3S Metal Printing Findings
Summary
Trivium Packaging is a leader in the metal packaging production. With nearly 7,500 employees across 60 global locations, Trivium faces challenges with tools prone to breakage and wear in their pull-tab production machinery. These tools, stored in a technical warehouse, are expensive and have long lead times. To address this, Trivium is researching and testing the use of 3D metal printing to reduce lead times and costs. Successful implementation could enhance tool availability, lower risks, and extend the benefits to other tools and products.
The company is concerned about production issues due to the wear of essential tools used in creating pull tabs. With numerous tools in use and long lead times for replacements, the company faces a high risk of production stoppages, leading to severe financial consequences. The tools in question are critical for bending pull tabs to prevent sharp edges and punching the final circular hole. These tools, composed of many complex parts, require replacement every 3-4 months and have a lead time of 10-12 weeks, making them expensive and challenging to manage. Thus, Trivium wants to look at 3D metal printing to try and circumvent the issue of long lead times.
Designing
The first design aimed to thicken the edge of the part performing metal bending in the wipe-down punch, as simulations identified it as a weak point. However, space constraints between the yoke and the die prevented this modification. Instead, the stripper was hollowed out since the spring it is attached to absorbs much of the impact, meaning it doesn’t need to support as much force. This change aimed to speed up printing and save material while maintaining strength through an infill with specific geometry. Using Materialise Magics for 3D metal printing, an “Octet truss relative density” infill with a 3 mm structure dimension and 2 mm wall thickness was selected. Two escape holes of 0.5 mm radius were added to prevent metal powder entrapment.
This redesign makes the piece more printable by saving material and time and improving heat dissipation. Simulations showed that even a completely hollow piece could withstand 10,000 N of force using steel, indicating that the infill would further enhance resistance. The test with a 5 mm radius was performed twice. Initially, the setup shifted slightly, leading to higher variability and lower force measurements. After adjustment, the second test was more consistent, and the force required was closer to theoretical calculations. The theoretical force for a 5 mm radius was 91.3 N, with the first test averaging 85.0 N and the second 90.5 N, showing a 1% deviation. For a 1 mm radius, the theoretical force was 303.5 N, while tests averaged 278.43 N, showing a 91.7% accuracy. For a 10 mm radius, the theoretical force was 48.7 N, but tests averaged 56.6 N, with a 14% deviation. Overall, the theoretical calculations largely corresponded to the tested values.
The first major research subject focused on 3D metal printing, conventional production, and the processes of die cutting and forming. All seven investigated 3D metal printing techniques were explained in detail, highlighting their advantages, disadvantages, and specifications. These techniques were compared to conventional methods to identify the inherent benefits of printing. An explanation of die cutting and forming was provided to clarify Trivium’s process.
The second research subject examined coating techniques, concluding that Physical Vapor Deposition (PVD) was the most promising for coating tools due to its strong adherence and no need for post-coating heat treatment. Titanium Carbonitride (TiCN) was chosen as the best coating material for its extended lifespan compared to Titanium Carbide (TiC).
The third subject, heat treatment, explored various techniques but lacked definitive results due to time constraints. Recommendations were made for further research into the phase diagram of the tool steel used, listing possible phases and their mechanical properties, and ensuring compatibility with coatings.
Results
Redesign efforts showed potential improvements in the pull tab machine’s tools. The first station we were redesigning was hollowed out to save material and costs, while an unnecessary bolt was removed from the second redesigned station, simplifying the design for 3D printing. The final subject, a 90-degree bending test, confirmed that theoretical formulas matched practical tests and highlighted the significant impact of the tool’s radius on the peak bending force required. Further research was recommended to better predict forces on the pull tab machine’s tools.
General recommendations included exploring CNC surface finishing capabilities, examining various coatings and their specifications, and obtaining more 3D printing models to minimize post-processing.