Highlights from MIM2023 as Seen through the Eyes of Joe Capus

The 2023 International Conference on Injection Molding of Metals, Ceramics and Carbides, sponsored by MPIF and APMI, was held as a live/virtual hybrid event February 27-March 1 at the Hilton Orange County, Costa Mesa, California. The conference was preceded by a tutorial on Powder Injection Molding given by Matthew Bulger, ATPM Consulting, as well as a reception at the ARBURG Technology Center. A tabletop exhibition and networking reception were also included in the program. Attendance was over 130 representing twelve countries. The conference was an outstanding event and would have been an “eye-opener” for anyone who had not attended the annual MIM conference for a few years. The MIM industry has embraced additive manufacturing as an adjunct technology that can assist in the design of mold tooling for injection molding as well as sharing common process steps such as debinding and sintering as well as materials. The MIM conferences have moved on to include a number of novel 3-D printing technologies that offer new application opportunities.

The keynote speaker was Diran Apelian, Figure 1, distinguished professor of Materials Science and Engineering at University of California, Irvine, and Director of the Advanced Casting Center. He gave an inspiring address with a dazzling flow of images in a wide-ranging overview of mega-trends influencing the future of work, industry and the processing of metals and materials. He touched on many themes related to light-weighting and reduction of carbon footprint and illustrated how “change was the universal constant” in reviewing the meaning of “Digitization” and “Industry 4.0”. The topic of sustainability was reviewed from the history of ore depletion to recycling. In a final word he quoted from Klaus Schwab (World Economic Forum) about the primacy of procuring and retaining talent versus capital or politics, in the 4^th Industrial Revolution.

Figure 1. Keynote Speaker Diran Apelian

MIM Industry Global Outlook

Paul Davies, Sandvik Additive Manufacturing, UK, drew from recent market studies and other sources to review the performance and current prospects for MIM industries in Europe and the world. According to figures quoted by Data Bridge Market Research, the European MIM market is expected to reach a value of about 1.6 billion Euros by 2027, indicating a CAGR of 11.6% between 2021 and 2027. With recovery from the pandemic, MIM powder demand increased by over 14% in 2021 vs 2020. Demand growth was said to be led by the automotive sector. The growth in Europe shifted the European share of the world market from an estimated 32% to 48%, replacing Japan and Asia (Table 1).

The report also indicated that the European market was divided roughly equally between Germany, UK, France, Belgium, and the rest of Europe.

Another report, from Business Market Insights, was quoted as forecasting that the European MIM market was expected to grow at a CAGR of 7.2% between 2019 and 2027 to reach US $708.72 million.

An EPMA survey was quoted as showing a “pandemic dip” in 2020 (Figure 2) followed by an increase of 22% to 517.6 million Euros in 2021. Several other factors were listed as having an impact:

• increased recognition by the automotive industry
• re-shoring and re-stocking
• growth in luxury products.

Figure 2: Estimated MIM sales growth in Europe, 2010-2021.  

The EPMA survey also gave a breakdown of MIM applications:

Automotive: 23%, medical; 21%, firearms; 19%, construction:12%, consumer goods: 12%, hand-tools: 2%, aerospace: 2%, others: 9%.

In North America, data provided by MPIF showed the breakdown in MIM applications by weight for 2021 as follows: Firearms: 41%, medical and dental: 26%, general industry: 11%, automotive: 11%, electronics: 5%, defense/aerospace:  4%, telecoms: 1%, others: 1%. Consumption in terms of materials showed stainless steels at 48%, low alloy steels: 38%, soft magnetic materials: 7% and tungsten alloys, titanium and others at 7%.

In the rest of the world, an APMA estimate for China showed a breakdown in terms of sales in 2021 as follows: Smart phones: 56%, wearable 3C devices: 12%, computers: 8%, hardware: 7%, medical and automotive at 4% each, and others: 9%.

JPMA has provided a breakdown of MIM sales in Japan for 2021. The largest application area was in industrial machines at 34.8%, followed by medical at 17.3% automotive at 13.1% and bicycles at 7.2%, the balance being found in electronics, industrial robots, watches, cameras, precision machinery, and other miscellaneous uses.

On the future of MIM in Europe, Davies quoted a comment from Dr Frank Petzoldt, consultant, formerly with IFAM in Germany, who said: “While the automotive industry is a key market [for MIM], the aerospace industry holds many opportunities. The most dynamic growth markets for the MIM industry being for applications in aerospace and medical technologies. MIM remains a technology with an awareness challenge and far more needs to be done to make potential users aware of its capabilities and its green credentials.”

Davies concluded with a review of some new MIM materials, and Sandvik’s commitment to sustainability.

MIM Feedstock and Process Developments

David Shore, North American Höganäs, gave the results of a study on the effect of particle size on the MIM properties of water-atomized 17-4 PH stainless powder manufactured expressly for MIM. Four particle size ranges were tested, from minus 10 μm to minus 30 μm. The powder was manufactured in a dedicated fine powder facility producing powders for MIM and Binder-jet printing (BJP). Chemistry and powder size details are shown in Figure 3. Powders from each size fraction were molded into MPIF standard MIM test bars and sintered in hydrogen at 1380ºC.  Sintered density as well as UTS increased with particle size, but % elongation peaked at the minus 20 micron fraction. Oxygen content reduction during sintering increased as particle size increased. Surface roughness was measured on sintered rectangular bars but did not show a consistent trend with particle size. Etched cross-sections of sintered bars showed a densified surface layer that increased with particle size.

Figure 3. Water-atomized 17-4 PH stainless steel powder chemistry and particle size data

John Johnson, Novamet/Ultrafine Specialty Products, reviewed the types of gas-atomized MIM powders manufactured for ferromagnetic applications such as in electronics (Permalloy, Permendur, and Sendust). He went on to discuss the effect of particle size and the various methods used to determine magnetic properties of powders, concluding that the VSM (Vibrating Sample Magnetomter) was the best method. Compared with bulk ferromagnetic materials powders showed very little hysteresis, similar saturation, low remanence, and permeability, but high coercivity.

Moving on to MIM process studies, Griffin Seidler, Ruger Precision Metals, talked about the effect of gate size in the injection mold. The small orifice that connects the runner system to the part cavity in an injection mold has two important functions:  the gate has a reduced cross-section to allow separation of the part from the runner, and it solidifies before the runner and part feedstock. Under-size gates can result in shrinkage voids due to premature freezing of the gate. Also “black lines” around the gate position can be caused by high shear rates through the gate. These can be cosmetic defects or may also cause mechanical weakness.

An experimental study was made to evaluate the effect of gate size using various combinations of gate sizes, shear rates and packing pressures, Data on green parts (weight, gate remnant, widths, and black lines) was compared with a mold flow simulation that was found to accurately predict how the MIM feedstock behaved during molding. Future work will study mechanical properties and gate types.

Caleb Spencer, ARC Group Worldwide, reported on a study of the “healing” of surface molding defects by “re-working” of green parts. Using a heat-gun in conjunction with a wetting agent, knit lines and surface cracks were successfully removed (melded). This procedure could be useful in working with high-cost alloys, but it adds an extra operation and green parts are easily broken or deformed. Future work will scale up to production level and will involve green re-working of other defects like cracks, and to weld parts together.

Still on molding, Vahid Momeni, at the Institute of Polymer Processing of the Montanuniversität, Leoben, Austria, described the investigation of binder systems for MIM feedstock for injection molding of NdFeB permanent magnets. The powder was produced by jet-milling under nitrogen and used at a powder loading of 55 vol,%. Several different combinations of binder components (stearic acid, paraffin wax, and LLDPE, linear low-density polyethylene) were tested for contamination, capillary rheometry, and pressure/flow stability at high shear rates. Feedstock samples were mixed at 160ºC and 60 rpm in argon. Small test cylinders were pressed at 50 bar/160ºC. Debinding by immersion was followed by thermal treatment in hydrogen at 620ºC. Sintering was done in vacuum at 1050ºC. Further work will be done to evaluate the maximum powder loading and measure magnetic properties and optimize the formulation.

Metal Additive Manufacturing and MIM

Animesh Bose (formerly with Desktop Metal, now consulting) gave a review of sinter-based metal AM processes. Sinter-based AM, which shares several process steps with MIM, has been growing rapidly alongside laser-based and electron beam-based AM processes. He began by noting that metal 3-D printing has so far barely scratched the surface of its potential and is now at an inflection point. A number of new processes and modifications have evolved in recent years. He mentioned filament extrusion and rod extrusion among others as examples but concluded that binder-jetting (BJP) had emerged as the leading high-volume process, and would grow fast, with several large companies already involved.

Andrew Roberts, Desktop Metal, described a simulation approach to tackle the problem of shrinkage and distortion in the sintering of printed parts. The Live Sinter program involves printing of “negative offset” geometry that compensates for the distortion that occurs during sintering (Figure 4). Live Sinter also offers (optional) HIP simulation following sintering, The approach was claimed to yield parts that consistently fall well within 1% of target dimensions, with as low as plus or minus 0.3% deviation.

Figure 4. “Negative offset” printing for compensation of distortion during sintering

Metal AM of different metals and alloys was the subject of several other speakers. Joseph Schramm presented Uniformity Labs approach to improving performance in laser-jet and binder-jet production by modifying the powder particle size profile. Uniformity has developed multi-modal powders that provide high packing density, low viscosity, negligible phase separation, as well as uniform and predictable sintering behavior. He reported on binder-jetting work with 17-4PH stainless steel spherical powder that achieved a sintered density as high as 99.5% and shrinkage as low as 9.6%. Mechanical properties were said to be well in excess of MIM minima, and the powders could be suitable for large MIM parts (Figure 5). Other benefits included tighter tolerances and reduced drag and warping during sintering.

Figure 5. Large parts produced with Uniformity Labs binder-jetting

Marina Valero, Universidad Castilla La Mancha, Spain, presented the work of her DYPAM research team on the development of Fused Filament Fabrication (FFF) AM of 316L stainless steel based on master alloys. She noted the synergy between FFF and MIM and compared the advantages of the two processes, as well as the relative merits of the master alloy route versus pre-alloyed powder. She went on to list the challenges in the filament-based AM process and the specific objectives of the work. She described the FFF feedstock development and optimization, FFF printing, debinding and sintering, and final part evaluation.

Also focusing on the synergy between BJP and MIM was Victor Villarini, Tritech Titanium Part, LLC, who listed the pros and cons of the two processes. Mechanical properties of Ti-6Al-4V made by MIM and BJP are compared with wrought alloy in Table 2.

Table 2: Mechanical Properties of MIM. BJP, and Wrought Ti-6Al-4V  

From France, Hong Wang, Institut Femto-ST, Université de Franche-Comté, went into more detail on the development of NiTi shape-memory alloy by metal extrusion AM (MEX). The MEX feedstock was prepared by pelletizing the binder with metal powder and feeding into the extrusion machine. The work was continued on to optimize the 3-D printing parameters with a view to maximize mechanical properties. Future work was planned to optimize the sintering process in a vacuum environment and to complete a numerical simulation of the 3-D printing process.

There were many other interesting research papers and design case studies as well as product and process presentations. For further information contact MPIF, 105 College Road East, Princeton, New Jersey 08540 USA.

About the Author: Dr Joseph M. Capus is an internationally-recognized authority on metal powders and their technology, having been involved in the industry in senior positions or as a consultant for the past 35 years. He has published over 200 technical papers and articles and compiled or edited ten volumes of PM conference proceedings in addition to the three previous editions of this report. He has co-chaired North American as well as World conferences on powder metallurgy and particulate materials and has been actively involved in PM standardization activities at national and international levels for over 25 years.