Tailored machining gains for trains

The acquisition of three highly adapted Correa gantry milling machines at train builder Alstom’s plant in the Czech Republic has reduced production times by 20% thanks to the extensive planning and collaboration with the customer by the machine builder’s local agent TGS. PES reports.

French multinational Alstom has purchased three Correa gantry milling machines for its ÄŒeská Lípa plant in the Czech Republic. The plant produces parts for commuter trains, trams, metro and other rail vehicles and with almost 1,300 employees, it is one of the largest employers in the region.

The project, worth several million euro, consists of a Fox-40 fixed bridge-type milling machine and two Fox M-80 gantry milling machines, co-produced with TGS, the Correa dealer in the Czech Republic.

The FOX-40 has travel ranges of 4,000mm (X), 3,000mm (Y) and 1,000mm (Z) and an automatic universal UAD head. The two M-80 gantry machines are equipped with three spindles each and have a travel of 8,000mm on the X-axis, 4,250mm on the Y-axis and 1,500mm on the Z-axis. The manufacturing process of the parts was a critical aspect of the project; however, the challenge to optimise the process was amply met with the new Correa machines, reducing processing times by around 20%.

The event held to mark the commissioning of the three machines at the plant was attended by José Nicolás Correa, chairman of the Correa Group, and José Manuel Revuelta, economic and trade secretary of the Spanish embassy in Prague.

Close cooperation

Czech company TGS is Alstom's local supplier. As such, communication between the two companies is constant, and the supplier is always up to date with the needs of Alstom's machining workshop, both in terms of machine tools and technical support.

This project required a thorough understanding of the machining process of the parts to be able to optimise it and create a solution completely adapted to the customer's application. TGS held numerous meetings with Alstom's machining department to carry out a time study and a process design to improve machining times.

"We addressed the design and technological aspects of the process so that the behaviour of the machines, the programmes and all service processes are safe and don’t require manual interventions by technicians. Production continuity is very important for downstream processes and logistics of a product as large as a train chassis," says TGS director Pavel Diviš.

In his opinion, the Spanish machines are among the best on the market and TGS is the exclusive representative for Correa in the Czech Republic.

Tougher head technology

The Alstom ÄŒeská Lípa plant makes bogies: mechanically welded, large and complex shaped parts with protrusions and projections, adding to the complexity of the machining process. This type of workpiece is very prone to vibration during machining operations which causes faster wear on the heads, among other issues so Alstom had to frequently carry out repairs on the heads of machines from other manufacturers. These machine downtimes were a critical factor for Alstom with a 24/7 production schedule.

For this type of operation, Correa’s spindle technology is well-suited as the spindle is rigid, stable and 100% mechanical with no delicate elements fitted that can be easily damaged during demanding machining operations. Among other things, the main spindle is supported by six bearings to provide good performance for this type of application.

For this project, a head has been manufactured specifically for the customer's application. The standard angled Correa head was ISO 50 and didn’t allow access to some parts of the workpiece. However, commercially available angled heads were not an acceptable solution – either because they lacked rigidity or because their dimensions did not allow machining in hard-to-reach areas. Correa's solution was an ISO 40 angled head directly attached to the ram for increased rigidity and compatible with the automatic head change system.

Commercial angled heads have also been incorporated into the machine for less demanding one-off operations. Nicolás Correa's engineering department prepared this solution in such a way that the coupling of these commercial heads is fully automatic (adaptation of the tool change system and design of a ‘stop-block’ or lock for the attachment of this head, which is better than the standard commercial elements).

Customised solutions

Like all Correa milling machines, the machines at Alstom have been adapted to the customer's workshop and the job requirements. To ensure high machine availability, a spare head has been included in the set up to avoid machine downtime and special operating conditions that require short response times.

"Alstom needed the machines within a short delivery time and the deadlines that were agreed were very tight. Despite the difficulties of recent months, such as the crisis in raw material supply, much longer delivery times for commercial elements and price increases, Correa managed to manufacture and install the machines while respecting these delivery deadlines," explains Raúl de la Peña, area manager of Nicolás Correa in the Czech Republic.

The specifications for Alstom included drawings of several parts for the preparation of time studies, which had to guarantee an improvement of around 20% of the production times of each part. Until then, the bogies at ÄŒeská Lípa had been machined on several machines. One of the requirements of the new project was to use a single machine, significantly improving downtime between machines and automating the process as much as possible by minimising the labour required.

TGS has a Fox milling machine at its facilities and Alstom's own engineers, together with TGS staff, carried out tests on this machine, perfecting the CAM projects, checking operation by operation and establishing potential improvements.

A further service provided by TGS was the design and manufacture of special tooling in order to optimise the machining process of the parts made at Alstom at its facilities.

In the UK, Correa machines are sold, supported and serviced by Chorley-based DTS.

Nicolás Correa
www.nicolascorrea.com/en

DTS
https://dtsuk.co.uk