The authors stated that the carbon contents of the three groups studied showed little difference as can be seen in Table 3, but the oxygen content was found to increase with the increase in sintering temperature. Because TA1 has a high affinity for carbon and oxygen elements, the impact of the distribution and forms of carbon and oxygen elements on the final properties was also analysed.

A group of researchers in China and New Zealand have been studying the use of MIM to produce TA1 components using spherical TA1 powder and a water-soluble binder and the results of this research have been published in a paper available online (February 2024) in the Journal of Adhesion Science and Technology entitled: ‘Microstructures and mechanical properties of TA1 sintered samples prepared by injection moulding using water-soluble binder’. The authors of the paper include Weichen Zhang, Lu Li, Peng Cao, Gang Chen and Muhammad Dilawer Hayat.

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Ideal for injection molding large, lightweight, durable structural plastic parts, the Milacron LPIM Structural Foam Technology creates a cellular foamed core surrounded by integral skins, forming a total integral and rigid structure. In this process, a foaming agent (nitrogen) is mixed with the polymer melt and short-shot through a modular multiple nozzle system into a mold (or multiple molds) in a volume less than is required to fill a solid part. The injection pressure and expanding gas/polymer cellular mixture act to fill the mold. The mold cavity pressures are 10–20 times lower than conventional injection molding which permits the use of lower cost aluminum molds with no additional hot runner system since the hot runner manifold and nozzle system is integral to the machine. Many molds and large parts of different sizes can be molded at the same time. The multi-nozzle machine design allows for multiple molds to be run simultaneously allowing for higher productivity.

In total, Milacron is currently rebuilding eight LPIM machines as well as four HPIM machines. “Milacron’s commitment to the LPIM side of the industry, their quality, performance, and service is second to none and is the reason that we made this decision to have them rebuild and upgrade this equipment,” said Ron Ernsberger, President, 20/20 Custom Molded Plastics.

The authors reported that three groups, each containing three MIM TA1 samples, were sintered at different temperatures (1250°C, 1300°C and 1350°C), and that the main focus of their research was to explore the reasons for the different properties in the sintered samples, such as the differences in relative densities, microstructures and mechanical properties. Because TA1 has a high affinity for carbon and oxygen elements, the impact of the distribution of these elements in the sintered microstructure and on the final properties of MIM TA1 samples was also analysed.

Parts molded with LPIM can replace many rotational molded or industrial blow molded parts with better aesthetics and better cycle times.

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Machines delivered in the 1980s and 1990s are being upgraded to outperform their original specifications, while new machine deals also are accelerating.

One sample was selected from each sample group A, B, and C to study its microstructure, and Fig. 2 shows the SEM images of three samples at different magnifications. The figure shows that the microstructure is dominated by equiaxial α phases. The authors established that the grain size of sample B is significantly smaller than that of sample A, as shown in Figs. 2 (a), 2 (c), and 2 (e). However, the grain size of sample C is larger. Obvious precipitates at the grain boundaries are visible in Fig. 2 (c), and many needle-like structures exist in Fig. 2 (d). Fig. 2 (f) also shows the same needle-like structures but in smaller quantities. These are presumed to be composed of β-Ti according to their locations, and further analysed by TEM. In addition to point-like precipitates, Figs. 2 (c) and 2 (e) also show lump precipitates (red circle). FESEM was employed to determine its composition further.

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Stephen has been with PlasticsToday and its preceding publications Modern Plastics and Injection Molding since 1992, throughout this time based in the Asia Pacific region, including stints in Japan, Australia, and his current location Singapore. His current beat focuses on automotive. Stephen is an avid folding bicycle rider, often taking his bike on overseas business trips, and is a proud dachshund owner.

Machine builder Milacron Holdings Corp. has seen demand increase for its Low Pressure Injection Molding (LPIM) Structural Foam machines following a successful NPE 2018 in Orlando, FL, including machine rebuilds. Milacron had a dedicated space in the NPE booth focusing on LPIM technologies and large part molding. An eye-catching display showed a replica platen of the massive Cincinnati 6,750 ton machine sold to 20/20 Custom Molded Plastics of Holiday City, OH.

TA1 is a commercial pure grade of titanium which exhibits low density, excellent corrosion resistance and biocompatiblity and, whilst its tensile strength is not high compared with many Ti alloys, it has good toughness and exceptional ductility. Typical applications include medical devices, dental parts, smart wearable devices, and in areas requiring high oxidation resistance in corrosive environments. Titanium is also known to be a difficult to machine metal and Metal Injection Moulding has been found to be an ideal high volume manufacturing process for TA1 titanium near-net shape components having complex shapes at lower cost.

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The authors concluded that the MIM TA1 samples in group B possess the best mechanical properties when sintered at 1300 C. The β-Ti is present in the sample, while TiC and a small amount of TiO2 are produced. TiC particles hinder the dislocation movement and grain boundary growth. Solid solution strengthening, second phase strengthening, and grain refinement increase the strength of the sample and grain refinement, and the presence of β-Ti improves the elongation of the sample.

Milacron CEO Tom Goeke stated, “Stories like 20/20’s machine retrofits reinforce the fact that Milacron has an unrivaled aftermarket offering. Our aftermarket offerings aren’t only spare parts, we can literally take an older machine and transform it to like new condition. Milacron has set the standards, driven innovation and led the industry in Multi-Nozzle Low-Pressure Injection Molding Technologies for more than four decades. These machines can be used for Structural Foam, Structural Web, Gas Assist, Solid Molding, or combinations of these technologies depending on the application.” Goeke added, “The LPIM market is strong for our customers that require either new or rebuilt machines in both North America and Europe, and we have a number of solid inquiries both domestically and internationally including many from Latin America and India.”

Eric Hallstrom, Business Manager, Milacron LPIM added, “Milacron has been promoting our proprietary Structural Web technology that allows for multi-point gas assist molding that can be added to as an option to our standard LPIM machine. The process allows for a cosmetic part appearance for large projected area parts and can reduce part weights by up to 20%. The gas assist process also creates an inherently strong and durable part, molded with low internal stresses and a dual wall thickness which can replace many rotational molded or industrial blow molded parts with better aesthetics and better cycle times for higher volume parts.”

The nine injection moulded tensile test samples were divided into three groups – A, B, and C which corresponded to the sintering temperatures used of 1250°C, 1300°C, and 1350°C, respectively. Fig. 1 (bottom to top) shows an example of the injection-moulded TA1 part in the as-moulded, debinderised, and sintered condition. Relative densities of the sintered MIM TA1 parts were found to increase with the increase in the sintering temperature from 1250°C to 1300°C, showing a rise of 1.07% to 4.189 g/cm3, or 92.85 ± 0.03% relative density, in sample B. At 1350°C the sintered density of sample C increased by only 0.28% to 4.202 g/ cm3.

The carbon and oxygen contents were determined for each of the three groups of sintered MIM TA1 samples as shown in Table 3. The carbon and oxygen contents were determined by plasma emission spectrometry. The sintered microstructures were observed by Optical Microscopy, and EPMA was used to measure the distribution of the compounds formed by carbon and oxygen elements with titanium. The microstructures and fractures of the MIM TA1 samples were observed by SEM, and the forms of carbon and oxygen were determined using a field emission SEM. The relationship between the forms of carbon and oxygen and the orientation of pure titanium matrix was analysed by TEM.

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Hallstrom added, “Essentially we are updating machines that have been in production for over 30 years and bringing them up to the same specifications as our new machines. This has been especially popular since we started to promote this capability to our customers, as they see a significant enough savings since we are re-using the most expensive parts of these large machines, being the bases, platens, and cylinders. The customer gets back a machine that outperforms the machine’s original specifications and is as reliable as a new machine with the same warranty.”

Milacron has aggressively expanded its rebuild and remanufacture capabilities for LPIM machines for customers. There are a large number of old LPIM machines in the field that were purchased in the late 1980s and 1990s that need rebuilds and upgrades to control systems and new motor and drive selections, moving away from DC to AC drives which provide better energy efficiency. Milacron’s full remanufacturing consists of fully rebuilding the machine to current model specifications, including full teardown and inspection, platen refurbishment, full re-painting of the machine, new controls, electrical system, and hydraulics. The major tonnage and injection cylinders and hydraulic accumulators are sent out for refurbishment and resealing. New screws, barrels, and injection melt accumulators are also included as part of this program.

The markets driving the increased level of activity are material handling (pallets and boxes), underground enclosures for telecommunications and utilities, drainage and irrigation products, all-terrain vehicle (ATV) components, commercial/institutional, and industrial and safety products. Milacron is also seeing other new products being developed that are conversions from concrete, metal, and wood in the building and infrastructure market as well.

TA1 spherical pure titanium powder having the composition shown in Table 1 was mixed with a water soluble binder composed of polyethylene glycol (PEG), polymethyl methacrylate (PMMA), and stearic acid, and the resulting pellet MIM feedstock was injection moulded to produce nine tensile test parts. The injection moulded green MIM TA1 parts were first soaked in a water bath at 50°C for 24 h to remove the main PEG binder component, and any residual PEG and PMMA binders were removed in the thermal debinding stage which was done simultaneously with sintering because of the cleanliness of PMMA.

At NPE, 20/20 entered into an agreement with Milacron to refurbish and upgrade two of their existing 400-ton LPIM machines to 500-ton LPIM machines, and one of their 500-ton LPIM machines to 750-ton LPIM machines. 20/20 is also having Milacron rebuild and upgrade five of their 750-ton LPIM machines. The machines will undergo a complete remanufacture and rebuild process at Milacron’s Batavia, OH manufacturing plant and be returned like new machines.

Ernsberger added, “Milacron worked closely with our entire team at 20/20 to identify the upgrades to the existing machines to be rebuilt that will put these machines above today’s current machine specifications and give us the widest capabilities for these size machines in the industry.” Ernsberger continued, “We also had Milacron integrate some proprietary technologies into their machines that allow us to have the most versatile LPIM Structural Foam machine fleet in the custom molding market. It’s a great partnership between the companies, as all equipment at 20/20 CMP is 100% Milacron.”