Established in 2002, subcontractor A&M EDM’s machining activities have grown such that it now boasts 18 Hurco machining centres, along with a developing grinding section, temperature-controlled inspection facilities, laser welding, and significant design capability, including laser scanning for reverse engineering projects.
As it happens, the company actually set out with the ambition of being the best sub-contract EDM company in the UK and, having achieved that particular aim, saw further opportunity in the metalcutting sector. Indeed, with the growth of this side of the business, a two-year, £4 million, investment and a move to a 26,000 ft2 factory was the culmination.
A&M EDM has worked with cutting tool supplier WNT (0114 249 6249) from the outset. Says Gary Surman, A&M EDM’s machine shop manager: “When the first four machines came in, they were accompanied by £10,000 of tooling from WNT and a commitment from the Sheffield-based tooling specialist to work with us to supply tooling to suit our strategies and optimise tool usage.”
An example of this was A&M EDM’s wish to operate unmanned overnight, with the lights switched off after the day shift and machines left running. Recalls Surman: “With our background in EDM, we were happy to run lights out, but when most machinists talk about lights out, they generally only leave finishing cuts running overnight. We were determined to carry out full roughing operations on components with cycle times up to 35 hours at 7,000 mm/min and in difficult-to-machine materials, such as 30 HRC Toolox 33 tool steels.
“This meant that process security had to be a high priority on tools that, in many cases, had extended overhangs, so we embarked on some serious strategy reviews, with every aspect of the metalcutting process investigated. The result of this approach has been optimum speeds and feeds, and multiple sister tools in the carousel.”
KEY TOOLS OFFER BENEFITS
The key tools used in these unmanned operations are WNT’s 63 mm diameter High Feed Cutter (HFC) indexable insert shell-mills (A-style HFC) that, having six close-pitched positive rake angle inserts, offer a combination of high feed rates and a cutting action that results in maximum tool life, reduced stress on the spindle, lower power consumption and reduced vibration. Taken together, these cutter attributes offer the necessary process security.
As confirmation of this, A&M EDM has only seen one insert crack under machining conditions over an 18-month period. Part of that success is down to the tool management in use. The company has some 30 HFC tools, with up to 28 in the machine’s tool carousel at any one time, because up to 35 hours of unmanned running is possible across a weekend.
Following unmanned machining, first thing in the morning, unskilled workers remove all the HFC tools from the carousel, with the machine then available for other operations during the day. In this way, tool servicing occurs without any loss of machine time. Again using unskilled workers, all inserts are either indexed or, if all edges have been used, exchanged – all tools used for overnight machining commence use with a fresh cutting edge. And if any of the Torx screws used to secure the inserts shows signs of wear or damage, all are changed since, explains Surman of what might be judged overkill, if one has gone, others are likely to follow.
Now, the inserts that have been used for overnight roughing are not fully worn, they have just been used up to a point where the company can be sure that they will not fail, he underlines. So these partially used inserts are subsequently employed on other cutters during the day.
And when the company wants to set up a machine for overnight running, the serviced HFC cutters are available to be returned to the carousel.
A&M EDM operates unmanned overnight rough machining, supported by WNT tooling
Emphasises the machine shop manager: “It could take two hours to take all of them out of the carousel, change the inserts and replace them. By doing this as a background operation, we save valuable machine time and also ensure tools are in peak condition all of the time.”
Standardisation operates in other related areas, too, he adds: “We also have standard tool tables that specify cutting data for each and every tool in use, and where those tools sit in the machine, so everyone working here knows exactly how those tools will perform on various materials.”
Indeed, A&M EDM worked closely with WNT, going through every tool – milling cutters, drills, reamers and taps – to establish operating rules. For example, every 63 mm diameter WNT HFC is held in the same length toolholder, while shrink-fit toolholding was specified for many cutters
so as to avoid vibration, improve surface finish and generate guaranteed tool life, which is often four or five times longer than if other toolholding methods, such as Weldon, were to be used.
All standard tools are stored on the shopfloor close to the machines, as this aids tool maintenance procedures, but A&M EDM also has a stock of tooling held in a WNT Tool Service vending system.
Concludes Surman: “At the end of the day, we are a subcontractor and we can never know for certain what work will come through the door next, so we have invested in a range of common cutters that we hold in the vending machine. We could choose any number of tooling suppliers, but we know with WNT that we can place an order up to 6:30 pm and get it the next day; this is our get-out clause, as we often get very urgent work at short notice, and this service level is a major benefit. In addition to delivery, we know that specific tooling requirements will be dealt with and we rely on Stuart Green, our WNT technical sales engineer, to supply the right tools for the job, based on what we tell him we need, and it works.”
This article was first published in the June 2016 issue of Machinery magazine.