Ultrasonic Pull Rod Cavity Pressure Measurement
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Solution Overview
Problem
Current methods for measuring cavity pressure in injection molding processes are invasive, costly, and lack accuracy, as they require surface-mounted sensors that damage molds and provide only point measurements, while soft measurement methods are complex and lack theoretical support.
Innovation Solution
An ultrasonic method that measures the force on pull rods to indirectly determine cavity pressure by emitting ultrasonic waves and calculating pressure changes based on echo time differences, using the formula P = πR2 * W * Δttotal / A, where R is the pull rod radius, Δttotal is the sum of echo time differences, W is a material constant, and A is the cavity projection area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a cavity pressure sensor is mounted on the mold cavity surface to measure pressure accurately in real time, then measurement precision is improved, but the mold is damaged and the product surface has defects
Solution Approach 1:
The patent uses pull rods as intermediary elements to transmit the cavity pressure to the measurement system. Instead of directly mounting sensors on the mold cavity, the pressure is transmitted through the pull rod structure to external sensors, thereby avoiding direct contact with the mold cavity surface and preventing damage to the mold and product surface while maintaining measurement accuracy
Solution Approach 2:
The patent replaces the direct mechanical mounting of pressure sensors on the mold cavity with an indirect mechanical transmission system using pull rods. This substitution allows the measurement system to obtain pressure data without requiring physical contact with the mold cavity surface, thus avoiding the harmful effects of direct sensor mounting
2Measurement precision
If a cavity pressure sensor is used to measure cavity pressure, then real-time pressure data is obtained, but the high cost of the sensor blocks its popularization in every mold
Solution Approach 1:
The patent uses multiple pull rods as copies or replicas of the pressure transmission path. Instead of using a single expensive sensor, the system uses several pull rods that can be measured by simpler, more cost-effective sensors, thereby reducing the overall cost while maintaining the ability to obtain real-time pressure data
Solution Approach 2:
The patent employs pull rods that are simpler and cheaper components compared to direct-mounting pressure sensors. These pull rods can be easily manufactured and replaced if needed, providing a cost-effective solution for widespread implementation in various molds while still enabling real-time pressure measurement
3Device complexity
If point measurement is used to measure cavity pressure, then the measurement system is simple, but only a certain point pressure is obtained which is insufficient for comprehensive process diagnosis
Solution Approach 1:
The patent divides the cavity pressure measurement into multiple segments by using several pull rods positioned at different locations. Each pull rod measures the pressure at its specific position, and by combining the measurements from multiple pull rods, the system obtains comprehensive pressure distribution information throughout the cavity while maintaining relatively simple measurement systems
4Object-affected harmful factors
If soft measurement method is used to measure cavity pressure nondestructively, then mold damage is avoided, but the method involves many parameters and lacks theoretical support resulting in reduced accuracy
Solution Approach 1:
The patent introduces pull rods as intermediary mechanical elements that provide a direct physical connection between the cavity pressure and the measurement system. This intermediary structure provides strong theoretical support through established mechanical transmission principles, avoiding the theoretical weaknesses of soft measurement methods while still achieving nondestructive measurement by not mounting sensors directly on the mold cavity
Solution Approach 2:
The patent replaces the soft measurement approach with a mechanical measurement system using pull rods. This substitution provides a physically grounded measurement method with clear theoretical support from mechanics, improving accuracy while maintaining the nondestructive benefit of not directly contacting the mold cavity surface
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 method enables real-time, non-destructive, and cost-effective on-line detection of cavity pressure, avoiding mold damage and providing high accuracy, with the ability to monitor and diagnose injection molding processes, and is applicable to various molds.
Implementation Method 1
emitting ultrasonic wave to each pull rod respectively along its axial direction at the same time, detecting a time difference between an ultrasonic wave echo of each pull rod and an ultrasonic echo when the pull rod is free
Implementation Method 2
emitting ultrasonic wave to each pull rod respectively along its axial direction at the same time
Implementation Method 3
detecting a time difference between an ultrasonic wave echo of each pull rod and an ultrasonic echo when the pull rod is free
Data Source
AI summary
The present invention discloses a ultrasonic method for indirectly measuring a pressure of a cavity of an injection molding machine, comprising: emitting ultrasonic wave to each pull rod along an axial direction of the pull rod respectively at the same time, detecting an ultrasonic wave echo time difference of each pull rod, and obtaining an average pressure inside a cavity of the injection molding machine. By the detection method and detection device of the present invention, the pressure inside the cavity may be detected in a certain state, the pressure inside the cavity in the injection molding process may be detected in real time, and the detection process is simple and the accuracy is high.