Robots are emerging as a key machine shop technology, bringing with them benefits such as reduced cycle times and fewer labour costs. Machinery reports
Image: DCMT's automated injector valve solution for Delphi uses Stäubli robots
The engineering sector is the world's biggest user of industrial robot technology. However, think of robots and operations such as welding, assembly, painting and inspection spring to mind: perhaps not so obvious is machine tool tending.
For whatever reason, investment in multi-axis robots has tended to lag behind that of new machine tools. However, the use of high precision industrial robots integrated with machine tools can offer benefits such as lower labour costs, reduced cycle times, lower floor space requirements and improvements in component quality.
One application where the use of multi-axis robots has brought significant advantages is in the machining of diesel injector valves at Delphi Diesel Systems. Douglas Curtis Machine Tools (01206 230032) was commissioned by Delphi to improve the production rates for these components at the UK factory in Sudbury, as well as at La Rochelle in France. The required operation was to extract part-machined components from the input pallet, precision gauge them (to sub-micron levels), present to a Supfina face grinding machine, unload, deburr and then re-palletise, all within the grinding cycle time.
When confronted with the challenge, DCMT decided to investigate the options of either adapting pick-and-place automation systems or the use of multi-axis robots. The application of three Stäubli RX60 robots (two at Sudbury) provided a less complex solution, requiring only 50 per cent of the floor space of the pick-and-place system, coupled with improvements in cycles times, quality levels, repeatability and reliability that were just not achievable with any other system. The Stäubli (01952 671917) robots can also readily incorporate changes in the operational sequence in response to design changes and product developments at Delphi.
Such is the demand for gains witnessed by companies such as Delphi Diesel that many machine tool builders, particularly lathe manufacturers, are beginning to introduce robots into their model specifications.
A case in point is multi-spindle lathe manufacturer Index, which has added Stäubli 6-axis robots into its latest models, contributing significantly to their performance and flexibility, especially for complex chucked components. Index's MS52C lathe can be converted into an automatic chucking lathe by the addition of a Stäubli RX60 robot to load blanks for machining and remove finished components, while a RX90 robot can also be added to the larger MS52C.
The open-front design of both machines, which are available in the UK from Geo Kingsbury (023 9258 0371), allows the robot to be flange mounted on the workspace cover. A dual-gripper removes blanks from storage in front of the machine before they are brought to the working spindle and exchanged for finished parts that are then correctly orientated and placed in the exit storage, also at the front of the machine.
According to Fastems (01322 282276), virtually any make of CNC turning machine can be transformed into an unmanned production centre by retrofitting one of its RPC-16G robotic cells, which automates loading and unloading of workpieces into and out of the machine spindle. Each cell is purpose-built and comes complete with workpiece grippers and a cylinder kit for automating the opening and closing of the lathe door.
Biglia is also adopting automation on its B745 Y3 and B765 Y3 14-axis CNC lathes. Available from Whitehouse Machine Tools (01926 852725), both machines feature an integrated CNC unloading arm that removes finished components from either the main or counters spindle, provided that the parts have been machined from bar.
The demand for automation is forcing many machine tool and robot manufacturers to work together to develop simple-to-use solutions. ABB Robotics (01908 350300) and Okuma (UK agent NCMT – 020 8398 4277), for instance, have together developed an ABB standard interface for Okuma machine tools. Providing operators with a single operating environment, the interface saves production time and reduces operator training.
Developed on the open PC platform used by Okuma, the interface consists of two parts: the graphical interface and the extendable robot controller program libraries and configuration files, which allows for the creation of code for the robot tending of various machines, without the need for complex routines.
Image: Delphi wanted to improve production rates for its diesel injectors at sites in the UK and France
It is generally acknowledged that machine loading and unloading is a more complex application than basic material handling, as the robot needs to provide both manipulative and transport capabilities. One of the chief problems for robotic arms is that machine tool working areas are often restricted by the presence of hardware such as chucks, vices, spindles, toolposts and coolant nozzles. To counter such obstacles, Motoman (01295 272755) has introduced its IA20 7-axis robot, nicknamed 'the snake', due to its ability to access restricted spaces.
The robot was shown for the first time last year at the MACH exhibition in Birmingham, where it could be seen automatically loading and unloading a Hardinge XV710 vertical machining centre (0116 286 9900). The robot loaded a hydraulic fitting into the first collet of a Hardinge four-station indexing unit. After the first 4-axis machining operation, the part was transferred to the three other collets for additional operations before being unloaded.
Other recently introduced robot arm solutions for machine tool tending operations include the IRB 4600 from ABB, which offers twice the working range, half the weight and a 25 per cent better cycle time than its predecessor; and the Comau Smart M1 (0151 486 0668), which features normal or extended forearm, two different wrist designs and the possibility of overhead assembly.
Manufacturers that venture down the robot route rarely turn back, finding the return on investment and ongoing advantages too good to ignore. Just one example is Coventry-based King Automotive Systems. Six years ago, the company installed its first Fanuc robot (024 7663 9669), which loaded castings into a brake disc manufacturing cell. The project saved 50 per cent of operators over three shifts, and King has since installed a total of 11 Fanuc robots, with the latest lines producing knuckle joints for BMW's Mini and for the Land Rover Freelander.
Robots as machine tools
Image: Biglia's lathe with integral robot arm Perhaps the next step-change in robotic application within machine shop environments is the use of robot arms to actually cut metal by holding and manipulating a spindle loaded with a cutting tool.
If it sounds futuristic, then think again, because it is already happening. Kuka (0121 585 0800), for instance, exhibited one of its KR100 HA robots at last year's IMTS show in Chicago, performing operations such as milling, routing and deburring, all made possible by the applications of its proprietary CAMROB software.
Delcam (0121 766 5544) is also exploring this area and has co-operated with Kuka to introduce easy-to-use routines within its PowerMill CAM software that support part machining by robot. "The main applications are in pattern-making and trimming and drilling of composite components," says Peter Dickin, Delcam's marketing manager. "However, the technology can be used in any area where softer materials need to be machined to accuracies of tenths of a millimetre. While this does not match the tolerances possible with a machine tool, it can often be more than adequate for components that might be several metres in length."
Motoman (01295 272755) also says flexible robots can replace CNC machines for the machining of complex surfaces. Its TruPath robot controller drives a Motoman robot directly from CNC-generated CAM toolpaths, with no conversion from machine G-code or point-to-point robot teaching required. Programming is fast and easy, using an interface that is familiar to machinists, says Motoman. Designed for path following, versus point-to-point movement, the TruPath controller provides positional accuracy of ±0.25 mm.
First published in Machinery June 2009