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Automated five-axis production at Stoneswood

Flexibility of operation proves key to securing multi-pallet machining-cell order

Posted on 02 Dec 2019 and read 1692 times
Automated five-axis production at StoneswoodThe first machining centre built by German manufacturer Hermle to be installed at a Hyde Group company has been operating round the clock since April this year at Stoneswood Precision Components, which is based in Dukinfield (Greater Manchester).

The C 400 five-axis vertical machining centre has been automated with the machine manufacturer’s HS Flex pallet storage and retrieval system, to enable unattended sub-contract production overnight and at weekends.

Stoneswood Precision’s managing director, Charles Day, said: “We looked at four options before deciding to buy the Hermle cell.

“Its major differentiator is the ability to stop automatic production quickly and use the machine in manual mode to manufacture a one-off part; the other solutions we looked at could not achieve this easily.

“The flexibility the machine provides is already proving useful, as it allows us to machine fixtures during the day and simultaneously set up the HS Flex for ‘lights out’ running overnight.

“The cell’s connectivity also fits well within the Industry 4.0 environment that we are creating in our factory.”

Stoneswood Precision’s current facility was set up in 2004 to produce 450 different aluminium and titanium components for a military aircraft (mainly wing parts).

Already a user of several multi-pallet production systems based on horizontal machining centres, the company needed an additional system to fulfil a contract for the manufacture of aluminium control boxes.

Initially, an older five-axis VMC with a B-axis spindle was used to produce the ‘suite’ of 48 bodies, sides and lids for the control box variants, which range in area from 75 x 150mm to 300 x 300mm and from 5 to 20mm deep.

Stoneswood 2The components are smaller and more complex than most of the predominantly aerospace parts produced at the Dukinfield facility, and the HMCs are too large to machine them efficiently.

The original process route used a coolant-driven right-angle attachment to drill holes in the sides of components, avoiding further set-ups.

The tool was in many ways fit for purpose, but it could not hold the positional tolerances required (down to 100µm true position).

Drilling was not sufficiently repeatable over a batch of components, so a new engineering solution was sought, resulting in the installation of the new production cell based on the trunnion-type Hermle C 400 five-axis machine — supplied by sole agent Kingsbury (www.kingsburyuk.com ).

A change in ‘attitude’

Mr Day continued: “Apart from the control-box work dictating the use of a five-axis VMC, there are parts of other aerospace contracts that lend themselves to a vertical-spindle production platform, and many new enquiries that we receive also require such capacity, so the choice of a second VMC — particularly one with automation — made business sense.

“I had never heard of the Hermle brand, but Paul Mellor — technical director of the Hyde Aero Products division, of which we are a member — was familiar with the manufacturer.

“Some of our staff visited a user of a smaller HS Flex system in the North East and came back with very positive reports, so we decided to place the order.

“Luckily, the C 400 was in stock at Kingsbury, so it was available quickly to solve a looming production bottleneck; other potential suppliers were quoting lead times of up to one year.”

The machine was quickly put into service after it arrived on site, with final commissioning within nine days, after which it started producing components straight away.

This was down to the prior provision by the supplier of a CAD model of the C 400, which allowed early 3+2-axis programming of parts in Catia, cycle simulations in Vericut, and the design and production of fixtures.

The latter exercise was further helped by Kingsbury’s early delivery of an actual machine pallet.

Other facets of the C 400 cell mentioned by Mr Day include its programmable coolant pressure between zero and 80 bar, which provides engineering flexibility, and the potential use of the coolant-driven drilling head for future projects.

Stoneswood 3The Hermle machine features a 20kW 18,000rev/min spindle, extended tool capacity (from the standard 38 pockets) by the addition of an 88-position magazine for HSK-A63 tools (tool breakage monitoring and measuring are included), a Heidenhain TNC 640 control, a work envelope of 850 x 700 x 500mm, +91/-139deg trunnion swivel, 500 x 400mm pallet size, and capacity for 12 pallets on two levels in the HS Flex store (this is served by a three-axis pallet-handling unit with rotary, lift and linear motions).

The store is controlled and managed by Hermle’s proprietary Automation Control System, which enables smart order management via a touch panel.

It is currently being linked with a manufacturing execution system — recently installed by Forcam — that is compatible with Stoneswood Precision’s SAP enterprise resource planning software.

It allows production orders to be sent directly to all machines for improved job sequencing, leading to optimised production output.

The resulting provision of enhanced data — including machine utilisation data — is taking the sub-contractor’s operation further along the road of Industry 4.0.

Currently, the Hermle C 400 HS Flex is devoted to the control-box contract, which entails supplying 300 assembled housings annually.

All components are machined either individually on a pallet or four at a time on a ‘tombstone’ (depending on size) from solid aluminium billet in two operations, involving milling, drilling and thread-milling cycles lasting up to 2hr per side.

The true position of the holes is now well within tolerance.