Rotating Carousel Injection-Compression Molds for PET Preform Production
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Solution Overview
Problem
One-stage plants for manufacturing thermoplastic preforms, particularly PET, face low production rates compared to two-stage plants, and there is a need to increase productivity without compromising preform quality, while also addressing issues of preform contamination and delayed fault detection.
Innovation Solution
An injection-compression apparatus with a vertical rotation axis and a rotating carousel featuring multiple injection-compression molds, a melted thermoplastic distribution device, and modular architecture to enhance rotation speed, reduce mechanical cycle time, and facilitate automation, ensuring higher productivity and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rotating carousel with multiple molds is used to increase production rate, then productivity increases, but the mechanical cycle time and rotation speed are limited by the complexity of opening/closing molds and distributing melted resin
Solution Approach 1:
The molding system is divided into multiple independent molds arranged on a rotating carousel, with each mold capable of operating in parallel. This segmentation allows simultaneous injection-compression cycles in multiple cavities, increasing overall production rate while maintaining manageable cycle times for individual molds.
Solution Approach 2:
Melted thermoplastic is pre-distributed to each mold cavity before the injection-compression cycle begins. The distribution device delivers molten material to predetermined locations in advance, eliminating waiting time during the molding cycle and reducing the overall mechanical cycle time.
2Productivity
If the rotation speed of the carousel is increased to reduce downtime, then productivity improves, but the distribution device complexity and resin delivery precision requirements increase
Solution Approach 1:
The distribution device is designed with a universal structure that serves multiple functions: it distributes melted resin to multiple molds simultaneously, maintains resin temperature through heated channels, and synchronizes delivery with the rotation position of the carousel. This multi-functionality reduces the need for additional separate systems.
Solution Approach 2:
A centralized distribution device acts as an intermediary between the single extruder and multiple molds. It receives molten thermoplastic from one source and efficiently divides and delivers it to multiple destinations, simplifying the overall system architecture while enabling high-speed operation.
3Ease of operation
If modular architecture is implemented to facilitate automation and reduce downtime, then ease of operation and productivity improve, but device complexity increases
Solution Approach 1:
The apparatus is divided into modular components including interchangeable mold sets, a separable distribution device, and independent carousel sections. This modular segmentation enables easy maintenance, rapid format changes, and automated operation while keeping each module relatively simple in design.
Solution Approach 2:
The modular architecture allows rapid changing of operational parameters such as mold cavity configurations, production rates, and resin types. By standardizing interfaces and using interchangeable modules, the system can adapt to different production requirements without redesigning the entire apparatus.
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
The apparatus achieves higher container production rates, reduced downtime, improved preform quality, and reduced waste, enabling better centering and concentricity of molded preforms, thus enhancing overall hourly productivity.
Implementation Method 1
Document US20080251974 describes a rotary carousel for manufacturing preforms having as main feature the use of a so-called "mass-drive", i.e. a system based on the centrifuge force.
Data Source
Figure 1
Figure 2
Figure 2a
AI summary
An injection-compression plant for manufacturing PET performs comprises an extruder (1) to produce a melted resin, a distribution joint (3) for distributing the melted resin from the extruder (1) towards the injection-compression molds (9', 9", 9"), gathered in modular groups of three on supporting frames (21) arranged about the peripheral surface of the rotary carousel (2). The joint (3) allows to transfer the fluid thermoplastic resin from the stationary channel (10) of the extruder (1) to the lateral feeding conduit (27) of each molding module (9), said lateral feeding conduit being rotating with the carousel (2). The injection-compression molds (9', 9", 9") have the two half-molds forming the molding cavity (41 ', 41", 41"') connected by means of bayonet couplings to the frame (21). The molded preforms are extracted from the carousel (2) by means of a wheel (50), which transfers them to an air cooling device (51).