Mold Insert Venting Cavity for Fine Filament Injection Molding
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Solution Overview
Problem
The existing plastic injection molding processes struggle to fill long filaments with fine tips due to high friction between molten plastic and mold walls, causing the plastic to freeze before filling the fine structures.
Innovation Solution
A mold insert manufacturing method involving at least two metal plates with a venting cavity of specific depth (1 µm to 20 µm) in air-conducting connection with the filament cavity, using ultra-short pulsed laser ablation for precise material removal, to allow air escape while preventing molten plastic from entering the venting cavity under high pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If regular injection molding is used to fill filament cavities, then the process is simple and straightforward, but the molten plastic freezes before filling fine filament structures due to high friction with mold walls
Solution Approach 1:
The mold insert is divided into multiple stacked metal plates, each contributing to forming the filament cavity. This segmentation allows precise control of the cavity geometry and enables the incorporation of venting cavities at specific locations to facilitate air escape during injection compression molding.
Solution Approach 2:
A venting cavity is introduced as an intermediary structure between the filament cavity and the external environment. This venting cavity provides a controlled pathway for air to escape during injection compression molding, preventing air entrapment and enabling complete filling of fine filament structures.
2Productivity
If high pressure is applied during injection molding, then the molten plastic can fill the cavity faster, but the friction increases causing the plastic to freeze before reaching fine tips
Solution Approach 1:
The injection compression molding process uses a two-stage pressure application: first, a lower injection pressure fills the base cavity, then a higher compression pressure is applied to push the molten plastic into the filament cavities. This periodic pressure application prevents premature freezing while ensuring complete filling of fine structures.
Solution Approach 2:
The process changes the pressure parameter dynamically during molding. Injection occurs at a controlled pressure followed by compression at a different pressure level, optimizing both filling speed and ability to reach fine filament tips without excessive friction-induced freezing.
3Reliability
If venting cavities are made deeper to allow air escape, then air can leave the filament cavity more effectively, but molten plastic may enter the venting cavity causing leakage
Solution Approach 1:
The venting cavity is designed with specific local characteristics: a depth in the range of 1 µm to 20 µm and positioned at the end of the filament cavity. This localized geometry allows air to escape through the venting cavity while the shallow depth and positioning prevent molten plastic from entering and causing leakage.
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 successful filling of filament cavities up to the fine tips during injection compression molding by de-aeration and preventing molten plastic from entering the venting cavity, ensuring complete filling of the filament structures.
Implementation Method 1
the venting cavity is in air conducting connection with the blind-hole end of the filament cavity
Implementation Method 2
using ultra-short pulsed laser ablation for precise material removal
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present application is concerned with a mold insert defining at least one filament cavity and having a stack of at least a first insert plate and a second insert plate, wherein the first plate has a front face that closely abuts a front face of the second insert plate, at least a portion of the at least one filament cavity is provided in at least one of the front faces of the first insert plate or second insert plate such that the filament cavity is open at a top surface of the mold insert but does not extend to a bottom surface of the mold insert, a venting cavity is provided in the same front face of the insert plate in which the portion of the at least one filament cavity is provided, which venting cavity is in air-conducting connection with the blind-hole end of the filament cavity, and the venting cavity has a depth in a direction essentially perpendicular to the front face of the respective first or second insert plate in which the venting cavity is provided that is the in the range of between 1 µm and 20 µm, in particular of between 2 µm and 10 µm. The present application is also concerned with a method of making such a mold insert and a mold machine comprising such a mold insert.