Technology in the round

7 min read

Andrew Allcock reviews latest turning technology developments, kicking off with a major development from Hardinge – a new generation of high precision turning centre

Already well known for its precision turning credentials, Hardinge (0116 286 9900) has pushed the envelope farther with its latest effort, the Hardinge Super-Precision T-42 turning centre. The machine, launched by Hardinge Group at IMTS in Chicago this month, claims to set a new benchmark in 'nano' precision machining, achieving an axis repeatability of within 0.76 micron, a roundness figure of 0.25 micron, overall accuracies within 3 microns and a surface finish within 0.15 microns. Chuck size is 150 mm, bar capacity 42 mm and spindle bore 48 mm. Maximum machining capacity is 315 mm by 368 mm long (diameter by length). Image: Hardinge's new benchmark in precision turning, the T-42 The Super-Precision T-42 has been designed for the production of complex components, typically for aerospace, defence, medical and automotive sectors, and to deliver cost and lead time reductions. High on the development agenda was improving consistency and quality by combining operations and, in particular, achieving hard turning and milling in a single cycle. FIRM FOUNDATIONS PAY OFF As Hardinge Machine Tools has found over the years, to achieve sub-micron tolerances and successfully work with super alloy, specialist aluminiums and hardened materials, the base/foundation of the machine sets the standard. This not only applies to initial production of precision parts, but also to the long-term ability to provide consistency from part to part, and the achievement of good and predictable tool life. Image: Under the covers of the new machine A true 45° slant bed machine, the Super-Precision T-42 has a one-piece cast iron base reinforced with Hardinge's HARCRETE polymer composite. Heavy duty linear roller guides help optimise stiffness and rigidity. This design weighs in at six tonnes, absorbs vibration and deformation, and provides a highly stable and rigid platform for extended periods of running. Also, according to trials in America, tool life can be extended by up to 30 per cent over that which can be expected from conventional machine beds. The inclusion of the Hardinge collet-ready, single-piece construction spindle technology adds to the level of precision obtained, as it provides the benefit of high orders of in-built stiffness and damping. Also, the collet-ready spindle enables the cutting tool to be positioned close to the spindle bearings The Super-Precision T-42 features modular build to enable it to be pre-configured to suit the application. The machine can be specified from a simple 2-axis version with tailstock, right up to a dedicated multi-axis variant with two spindles, C and Y axes, and up to 16 driven tools, having speeds up to 16,000 rpm. Special toolholders, in conjunction with the half-axis turret indexing, provide 32 tool positions and auto unloading ensures components are not damaged as they exit the machine. A detached stand houses coolant pumps, filtration, the machine power case and hydraulics. As a result, heat and vibration are prevented from migrating into the primary metalcutting area. Oversize, 32 mm diameter ballscrews are used to drive the X-axis at up to 24 m/min, Z-axis is 30.5 m/min and Y-axis at 6 m/min. Subspindle rapid traverse is 30.5 m/min and high precision linear glass scales from Heidenhain are fitted as standard. The 16-position all-driven turret is carried on Hardinge's own BMT-45 live tooling top plate, having a tenon drive, with special toolholders designed to accept modular add-on tool blocks for live and static tooling. Live toolholders provide superior levels of runout, within 3 micron, claimed to be a "best-in-class" performance. This capability not only equalises tooth loading on the cutter to maximise cutting life, but also enhances the ability to maintain an excellent and consistent surface finish. The belt drive to rotating tools is via a 3.7 kW motor delivering 33 Nm of torque. Standard speed is 8,000 rpm, with 16,000 rpm available. Turret index time is 1 sec (clamp to clamp) and 80 bar high pressure through-the-tool coolant is available. A range of special live toolholders is offered for the BMT-45 system that provides cross-working with internal or external coolant, 90° approach, double endworking and adjustable angular approach between ± 90°. By incorporating an independent Y-axis with 84 mm (+50 mm, -35 mm) travel, Hardinge says its design offers ultra-fine adjustment for pin-point tool alignment, another factor helping to maintain machining consistency. With this design, offset error is far lower than that achieved by machines with the more conventional 'wedge' design, says the company. Both main and subspindles are identical, having wrap-around high voltage motors delivering 11 kW, 101 Nm of torque and 6,000 rpm. Offering fast acceleration and deceleration, they are cooled via an oil jacket, with a chiller enhancing thermal stability. Image: Hard turning is a Hardinge speciality, which this machine will clearly satisfy Hardinge has developed its own precision part removal system to work with the subspindle and prevent component marking or damage from handling. The parts gripper includes nylon inserts than can be machined to enable a 'soft' removal and placement onto the integrated parts conveyor. Parts are then moved to the left side of the machine where they can be manually unloaded or linked to a robot or pick and place unit to enable unattended running with the barfeed option. LUCKY FOR SOME – 13 From newest product launches to applications of the very latest existing technology and, at IMI Components, single cycle turn-milling on a 13-axis Miyano ABX-64THY3 (01384 489500) has replaced four separate CNC turning and milling operations on a range of smaller components destined for the energy and power generation industry. And having installed it, the company found itself on the threshold of significant new orders for components destined for both the UK and overseas. During initial commissioning, reported in July, the recently installed £350,000 ABX-64THY3 turn-milling cell with fully integrated gantry loader had already reduced total machining times on four critical valves. Indeed, such is the level of increased productivity that, for one particular component, three can now be produced complete in the previous floor-to-floor total time for one. As an example of the level of complexity involved, one of the parts has some 100 dimensions. Using 17 driven tools, the Miyano is able to carry out the cycle in just one operation – well within the tool-carrying capacity of the ABX's 36 driven positions. "The turnkey installation by Miyano Machinery UK has already achieved so much, apart from significantly reducing production times," reports Adrian Floyd, engineering manager "For example, it can run for up to 19 hours in an unmanned single cycle operation, against our previous methods that were operator-dependent, with the added lead time restrictions of part-buffering between the different machines."The Miyano has also saved most of the manual deburring required by combining the process in cycle. Setting times have also been significantly reduced from half a day to around 30 minutes 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. Says Mr Floyd: "We now have even greater flexibility to cater for new components as they are introduced and our latest methods will significantly contribute to our year-on-year cost down demands." Image: The turnkey Miyano installation supports extended unmanned running WIDE RANGE OF MATERIAL Materials processed at IMI Components vary from magnesium alloys through a wide range of stainless steels and other exotic alloys to aluminium. With market demand escalating for high precision, high integrity products, the levels of production are set to rise farther. The selection of the 64 mm bar capacity Miyano ABX-64 TH3 was made against three other suppliers 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 19 minutes to produce, using the original four-operation method that was reduced to just six minutes on the Miyano. Explains Mr Floyd: "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." 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, which is always under observation by the customer's quality audit team. 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' 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. Image: There are plenty of tools in the work envelope to support complex machining in a single cycle General tolerances on the aluminium components are within 0.02 mm, with certain specific dimensions maintained within 0.01 mm. As sealing faces and 'O' ring grooves are required, surface finish below 0.8 RA is high on the requirement list and these are generally maintained to within 0.5 RA by the machine and tooling set-up. 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 opposing ends of the part. CONSTANT CHIP PATTERN 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," Mr Floyd explains. 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. See also the Machinery feature about Doosan's new 36-machine Puma range (August issue, page 20. 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