Rotary Positioning Stages / Tables
Subcontractor Exploits High-Speed and 5-Axis Machining to Raise Competitiveness
Share:
Some parts are produced in half the time
An aluminium billet was put on a new Brother TC-22B-O vertical machining centre shortly after it arrived last summer (2010) at the Crediton works of Adaero Precision Components. The finished component came off in 13 minutes, whereas previously it took over twice as long (28 minutes) on one of the subcontractor's older machining centres, which are systematically being replaced.
The part required like-for-like, single-hit, 3-axis milling and drilling on both machines, underlining the raw speed of the Brother. It has a 16,000 rpm spindle, 60 per cent faster than on the other machine, and has commensurately higher cutting feed rates of 20 m/min. Very high speed tapping at 8,000 rpm is another feature.
However, the Brother's ability to take so much time out of the cycle was also down to minimising non-cutting time. 70 m/min rapid traverse in all linear axes contribute significantly in this respect, and so too does the fast automatic tool change (ATC) time, which at 900 milliseconds tool- to-tool including spindle acceleration and deceleration, is described by Adaero's managing director, Andy Dickinson, as amazingly fast.
Since it was installed to raise production capacity for servicing new and existing customers, the TC-22B-O has been retrofitted by Brother's UK agent, Whitehouse Machine Tools, with a 2-axis Nikken table. It sits at one end of the machine table while a conventional workholding arrangement is positioned at the other end. Converting the machining centre into a 5-axis facility was planned at the outset and was a key reason for Adaero choosing the equipment.
Mr Dickinson continued, "The Brother / Nikken combination is programmed as a 5-axis machine.
"It is useful to us that the Brother control is Fanuc-based with a proprietary front end. It means we can run programs from our other Fanuc-controlled machining centres with very little modification."
Adaero's migration of jobs from older technology, 3- and 4-axis machines onto the 5-axis TC-22B-O stems from a desire to reduce the number of set-ups for each job by at least one. Single hit machining is the goal. The results are shorter floor-to-floor times and reduced work-in-progress. Accuracy is also improved, as it is easier to control tolerances and there is less risk of operator error.
So far, more than two dozen components have been moved over to the 5-axis machine. All jobs so far have used the extra two axes to position the parts for 3-axis machining, rather than involving fully interpolative cycles.
Second Brother machining centre installed
In January 2011, another vertical machining centre from Brother was installed at the Crediton factory, this time a 4-axis model with twin automatic pallet change (2APC). Designated TC-32BN QT (quick table), the machine joins several rotary pallet machines on the shop floor as well as a long-bed machining centre that is used for pendulum machining.
The Brother specification includes the same spindle speed, rapids, cutting feed, ATC and tapping performance as the TC-22B-O, plus pallet change of 3.4 seconds, which takes place simultaneously with tool change, speeding the start of the next cutting cycle.
To make the machine as flexible as possible for carrying out several jobs at once, Adaero asked Whitehouse Machine Tools to supply 4th axis rotary indexers for both pallets. Each trunnion-type Nikken indexer has two sides on which multiple workpieces can be fixtured, so in theory four different components could be set up at the same time. Adaero has already produced a family of three different components concurrently.
Even the addition of one extra CNC axis leads to significant savings over 3-axis machining times. In one example, an aluminium correction mounting bracket for an industrial laser manufacturer used to be machined one at a time in two operations in a floor-to-floor time of 6.6 minutes. Production is now completed in a single, 2.75-minute cycle on the TC-32BN QT. This represents a 58 per cent production time saving, albeit not in pure machining, as component handling is factored in.
A second example cited by Mr Dickinson concerned the manufacture of surgeons loupes, bespoke magnifying elements mounted in the lenses of glasses to aid visibility when working on delicate structures. Machined from L168 aluminium, the cycle was previously 3.66 minutes whereas it is now 2.22 minutes. This is more typical of the percentage saving across the range of parts that has been transferred to the TC-32BN so far.
A further advantage is that four loupes can be fixtured at the same time on the two trunnion-mounted Microloc plates on each pallet, whereas parts were individually fixtured before. Surface finish of the machined component is also better on the Brother, reducing the previous requirement to polish out machining lines by hand.
Further flexibility is provided by the use of the Wixroyd Zero-Point quick-change fixture system on all machining centres at Crediton, including the Brothers, so the Chick, Microloc and other workholding devices can be put on and taken off quickly and accurately. The system contributes to shortening idle time between batches, resulting in significantly increased production output since Zero-Point was introduced in the mid 2000s.
About Adaero Precision Components
Despite its name, less than 10 per cent of Adaero's work is in the aerospace industry, although a majority involves machining of aluminium. The company's main business is in the medical and ophthalmic industry, which accounts for 40 per cent of turnover, and the subcontractor is also active in the industrial laser sector. Some plastic and brass are machined, as well as stainless steel for a relatively new customer in the gas detection industry, although that mainly involves turning.
Competition from China, India and former Eastern Bloc countries prompted Adaero to put considerable emphasis some years ago on lean manufacturing, which is now being overseen by newly appointed manufacturing manager at Crediton, Dave Wheeler. Reduction of set-ups and quick changeover when a set-up is needed are key, together with high speed machining, both in and out of cut.
In conclusion, Andy Dickinson commented, "The Brother machines fit well with this philosophy. Both are nimble, highly productive, 30-taper machining centres but nevertheless are still surprisingly heavy and rigid.
"We are so busy now that all our of machines, including the Brothers, are close to capacity, so we have decided to put on a second shift from 5.00 pm to 2.00 am to supplement our 8.00 am to 5.00 pm day shift.
"Having worked hard on our competitiveness, contracts are returning to us from China due to increasing manufacturing costs over there. Some buyers in the UK do not see the point of ordering six months' production in one go, waiting six weeks for it to arrive and risking disappointing their customers if the parts are not right.
"By coming to UK subcontractors like us, they get good prices as well as much closer control over production, especially if designs change suddenly, plus the convenience of kanban or other delivery schedules to suit their needs."
Whitehouse Machine Tools Ltd
Princes Drive, Crackley Industrial Estate
Kenilworth, Warwickshire, CV8 2FD
Tel: 01926 852725. Fax: 01926 850620
E-mail: timw@wmtcnc.com
Web: www.wmtcnc.com
Contact: Tim Whitehouse.
THE RIGHT IMAGE Ltd
PO Box 42, Twickenham, TW1 1BQ
Tel: 020 8891 0603
E-mail: therightimage@aol.com
Contact: Chris Wright.
