The manufacturing tolerances of injection molded parts are very high, and thermoformed parts usually have some deviations, but recent developments have shown that thermoforming is far behind injection molding with attention to technological progress. High-speed, automated, more intelligent process control, integrated vision system and better decoration technology are becoming more and more common in the practice of thermoforming.
In this article, the editor of Xianji.com will focus on five areas of thin-gauge thermoforming. The technology in these areas is developing rapidly, focusing on the interaction of plastic materials, metal molds and production equipment. This does not mean to be comprehensive, and the adoption rate is not uniform across the world. Like any professional subject, the deeper you go, the more details you will discover. Thermoforming has a wide range of applications, covering heavy gauge and thin gauge processes.
Automation 1: Parts handling
It is safe to say that when most thermoformers are asked about automation, they usually think of the final solution related to part disassembly. However, this is not a panacea. From simple A/B stacking mechanisms to automatic stacking systems, thermoforming machines have many ways to move parts. Perhaps the most common automated method is to use a two-axis processing system, in which molded parts are clamped and broken from the coil as part of the basic stacking system, and then transferred to a conveyor belt via a linear drive. Set the stacking motion parameters through the teaching mode. Through optimization, the standard upward stacking movement can reach a speed of 40 cycles per minute. Other options include 180° or 90° rotation to create A/B stacks.
Once the parts are stacked, they can be moved to the final packaging station, which can be as simple as an automatic casing system or as a fully articulated robotic arm that puts the entire stack into a pre-installed box Just as complicated. Of course, these machines are usually not the “core” of the thermoforming process itself, but the ability to integrate downstream equipment is the key to providing an overall solution. The signal exchange from the host to the automation equipment is relatively simple. Gerhard Zdebor of Austria-based HOT&T Consulting explains this connectivity: “When the stack needs to be moved, downstream components receive signals from the thermoforming machine. On the other hand, if any failure occurs, the thermoforming opportunity receives signals from the automation system. .Due to the large number,
The labor savings associated with automation are well understood in many industries. The economy varies by country, region, and market segment. Labor costs may be the biggest investment driver, but low value-added projects may limit the CFO’s willingness to implement automation.
Automation 2: Inspection and Quality Control
However, automation is more than part handling. High-quality parts or high-precision parts require increased quality inspection and related costs. These parts are manufactured on high-speed thermoforming lines with integrated cameras and reject stations. In a globalized economy where commoditization is rampant, especially in the packaging industry, it is not easy to prove investments that may adversely affect the cost structure. Over the years, containers of thermoformed parts have been shipped from Asia to the West Coast. Of course, not all products need to be perfect, and “really good” is indeed the standard for most disposable or disposable containers (recyclability is another topic entirely). However, when it comes to food safety or surgical requirements, the situation changes.
Until recently, it was believed that the cost would exceed the benefits of the thermoforming visual inspection system. The actual cost calculation will include quality, such as scrap rate, part failure, and scrap rate. However, what is more difficult to measure is the reputation cost associated with defective products. What is the cost of part failure on the baby food automatic filling line? The inspection system provides greater awareness and visibility. This information serves as a process control tool and highlights the problem. Initially, the scrap rate will definitely increase, but over time, the percentage of quality parts will increase. Determining the concentricity, flange thickness and side wall accuracy and other parameters defects or defects before packaging and transporting parts can fully ensure profits.
Increase productivity: software and process control
At best, software is a tool to increase productivity. Worst of all, it will bring extra work and frustration to users. Generally speaking, when we adopt new software, we must adapt to behavior. Part of the dialogue of K 2019 shows the various elements of process control, especially a closed-loop system, through which changes in the temperature of the plate or the auxiliary force of insertion and removal will cause the automatic adjustment of machine parameters. It can be classified as software that improves the way the machine operates or makes the machine smarter. The dynamic optimization of machine settings takes this step one step further. After the operator enters the product data (part size, material type and thickness), the machine can automatically calculate the heating and forming parameters.
Creating a network between the machine and the Manufacturing Extension System (MES) is a known best practice, and it is getting more and more attention under the column of Industry 4.0. The input parameters can now be controlled by 1 millisecond, and exporting the data to a csv file will create a large amount of data. However, separating the signal from the noise is the critical first step in evaluating the data. The arrival of “big data” means that we have more information available, but not necessarily more time for analysis. As data science training becomes more and more important, it also has important implications for operators and employees. Remote access or remote monitoring of equipment, recording and archiving of machine or tool settings, order management, and time-stamped data sets (for audits) that comply with FDA or GMP requirements are some of the new features and advantages of the connected system. Software that can improve user productivity.
Infrared scanning of point-based or line-based slices has been used intermittently for at least 15 years, but with the advent of improved data visualization tools, the technology is gaining more and more acceptance. However, there is another way of thinking, that is, by concentrating the surface temperature of the recording material across the width of the paper, calculating the power control (ie, the required force) of the plug assist or pre-stretching machine. In order to keep the process time constant, the valve action will be monitored and the process parameters will be automatically adjusted when necessary to compensate for the switching time.
Nowadays, most machinery runs on servo-driven platforms, mainly in chain indexing, press movement and parts disassembly systems. The servo drive works like a generator, so energy is generated during braking. Normally, this braking energy is discharged into the surrounding environment as heat. Feedback drive technology means that the energy generated by the brake flows into the intermediate circuit storage area (battery). The drive controller is connected to this circuit, allowing energy to be used for other servo drives.
Material issues: mold technology
In the heavy and thin industries, tool cost and turnaround time are often referred to as the key advantages of the thermoforming process. For some thermoformers, it is still common practice to manufacture their own tools in-house. Before studying actual tool technology, it is important to note that tool manufacturers have benefited from advances in CNC technology. Gone are the old manual lathes and Bridgeport presses.
Equipment from the United States, Germany and Japan dominate the field of machine tools. Lights-out automation enables greater flexibility in scheduling and reduces the need for operator supervision. The surface treatment has been improved, adding more time and labor to the tool shop. In the extrusion field, changes in the formulation of CPET and CPLA materials have led to new tools that avoid the use of oil-heated two-stage molds, and instead use electrically heated single-stage molds.
The main developments of tooling technology can be summarized as follows: material selection, air flow and water flow. The increased use and acceptance of Aluminum has helped increase speed through better temperature management and reduced weight, thereby accelerating machine movement. The cooling rate with aluminum tools can be increased by up to 7 times. The use of a closed water system with minimal sealing, anti-corrosion materials and optimized water pressure can reduce condensation in a wide temperature range and produce a “sweat-free” effect. In particular, the use of in-situ adjustment tools, independent clamping ring pressure and independent lower clamp cooling function can achieve highly accurate and repeatable parts.
Tim Douglas, a scientific technician at PinnPack Packaging in Oxnard, Calif., sees the important benefits of test tool coatings. He said: “From a simple hard anodizing treatment to a PTFE coating that allows the undercut to be released for stripping, these coatings help extend tool life and prevent wear,” he said. “Some high-end coatings from Endura Coatings or Sun Coating Co.. Add material-specific protection. For example, when running CPET, the stopper and cavity are coated to better release and reduce friction.” All of these are FDA, NSF and USDA are safe.
Improved airflow management, including air-saving technologies, can fill and vent faster, and place the valve close to the cavity, which also helps increase production speed. The tool can be equipped with sensors to monitor strain, pressure, and temperature. The latest tools from Germany are now equipped with user-friendly NFC or RFID tags that can provide complete life cycle documentation to remind operators of maintenance requirements.
Comprehensive decoration
The use of preprinted paper in thermoforming has been mastered for at least 25 years. Nowadays, AB and ABA configurations, hinged flaps and candy bars can run on most devices. Before production, computer simulation tools such as T-Sim can be used to effectively model deformation printing, and only a sensor eye can detect a specific area of the paper. Auxiliary processes such as labeling, dry glue printing, and digital printing can provide higher speeds, but they increase capital expenditures while increasing the footprint of the system.
A key attribute of thermoforming is the ability to use materials to form parts with 100% barrier protection, usually in structures like PP/EVOH/PP. Adding decoration to the barrier film can create new ways for part designers and product sellers, especially in mass customization environments (such as supermarkets or specialty food stores). Compared with injection molding of similar injection molded parts, in-mold labeling (IML-T) for thermoforming offers significant weight reduction opportunities. Since the label has been integrated into the forming process, IML-T reduces capital expenditure and floor space, while providing more graphic options related to label printing. And because the material is not pre-printed, it will not release gas from the printing color during the heating process, and the frame sheet can be easily pelletized for reuse without being contaminated.
Now, the latest development of IML-T includes the ability to make labels using polymer substrates, paper and even cardboard. The focus on recycling (especially sorting) has driven the demand for packaging that can be easily separated when using two or more materials.
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