Friday, July 09, 2010

Turn-Mill Cell Increases Machining Productivity

Miyano has revealed that IMI Components has installed a 13-axis turn-milling cell with fully integrated gantry loader to reduce machining times on small components for the energy sector. IMI adopted single-cycle turn-milling to replace four separate CNC turning and milling operations on a range of small components destined for the energy and power generation industry. The 13-axis Miyano ABX-64TH3 turn-milling cell with fully integrated gantry loader is on final commissioning trials and has already reduced total machining times on four critical valves.

Such is the level of increased productivity that for one particular component, three parts can now be produced complete in the previous floor-to-floor time total for one part. As an example of the level of complexity involved, one of the parts has some 100 dimensions that have to be maintained. Here, the Miyano has the advantage of being able to apply the 17 driven tools to carry out the cycle in just one operation - well within the tool-carrying capacity of the ABX's 36 driven positions. 'The Miyano machinery can run for up to 19 hours in an unmanned single-cycle operation against our previous methods, which were operator-dependent with the added lead-time restrictions of part buffering between the different machines,' said Adrian Floyd, engineering manager at IMI.

The Miyano has also saved most of the manual deburring required by combining the process in cycle, setting times have also been reduced from half-a-day to around 30mins for a complete changeover as programs and 95 per cent of tools required for all the components are held permanently on the machine's three turrets. Materials processed at IMI Components vary from magnesium alloys through a range of stainless steels and other exotic alloys to aluminium. With market demand escalating for high-precision, high-integrity products this level of production is set to rise further. The selection of the Miyano ABX-64TH3 was made against three other supplies of multi-axis, turn-mill centres.

The inclusion of Stealth technology, enabling the machine to be thermally efficient and high on accuracy and repeatability due to its ability to be tailored or tuned to the working environment and operational demands, was an important factor in the decision. Also high on the agenda was the level of flexibility available from the two spindles and three, 12-position driven tool turrets to provide overlapped cutting operations and reduce cycle times. Indeed, this is qualified by one component that took 19min to produce using the original four operation method that was reduced to six minutes on the Miyano. 'During quotation stages the volume of parts was constantly shifting upwards and we were becoming concerned that with our existing methods the amount of handling involved through the four machining operations and manual deburring, that even with the greatest care and attention we were susceptible to marking or damaging the components,' Floyd said.

By incorporating a programmable gantry into the cell, IMI can now control part handling as well as dipping the component after machining to prevent any staining. The Miyano is fed from its Iemca gantry system that incorporates a buffer magazine able to store up to 190 billets giving up to 19 hours of unattended running. Both machine and gantry have independent control systems with the software interface created once the cell was installed at the plant. However, all machining programs and job set-up sheets were written by Miyano application engineers in Birmingham along with the supply of a full complement of mostly standard tooling.

Prior to shipment, the machine package was proven to achieve production targets and CPK target values at the Miyano showroom. General tolerances on the aluminium components are within 0.02mm with certain specific dimensions maintained within 0.01mm. As sealing faces and 'O'-ring grooves are required, surface finish below 0.8 micron Ra is high on the requirement list and these are generally maintained by the machine and tooling set-up within 0.5 micron Ra. Operations carried out on the four component types include turning and extensive milling and drilling. Boring cycles, the creation of numerous 'O' ring grooves and sealing faces, drilling of deep holes and reaming are required on all the parts.

Thread milling is also performed to produce M4, M6, M8 and M12 threads and there are several off-centre line hole features, ideal for the Y-axis combination movements of the two upper turrets to allow the holes to accurately break into each other from opposed ends of the part. Important in the application development of the components by Miyano engineers was the focus on maintaining a constant chipping pattern of material rather than creating stringy swarf to ensure unmanned security of operation. With the tool load monitoring set to 50 per cent, this also provides an insurance against tool failure.

'Due to the nature of the material and by including some diamond tools in the set-up, we can take advantage of the rigidity of the machine and are expecting two years or more of cutting life before they will need changing,' Floyd said. The inclusion of a Sheffield Discovery CMM in the cell provides a 3D measuring overview of the levels of positional tolerances. Here, the machine gantry loader has been programmed to place aside a regular selection of parts in order to verify if any drift in tolerance or out-of-position is detected. Later, the plan is to integrate automatic offset shift from the control system on the Miyano using direct feedback from the CMM. One important element in the Miyano is confirmed by Floyd in that the inclusion of Stealth technology will enable the machine to compensate to any thermal changes.

Using Stealth, the machine has been tailored within the control software to suit the working environment, accommodate the heat from the motors, swarf and coolant temperature, which will help maintain production consistency and predictability - vital when running in unmanned situations on critical workpieces. The ABX-64TH3 is powered by a 15kW, 4000rev/min motor in the main spindle and 7.5kW, 5000rev/min in the second spindle. Each of the two upper turrets have +/-40mm of travel as cross-feed in the Y-axis while the lower turret is able to position to either spindle and create an overlap situation.

The 36 powered tool positions have 2.2kW, 6000rev/min available for use on both front and back position of the component in its single-cycle capability. The maximum bar size capacity of the ABX machine is 64mm or in the case of IMI, 6in chucks are employed on each spindle with the gantry initially feeding an aluminium billet to spindle one. The part is then machined and the component automatically exchanged into spindle two for the cycle to continue after the gantry has removed the part for dipping in the cleaning tank prior to returning the finished part to the magazine.

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