Injection Mold Clamp Rate Control Using External Strain Gauges
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Solution Overview
Problem
Current injection molding processes face challenges in accurately controlling clamping force and rate, particularly in monitoring and addressing flow filling challenges, which can lead to defects such as short-fills, warping, and reduced mechanical properties, due to limitations in existing sensor technologies that are either direct and costly or indirect and less accurate.
Innovation Solution
The use of strain gauge sensors placed on the exterior of molds to measure strain changes and adjust the clamping force and rate of electric or hydraulic clamping units based on sensed strain, allowing for a variable force clamping profile that can be optimized in real-time, reducing energy consumption and wear on mold components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct sensors are used to monitor clamping force, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses strain gauges as intermediary sensors placed on the mold exterior surfaces. These strain gauges measure strain on the outer surfaces, which serves as an indirect but accurate indicator of internal mold cavity pressure and clamping force, avoiding the need for complex direct pressure sensors inside the mold cavity.
Solution Approach 2:
The patent replaces complex mechanical pressure sensing systems with electrical strain gauge measurements. By measuring mechanical strain on the mold exterior and converting it to pressure information through calibration curves, the system achieves accurate measurement with simpler, more cost-effective sensors.
2Manufacturing precision
If clamping force is increased to prevent defects, then manufacturing precision is improved, but energy consumption increases
Solution Approach 1:
The patent implements dynamic clamping force adjustment based on real-time strain gauge measurements. The system continuously monitors mold strain and adjusts clamping force dynamically throughout the injection cycle, applying maximum force only when needed (during peak pressure moments) rather than maintaining constant high force, thereby reducing energy consumption while preventing defects.
Solution Approach 2:
The system uses feedback from strain gauge measurements to continuously adjust clamping force. The measured strain information is fed back to the control system, which modulates hydraulic valve operation to maintain optimal clamping force levels, preventing both defects and unnecessary energy waste.
3Reliability
If constant high clamping force is applied, then reliability is improved, but loss of energy increases due to extended operation at high power
Solution Approach 1:
The patent employs periodic modulation of clamping force based on the cyclic nature of the injection molding process. The system applies high clamping force periodically during injection and holding pressure phases, then reduces force during cooling phases when pressure is lower, matching energy input to actual process needs while maintaining mold integrity.
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 provides a more accurate and consistent delivery of clamping force throughout the molding process, reducing defects and improving part quality by using external sensors to monitor and adjust clamping parameters, thereby enhancing the precision and efficiency of the injection molding process.
Implementation Method 1
identifying changes in strain in a mold during an injection molding process using at least one strain gauge
Data Source
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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.