Roll-Molding Nip Pressure Control for Fastener Manufacturing
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Solution Overview
Problem
Roll-molding processes for producing continuous flexible strips with arrays of molded projections, such as touch fastener elements, require high nip pressures, which can damage equipment and are time-consuming to set up, especially when changing mold rolls.
Innovation Solution
A method and apparatus where molten resin is introduced between counter-rotating rolls with a mold roll and a pressure roll, forming discrete projections on the mold roll surface, and a reaction roll applies pressure to maintain nip pressure, allowing for efficient molding and easy reconfiguration of the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high nip pressures are applied to mold viscous resin, then molding quality and product strength are improved, but equipment wear increases and roll surface damage occurs
Solution Approach 1:
The pressure application is segmented into two distinct stages: a high-pressure molding stage to ensure quality, and a low-pressure cooling stage to protect equipment. The system transitions from high nip pressure during resin injection and molding to reduced pressure during the cooling phase, preventing roll surface damage while maintaining manufacturing precision.
Solution Approach 2:
The system applies high pressure preliminarily during the molding phase to ensure quality, then transitions to a protected state during cooling. The high nip pressure is applied only when necessary for resin injection and cavity filling, before the resin solidifies and requires reduced pressure for cooling.
2Stress or pressure
If hydraulic cylinders are used to force rolls together for high nip pressure, then molding capability is improved, but system complexity and setup time increase
Solution Approach 1:
The mold roll is designed to be self-powered, utilizing the viscous drag of the injected resin to rotate the mold roll and maintain nip pressure between the rolls. This eliminates the need for external hydraulic cylinders or complex actuation systems, reducing device complexity while maintaining the necessary high nip pressure for molding viscous resin.
Solution Approach 2:
The patent replaces complex hydraulic mechanical systems with a simpler resin-driven mechanical system. The viscous resin itself serves as the driving force, creating a self-regulating system where the resin's own viscosity provides the necessary pressure and rotation, eliminating hydraulic cylinders and reducing system complexity.
3Adaptability or versatility
If mold rolls are changed to produce different products, then product versatility is improved, but setup time and production downtime increase
Solution Approach 1:
The system employs dynamically adjustable nip pressure that can be quickly modified without physical roll changes. The variable pressure system allows different product configurations to be produced by adjusting pressure parameters rather than changing mold rolls, enabling rapid reconfiguration and reducing setup time while maintaining product versatility.
4Productivity
If high run speeds are used to increase productivity, then output is improved, but molding quality and resin solidification may be compromised
Solution Approach 1:
The system maintains continuous high nip pressure throughout the resin injection, molding, and cooling phases by using the resin's own viscous drag to sustain pressure. This continuous pressure application ensures proper solidification and molding quality even at high run speeds, as the pressure is maintained without interruption throughout the entire process cycle.
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 method allows for efficient molding of continuous or discrete resin layers with reduced equipment wear and faster setup, maintaining quality at higher run speeds and enabling the production of longitudinally continuous products with arrays of molded projections.
Implementation Method 1
the reaction roll is spaced from the pressure roll by a distance less than an outer diameter of the mold roll... the mold roll is simultaneously held against both the pressure roll and the reaction roll while the resin solidifies
Data Source
Figure 1A
Figure 1B~1C
Figure 2~2A
AI summary
Discrete male touch fastener elements (20) are molded of thermoplastic resin extending from a common, flexible base sheet (19), by introducing molten resin to a molding nip (22) between two counter-rotating rolls consisting of a mold roll (106,106a,106b,106c) and a pressure roll (12) arranged such that their rotation axes are parallel and together define a common plane (g) containing each of the rotation axes. Solidified resin is stripped from molding cavities (111a) of the mold roll after the cavities have passed a rotating reaction roll (14) forming a pressure nip (24) with the mold roll. The reaction roll (14) is spaced from the pressure roll (12) by a distance less than an outer diameter of the mold roll (106,106a,106b,106c), and the mold roll is simultaneously held against both the pressure roll (12) and the reaction roll (14) in a non-planar roll stack.