2024 JPMA Awards Announced
The Japan Powder Metallurgy Association (JPMA), Tokyo, Japan, awarded 8 prizes in the following categories: Development, New Design, Process Development, New Powders and Effort.
DEVELOPMENT PRIZE
Grand Prize
Development of Soft Magnetic Composite Cores with Double Pole Shoes to Enhance the Performance of Axial Flux Motors
Sumitomo Electric Industries, Ltd.
This component is the stator core for an Axial Flux Motor (AFM) used in air cleaners. In response to the increasing emphasis on miniaturization, weight reduction, and high efficiency of motors in recent years, AFM that can achieve both thinness and high torque, is attracting attention and is expected to become widespread and replacing conventional radial flux motors made of Laminated Steel Sheets (LSS), which have the disadvantage of reducing torque when they are made thinner due to their motor structure. Compared to LSS, soft magnetic composite cores (SMC) are suitable for the three-dimensional magnetic circuit required for AFM due to their magnetic isotropic properties and high design flexibility in shape.
In order to increase the facing area between the SMC and the magnet, we developed a shape with pole shoes extended on both the top and bottom sides of the SMC. As a result, the high dimensional accuracy of the distance between the double pole shoes’ surfaces (total length of double pole shoes’ cores) and QC superiority of the SMC to the competing material, LSS, has been achieved.
At first, we verified the superiority of motor performance using the double pole shoes’ cores. Then we confirmed an 18% increase in motor torque and a 2.6% increase in efficiency compared to the conventional method of using the SMC without the pole shoe. However, it was difficult to eject the core with double pole shoes from the mold using conventional compacting methods. Therefore, we focused on changing the compacting direction and developed a new method of integrally compacting both pole shoes and teeth. This development has made it possible to combine the formability of the SMC with improved motor performance.
The newly developed compacting technology meets the accuracy standard for the dimensional accuracy of the thickness of the double pole shoes, which has been reduced by 70% compared to conventional compacting technology. This is because the dimensional accuracy of the thickness of the core is not affected by the powder fill volume but is primarily influenced by the accuracy of compaction tools. In addition, the new technology has reduced the manufacturing cost by half, as it requires only one part, whereas the conventional manufacturing method requires two parts and compaction tools for them. With these developments, we started mass production of double pole shoes’ cores for AFM, which contributes to the popularization of AFM using SMC.
NEW DESIGN
Sintered Bushings that Realize High Performance Electric Solenoid Valves
Diamet Corporation
This product is a bush that supports a plunger shaft of solenoid valve for vehicle. The solenoid valve is a component that generates an axial force from the output part by electrical input. In recent years, in automobiles, automation has progressed from the conventional manual operation system, and it is a component that is expected to be installed in an increasing number of vehicles.
Since this product is used as a bearing that supports the shaft, it is necessary to maintain good sliding properties during the linear movement of the shaft. In addition, unlike normal bearings, magnetic properties are also required to function as a solenoid, so sliding performance and magnetic properties must be compatible. In selecting the material, magnetic properties are important, so we adopted an iron-based material.
In iron-based materials, graphite is generally added to give them sliding properties, but if the graphite content increases, magnetic properties will decrease. Therefore, we considered the optimal ratio that can achieve both sliding properties and magnetic properties and selected an Fe-Cu-C-based material.
In considering the shape, we considered the cost, usage conditions, assembly, etc., and decided on the optimal shape through repeated design-in discussions with the customer. We were able to satisfy the strict cleanliness standards for preventing foreign matter contamination by examining barrel conditions that would remove burrs without damaging the sliding surfaces and implementing measures such as protective covers within the manufacturing process. Through these developments, we were able to meet multiple requirements and successfully switch from the conventional molten material to sintered material.
Vane Pump Side Plate Development with Molded Body Processing
Fine Sinter Co., Ltd.
This product is a side plate for a vane pump, used as a transmission oil pump. With the accelerating shift to EVs, there is an even greater requirement for existing automobile structures to reduce CO2 emissions and to be quitter, requiring higher levels of performance from each unit. Therefore, transmission oil pumps are being replaced by vane pumps, which have less vibration and higher volumetric efficiency than inscribed gear or trochoidal rotor type pumps.
This product has a blind groove of 2mm wide and 9mm deep, and a blind groove of 3.5mm wide and 5mm deep on the opposite side, creating a special shape that curves through the groove. These grooves are difficult to form through compacting, and when using normal machining there are issues with burrs and costs. Thus, efforts were made to solve the issues through green machining process that suppresses the generation of burrs. Reduced iron powder was chosen as the material to ensure the green strength. A Fe-Cu-C system was then chosen that would meet the requirements.
Green machining process conditions were optimized through a detailed investigation into cutting depth to prevent chipping during processing, product gripping conditions to prevent cracking, and peripheral speed and cutting depth to prevent cutter breakage.
These developments made it possible to produce this product with a complex groove shape. A cost reduction of about 20% was achieved with the adoption of the green processing, which reduced the torque required for machining process down to 10% or less compared to that of sintered bodies. It allowed the miniaturization of equipment and the shortening of processing time, and also eliminated the need for burr removal processing.
PROCESS DEVELOPMENT
Full Automatic System Development on Magnetic Particle Inspection Method
for Induction Hardened Products
Diamet Corporation
This technology is the full automated system which exploits robotics and AI system to apply on a process of magnetic particle inspection method to detect cracks on induction hardened products. The development on this automation is covered whole process of magnetic particle inspection method such as pre-processing (magnetization and magnetic powder coating), observation (flaw detection), judgment, and post-processing (demagnetization). The composite magnetization method is applied for a pre-processing stage because of a process efficiency, which allows stable detection even if the crack direction is (either circumferential or radial direction) changed. In addition, a robot handling method allows to prevent magnetic powder been peeled off from a surface of products.
For the process of inspection and judgment, the AI system was learned and optimized with thousands of samples to enable it to make judgments that are close to the senses and judgments of an expert inspector. In a case, magnetic powder liquid remains on a parts surface more than adequate, it can result in false positives and/or over detection. Therefore, we applied some technical measures to control the right amount of magnetic powder and liquid at the inspection spot, we have finally achieved false positives of 0% and over detection of approximately 5%. Although this is the first case of automatic process for sintered parts inspection system, it has already been approved by multiple customers. Furthermore, this technology has obtained the higher and stable level of inspection quality by eliminating discrepancies of various skilled judgement and improved stabilizing inspection accuracy. Also a human inspector’s judgement are sometimes affected from a lack of concentration or fatigue, this system wiped out such errors and even improved the working environment and reducing the various burden of inspectors.
NEW POWDERS
Die Steel Powder with High Printability for 3D-Printing
Daido Steel Co., Ltd.
This raw material is a die steel powder with high printability which reduces strain during 3D-printing and makes it possible to manufacture large-scale molds larger than 150mm square. Practical use of die-casting molds and plastic injection molds manufactured by metal 3D-printing is now advancing.
These printed molds are mainly made from 18%Ni maraging steel powder. However, maraging steel(powder) contains a high amount of cobalt (Co), which is regulated under the ordinance on prevention of hazards due to specified chemical substances, and also is designated as a list-controlled item under Japan’s Security Export Control regulations. Therefore, the demand for 3D-printing JIS-SKD61 hot work die-steel powder has been growing. On the other hand, SKD61 powder has an issue regarding its printability. Due to its high hardness in the as-printed state, this powder cannot withstand the strain generated during printing, making it prone to cracking and difficult to print. Thus, we developed a novel hot work die-steel powder with higher printability which can suppress strain during printing and manufacture large-scale 3D-printed molds.
The chemical composition of this raw material powder, based on JIS-SKD61, is designed to reduce the amounts of carbon, silicon, and vanadium and to add 6% nickel so that its martensite transformation start temperature (referred to as the Ms point) is set around 200℃ equivalent to that of maraging steel. With this chemical composition design, a supercooled austenite state is maintained during printing at temperatures higher than the Ms point, which decreases hardness. Consequently, the strain caused by thermal stress generated from melt-solidification by laser and subsequent cooling process is relieved through the small deformation of the super-cooled austenite.
Additionally, after the printing is completed, turning off the preheating of the base plate allows the entire printed object to gradually cool down, which enables marquench The volumetric expansion of the object during marquenching further reduces strain. The above-mentioned mechanism has made it possible to achieve large-scale 3D printing. Furthermore, quenching process can be eliminated since the printed object becomes a martensite structure. Thus, this raw material is expected to contribute to process omission and energy savings.
High Density Iron-based Mixed Powder with improved Flowability
Kobe Steel, Ltd.
This powder is a new concept iron-based premix that combines the high density in sintered parts by reducing the amount of lubricant and improving the flowability of the powder.
Powders with good compressibility can achieve high green and sintered density, which contributes to the overall improvement of sintered part qualities. Reducing the amount of lubricant in the premixed powder is an effective method for increasing green density without additional equipment such as warm compaction or die wall lubricating compaction. Therefore, there is a growing demand for lubricants that can provide effective lubrication in low quantities by enhancing lubricity. However, lubricants with good lubricity tend to have high adhesion, causing agglomeration with iron powder and worsening the flowability of the premixed powder, making it very difficult to achieve both lubricity and flowability.
As a new approach, a substance with low adhesion to the lubricant is introduced on the surface of the iron powder, achieving both improved lubricity and flowability. This material has achieved a 30% reduction in shear adhesion stress compared to conventional powder, with improvements in die fillability and evaluation of weight variation during continuous compaction. The green and sintered properties are consistent with the density obtained, making this powder mix a promising solution for the easy production of high density parts, with its widespread adoption in the industry anticipated.
EFFORT PRIZE
Development of ECU Cooling Fan Bearings for ADAS
Porite Corporation
This product is a bearing used in ECU cooling fans that control ADAS (Advanced Driver Assistance System). In recent years, more and more ADAS ECUs are being installed in conjunction with “connected,” “automated,” and “electrified” systems. Since increased processing speed is essential for the ADAS ECUs to perform their respective functions, heat generation is high and cooling fans must be installed.
This product is a bearing for a fan motor that is grounded downward and requires countermeasures against oil leakage due to oil expansion and viscosity decrease at high temperatures. As countermeasures, the outer diameter chamfer was enlarged to secure an oil retention space, and the inner diameter chamfer angle was reduced from 45° to 30° to strengthen capillary force and make it easier to retain oil. In addition, a groove is provided on the outer diameter to allow air to escape during motor assembly and motor operation. For the impregnating oil, we have secured durability by selecting a unique oil with low viscosity change with temperature and low evaporation for long life in response to the demand for use in a wide range of temperatures from -40°C to 105°C.
These developments have improved oil leakage and reliability, and have made it possible to use the motor in a downward position. As a result, the bearing was adopted for ECU cooling fans for ADAS, where ball bearings were the mainstream.
Sintered Actuator Components from the Development of Pressed Component Caulking Technology
Fine Sinter Co., Ltd.
This product is a component for a four-wheel drive vehicle transfer actuator. A transfer is an important power transmission component that supports high traction performance and driving stability on a wide range of on- to off-road conditions, by dividing power from the engine to front and rear wheels in four-wheel drive vehicles. It consists of a plate which receives the output from the motor and a sintered gear that provides output to the rack. Sintered gears require tensile strength and wear resistance so that they are able to withstand driving force, and the joints require rotational torque strength to withstand power transmission and vertical gear pullout strength.
Given that this is an assembled component, the assembly phase for the gear teeth and plate also needed to be devised. For the sintered gear materials, an Ni-Mo alloy steel was chosen, which achieved the required strength and wear resistance by sintering without the need for heat treatment, and the green density and heating/cooling conditions during sintering were further optimized to obtain a tensile strength of 700MPa or more.
Caulking was adopted for the joint, and the joint shape was that of a petal-shaped boss, where the size and number of petals were studied to obtain torque strength and the slit width was designed to prevent phase errors, and the gear end surface shape was devised with clearance/allowance to prevent floating and tilting. These developments have succeeded in realizing a mass-produced actuator that combines different materials.