Thick Plastic Parts via Sequential Layer Injection Molding
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Solution Overview
Problem
Conventional injection molding struggles to produce thick plastic parts greater than 5 mm in thickness without defects like sinks, bubbles, or voids, and extrusion processes are costly and not adaptable for all material grades, especially during the development stage of new resin materials.
Innovation Solution
A sequential multiple-layer molding process using a tool with a movable internal core, removable support plates, and an ejector plate to create gaps for additional layer injection, ensuring controlled thickness and effective adhesion between layers through surface texturing and undercut features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional injection molding is used to produce thick plastic parts, then the manufacturing process is simple, but the part quality deteriorates with sinks, bubbles or voids inside the part when thickness exceeds 5 mm
Solution Approach 1:
The molding process is segmented into multiple sequential injection stages, where each stage forms a layer of the thick part. The mold cavity is divided into multiple zones that are filled in sequence, allowing each layer to be properly compacted and bonded before the next layer is added. This segmentation enables production of parts up to 65 mm thickness without internal defects.
Solution Approach 2:
Before injecting the full thickness of material, preliminary layers are injected and allowed to partially cool and set. Support plates are strategically positioned in advance to control layer thickness and provide structural support during subsequent injection stages, preventing void formation in thick sections.
2Length of moving object
If extrusion processes are used to make thick parts, then the part thickness can be achieved, but material consumption increases and costs rise
Solution Approach 1:
The sequential injection process allows each layer to serve as a support structure for the next layer, eliminating the need for excessive material to be added and removed. The process inherently controls material usage by injecting only the required amount for each layer thickness, reducing resin consumption compared to extrusion methods.
3Length of moving object
If extrusion processes are used for thick parts, then the manufacturing capability is achieved, but adaptability to different material grades is reduced
Solution Approach 1:
The sequential injection molding process is a universal method that can accommodate various thermoplastic materials including NPI grades. The process parameters (temperature, pressure, injection rate) can be adjusted for different material properties, making the system versatile for prototyping and production with diverse resin types, unlike extrusion which is more material-specific.
4Productivity
If conventional injection molding is used, then the process is efficient, but the maximum part thickness is limited to 5 mm without defects
Solution Approach 1:
The sequential injection process maintains continuous productive action by immediately injecting the next layer after the previous layer is formed, without removing material or repositioning the part. This continuous layer-by-layer construction enables thick part production while maintaining high manufacturing efficiency and productivity.
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
Enables the production of thick plastic parts without defects, achieving thicknesses up to 65 mm with effective layer adhesion, reducing material waste and costs, and accommodating various resin materials, particularly useful for CNC prototype parts and new product initiation.
Implementation Method 1
Injection molding is a process for manufacturing products made of plastic. In general, molten plastic material is injected into a mold wherein the material solidifies upon cooling.
Implementation Method 2
opening the tool and removing a support plate; closing the tool, wherein a gap having a thickness is created in the tool, the thickness of the gap being determined by the thickness of the support plate removed
Implementation Method 3
molten plastic material is injected into a mold wherein the material solidifies upon cooling
Data Source
AI summary
In some embodiments, a tool includes, in an injection molding machine, a movable internal core configured to receive a molded plastic layer thereon, the molded plastic layer having a thickness. The tool also comprises an injection nozzle configured to inject plastic material over the movable internal core to form the molded plastic layer; an ejection plate connected to the movable internal core; and multiple, movable support plates each having a thickness. The multiple, movable support plates are located behind the ejection plate. A movable support plate of the multiple, movable support plates is configured to determine the thickness of the molded plastic layer.