Alot of electric-discharge machining previously carried out by Galway Tool & Mould (GTM) (
www.galwaytoolandmould.com) has been replaced by high-speed cutting at up to 42,000rev/min on three German-built Roeders machining centres. These machines are all installed in a temperature-controlled environment, and two of them have been fitted with pallet changers so that they can be operated round the clock, unmanned at night.
GTM’s owner and managing director, Padraig McFadden, said: “As a result of this and other measures, mould lead times have been cut by up to 20% — typically to 14 weeks — and we have increased productivity significantly.”
The main specialism of the company, which was founded in 1990, is the manufacture of high-precision injection moulds for the medical, pharmaceutical and high-volume packaging sectors world-wide. These range from single-impression moulds for prototyping to 48-cavity types for producing complex plastic devices such as inhalers. In addition, a small number of micro moulds are produced to make — for example — miniature rotor gears and screws for medical assemblies or for over-moulding stents (components down to 10 milligrams can be moulded to tolerances of ±0.005mm, consistently and reliably).
The successful working practices implemented by GTM at its Galway factory resulted in a doubling of turnover between 2012 and 2015 — and an increase in floor area from 4,000 to 15,000ft2 (an 8,000ft2 extension is currently being added). The company has 30 employees, of whom three are apprentices.
The migration from EDM to high-speed milling is one factor in that success, but others are the opening of a metrology laboratory for tool validation and an in-house trial facility for moulds; this is equipped with Fanuc electric moulding machines with capacities ranging from 100 to 300 tonnes. Mr McFadden emphasised that customers get a perfect turn-key mould every time, which has been designed, manufactured and tested for process viability, including correct shrinkage allowance.
The year 2007 was a time of change for GTM, which until then had derived a large proportion of its turnover from automotive mould making. Much of this work rapidly disappeared overseas, notably to China, so Mr McFadden diversified into other areas — particularly the medical industry, for which Ireland had become a global manufacturing centre.
Characteristic of medical mould work is the requirement for tighter tolerances, better surface finishes and shorter lead times than are normal in the automotive sector.
GTM was ‘sparking’ a lot of small parts for moulds, but electrode manufacture is time-consuming, and EDM is itself a slow process. The decision was taken to replace as much EDM working as possible with high-speed machining, using small-diameter ball-nose milling cutters.
According to shopfloor manager Mark Walsh, that would save 70% of the time needed for this part of the manufacturing process. Every mould that passes through the Galway factory now undergoes some high-speed cutting on one of the Roeders, which were supplied by High Wycombe-based Hurco Europe Ltd (
www.hurco.co.uk) through its local sales representative in Ireland, Michael Gannon.
Mr Walsh says: “Back in 2007, we asked several potential HSC machine suppliers to make test cuts on one of our moulds. The Roeders machine beat all the others in terms of speed, accuracy and surface finish. It was noticeably better in all areas, partly because the German machine builder was an early adopter of linear motors for the axis drives. Coupled with glass-scale feedback to the control and compensation for spindle growth via a high-precision sensor, it allows us to hold ±2µm accuracy. This was three-times better than that achieved by a ballscrew-driven machine we trialled, which also had the drawback of not being able to achieve the surface finish we require for our moulds.”
A Roeders RXP500 three-axis VMC with a 40-tool magazine was duly installed. Despite it having run 24/5 and extensively at weekends for more than eight years, Mr Walsh confirmed that the machine is just as good today (in terms of the accuracies and surface finishes achieved) as when it was new. This level of performance led to the purchase of a second Roeders three-axis RXP 500 in 2013; this was required to cope with increased production levels.
Automation was fitted in the form of an automatic eight-pallet changer that allows any mix of jobs to be set up and run unattended overnight — or over an entire weekend if longer-running jobs are selected. The automation fitted to the second machine means that both RXP500s can be attended by just one person during the day.
More recently, work has been heavily centred on complex pharmaceutical moulds that require multiple set-ups on a three-axis machine, the use of long cutters to access awkward areas from above, and repeated repositioning for side
features to be included.
A five-axis VMC was the obvious solution, so in May 2015 a Roeders RXP601 DSH with a 96-tool magazine was installed, again with automation — but this time a 38-position pallet-change system to allow longer periods of unattended running (a second RXP601 could be served by the same automation equipment if required in the future).
The advantage of using five-axis machining on some jobs is dramatic. Take the inhaler mould mentioned earlier; this was previously machined in a total of 8hr on a three-axis Roeders and an EDM machine in five operations. These comprised milling with an 80mm-long 16mm-diameter cutter that was slowed to 3,000rev/min to avoid undue vibration, followed by a set-up on either side for further milling, then sparking on four sides and around the skirt. The five-axis HSC machine tackles the same job in a single set-up in a quarter of the time — just 2hr to complete.
The time saving is a result of eliminating four set-ups and maintaining a spindle speed at 30,000rev/min, as the better access afforded by a five-axis configuration allows the use of shorter cutters. Consequently, more and more work is finding its way onto the five-axis cell at the Galway factory. The latest innovation is the introduction of off-line job set-up on a co-ordinate measuring machine. When fully implemented, this arrangement will add an extra 10hr of production per week across the three Roeders machines.