Sequential Injection Molding Pressure Homogeneity
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Solution Overview
Problem
The existing sequential injection molding process results in non-homogeneous pressure variations in the mold cavity, leading to anti-aesthetic surface defects on molded articles due to uneven injector actuation.
Innovation Solution
The electronic control system of the injectors is configured to open the central injector rapidly, then hold it partially closed, while intermediate and end injectors open successively at lower speeds and to lower maximum opening values, and close partially to higher minimum values, ensuring more uniform pressure during filling and packing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all injectors are opened simultaneously to complete opening position during filling step, then filling speed is improved, but pressure becomes non-homogeneous causing surface defects
Solution Approach 1:
The filling process is segmented into multiple phases with different injector configurations. During the filling step, injectors are opened to different degrees (central injector to 100%, intermediate to 70%, end to 50%) rather than all simultaneously to completion, segmenting the material flow to achieve homogeneous pressure distribution while maintaining filling efficiency
Solution Approach 2:
The injector opening positions are made dynamic rather than static. The system transitions from a static complete opening position to a dynamic configuration where each injector group opens to different degrees during filling, and then all open completely during packing. This dynamic adjustment optimizes both filling speed and pressure homogeneity
2Manufacturing precision
If high packing pressure is applied to ensure complete filling, then filling completeness is improved, but surface defects increase due to pressure lines
Solution Approach 1:
Different packing pressures are applied locally to different regions of the mold cavity. The central injector region receives higher packing pressure (100% opening) while intermediate and end regions receive progressively lower pressure (70% and 50% opening respectively), matching the local filling requirements and eliminating pressure lines on the surface
Data Source
AI summary
A molding apparatus for the production of articles molded through sequential injection includes a mold having a cavity, a plurality of electrically actuated injectors arranged at central, intermediate and end positions, respectively, with respect to the mold cavity, and an electronic system for controlling the injectors for the actuation thereof according to a sequential cycle which provides for opening the central injector first, followed by the intermediate injectors and then the end injectors. The electronic control system is configured so that the opening sequential cycle occurs in such a way to obtain more linear and homogeneous pressure in the mold filling step, and lower packing pressure.