Read how this sub-contractor reduced machining time from 60 minutes to 8 minutes by switching from 3-axis to 5-axis.
The installation of two new Hurco machining centres has allowed Lancashire subcontractor, A&G Precision, to attract more work and produce components more efficiently in fewer set-ups.
The company is a leading producer of complex components used in key military and civil aircraft programmes. It is also active in other sectors, principally defence, marine, petrochemical, motorsport, rail and pharmaceutical engineering.In addition to batch production of high-precision components, A&G provides a range of additional services including prototyping, sub-assembly manufacture and reverse engineering.
One long-running job, an aluminium part, used to be produced in three set-ups on a 3- axis machining centre at the subcontractor’s Poulton-le-Fylde works. The complexity of the component necessitated a lot of step-down profile generation using a ball-nose milling cutter, so overall machining time was around one hour. The same part has been re-programmed and is now completed in a single, eight-minute cycle on the company’s first 5-axis machining centre, a Hurco VMX42SR installed in mid 2008. Not only is there a large saving in machining time, but two set-ups are eliminated as well, considerably reducing the cost of manufacture.
Another component to benefit from one-hit, 5-axis, prismatic machining, in this case after a turning operation, is a steel eye bolt that previously required three separate operations on a 3-axis machining centre. The bolt is of relatively simple design, so there is little difference in overall machining time, but two set-ups are saved.
Michael Pinder, a director of A&G, commented, “Generally, we do not reprogram existing components to run on the 5-axis Hurco unless they are ongoing jobs and savings are significant. However, the availability of the machine has changed the way we approach the machining of new components.“In the first year after we started operating the VMX42SR, we produced 73 different parts on it in titanium, aluminium and various steels including stainless. A proportion of those contracts we previously would not have won, as the prices for producing them conventionally would not have been competitive.” He went on to explain that the machine was not purchased in anticipation of receiving new contract, but was bought on spec after a number of customers repeatedly offered A&G 5-axis work that it could not fulfil.
Several machines were shortlisted and reviewed at MACH 2008. One reason for choosing the Hurco was the powerful 36 kW / 12,000 rpm spindle. Another was the easy-to-use Ultimax twin-screen control, which includes a special version of the proprietary WinMax software specifically designed to simplify programming of complex, multi-sided parts.
A further significant factor in the purchasing decision was the swivelling head design with horizontal rotary table, which Mr Pinder says offers a larger working envelope than the more usual configurations based on a vertical spindle and two-axis, trunnion-mounted table. In some instances, components are set up in the space at the side of the rotary table on the VMX42SR for second-operation work to be carried out.
At the end of 2008, A&G installed a second Hurco machining centre, this time a 3-axis VMX60t with two-metre capacity in X. It was in response to an approach from an existing customer that wanted some ribs machined, knowing that the subcontractor had the necessary ISO 9001:2000 and AS9100 approvals.
The rib contract was limited, but Mr Pinder found that once the machine was installed, its existence on the shop floor created work as soon as customers heard that the facility was available. A couple of dozen different jobs approaching the machine’s capacity have already been won as a result. Additionally, several smaller jobs can be fixtured in separate vices on the table to meet demand when the smaller machines are working flat out, so very little time is wasted.
Programming of the Hurco machines is carried out either at a PC in the office running WinMax software or on the shop floor at the Ultimax control. In the case of the 5-axis machine, most programming is off-line, as components tend to be complex. Customers supply mainly Catia models that are converted to STEP files. Open Mind’s hyperMILL CAM software converts these into efficient cutter paths that are post-processed and downloaded to the Ultimax control.
The reverse is true of program preparation for the VMX60t. So far, most has been done at the machine, owing to the simpler nature of the work, except for the ribs. Some of the shop floor staff had already used Ultimax at previous companies, so were familiar with its strengths.
Continued Mr Pinder, “The conversational control is the easiest to use of all our CNC systems and is practically foolproof. The operator simply follows instructions on the touch screen, working his way down, filling in the boxes.
“At any point, pressing the ‘draw’ button produces a component graphic on the second screen that shows exactly where he has reached in the program. My brother, Jordan, who is an apprentice here, learnt the system very quickly and is now able to program quite complicated jobs.“We do a lot of prototype work here as well as one- and two-offs. Typical batch size is 10-off. So speed of programming is essential to keep production costs down.”
A&G’s purchase of the two Hurco machines is part of an expansion programme over the past 18 months that has seen more than £1 million spent on plant acquisition and buying, extending and refurbishing its previously rented Poulton-le-Fylde premises, a Grade 2-listed corn mill.
The 38-strong, £3 million-turnover business has become an integral part of the North West of England’s regional aerospace supply chain. It is still a family-owned company, established in 1989 by the current managing director, Arthur Pinder, and another son, Scott.