The launch by Avery Weigh-Tronix of a new range of on-board weighing products based on digital load cells, designed to fit to the axles of commercial vehicles to prevent them being overloaded, prompted a comprehensive review of the prismatic metalcutting equipment in use at the company’s Smethwick factory.
The result has been the appearance on the shop floor during 2008 of three vertical machining centres from Hurco Europe, each fitted with the manufacturer’s proprietary, conversational control system. Avery calculates that the machines will have paid for themselves in less than a year.
Said Paul Bates, Production Engineering Manager, “We are ramping up production of the digital underbody weighing systems to 70 per month by the first quarter of 2009, and there are between four and six load cells per system each requiring a tough EN19T steel body to be machined.
“In addition, we have to machine the aluminium bodies of the in-cab indicators, plus there are even newer weighing systems on the way for tipper and skip lorries.”
The consequent sharp increase in prismatic metalcutting meant that Avery had to replace some of its older machining centres. Either they were not big enough to produce the new components, or they were too slow in terms of the feeds and speeds to achieve the required production levels. One machine was of the right size and had a high-speed spindle, but the torque was not sufficient to mill EN19T.
Continued Mr Bates, “Three years ago we had 10 machining centres on site with a variety of CNC systems – Fanuc, Heidenhain and in a couple of instances, the manufacturer’s own control. “However, we have almost lost the G- and M-code skills needed to program these machines, added to which batch sizes have become smaller – typically 30 to 60 for larger components rising to 120-off for smaller parts. So we need to be able to program and change over machines faster.
“Due to our lack of conventional programming expertise, it took a long time to write the programs and they tended not to result in cutting cycles as efficient as they should have been. Combined with the slowness of some of our older equipment, it had the effect of limiting production output.”
He went on to explain that with the Max conversational control on the Hurco machining centres, programming is at least twice as fast and the resulting cycles are optimal. Picking three components at random, not from the on-board weighing project, he said that their machining times on the Hurco VMX30, VM2 and VM1, compared with those on the machines formerly used, were down from 6.75 to 2 minutes, 8 to 4 minutes and 19 to 10 minutes.
Similar savings are achieved when machining the metric and Imperial, long and short versions of the new on-board weighing elements. These are mainly produced on the VMX30, as it is equipped with a Hurco 4th-axis indexing unit that allows access to three sides of the component, enabling Op2 to be completed in one hit. For Op 1, which involves machining on one side only, a steel billet is clamped in MicroLoc vices on the table in front of the indexer.
Each time the door opens, a finished component is removed. Total cycle times are 38 minutes for a short element and 48 minutes for the long version. Part of the Hurco service included advice on the best indexable-insert and solid carbide tooling to use, which is partly responsible for the fast cycle times being achieved at Smethwick, not only on the Hurco machines but right across the shop floor.
Looking at the bottom line, Avery is making enormous savings. One component that the company was previously unable to machine used to cost £92.50 to have made outside, whereas in-house production cost is now £20.00. A large amount of work for the new on-board weighing product range as well as 20 or so other parts, all of which were formerly subcontracted, are now produced on the Hurco machining centres.
Investment in the three machines and tooling was just £102,000, as the VM1 was acquired from the previous owner in part exchange for another machine at Smethwick. Mr Bates’ calculations indicate a saving in the first year of £111,000 through improved in-house productivity and reduced spend on subcontract services. Therefore a six-figure saving will result for every additional year that the Hurco machines are in service.
Tolerances on the steel weighing elements and aluminium indicator bodies are ± 0.15 mm and ± 0.025 mm respectively, so when it came to choosing the new machines, three makes of mid-range machining centre with conversational programming capability were researched.
Hurco machines were selected due to their smaller footprint for the working envelope, heavier duty construction and most particularly, for the ease of use of the Max control. Six Avery staff have been trained to write programs on the shop floor using the touch-screen navigation, drop-down menus, question and answer routines and scalable colour graphics, without recourse to any conventional programming methods. www.averyweigh-tronix.com