Emerald Group Publishing Limited
Copyright © 2004, Emerald Group Publishing Limited
Providing an ideal turning solution
Providing an ideal turning solution
Keywords: Machines, Turning, Equipment
When Managing Director, Andrew Dobson, went looking for a computer driven centre lathe at MACH 2000, he also knew that his company SG Equipment would need further machines over the next 12 months. In the event, it was the effect on the business of the performance and ease of use of the first Colchester Combi K2 installed that led him to speed up the purchase programme and install three machines within 6 months (Plate 3).
Plate 3 The Combi Trio at SG equipment has proven to be the solution to small batch turning
The key to this accelerated rate of introduction was the speed of operator conversion as Andrew recalls: “The first operator to use the Combi was Alan Corless, a very experienced centre lathe operator, who had no previous CMC experience. Within a matter of hours he was able to program and produce production components using the icon-based commands, virtual tool display and graphic support and has since progressed to develop very good CMC skills.”
He then recounts how they moved another operator from an existing Colchester Electronic centre lathe: “He was well up to speed within half a day,“ said Andrew. While it was the apparent ease of use that won the initial order for Colchester, today Andrew freely admits he was surprised at how well it was translated into practice on the shopfloor.
SG Equipment is a subsidiary of the Hyde Group plc. It specialises in design, development, refurbishment and manufacture of ground support equipment for civil and military aircraft. This embraces a wide range of activities covering production of locking pins for weapons systems, fabricated staging for external maintenance and sophisticated electronic and hydraulic test equipment. Whilst much of the equipment is highly sophisticated, batch quantities are normally quite small averaging around 15 parts with single component requirements being quite common. There is also the occasional need for batches up to 500.
As Andrew outlines, with the type of work the company produces, a production type CNC lathe would probably be counterproductive. However, he acknowledged the benefit from batch-to-batch consistency and repeatability offered by CNC turning. “We produce components such as dynamic seals out of stainless steel with dimensions tied to 0.012 mm and a high standard of finish. Our original Colchester Electronic lathe provided part of the solution with its ability to repeat cycles but it had insufficient capacity for our largest components and was far less sophisticated than the Combi K2,” he says.
The type of turned parts machined by SG Equipment generally range from 8 to 60 mm diameter, however, the company has one regular job which requires a 2 ¾ in. Acme thread to be cut on a 1,320 mm long shaft produced from a 180 mm diameter bar. This part is well within the 400 mm swing capacity of the Combi. Material specifications cover anything from EN3A to S154, which is an high tensile aerospace quality stainless steel and here, the 11 kW spindle with its gearless drive with a 6-2,500 rev/min speed range, is ideal.
As Andrew maintains, the company is reducing its past dependence on form tools. This means we have a lot of quite complicated component shapes to produce which can now be single point turned and easily programmed through the software and graphics with detail scaling of features. Also, as we have to carry out more reverse engineering tasks we now have the ability to adapt or modify a CMC program quickly which is extremely useful. The combination of specialist Colchester windows- based software and Fanuc 210J-TA control on the Combi K2 provides us with those facilities and much more besides. For instance, the constant surface speed machining is particularly valuable as it guarantees that we achieve a consistently high standard of finish and overcomes possible problems such as not being able to tolerate rips or tears when machining threads and we need to comply with aerospace standards.
From its machining experience, SG Equipments are very complementary over the accuracy capability of the Combi machines and in particular the repeatability and reaction to respond to minor size adjustment. According to Andrew: “Colchester support is extremely good; if we have a programming query we get an answer on the phone, while if we have a need for something like a steady, it arrives next day.”
The operators have found that when setting up, the ergonomic aspects of the machine's design have proven to be a key benefit. Alan Corless commented: “Everything on the machine falls easily to hand and the shallow 30° slant of the bed definitely makes it easier to load and unload the machine and work on the far side of a job. The guarding also gives an excellent view of what's happening and you can use the on-screen graphics simulation to monitor internal machining and areas which are flooded with coolant.”
All three of SG Equipment's Combi K2s are identically equipped as chucking machines with the eight station electric turret option. Six tools are common to almost every component produced while two are variable to accommodate specific requirements, such as different thread forms. This commonality of set-up provides the company with a lot of flexibility, while ability to save programs to a flash memory card has allowed the building up of a CMC program archive for future repeat operations.
From a productivity standpoint, Andrew feels that the machines have demonstrated at least a 25 per cent improvement over a centre lathe though this is in direct proportion to the demands of the job and the size of the batch. A prime example is the turning of the 2 ¾ in. Acme thread where production of a single part on a manual centre lathe used to take 16 h. The Comb! K2 is able to complete the task in around 9 h.
As Andrew Dobson concluded: “We're extremely pleased with the performance of these machines, to the extent that we would have no hesitation in adding a fourth as and when our production requirements justify. The outstanding thing about the Combi is definitely the control interface. It has good simulation facilities that give the setter/operators the confidence needed to push along and in the early days quickly develop their programming skills.”