Mold Clamp Strain-Gauge Control for Variable Clamping Force
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Solution Overview
Problem
Current injection molding systems face challenges in accurately monitoring and controlling clamping force and pressure within the mold cavity due to limitations with external strain gauge sensors, which often pick up noise and require time-consuming calibration, and direct sensors can mar high-gloss finishes or be prohibited in medical applications.
Innovation Solution
The use of external strain gauge sensors on the mold surface to measure strain changes, with amplification techniques to distinguish meaningful measurements from noise, allowing for more accurate control of clamping force and pressure through a variable force clamping profile, adaptable to different molding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If external strain gauge sensors are used to measure strain changes on the mold surface, then clamping force and pressure control can be achieved without direct contact with the mold cavity, but the sensors pick up noise and require time-consuming calibration
Solution Approach 1:
The patent uses the mold surface itself as an intermediary medium to transmit strain information from the mold cavity to the external strain gauge sensors. By placing sensors on the mold surface rather than inside the cavity, the system indirectly measures cavity pressure through the mold's structural response, avoiding direct contact that would damage high-gloss finishes while still obtaining usable measurement data
Solution Approach 2:
The system implements feedback control by continuously monitoring strain gauge readings and using this information to adjust clamping force in real-time. The strain measurements feed back to the control system, which modifies the clamping profile to maintain optimal pressure throughout the molding process, compensating for the noisy signals through continuous adjustment
2Ease of manufacture
If external strain gauge sensors are used on the mold surface, then high-gloss finishes are maintained and medical applications are suitable, but the sensors require time-consuming calibration
Solution Approach 1:
The patent performs calibration as a preliminary action during mold setup or maintenance periods, rather than during production. By establishing baseline strain readings and calibration factors in advance, the system prepares the measurement system beforehand, allowing for quick changes between molds while maintaining measurement accuracy throughout production runs
Solution Approach 2:
The system uses parameter changes in the clamping profile based on strain measurements to compensate for calibration variations. By continuously adjusting clamping force parameters according to real-time strain data, the system adapts to different mold conditions and reduces the impact of calibration timing on overall process efficiency
3Stress or pressure
If traditional constant high pressure clamping is used, then mold cavity pressure is maintained, but energy consumption increases and mold wear accelerates
Solution Approach 1:
The patent transitions from static constant pressure clamping to dynamic variable pressure clamping. The clamping force is continuously adjusted during the molding cycle based on real-time strain measurements, applying high pressure only when needed during injection and maintaining lower pressure during other phases, thereby reducing overall energy consumption while maintaining adequate cavity pressure
Solution Approach 2:
The system uses feedback from strain gauges to continuously monitor and adjust clamping force. By measuring actual strain conditions and comparing them to target values, the control system modulates clamping pressure to maintain optimal cavity pressure only when necessary, reducing energy waste from maintaining constant high pressure throughout the entire cycle
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 enables more precise control of clamping force and pressure, reducing energy consumption and mold wear, while maintaining high-gloss finishes and being suitable for medical applications by providing a more accurate estimation of melt pressure and flow front position.
Implementation Method 1
at least one strain gauge secured to an exterior surface of the mold is used to identify changes in strain in the mold
Data Source
AI summary
A method of monitoring and controlling a molding clamping apparatus in an injection molding or other molding process is disclosed. The method includes creating a target strain profile, receiving a deviation limit, receiving a change in strain relating to a mold while it is closing from a first strain gauge, identifying a deviation from a target strain profile based on the output from the first strain gauge, determining that the deviation exceeds the deviation limit, and adjusting the rate or force of clamp movement. The target strain profile may have a first portion relating to a clamp closing process, a second portion relating to a filling process, and a third portion relating to a clamp opening process. The first portion relating to the clamp closing process may include an intermediate portion relating to a coining process having an intermediate clamp force setpoint.