Semifinished Product Pre-Compression in Injection Molding
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Solution Overview
Problem
In injection molding, the high fluidity of silica-gel forming materials often results in spills or burrs at joint locations due to insufficient mold joint force, leading to decreased yield and increased labor costs for trimming these defects.
Innovation Solution
The method involves a semifinished product emplacement step, pre-compression using a press-fit jig to secure the product within the mold, followed by injection of the forming material, which is then cooled and formed into a finished product, utilizing a middle plate and ejection mechanism to prevent material from spilling or burring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If silica-gel is used as the forming material due to its excellent fluidity, then the forming capability is improved, but spill or burr is easily formed on the joint location of the mold
Solution Approach 1:
The semifinished product is pre-compressed and tightly fitted with the loading member before the actual injection molding process. This preliminary action ensures that the product is securely positioned, preventing spill or burr formation when the high-fluidity silica-gel is injected into the mold
Solution Approach 2:
A loading member is introduced as an intermediary component between the mold and the semifinished product. The loading member facilitates secure positioning and tight fitting of the product, acting as a mediator that prevents direct contact issues between the high-fluidity material and the product, thereby preventing spill or burr
2Object-generated harmful factors
If sufficient joint force is applied to prevent spill or burr, then the mold joint becomes tighter, but the complexity of the mold structure increases
Solution Approach 1:
The semifinished product is pre-compressed to achieve tight fitting with the loading member before injection. This preliminary compression action creates sufficient joint force in advance, preventing spill or burr during injection without requiring complex mold structures with excessive clamping mechanisms
Solution Approach 2:
The pressing function is extracted from the mold structure itself and transferred to a separate press-fit jig. This allows the mold to maintain a simpler structure while still achieving the necessary joint force through the external pressing device during the pre-compression step
3Manufacturing precision
If a press-fit jig is used to pre-compress the semifinished product, then the tightness of fitting is improved, but the device complexity increases
Solution Approach 1:
The press-fit jig acts as a temporary intermediary tool that facilitates tight fitting during the pre-compression step. After serving its purpose, the jig is removed, allowing the mold structure to remain relatively simple while still achieving the desired tightness of fitting for the injection process
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 effectively reduces spills and burrs on finished products, enhancing the yield of injection molding and minimizing labor costs associated with trimming these defects, particularly when using silica-gel as the forming material.
Implementation Method 1
The press-fit jig presses the semifinished product into the first mold base by the pre-joint force, allowing the semifinished product to be tightly fitted with a loading member
Implementation Method 2
After the forming material is cooled down and formed in the forming space, a finished product can be formed
Implementation Method 3
When the forming materials are in the liquid state, the fluidity of silica-gel is larger than that of plastic... After the forming material is cooled down and formed in the forming space
Data Source
AI summary
An injection molding method for a semifinished product includes a semifinished product emplacement step, a semifinished product pre-compression step and a forming step. First, a pair of mold with a forming space is provided. A semifinished product is put into the mold, and a first joint is performed to the mold by a press-fit jig, fixing the semifinished product in the forming space. The semifinished product is also tightly fitted with the mold. Next, a first open-die is performed and the press-fit jig is removed. After that, a second joint is performed, and a forming material is injected into the forming space. Finally, a second open-die is performed, and then a finished product is formed. By the semifinished product pre-compression step, the forming material can be prevented from resulting in spill or burr on the semifinished product, thereby improving the yield of injection molding.