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Delivering Trusted, High Quality Swing Bearings for Construction Equipment, from Ibaraki to the World
HAX CORPORATION, K.K. Takahagi City, Ibaraki
Yu Kamei, President (center) with Takashi Hanari, Head of the Quality Assurance Section, Production Control Department (left) and Yoji Yamaguchi, Foreman, Quality Assurance Section, Production Control Department (right)
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Businesses |
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January 2013 |
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Manufacture of large swing bearings for hydraulic shovels |
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Sweeping across global markets, Japanese construction equipment is trusted by an overwhelming number of sites around the world. One example is the large power shovels running 24/7 in harsh mining environments. For this edition, we visited HAX Corporation, K.K. in Takahagi City, Ibaraki, a manufacturer of the swing bearings essential for these large power shovels.
Critical parts that connect the upper and lower chassis of large power shovels and allow them to swing
Ultra-large swing bearing
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HAX Corporation manufactures the swing bearings used in large power shovels produced by Hitachi Construction Machinery, a major construction equipment manufacturer. An equal entity joint venture between Hitachi Construction Machinery and swing bearing manufacturer Antex Corp., HAX Corporation was established in January 2013.
The role of swing bearings is to join the upper chassis where the operator sits to the lower chassis that contains the drive unit. It then allows the upper chassis alone to swing while the lower chassis remains stationary.
HAX Corporation manufactures a range of different sized swing bearings but this report will focus on the swing bearings for the world’s largest hydraulic shovels manufactured by Hitachi Construction Machinery. Designed for ultra-large power shovels that, at about 10 meters high and 10 meters wide, are the size of a building, these bearings are almost too big to be called a part of a machine, with a diameter of 4,500 millimeters and weight of 20 tons.
President Yu Kamei talks about his products; “Swing bearings require high rigidity to handle all the forces they are subjected to, including the weight of the chassis and excavating forces. On the other hand, they also need to rotate smoothly and to stop quickly at the end of their rotation. To achieve both high rigidity and the functionality to enable these fine movements, they are both gentle and strong."
Repeated verification testing to resolve issue of temperature variations, and optimum measurement method proposals
Swing bearings consist of a circular inner part with teeth cut to enable swinging (inner ring), a circular cover part (outer ring) which houses the inner part, and rollers located between the inner ring and the outer ring. The structure enables the inner ring to rotate smoothly, but there is too much play if the gap between the inner and outer rings is too large, and the bearing does not rotate at all if the gap is too small. For this reason, the parts are precision machined to a tolerance of hundredths of a millimeter even for large parts with diameters of 4,500 millimeters.
HAX Corporation has installed a large Mitutoyo FALCIO-Apex 456015 CNC coordinate measuring machine to enable measurement of 4,500 mm on the X axis, 6,000 mm on the Y axis and 1,500 mm on the Z axis to verify the precision of its machining.
Moving such large products requires considerable attention to safety, but once lifted into place, the machine can efficiently measure the required level of precision. It is apparently in regular and broad use at present.
According to Takashi Hanari, Head of the Quality Assurance Section of the Production Control Department, and Yoji Yamaguchi, Foreman of the same section, it took a lot of trial and error when the machine was originally installed.
“We were seeing large measurement errors with large work pieces for a number of reasons, and we had a lot of trouble with temperature control in particular. With metal parts, the larger the part the slower the temperature change, so it takes an enormous length of time for the parts to reach the same temperature as the measuring room. We measured the temperature of work pieces every few hours and collected data on how long they took to reach the temperature of the measuring room. With the largest work piece, we spent three days and nights steadily building up data, but we do believe it was an important job."
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Large Mitutoyo FALCIO-Apex 456015 CNC coordinate measuring machine
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After repeated experimentation, they discovered that once the temperature differential between the measuring room and the work piece got within ±5 degrees Celsius, that there was very little further change. They also used a method of using temperature sensors and automatic correction of measured values. These days, the company is easily achieving high precision measurement results.
Showing an uncompromising attitude to quality, President Kamei commented; “The swing bearings we manufacture are used in power shovels operating 24 hours a day. We ship them from Hitachinaka Port, which is about 50 kilometers from here in Takahagi City. If these parts break down, they have the potential of stopping mining production across the whole line and may even lead to a major accident. That is why we are always serious about ensuring quality.”
The world-leading quality of Japanese construction equipment comes from efforts like these in the manufacturing workplace. With a world focus from Ibaraki Prefecture, and a sincere pursuit of quality, we expect great progress to continue at HAX Corporation going forward.
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