Andover-based MRT Castings, which has long used robotic systems in its aluminium diecasting foundry, has started to introduce automation in its machine shop after the installation of a Japanese-built Brother Speedio M140X2 five-axis mill-turn cell; this is fed automatically with raw material by an interlinked Feedio robotic-handling system (from the same manufacturer).
The turn-key cell, the first of its type to be installed in the UK, was supplied in April 2019 by the Kenilworth-based sole sales and service agent Whitehouse Machine Tools Ltd (
www.wmtcnc.com).
At MRT Castings (
www.mrt-castings.co.uk), one-hit machining is applied to keep production costs down and remain competitive on world markets, as well as to avoid tolerance build-up and hence to maximise component accuracy.
A user of Brother 30-taper four-axis machining centres since the early 1990s, the company now operates 20 of these machines, half of which are equipped with a pallet changer.
In addition, there are three twin-spindle CNC lathes with driven tooling on the shopfloor.
MRT’s managing director, Phil Rawnson, said: “Our unwavering pursuit of single set-up production means that we sometimes find ourselves processing parts on our lathes that entail only one-third turning, with the remainder of the cycle taken up by prismatic machining using live tools in the turret.
“This is an inefficient method of milling and drilling, as the rotational speed and power of the limited number of tools in a lathe are considerably lower than those of the spindle on a machining centre, which also has the benefit of access to more tools.
“We decided to invest in a mill-turn machine and identified the five-axis Brother M140X2 as ideal for our needs.
“It has a powerful 16,000 rev/min face-and-taper-contact spindle and a 22-tool magazine — plus a 2,000rev/min turning table with a 55Nm direct-drive.
“Furthermore, when not performing a turning function, the combined C-axis table and A-axis trunnion can be used to position a component in the two rotary axes for 3+2 prismatic machining — as needed for most of our components.”
Maximising potential
To ‘leverage’ the high-productivity potential of the M140X2, MRT Castings’ plan is for any rotational part that requires a majority of milling and drilling in its cutting cycle — whether machined from a casting, billet or bar — to be put onto the five-axis machine.
The Feedio system, which is equipped with a six-axis ABB robot, can handle billets up to 80mm in diameter (or aluminium castings up to 120mm in diameter) and ‘deliver’ them to a hydraulic chuck on the machine table.
A vision system and a built-in PC allow the robot to detect where on the upper input conveyor of the Feedio the raw material has been placed, so the billets or castings do not have to be aligned on a grid or in a tray.
After machining, components are returned to an output conveyor that (to minimise the footprint) is positioned below the input one rather than to the side.
Mr Rawnson added: “Until recently, we operated a day shift with a few hours of overtime in the early morning and evening.
“The new Brother cell has added to this capacity by allowing us to run ‘lights out’ for up to 8hr, depending on component size and cycle times — and unattended during the day.”
The first contract to be fulfilled in the automated cell was a family of aluminium bodies for a range of LED light fittings.
Prototypes were produced on twin-spindle lathes with live tooling, but as only around 30% of the machining is rotational, the parts were better suited to production on the M140X2 mill-turn machine.
The cycle time was almost halved (from 15 to 8min), thanks to the speed and power of the milling spindle (and its rapid acceleration/deceleration), tool change in less than 1sec, up to 30m/min cutting feed rate and 50m/min rapids.
Considering automation
The production team at MRT had for some time been looking at different possibilities for automating its Brother machining centres to increase the efficiency of producing parts in batches of typically 500 to 1,000-off.
However, Mr Rawnson says such medium-size volumes do not lend themselves readily to automated solutions, which often require the use of costly and dedicated hydraulic clamping fixtures.
However, he points out that machines like the M140X2 have a hydraulic chuck and therefore the work-holding function already in place — and with no extra fixtures needed, they are the ideal machine type on which to trial automation.
To assist in finding the best robotic-handling configuration to go with such a machine, MRT enlisted the help of the Manufacturing Technology Centre in Coventry.
After researching the market (towards the end of 2017), its advisers concluded that a conveyor system and a teach-in-programmed vision-enabled six-axis robot with interchangeable 3-D printed grippers would best suit the types of components produced and the machines in use at MRT Castings.
Coincidentally, that was just when Brother launched its Feedio system at
EMO 2017 in Hanover.
Mr Rawnson said: “This system was a perfect fit for our needs, which was to acquire a standard, compact and entry-level cell that does not need complex robot programming or workpiece trays — delivered and commissioned by a single-source supplier, in this case Whitehouse Machine Tools.
“Feedio can also be retrofitted to all our Brother machining centres, both non-APC and twin-pallet types, allowing us to reduce operator attendance and maximise production hours during the day.
“Quality is also enhanced, as workpiece loading is more consistent.
“In addition, we can extend our single day shift by taking advantage of ‘lights out’ running into the evening or even overnight, raising output without increasing our head-count.
“Importantly, all our operators are supportive of introducing new technology like this.”
He went on to cite other advantages of the automation system.
At present, the LED lighting components are still produced by first completing Op 10 and then reloading them for Op 20.
However, they could be produced in one hit, if a turnover station were to be introduced.
Alternatively, one Feedio could serve two machining centres, carrying out both operations simultaneously.
There are also possibilities to integrate other functions such as component deburring and washing.
Mr Rawnson concluded: “We see automation as the future for our company. Aluminium billets have been machined so far, but the suitability of automatically handling castings is being investigated.
“We plan to target a wide range of different components for production in the new mill-turn cell and will be looking in particular at parts where the turning content is less than half of the cycle time.”