Three large, travelling-column bed mills at the Swansea factory of subcontractor Afon Engineering have been retrofitted with a Heidenhain TNC 320 control and new drives to improve their reliability and performance.
It has been an object lesson in how mechanically sound machine tools built in the late 1980s can be given a new lease of life for a fraction of the cost of investing in new equipment.
CNC milling forms the mainstay of the company's business and upgrading three of the Elgamills on site was a prime objective. Engineering Director Andrew Beaujean commented, "The project has given us more confidence to take on a much broader variety of contracts and is bringing in new business as a result, such as evaporator tube plate machining.
The refurbished machines have beds measuring 12, 10 and 8 metres respectively in the X-axis and the mid-size model, when it was installed in 2009 with an earlier Heidenhain TNC 355 control, was the first CNC machine on site. The other two Elgamills, which arrived five and 11 years later, were fitted with a TNC 155 CNC system. Two smaller, as-yet unmodernised machines from the same manufacturer are also on the shop floor.
The ageing electronics and wiring on a pair of even older manual Elgamills, previously in operation in Swansea, had become unreliable. Replacement parts were no longer supported, and it was necessary to go to internet marketplaces to try to source spares. Refurbished parts were becoming very difficult to obtain. Consequently breakdowns were frequent, lasting from a few days up to one month, making job planning problematic.
Afon Engineering had been firefighting in this way for many years before it started to invest in CNC machines. Even with the more modern 12-, 10- and 8- metre models on the shop floor, reliability issues meant that the three machines were rarely all operating together and sometimes only one of them would be running. With a lot of mainly one-off emergency work carried out on the Swansea site for the steel and energy supply power sectors, and some parts requiring to be on the machines for up to three weeks, it caused a lot of difficulties for Mr Beaujean and his management team.
Steve Wright from the technical sales department at Heidenhain (GB), Burgess Hill, and Simon Hopkins, Engineering Director of approved CNC retrofitting company SDH Controls and Services, Worcester, met with Mr Beaujean in 2020 to discuss the problems.
Due to the age of the CNC Elgamills, well in excess of three decades, they all had the original analogue drives. A decision was taken to retain analogue technology and perhaps even keep the original motors. However they were no longer supported, so new, more economical analogue drives and motors were fitted, together with the TNC 320 control. Assurance was given by the Heidenhain factory in Germany that the latter would be fully supported for at least the next 15 years, while the drive manufacturer gave a similar undertaking.
Reliability is of the essence in the Swansea factory, rather than speed. Dimensional accuracy is also important, as some milled features are tied up to ± 0.1 mm. Machining versatility is needed as well, so the 12- and 8-metre machines have 5-position spindle heads driven by M-codes from the control, while the 10-metre machine has a one-degree rear head controlled by an analogue signal from the TNC 320 and a 2-position front head controlled by M-codes.
Another advantage of having new controls is that off-line programming is now feasible, whereas on the older controls this was cumbersome and time consuming. Being able to prepare cutter paths away from the machines maximises spindle uptime. Reliable connectivity also allows input of data from reverse engineering of complex components that could not realistically be programmed in any other way.
Take for example a recent job, a sugar industry evaporator tube plate measuring four metres in diameter and containing 4,500 holes. Scan data, in this case provided by the customer, was loaded into Afon Engineering's OneCNC CAD/CAM system. A program was then created, post processed and run on one of the Elgamills, the whole project lasting about one month.
afonengineering.com