Resin Sheet Feeding via Temperature-Controlled Rollers
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Solution Overview
Problem
Conventional methods for forming resin molded articles using thermoplastic resins face issues such as uneven sheet thickness due to draw-down or neck-in, where the sheet becomes thinner at the upper part, and the sheet may get caught or wound around rollers, affecting forming efficiency and quality.
Innovation Solution
A method involving intermittent extrusion of thermoplastic resin as a molten sheet, which droops downward, is sandwiched between rollers with a widened gap to prevent sliding contact and winding, and the rollers' surface temperature is set lower than the resin's to maintain dynamic friction and ensure even feeding, adjusting the rotation speed to counteract draw-down and neck-in, and using split mold blocks for secondary forming to achieve desired thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the sheet-shaped resin is fed through a pair of rollers to prevent draw-down, then the thickness uniformity is improved, but the sheet may get caught or wound around the rollers
Solution Approach 1:
The invention changes the temperature parameter of the rollers to be lower than the resin temperature, which prevents the resin from adhering to the rollers and winding around them, while still maintaining sufficient friction for feeding and achieving uniform thickness
Solution Approach 2:
The invention dynamically adjusts the rotation speed of the rollers to match the extrusion speed of the resin, ensuring smooth feeding without catching or winding, while maintaining the temperature differential to prevent adhesion
2Manufacturing precision
If the extrusion speed is increased to compensate for draw-down, then the thickness uniformity is improved, but the extrusion pressure changes cause swelling that accelerates thickness unevenness
Solution Approach 1:
The invention replaces the approach of adjusting extrusion speed/pressure with a mechanical feeding system using rollers that physically control the resin flow, eliminating the harmful effect of pressure-induced swelling while maintaining thickness uniformity
3Ease of operation
If the roller temperature is set close to the resin temperature to ensure smooth feeding, then the feeding ease is improved, but the resin adheres to the rollers and winds around them
Solution Approach 1:
The invention optimizes the temperature parameter by setting it lower than the resin temperature, which provides sufficient temperature differential to prevent adhesion and winding while maintaining high enough temperature to ensure smooth feeding and avoid excessive friction
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 prevents uneven thickness and sheet winding, maintaining forming efficiency while ensuring even thickness and quality in the resin molded articles, allowing for reliable feeding and secondary forming without adverse effects.
Implementation Method 1
a downward feeding speed of the sheet-shaped resin by the pair of rollers becomes an extrusion speed or more... a dominant factor for feeding the sheet-shaped resin downward by the pair of rollers is a dynamic frictional force acting between outer surfaces of the pair of rollers and outer surfaces of the sheet-shaped resin
Implementation Method 2
a surface temperature of each of the pair of rollers lower than a temperature of the extruded sheet-shaped molten resin... lowering the surface temperature of the pair of rollers by cooling an inside of each of the pair of rollers with water
Implementation Method 3
extruding the stored thermoplastic resin intermittently in a predetermined extrusion amount per unit time from an extrusion slit provided in a T-die
Data Source
AI summary
A method for forming a resin molded article includes a step of extruding a thermoplastic resin intermittently at a predetermined speed from an extrusion slit, such that the resin droops downward in a shape of a sheet. The method further includes the steps of: feeding the extruded sheet-shaped resin downward by a pair of rollers; and forming the sheet-shaped resin with a mold. In the step of feeding the sheet-shaped resin, one of the rollers is pressed against the other, but not to the extent of crushing the sheet-shaped resin, regardless of the thickness of the sheet-shaped resin. In addition, a surface temperature of each of the rollers is set lower than a temperature of the sheet-shaped resin and within a predetermined temperature range. This method can prevent sliding contact between the rollers and the sheet, while preventing the sheet from being wound around the rollers.