IndraMotion MTX advanced controls the efficient rotary transfer machine

March 2016

Up to 144 axes simultaneously rotate, drill and saw metal workpieces in the electro-hydraulic rotary transfer machines from Pfiffner with just one CNC control – thanks to the IndraMotion MTX advanced.

Rotary transfer machines are efficient because the circularly arranged machining stations process workpieces simultaneously. With them, users produce everything from components for cars, valves and locking equipment to electronics and telecommunications in large quantities. But the concept also poses a challenge to manufacturers: simultaneously controlling a multitude of axes. Until recently, there was no CNC control that could handle it alone. “Until now, we had to combine several NC controls with our rotary transfer machines”, says Uwe Krause, Managing Director Germany of K. R. Pfiffner regarding the initial situation. The time and costs associated with the programming increased, at the same time, the cycle times were prolonged.

A control system for up to 250 axes

Pfiffner has delivered more than 2,700 rotary transfer machines worldwide and it is the leader in this segment. For decades, developers observed the market looking for the perfect CNC solution. “So we were very excited when Rexroth introduced us to the IndraMotion MTX advanced”, the Managing Director recalls. The control system is the most powerful version in the CNC system family. It offers high-performance computing power with modern multi-core processors and large memory capacity in compact, high-performance industrial PCs. Currently it controls up to 250 axes in up to 60 NC channels, up to 60 of which as spindle drives – more than enough, even for Pfiffner rotary transfer machines.

In the latest machine series, Pfiffner combines up to 24 machining stations. These basic modules each have one to five electric and hydraulic NC axes and a spindle drive. Mathematically, that equates to 144 axes, but it can be even more if, for example, an additional handling system does the loading and unloading. The electro-hydraulic axes handle the feeding very neatly and take up little space in the basic modules. Pfiffner uses the cabinet-free IAC multi-Ethernet single-axis controller with position controller from Rexroth. These have the electronics fully integrated in the valve. Just like the intelligent IndraDrive servo drives, they close the control loop locally and relieve the control. The drives communicate with the CNC control via the Ethernet-based, real-time Sercos standard.

Simply engineered

The programming and commissioning of a new rotary transfer machine series is complex and often lengthier than that of standard machine tools. “Thanks to the great collaboration with specialists from Bosch Rexroth we needed less than a year for the development. That’s very, very good given the complexity of our rotary transfer solutions”, says the Managing Director. Pfiffner has completely re-developed the entire PLC and CNC software. The programmers and commissioning engineers completed all tasks using the IndraWorks engineering environment. The combination of software tools, built-in technology functions and open standards in a single environment accelerates the entire engineering process.

Machine safety plays an important role at Pfiffner. Here, as well, the developers quickly came up with results that conformed with standards. “We implemented a simple, consistent security concept with only one controller and built-in security features at the drive level”, says Uwe Krause.

IndraDrive servo drives locally monitor a variety of safe, certified movement functions. With the safety zone module from Rexroth, Pfiffner was also able to reduce the time and the cost of materials for the installation. Without higher-level control, developers simply consolidated certain drives via CIP safety on Sercos in a security zone with a zone module. There, they centrally connect the secure peripherals, such as sensors. This eliminates the other-wise necessary need for a two-channel connection of the peripheral to each drive.

Smart hydraulics quickly integrated

A special feature of Bosch Rexroth also contributed to the fast progress of the project: As the only drive and control manufacturers, the company’s decades of application experience in electric hydraulics have gone into the software of the motion controls. In addition, the control strategies for hydraulic and hybrid drives were optimized. These controllers automatically compensate for the non-linear characteristics of fluid technology. The user simply selects preprogrammed functions, such as position control, and parameterizes them. The setup wizard leads you through the commissioning logically, suggests parameter values and helps you to avoid errors.

“The new machine software is so modular that we will use it in all our machine series in the future”, says Uwe Krause. Pfiffner was able to completely borrow the existing visualization. There’s a special advantage for the operators of the rotary transfer machines: “We have also made sure that our customers can change the machine configuration themselves. You have the ability to independently add or remove functions of a unit. This is an important selling point for us.”

Pfiffner has already delivered the first machines with IndraMotion MTX advanced. The customer response has been very positive, says Uwe Krause: “It exceeds customer expectations when it comes to cycle time, precision, availability, and especially the short changeover times of the machine. With the CNC system solution from Rexroth, we have increased the overall performance by about 20 percent.”