Engineers at DavyMarkham check the final machining of the press table for the hydraulic screw press that was installed recently at Bohler Schmiedetechnik, in Austria. DavyMarkham was contracted by the press builder, SMS Eumuco, to perform the required machining on the 350-metric ton steel casting.


In April, Bohler Schmiedetechnik put into operation the world's largest hydraulic screw press at its plant in Kapfenberg, Austria.

The press was designed and built by SMS Eumuco (www.sms-eumuco.de), Leverkusen, Germany, with an assist by DavyMarkham. The Model SPKA 22400N clutch-operated screw press, with a blow force of 35,500 metric tons and a gross energy of 10,000 kj, was installed so that Bohler might increase its production capacity substantially.

Construction of this giant press depended on casting and machining two huge components. The order for the castings went to Sheffield Forgemasters (also in Sheffield), and the machining was subcontracted to DavyMarkham, which employed its extensive CNC milling and boring resources.

The new screw press is 17-m high, with a screw diameter of 1,320 mm. It weighs more than 5,000 metric tons. The size and complexity of the main table and the traverse are such that only steel castings were viable.

The table, measuring 7.5 m long X 4 m high X 3 m high, and the traverse, which is slightly higher at 3.25 m, were cast by SFM from almost 600 metric tons of liquid steel, with six melts poured into a giant mold in a carefully planned sequence. After cooling over several days, the castings were heat treated to enhance metallurgical structure and surface cleaned, then transported to DavyMarkham for final machining.

Machining was a giant undertaking, calling upon all of DavyMarkham's engineering skills and machining resources. Its largest Waldrich Coburg gantry milling machine was programmed using established CNC methodology, to enable circular interpretation-mode milling of large bore diameters. These tapered bores ranged in diameter from 1,300 to 3,300 mm, with a required accuracy of ±0.1 mm and a geometric tolerance of 0.15 mm between bores, which were up to 4 m apart; only a very sophisticated machine could meet such tight tolerances. To machine these large internal diameters, DavyMarkham designed and manufactured two large custom boring heads, one for the gantry miller and one for a horizontal borer.

Shot peening was employed at certain critical radii, too, to enhance fatigue limits of the material and prevent crack initiation. The finish-machined traverse casting finally weighed just over 325 metric tons, including a series of 2,500 mm diameter, 3-metric ton alloy steel rings also produced by DavyMarkham, while the machined table tipped weighed 300 metric tons.