PVC Sheet Extrusion and Calendering Process for Thickness Control
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Solution Overview
Problem
The existing flat die extrusion process for producing plastic sheets or slabs, particularly PVC, faces limitations such as low production speed, poor thickness accuracy, and a short extruder lifetime, especially when processing rigid materials with high filler content.
Innovation Solution
A two-step process combining extrusion and calendering, where the material is first extruded to a plastic state and then calendered between counter-rotating cylinders under high linear pressure (100-1000 kg/cm) to achieve the desired thickness, relieving stress on the extruder and enabling higher production speeds and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flat die extrusion is used to produce plastic sheets or slabs, then the process is simple and direct, but production speed is low and extruder lifetime is short
Solution Approach 1:
The patent divides the sheet production process into two separate stages: extrusion and calendering. The extrusion stage prepares the material by melting and forming it into a preliminary sheet shape, while the calendering stage completes the thickness control and finishing. This segmentation allows each stage to be optimized independently, enabling higher production speeds without compromising extruder lifetime.
Solution Approach 2:
The patent introduces an intermediary calendering stage between extrusion and final product formation. The calender acts as a mediator that receives the extruded material, applies controlled pressure through rollers, and achieves the desired thickness and surface finish. This intermediary process relieves the extruder from the burden of precise thickness control, allowing it to operate at higher speeds with reduced stress.
2Manufacturing precision
If flat die extrusion is used to produce plastic sheets, then the process is straightforward, but thickness accuracy is poor
Solution Approach 1:
The patent segments the thickness control function from the extrusion process and assigns it to the calendering stage. The extrusion stage focuses on material preparation and basic forming, while the calendering stage with its precision rollers handles the critical thickness control. This segmentation enables high thickness accuracy without requiring the extrusion equipment to be overly complex.
3Adaptability or versatility
If high filler content materials like stone dust are processed by extrusion, then SPC floors can be produced, but extruder lifetime decreases due to increased wear
Solution Approach 1:
The patent introduces calendering as an intermediary process that handles the high filler content materials. The calender rollers are designed to accommodate abrasive fillers like stone dust, protecting the extruder from excessive wear. This allows the system to process versatile materials with high filler content while preserving extruder lifetime.
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 allows for increased production speed, improved thickness accuracy, and extended extruder lifespan, while ensuring uniform thickness and enabling the production of thin films and thick slabs with high filler content, such as SPC floors, with enhanced surface finish options through embossing.
Implementation Method 1
The calendering of the invention is performed with a linear pressure, measured parallel to the axis of the cylinders, of at least 100 kg/cm, preferably 100 to 1000 kg/cm or 200 to 1000 kg/cm
Implementation Method 2
The invention adopts a two-step process in which the material is extruded and subsequently calendered
Data Source
Figure 1
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AI summary
Process for making sheets or slabs of a plastic material that is optionally mixed with at least one filler material, for example, thin PVC films or PVC slabs filled with stone dust for flooring, wherein said process comprises a step of extruding the material through a flat die extruder (1) and calendering (2) the extrudate, thus obtaining the sheet or slab of desired thickness.