Handwheel mode for specialized processing operations in locomotive wheel manufacturing
The SCHÖMA machine factory opted for a cycle turning machine with Sinumerik 840D solution line CNC for the manufacturing of individual parts and small batches of locomotive wheels; this machine also features Siemens ShopTurn with Manual Machine function. This hardware and software solution combines the flexibility and benefits of conventional machining with the productivity and efficiency of a CNC and this is what tipped the balance in its favor for one customer.
Christoph Schöttler Maschinenfabrik GmbH (SCHÖMA) is based in Diepholz, Germany. The company specializes in the development and production of diesel-engine locomotives. The model range includes tunnel and shunting locomotives; service, field and narrow-gauge locomotives; handcars, passenger carriages and gang cars. Around 90 percent of the locomotives produced each year at SCHÖMA are destined for use in tunnel construction.
Each construction project brings its own specific requirements and each country through which the locomotives travel has different environmental and safety legislation. SCHÖMA uses a modular system to meet a diverse range of customer requirements and the resulting need for a variety of equipment and product versions. One of the tasks facing the company is working out how to equip the locomotives for transportation by rail on differing track widths. Another requirement is locomotives with driving wheels featuring diameters between 600 mm and 900 mm, depending on local track usage.
The right decision
Faced with even more demanding requirements in terms of production capacity and flexibility, SCHÖMA’s Managing Director, Christoph Schöttler, last year decided to add a cycle-control Seiger Record LC 1400 lathe to his inventory of machines. “We opted for a head turning machine, as we do not need a tailstock to produce driving wheels, axle bearing housings and gear wheels. It is working just as we envisioned, so we obviously made the right decision,” says Schöttler.
SCHÖMA constructs around 120 locomotives each year, which equates to 480 wheels. In addition, there are also repair orders, which increase the workload to between 560 and 600 driving wheels per year. These wheels are produced in two mountings from forged blanks on the cycle turning machine. The first mounting is used to machine the wheel flange on the reverse side and the wheel hub. The shaft locating bore is pre-turned. In the second mounting, the first task is to pre-turn the driving wheel profile, then the rolling circle level and the wheel shaft locating bore are finished.
Careful approach
The cycle turning machine is controlled by a Siemens Sinumerik 840D sl CNC, equipped with the ShopTurn software package with Manual Machine feature. If required, ShopTurn programming can be performed on a separate PC as part of an operator’s work planning, without interrupting the work sequences on the machine. The programs are routed to the machine via the network, where they are called up as required, depending on the workpieces to be produced. The Sinumerik CNC is used for both numerically controlled machining and manual operation with the ShopTurn’s Manual Machine functions. In manual mode with electronic handwheels, the machine behaves just like a conventional lathe with an actual value display.
During face and longitudinal turning, the process operates with the entered feed and spindle speed. The real highlight of the system is that every cycle can be used straightaway, without having to create a custom program. At SCHÖMA, the option for 
manual intervention is used for setting the zero point or for simple contours. Diameters are determined manually, if driving wheels have been newly profiled or if driving wheel profiles require resurfacing. The wheel profiles abrade as a result of the high loads experienced in heavy-duty operation or on poor-quality tracks or as a result of the driven wheels skidding.
“With a machine that uses only CNC, it is difficult to rework the driving wheels, as it is not possible to determine how much material needs to be removed. With this optional manual mode, however, users can adopt a careful approach. This sums up the ease of control,” explains Walter Horstmann, head of mechanical production and wheel set construction at SCHÖMA.
Siemens ShopTurn with Manual Machine for the job shop
After machine start-up, the basic MANUAL screen is immediately displayed and offers direct access to choosing machining options without having to create a parts program.
Machining procedures such as “taper turning” and “straight line face and longitudinal turning” can be executed immediately. The operator simply selects tool, feed speed, spindle speed and orientation, plus, if required, machining angle, then presses “Start”. The active direction is graphically displayed in the basic screen, using a compass rose symbol. All machining steps such as entry, thread grinding and drilling can also be started in manual mode.
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Attention: John Meyer, Manager, Marketing Communications
