Turnover doubles in six years despite headcount increasing by only 14%
Automated machining cells are the route to high production output in a small footprint with minimum operator attendance and in hot pursuit of this goal is Alford, Lincolnshire-based Drury Precision Engineering. The firm carries out a small amount of subcontract machining, its main business being the production of its own globally-recognised motorcycle accessories for road and racing bikes, which it markets under the Evotech Performance (www.evotech- performance) brand name.
Between March 2020 and February 2021, the company installed three automated, Japanese-built Brother machining centres from sole UK and Ireland agent Whitehouse Machine Tools, Kenilworth (www.wmtcnc.com). Supplied with two of the machines were the same manufacturer’s Feedio vision-based, robotic systems for component load/ unload, while a System 3R WorkPartner pallet storage and handling system was integrated with the other machining centre.
In the area of turn-milling, Drury has long used a bar-fed, single-turret lathe and there has been a succession of different makes on the shop floor. This lathe has been swapped for a much more efficient Biglia B438-Y2 twin-spindle turn-mill centre with two Y-axis turrets, also supplied by Whitehouse Machine Tools, sole agent in the same markets for the Italian turning machine manufacturer.
Additionally, specifically for producing motorcycle bobbin head bolts up to 200 mm long from stainless steel bar, Drury bought from a different source its first sliding-head, bar-fed lathe in January 2019. The machine manufactures the bolts to a much higher quality than can be bought in from external suppliers.
“It is not always just about the machine, but perhaps even more importantly about after-sales backup. Since 2015 Whitehouse has provided us with exemplary service.”
Chris Vines, Director, Drury Precision Engineering
High-efficiency prismatic machining
The company decided in early 2015 to transition from conventional 40-taper machining centres to 30-taper models to raise production efficiency to meet rapidly increasing demand for its Evotech products, which are mainly produced by taking light cuts from aluminium billets of rectangular cross section.
First to be delivered was a Brother Speedio R450X1 twin-pallet, 22-tool, 30-taper machine for 3-axis work. Output from the machine equalled that of two 40-taper machining centres. A typical crash protector, for example, took 20 minutes to machine instead of 40 minutes. The dramatic improvement was due to minimisation of idle times through linear rapids, tool change and pallet change all taking place simultaneously coupled with fast ATC and APC, a 16,000 rpm spindle and 200-block look-ahead in the Brother control.
The tool change in particular is so fast, delivering a chip-to-chip time of typically two seconds, that Drury has not only boosted production output but additionally been able to allow its designers more flexibility in SolidWorks. A couple of extra tools are introduced into a cycle, for instance, to add cosmetic features with very little time penalty. To do this on a 40-taper VMC would have unacceptably impacted productivity.
The doubling of throughput and the extra design flexibility were a revelation for Drury. Unsurprisingly there are no longer any 40-taper machines on site and the R450X1 was followed by four further 30-taper Speedios. The company’s first R650X1 arrived soon after, equipped with a Nikken 2-axis table to provide 5-axis machining capability.
Next to be delivered was another 3-axis R450X2, a 3-axis R650X1 and at the end of 2019, a 5-axis S700X1 with Nikken table to provide a larger working volume. This machine was originally to have been reserved for prototyping but was quickly co-opted into production due to ever increasing demand. All five machines are positioned in a line on the shop floor and are manually operated.
Automated prismatic machining
In early 2020 the three engineers who jointly run the company, Dan Rack, Chris Vines and Nick Cooper, recognised that prismatic machining capacity needed to be increased further, but space on the shop floor was tight. So in March that year, having had good experience with the other Brother machines, they purchased a Speedio M140X2, another 5-axis machine, and decided to automate it with a Feedio component storage and robotic handling system developed jointly by Brother and ABB.
Mr Vines said, “It is not always just about the machine, but perhaps even more importantly about service backup. Since 2015 Whitehouse has provided exemplary service and are always on site within 24 hours on the rare occasion that something goes wrong. We saw no reason to gamble on involving another company in the supply of an automated cell.”
The Feedio is designed specifically for Brother machines, rather than being a generic solution provided by a third party, although a couple of other potential automation suppliers were briefly considered at the outset. The unit communicates with the machining centre control via a Profibus interface and a smart ABB teach pendant incorporating a customised Speedio page is provided for programming the 6-axis robot.
The Feedio version supplied with this machine at the outset had a pair of standard, two-metre long conveyors, which are positioned one above the other. However, Drury soon realised that insufficient components could be accommodated to last for the whole of the ghost shift. So to avoid losing night-time hours, the company asked Whitehouse
to extend the conveyors to four metres in a simple exercise that took less than a day. The extra capacity also had the effect of allowing the entire weekend to be utilised for production. In fact when machining certain parts, up to three days’ uninterrupted production can be obtained without manual intervention.
A camera and PC built into the Feedio unit allow the robot to detect where on the upper input conveyor billets have been placed. After machining, components are returned to the output conveyor below. This particular cell has been configured for Op 1 work on parts weighing up to 10 kg in batches of from 100- to 2,000-off, completion of Op 2 being carried out on the manually-loaded Speedios. To ensure system reliability, the M140X2 has been equipped with two Blum probes, one to check the tool and the other to confirm correct loading of each billet before machining commences.
Careful attention is paid at the component design stage to maximise Op 1 time and thereby minimise the amount of Op 2 metal cutting. In one instance Mr Cooper, who manages the machining department at Alford, achieved a 9.5-minute Op 1 and a 22-second Op 2. So far, around 50 different component types have been produced in the cell within the machine’s working volume of 200 x 440 x 305 mm.
Nearly one year later the two other automated Speedio cells were delivered. One was a larger, 3-axis S700X2 with a 700 x 400 x 300 mm working volume, a Schunk pneumatic centric vice and a four- metre Feedio system capable of handling heavier components up to 20 kg, again for Op 1 work. The other was another 5-axis M140X2 but this time fitted with a System 3R WorkPartner 108-pallet storage and handling system.
The latter, supplied as a turnkey installation by Whitehouse, is a closed cell whose purchase was specifically intended to target Op 2 inefficiencies within the factory. Six motorbike parts required in left and right hand versions were identified as ideal for production in this cell. They are set up permanently so that both Op 1 and Op 2 are completed automatically, unattended for up to 20 hours.
Mr Vines added that automated machining of aluminium requires special attention to be paid to management of the swarf produced, which is approximately 10 times the volume of the solid. When the first Speedio was installed, Whitehouse recommended the installation of a briquetting system for swarf compaction, which went on to serve the subsequently installed machining centres. A second such compactor was added with the arrival of the Brother / System 3R cell.
On the topic of swarf management, Mr Cooper pointed out that the M140X2s are equipped with a 2,000 rpm table capable of turning operations within a prismatic machining cycle. Although this facility has not been used yet for metal cutting, it has proved useful for spinning components after machining to remove chips, first with coolant to wash down and then without to dry the parts before extraction by the Feedio or WorkPartner.
Extra turret delivers three-fold decrease in machining times
The former turning machine at Drury, which dated back to 2016, was capable of turning components up to 65 mm diameter from bar, However, its single turret meant that productivity was low and the machine was inefficient at producing small turned parts. So the decision was taken to concentrate on in-house turn-milling of sub-38 mm diameter components, which accounts for around one-third of throughput, and subcontract out the remainder of turned parts production. It is important for the manufacturer to retain some turning capability for the prototyping phase of new products so that designs can be tweaked early on, assembly fits checked and at least a first production run completed.
Mr Rack, who heads the turning section explained, “We knew we wanted a twin- turret machine to raise productivity by being able to carry out Op1 at the main spindle and simultaneously complete Op 2 at the counter spindle.
“We considered two alternatives but decided in favour of the Biglia B438-Y2 due to the high level of service we receive from Whitehouse on the prismatic machining side. The supplier does not put any limit on future back-up, whether or not it involves an engineer’s visit, even though it is free of charge.
“It is especially welcome considering this is our first twin-turret lathe, on which it is possible to have three tools in simultaneously. Although we have not done this to date, it is reassuring to know help will be there when it is needed.”
Other points in favour of the Biglia were the ready availability of a post processor and the machine’s ability in its standard configuration to extract up to 150 mm long components without the need for special handling equipment, which would have introduced delay at the end of some cycles.
The machine is the most recent to be installed by Whitehouse at the Alford factory. It has proved to be highly efficient at producing spacers for bar ends and crash protection brackets, for example, in a cycle time of around one minute compared with the three minutes previously needed.
Mr Rack advised that every turned and turn-milled part seems to be produced in around one-third of the time it took before on the single-turret lathe. The manufacturer’s EDGECAM system helps to balance operations at the main and counter spindles, with the aim of carrying out 60 percent of the cycle during Op 1 so that the counter spindle can complete the other 40 percent plus part extraction in a similar time.
While some components do not require any milling or drilling, around half of the lathe’s throughput involves some driven tool work. Occasionally a part is produced without any turning at all, such as a component required for a satnav system. A lot of use is made of pinch turning and milling using both turrets at either spindle, as well as of deburring the reverse of components to avoid another operation.
Around 25 percent of production on the Biglia lathe is from 303 and 316 stainless steel bar, with the remainder from free cutting 6026 hollow aluminium extrusion up to 37 mm diameter, which avoids the need for gun drilling long tubular components.
Although turning in Drury’s factory has always been automated by a bar feeder, the inception of automatic loading and unloading of prismatic machining plant has seen a step-change in production efficiency. Six years ago the company employed 22 staff, yet today with only three extra operators and in the same shop floor area, turnover has more than doubled.
Mr Vines likens the current factory environment to The Elves and The Shoemaker fairy tales written by the Brothers Grimm. Production continues throughout the night with no effort by Drury’s staff and the next morning there are a lot of finish-machined components ready to be powder coated, assembled or packaged for sale.