Schramberg, 05.10.15. Schwäbische Werkzeugmaschinen GmbH (SW) is presenting the highest machining performance available in a series production machine at EMO 2015 with the BA 742 four-spindle machining center. The four HSK-A100 motor spindles engage in large workpieces in parallel at a distance of 350 mm with a total of up to 1360 Nm. Like the two and three-spindle designs of the BA 7 series, the BA 742 ensures high-precision 4- and 5-axis machining of cast iron, cast steel or steel chassis parts, brake components and industrial gear units. Compared to four single-spindle units, the BA 742 has greater productivity and requires 60% less total connected electrical load as well as 65% less installation area.
The automotive industry relies worldwide on modular building block systems with a high proportion of identical parts. This greatly increases the quantities of machined components. "Four-spindle machining centers enable manufacturers to increase their capacity and productivity as is only possible otherwise with rotary transfer machines, but with the ability to respond much more flexibly to shorter and shorter lifecycles," explains Reiner Fries, Managing Director of Sales at SW. "With four HSK-A100 motor spindles, we provide the highest machining output available on the market in a series production machining center, thereby enabling our customers to achieve the shortest cycle times in manufacturing of large parts."
Reduced main and auxiliary times
Working at feed rates of up to 70 m/min, the four HSK-A100 motor spindles, each with 28 kW of power, can even machine workpieces with large-area tools at high speed, reducing the time required for machining by means of high machining output for four workpieces in parallel. SW also shortens auxiliary times. Loading takes place in parallel to machining time with a double swivel carrier clamped on both sides. For 5-axis machining it is equipped with four independent planetary axes driven by torque motors. The chip-to-chip time for a tool change is just 3.75 seconds for all four workpieces. A fixture change lasts less than 30 minutes. Inductive broken tool monitoring monitors four tools simultaneously and cycle time-neutrally in the magazine area.
Energy efficiency: 60% less total connected load
Despite the high output, the BA 742 is setting new standards in efficient use of resources. "Four one-spindle machines with only approximately the same output data require an overall connected load of well over 400 kVA. The BA 742 needs only 160 kVA, which is at least 60% less," notes Wolfgang Armleder, Director of Development at SW. Contributing factors are the energy-saving controllable coolant pumps, accumulator/charging circuits in the hydraulic system and lower movable masses in all the axes. The crane hook machine, with the same dimensions as series BA 7 two- and three-spindle machines, also makes do with an installation area about 65% smaller than 4 comparable one-spindle machines.
The same precision in the entire series
The basic design in monoblock construction minimizes deflection and ensures optimum flow of force between the machining unit and the workpiece carrier. The practically complete weight compensation in the vertical axis ensures high positioning accuracy, even with eccentric loads, and reduces thermal stress on the feed motors. All the feed axes are equipped with direct absolute distance measuring systems. In this way the four-spindle BA 742 is able to achieve the same precision as the two- and three-spindle machines of the BA 7 series.
The modularly expandable tool magazine holds up to 96 tools. Tools can be loaded either from the front or from above. SW implements complete solutions through its subsidiary bartsch GmbH, offering custom-made automation systems for loading and unloading four-spindle machines. The movable arrangement of robots on a work platform has proven effective in this regard, as it ensures free accessibility to the machine from all four sides. Reiner Fries summarizes confidently: "With the BA 742, manufacturers can reach the next level of productivity in heavy machining of large workpieces".