New - CNC Machine Classifieds
Click Here to get free $20 instant credit to list your CNC
Click Here to get free $20 instant credit to list your CNC
Best CNC Resources:
Precise travelling gantry miller has 99.9% uptime
|
|
A CNC travelling gantry universal milling machine has allowed a precision engineering firm to achieve sub-10 micron precision and record a 99.9% up time over 15 months. Brownhills, UK-based Forth Engineering machines large and heavy components for a wide range of industries and said that what it had found remarkable was achieving better-than-grinding tolerances of sub-10 micron flatness and straightness on a machine tool with 18 tonnes capacity and achieving 99.9% availability Forth Engineering serves scientific research establishments, which need to achieve quite exceptional precision To meet the requirement, Forth is using an AsquithButler Starmill 280 travelling gantry universal milling machine. Forth's managing director, Mike Hedley, said: "The AsquithButler machine allows us to explore the full range of metal cutting and provides us with the competitive edge". * Machine tool requirements - the requirements for the machine was a high degree of accuracy, high reliability, minimal maintenance, minimal use of energy resources, and no infringement of health and safety considerations. The Starmill 280 gives far greater accuracies in flatness and straightness than has previously been possible with travelling gantry machines, said AsquithButler. It is a high performance, large capacity machine offering a high metal removal rate when rough milling as well as fast, accurate finishing operations. The machine's modular construction allows economical customisation. The provision of the extremely accurate rotating servo controlled ram (C-axis) gives great versatility to the machine. Using an appropriate attachment, any of which have automatic load/unload facilities, five-sides machining of a component in one set up is possible. Five-sides machining eliminates time-consuming re-setting and allows the best manufacturing practices to be employed. In addition, unusual machining operations are possible, for instance roughing of large bores by helical interpolation using a face mill in the right angle head. Milling of inaccessible faces is possible using contouring with a planetary milling attachment. * machine tool design - based on the proven design of the Starcut machine, design engineers working at AsquithButler's manufacturing headquarters in Brighouse (West Yorkshire) undertook a total re-evaluation of the Starcut performance to achieve the outstanding performance of the Starmill machine. Using the finite element analysis (FEA) system, the existing machine tool beam design was modelled using the known deflections. New beam designs were modelled using different types and arrangements of the ribbing and different plate positions to achieve the enhanced torsional stiffness. Using the software to simulate the load, adjustments were made until the optimum torsional stiffness was achieved. The new design of beam is 54% stiffer than the previous design, uses less material and additionally is easier to manufacture. * Machine bed - AsquithButler also redesigned the bed, also using FEA, to be manufactured from steel rather than cast iron. The idea was to eliminate the wave created by the travel of the gantry. Any deflection in the transverse bed would have a resultant effect on the surface flatness results achievable. * Machining head slide - the head slide was redesigned as was the ram bore which has the advantage of two quill clamps and an epoxy resin Moglice bearing liner. The attachment clamping force was increased to 12 tonf (120kN) from the existing 8 tonf (80kN) to give much enhanced rigidity. Diameter of the head was increased to dia 280mm from 250mm, giving greater bending and torsional stiffness. Power was increased to 60kW from the previous 45kW and maximum spindle speed increased from 2000 to 4500 rev/min. The Starmill series begins at X-axis of 3000mm upwards, Y-axis of 2500mm upwards and Z-axis of 1000mm or 1250mm. Hedley said "The Starmill 280 has allowed us to achieve previously unattainable precision from a gantry milling machine even on very large, heavy components. In addition to sub-10 micron precision, the Starmill delivers 99.9% up time (as measured over fifteen months), a figure unheard of in almost any sphere of manufacturing". He added: "Cycle times are lower than on equivalent machines because of the machine's inherent rigidity, permitting higher feed rates for roughing operations, so we are experiencing a tremendous improvements in productivity as well as reducing costs by eliminating the grinding operation. The results from the AsquithButler are very impressive.". http://www.manufacturingtalk.com/news/agj/agj103.html |
For more information visit CNC Gantry category