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Japanese Powder Metallurgy Association Announces 2020 Awards

The Japanese Powder Metallurgy Association (JPMA) has announced their 2020 award winners. Awards were given for New Design, Process Development, and Effort.

A-1 Sintering of bearings for automotive LED headlight cooling fans—Porite Corporation 

This product is a bearing for a fan motor for cooling LED headlight bulbs. 

In recent years, LED headlights are required to have higher heat dissipation due to the increase in the amount of light and the miniaturization, and cooling fans are being installed. This bearing has the required characteristics such as quietness, long life, low temperature (-40 dec C) startability, wide practical temperature (-40 dec C to 120 dec C) range, and prevention of brightness decrease due to outgas. Therefore, fluid bearings and ball bearings are used even though they are expensive. 

In this development, we have ensured slidability and startability by optimizing the sliding parts and reducing shaft loss by taking advantage of the characteristics of the center free bearing, quietness has been improved by ensuring coaxiality with an inner diameter tolerance width of 4 μm, which was difficult for bearings with an aspect ratio of more than 5, and reducing the clearance with the shaft.  

The inner diameter chamfered shape makes it possible to extend the life of the bearing by giving the end face and the groove shape on the outer circumference a function to retain the impregnated oil that leaks due to thermal expansion during operation.  

For the material, copper-coated iron powder is used, and by achieving both high oil content and low air permeability, the oil film strength of the bearing surface is secured, and quietness and wear resistance are improved. 

For the impregnated oil, we have developed an impregnated oil with a small amount of evaporation in a high temperature environment by selecting ingredients that have little change in viscosity index from low to high temperature and that take into consideration the adverse effects of outgas (decrease in brightness and chemical attack). 
As a result, it satisfied the characteristics superior to ball bearings and was adopted to bearings for fan motors in LED headlight bulb cooling system, which contribute to the expansion of the sintered oil-impregnated bearing market.

A-2 Cost-down by using shape molding for the curved groove of parking lock part—FINE SINTER Co., LTD. 
This product is a pole support part used for the parking lock mechanism in an automatic transmission. 

In the trial evaluation process of this development, a groove shape with a changing curvature was required to prevent deformation of the mating part (cam). This groove and the bolt hole, which is used to assemble and fix the product, are in an orthogonal relationship. The normal process design is net-shaped and the rest is machined, but the product with the net-shaped groove has been formed without machining by using undercut compacting. 

Undercut compacting requires control of the compression ratio for the undercut portion, such as using CNC for tool control, therefore the mechanism becomes complex. However, by using the general withdrawal mechanism (with one upper and two lower stages of mold configuration), the position of the punch, which is used for forming the undercut portion, is synchronized with the die by the operation of the upper punch. The stable net shape has been made successfully and inexpensively. 

Local tool lubrication with oil plays an important role in this undercut compacting. The undercut portion forming punch receives a high stress to the outer peripheral direction during compaction. The structure of die inner diameter is designed to endure this stress. The tool lubrication is to maintain the stable sliding of the punch, and to prevent the tool galling as well. 

A-3 Sintered part for motorcycle transmission—DIAMET CORPORATION 
This part is the cam used for shift mechanism of motorcycle transmission. 

When the power from a shift lever is transmitted to the shift fork, the pins of this part receive high bending and impact load. The sinter forging method has long been adopted for this part, even though it is expensive. In recent years, the adoption of investment casting method or replacement with steel pin method has been expanding.  

This time we enabled press and sinter method applicable to this part. We increased the density of the pins, which improved the strength and reviewed the pin shape which relieved stress concentration. We optimized the raw metal powder, lubricant and filling method, which realized the sintered density of 7.4g/cm3, applying a high-pressure compaction and high temperature sintering. Furthermore, we abolished machining by suppressing the variation of pin height down to less than 0.1 mm.  

Although the risk of cracks caused by the mold distortion remained, we guarantee it by 100% inspection using load test of the pins. As a result, we realized the equivalent strength to the sinter forged part, with cost reduction of 40%. 

C-1 Soft Magnetic Composites for reactors in HEV that secures magnetic flux density and reduces iron loss—SUMITOMO ELECTRIC INDUSTRIES, LTD. 

This manufacturing method is a compacting method that prevents damage to the surface insulating coating of Soft Magnetic Composites (SMC).   

When the compacted product is ejected from the tool, the friction between the tool and the product damages the insulating coating which induces the iron powders conduct with each other, causing an overcurrent on the surface of SMC and increases the iron loss.  Although the countermeasure for the iron loss mentioned above had been taken, which prevents eddy current loss by generating iron oxide in the conductive part by laser processing, the cost for laser processing had been an issue. 

In order to solve the issue of damage to the insulation coating in the conventional compacting method for one piece of product due to the outer peripheral surface being entirely formed by the die, the following developed processes were introduced; a simultaneous compacting method for two pieces in a die and a floating core rod as a tool between two pieces of products that moves along with those two compacted products when they are ejected.  As a result, the additional laser processing was eliminated and the cost reduction was realized. 

As for the development of materials, the density of products was increased by optimizing the particle size of the raw material powder and compacting conditions.  In the annealing process, the stress of the product was relieved by optimizing the conditions, which resulted in the reduction of iron loss by 25%. It is expected that the production volume will increase due to the expansion of the share of HEV and EV in the future, and this development is anticipated to be greatly advantageous. 

F-1 Development of Bearings for Refrigerator Evaporator and Condenser cooling fans—Porite Corporation 

This product is a bearing that can be used for both evaporator and condenser cooling fans in refrigerators.  

Normally, the evaporator fan is used in an environment of -30 dec C, and the condenser fan is used in an environment of + 60 dec C. Previously, each of them uses optimized type of bearing different from each other. 

In this development, we have achieved a long life by selecting the optimum material and setting it to a high oil content. In addition, developing a new silicone-based lubricating oil, the requirement in the low 
temperature environment:  quietness, low friction characteristics, and corrosion resistance and that in the high temperature environment: wear resistance, low friction characteristics were satisfied. By unifying the bearings for refrigerator evaporator and condenser fans, cost competitiveness and shortening of lead time due to economies of scale were gained. In addition, as customer merits, it is expected to simplify ordering and inventory management and prevent mixing up of different types in assembling lines. 

F-2 Development of lower cost C/C composite metalized carbon contact strip—FINE SINTER Co., Ltd. 
This contact strip is attached to the uppermost part of the pantograph on top of a railway vehicle to collect electric current by contacting trolley wire to supply electricity to the railway vehicles. 

Contact strip can be classified roughly into two types: metallic and carbon type (copper and carbon composite). The carbon type is further classified into copper impregnated type, copper-carbon mixed sintered type, and copper infiltrated C/C composite type. We chose the copper infiltrated C/C composite type which is characterized by light weight, high strength, low wear, and low trolley wire aggression. The issue was the cost of C/C composite. 

Our development aimed to reduce the amount of expensive carbon fiber. In order to reduce the amount of carbon fibers and ensure the strength, it is necessary to increase the amount of binder. At first, in order to simplify the manufacturing process, the carbon base material is made by the preformed yarn method, where carbon fibers and binder are bundled together to form sheets. However, when the amount of carbon fibers is reduced and the amount of binder is increased, the copper infiltration route becomes narrower, and sufficient copper infiltration becomes difficult. This leads to difficulty in obtaining electrical characteristics. Therefore, we modified the composition of the Cu-Ti infiltration material and optimized the infiltration conditions (two step temperature setting). As a result, our contact strip ensured the required electrical conductivity and strength is improved by about 20%. The wear rate is reduced by 20% and the wear limit is increased by 10%. Cost performance is improved by 35% compared to conventional products. 

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