Harmonized production flow

Sicor is a leader among elevator traction solutions builders. Its portfolio ranges from gearless motor machines to worm gear reducers. All models are manufactured at the company’s plant in Rovereto, in the Trentino region of north-eastern Italy. Production lines at the plant are highly automated, and precision to a few microns is required.

Worm shafts for worm gear winches are made from a drawn, reclaimed 42CrMo4 steel bar, hardness 290-310 Hb. The machining process requires 15 profile changes.

However, problems with the production line flow at Sicor were occurring because of a bottleneck on the first work station, where the bars are roughened and finished using an Emco MaxxTurn 110 machining centre. “Even if we stressed the traditional production methods to the maximum, the speed of this process was still too low,” says Christian Girardi, plant director at Sicor. “We were thinking about doubling the entire production line, to keep the pace up as required from the market.”

Massimo Miorandi, CEO of Emmedue, a Sandvik Coromant authorized dealer, explains, “Cooperation between Sicor and Sandvik Coromant Italia has been long-standing and founded on a well-established mutual confidence that leads to successful results.” Thus, when Sandvik Coromant released its Prime Turning system and Coro Turn prime tools, Massimo together with the Sandvik Coromant Distributors Sales Engineering, Stefano Premoli, realized that Sicor could be interested and proposed the implementation with commitment and passion:

“The performances of the new system immediately convinced us to test it,” says Matteo Arbetti, responsible for the mechanical processing area at Sicor, “but introducing it meant a paradigm shift in our production cycles.” This workpiece, he says, entails the use of a QS-CP-25BL-2525-11B shank tool and, as first choice, a CP-B1108-M5 GC4325 B-type insert, with a 25-degree clearance angle and three-millimetre cut depth.

Some vibration occurred at the beginning, particularly with smaller workpieces, but fixing the workpiece with a double-contact steady rest, which guaranteed a better grip, helped the spindle and the tailstock. Other critical points were the insert wear and its subsequent breaking, which decreased machining accuracy. “After many test cycles we fine-tuned the machine torque delivery, adopted a new chip breaker geometry and tweaked the steel alloy specifications in order to improve its machinability,” Arbetti says. “The entry angle was eased and corner radius was reduced as well, compared to our usual standards.” Speeds remained more or less the same as those used formerly with ISO inserts from a competitor; cutting speeds remained almost the same (200 metres per minute, approximately) and in some cases increased. At the same time, feed per revolution increased from 0.5 to 1.2 millimetres per minute. “The cost of each insert was increased, but Sicor saved significant money, thanks to the quadrupled insert life aand the reduced machine downtime for insert changes,” says Paolo Gonzato, CAM and turning specialist at Sandvik Coromant South Europe. Productivity was raised by 82 percent and machine time was decreased by 47 percent, resulting in a 37 percent decrease in production costs. “The production line is now perfectly balanced and the first work station has the same output rate as the following ones, without bottlenecks,” says Girardi.

Introduction of the PrimeTurning system combined with CoroTurn Prime required the modification of many programs as well as the programming method, but Sandvik Coromant, Emmedue and Sicor shared and exchanged knowledge and technologies, working side by side at the plant to define tool paths and torque and speed output for the spindle. “Simulating all steps of the tool path in the CoroPlus Tool Path software from PrimeTurning allowed us to accurately predict interferences and collisions and gave us a great help,” says Arbetti. “A further saving was obtained from the introduction of a right tool that was symmetrical to the left one already in use, which allowed us to make the most of the two sides of an insert and double its life.”