Flow line for machining centre production

The Worcestershire factory started operating in 1995, 21 years after the formation the UK subsidiary of Heller Maschinenfabrik, Germany. As part of the latest initiatives, activities in Redditch have expanded into assembly of five axis machines in addition to four axis models for world markets. The site is also a global competence centre for high quality, high precision turnkey projects and innovative manufacturing solutions.

David Evans, Operations Manager at the plant commented: "As part of our expansion, we recently installed an 11 station Strothmann flow line and new logistics system for complete manufacture of horizontal machining centres. Originally, our machine assembly was purely a mechanical process on an adjacent flow line and the machine had to be lifted off to be finished in a separate part of the factory.

"When we first moved from block assembly of machines in one location to the old flow line, there was an immediate 20% increase in productivity. The new Strothmann system has resulted in a further reduction of at least 20% in overall assembly time and we intend to improve on that further by making the process even leaner."

Mechanical assembly of horizontal machining centres is completed over the first four stations in the line. All bed assembly is carried out off line and the casting is delivered to the first carriage with the linear guideways already fitted. A majority of the pre-assembled groups of components are added at this first station, including the machine column, pallet changer and the energy unit powering the hydraulics and pneumatics.

The Strothmann carriage is raised pneumatically and pushed along rails set in the floor to the next station location, where the air pressure is released to allow the carriage to lower to the floor, a process that takes about two minutes. The main part of the work here is to attach the electrical cabinet, which is craned across from another part of the factory. Some of the ancillary equipment including cables and pipework is also fitted.

At the third station, two further major groups are added, namely the tool magazine and changer assembly and the machine guarding. Station four, which completes the mechanical assembly phase, sees all of the pipework and cabling routed from where it originates to where it needs to be connected. 

Electrical commissioning can take two, three or even four days, depending on the technicality of the software, customisation and everything else that needs to be completed, so occupies the next one or two stations. Later stations in the line are deployed similarly flexibly according to the amount of work required. It includes geometrical alignment, laser calibration of the axes to ensure repeatability of the machine and an alignment test carried out by a dedicated team in the Heller factory. 

The last part of the process is to machine a standard NAS (National Aerospace Standard) test piece, which is inspected by an independent team of metrology staff to give the customer a guarantee of the machine's accuracy.

Once each horizontal machining centre reaches the end of the line and is removed for dispatch, the Strothmann carriage is lifted by crane and carried back down the gangway to the start of the line to begin the process again.

At every stage of the manufacturing process, work carried out on the machine is documented by the individuals concerned, providing full traceability as required in order to comply with the factory's ISO 9001 accreditation.

Heller's Managing Director in the UK, Matthias Meyer concluded: “The fact that we manufacture in this market gives our customers in the UK and Ireland considerable added value. Not only does our staff have a level of product knowledge that is much deeper than it would be otherwise, but also we can call on shop floor operatives, all of whom are apprentice trained, to help out with installation, commissioning and service if required.

“Another benefit is that customers are welcome to visit us and see their machining centre actually being built, if it happens to be a model that we produce. Whatever machine they are buying, they can see the quality of engineering input, which is standard across all of our factories.”