Mandelli Sistemi employs a 5-axis machining centre to process hard titanium alloys for the aerospace industry. The company uses a safe solenoid interlock with Bowden cable from Schmersal to automate and secure the closing process on the large sliding doors fitted to the titanium machine.

Over its 80-year history, Mandelli Sistemi S.p.A. has continuously focused on innovation and custom-made solutions. Based in the northern Italian town of Piacenza, this medium-sized enterprise, now a part of the Riello Sistemi Group, has become one of the leading Italian companies for the manufacturer of machine tools. Over the past decade, Mandelli has turned its focus to industries such as aerospace and energy, where difficult-to-machine materials combined with complex geometries require demanding turning and milling operations.

At the turn of the millennium, Mandelli Sistemi completed the development of a new series of five-axis machining centres, the SPARK series — fast, high-performance machining centres with compact dimensions and outstanding productivity. In 2015, Mandelli Sistemi added a new version to the SPARK series in the form of the Spark Ti (for titanium), a five-axis horizontal machining centre, with a fixed machine bench capable of very precise machining, in spite of high material volumes. The machine is able to process very hard titanium, steel and HRSA alloys that are typically used in the aerospace industry. At the heart of the Spark Ti is a continuously controlled high-torque swivel head equipped with an automatic mechanical backlash recovery system, plus a dual-drive rotary axis with 12,000 Nm of power and a vibration damping system on every machine axis. In addition, all turning tables are highly dynamic, allowing for high acceleration in the complex machining phase for both the workpiece geometries and the material composition (titanium, HRSA – heat-resistant super alloys).

A new generation of machining centres for Industry 4.0

The new generation of machining centres from Mandelli Sistemi is already compatible with Industry 4.0 concepts, with all machines incorporating a complex system of anti-vibration, noise and vibration sensors to be able to detect critical conditions early on and adapt machine parameters when required. This helps to avoid machine downtime and minimise production waste. Mandelli Sistemi has also developed the new iPum@Suite 4.0 software package for the ‘factory of the future’. This software guarantees that networked machines can be fully monitored by a remote setup through a series of sensors and an intelligent vibration monitoring system — an intelligent diagnostics system in which the operating data from the machining centre is transferred to a cloud database where statistical calculations are carried out to identify faults before a malfunction occurs.

‘For our high-performance Spark Ti, with its considerable size, we need to have a robust safety system in place. If a machine operator accidentally finds himself trapped inside the accessible part of the machine, the safety solution needs to allow the operator to leave the area as quickly as possible and needs to block the system at the same time,’ explains Ing. Giuseppe Galbiati, Project Manager at Mandelli Sistemi. The safety system requirements for the Spark Ti were mapped out at a meeting of the engineering department of Mandelli Sistemi and safety machinery experts from Schmersal, a leading international provider of machine safety products.

A safety locking system that satisfies all of these requirements is the AZM400 secure bolt retention system from Schmersal, in conjunction with Bowden cable release. Mandelli Sistemi has been impressed by the extraordinarily high locking force of the AZM400 when used on the heavy protective doors on its Spark Ti, but, when used in conjunction with the Bowden cable, the AZM400 also offers high protective performance, a feature that is particularly valuable in the event that an operator becomes trapped in the machining centre accidentally, such as when carrying out maintenance work. Within the hazard area, the Bowden cable can, therefore, be used as an emergency release, with the operator merely having to pull on the pull rope. When used outside of the hazard area, the device can be used as an emergency unlock. The pull rope has a standard overall length of 6 m and a sheath length of 4 m, thereby allowing for protection of large systems as well.

Solenoid interlock especially for large machining centres

Schmersal launched the AZM400 solenoid interlock in 2015. The system comprises the locking unit with sensor system, a motor-driven locking pin and the actuator. The actuator contains an encoded RFID tag and a locking opening into which the locking pin is inserted. As soon as the locking pin has reached a sufficient insertion depth into the locking opening in the actuator, the safety device can be considered safely locked.

In developing the AZM400, Schmersal kept the special requirements of large machining centres in sharp focus, particularly the fact that most machining centres require very high locking forces capable of locking heavy protective doors, many of which have motorised actuators. The AZM400 safety locking system has a locking force of 10,000 N, which is an exceptional feature amongst solenoid interlocks.

The AZM400 achieves safety level PL e and Cat. 4 in accordance with DIN EN ISO 13849-1 and SIL3 in accordance with DIN EN 61508 for both the interlock and locking functions. The high safety level of the locking function is achieved by features including a two-channel unlocking signal, which ensures that should, for example, a cross-fault occur, the system remains locked to prevent unauthorised access to the hazard area.

High level of safety and maximum plant availability

The AZM400 ensures not only a high level of safety but also seamless process execution for maximum plant availability. For example: protective doors often have dampening at their limit stops such that, when they are closed, they spring back a little. As a consequence, the locking pin does not sit fully in the centre of the locking opening in the actuator and must overcome cross forces. If it is unable to overcome the cross forces, the protective door is not opened and the production process is delayed. The solenoid interlock AZM400 offers the advantage of unlocking against a cross force of up to 300 N. In addition, the electronic system combined with the sensor system offers numerous additional functions, including error state identification: if the locking pin fails to reach a ‘locked’ status on the first attempt, it attempts to lock again automatically. Only if this second attempt fails will the AZM400 report a fault. This helps to reduce the number of fault notifications and at the same time, protects the device from damage.

‘Protective doors must always reliably lock and unlock. At the same time, the safety technology must help to maximise plant availability. The AZM400 is, therefore, the optimal solution,’ explains Maicol Garavaldi, Safety Machinery Expert at Schmersal Italia.