material dispensed decreases
Solution Approach 1:
The system dynamically adjusts the stroke distance parameter based on the desired deposit weight and the characterized relationship between stroke distance and material dispensed. By selecting optimal stroke distances from the calibrated data and making precise adjustments to this parameter, the system can achieve both high dispensing rates and accurate material quantity control, resolving the trade-off between productivity and precision.
Data Source
AI summary
A method of calibrating a dispenser (10) of the type having an actuator that is movable over a variable stroke distance includes dispensing a quantity of viscous material from the dispenser (10) by moving the actuator over one of a plurality of stroke distances, weighing the quantity of viscous material, repeating the acts of dispensing and weighing for each of the plurality of stroke distances, and displaying the weight of each of the dispensed quantities to a user using a user interface device (28).