Fixed-head turn-milling at Davturn

Able to cut with three tools simultaneously, Davturn’s latest machine is slashing cycle times

Posted on 25 Jan 2018 and read 1338 times
Fixed-head turn-milling at DavturnDavturn, a small family-owned precision sub-contract machinist based in Bromsgrove, has found that increasing its production capability by installing a Miyano turn-mill centre has added to the need to move the five-strong business into new larger premises — and install further similar machines.

Speaking of the Miyano BNE-51SY6 — supplied by Bushey-based Citizen Machinery UK Ltd (www.citizenmachinery.co.uk) — Davturn’s managing director Mark Birley said: “We installed the multi-axis 51mm bar-capacity Miyano in June last year; it joined our existing Miyano BNA-42DHY, which was an outstanding success for the business following its installation in 2012.

"It enabled us to increase the diameter of bar we machined on our bank of five sliding-head machines from 32mm to 51mm, allowing us to immediately attract a host of new orders.”

Mr Birley has been involved in turned-part machining since he left school; he set up Davturn 13 years ago, basing the business on the experience he had gained working with cam autos.

He bought his first CNC machine in 2007 — a move that he says set the firm “on a road of steady growth”.

The same year, he was joined by his son Matthew, who reckoned he would have a longer and more secure future in machining than he would as an ‘early career’ footballer playing for Birmingham City.

Indeed, with training from his father, Matthew Birley soon became a highly skilled programmer and machine setter, and he is now a director of the company.

The firm also has two apprentices, who are being taught how to use the latest production technology and modern machining
techniques.

Today, Davturn has some 20 customers (mostly Midlands-based) from sectors that include hydraulics and pneumatics, electrical, door closure, fastener, construction, vehicle and rail — plus producers of control cabling.

This means that it has to produce a wide variety of components, with batch sizes ranging from 1,000 to 500,000 (equating to almost continuous production).

Cycle times vary from 15sec to 5min, with materials ranging from plastics to aluminium and high-grade steels.

Continous production


cit 2Since it was installed, the BNE-51SY6 has not stopped producing components; it runs ‘round the clock’, seven days a week. During nights and weekends, machine monitoring creates a call-out and an “immediate return to the workshop” request.

Matthew Birley says: “The capability of the machine to hold a large number of tools on its two 12-station all-driven turrets means that we can easily accommodate a suite of common tooling and rarely need to change a tool-holder.

“When re-setting is required, pre-preparation ensures that this generally takes less than 40min, which helps to keep machine utilisation very high.”

He also says that he uses the latest Citizen Wizard programming aid for both Miyano machines.

“This enables new multi-featured parts — often involving difficult materials such as high-tensile EN16T and EN24T, 303 austenitic stainless steel and heat-treatable bearing-grade 404-C stainless steel — to be efficiently programmed with a good balance in the cycle times between the two spindles.

"For example, when machining a truck suspension part in batches of 2,000 from 25mm-diameter EN16T bar, we held 0.025mm in the bore and 0.02mm on the outside diameter; this has a 0.8CLA surface finish, and we achieved this without any interruptions for adjustment — and benefitted from overlapping operations between the two spindles and two turrets.

"The part involved turning, drilling and counterboring, plus rolling an M10 internal thread and milling an 18mm hexagon — all completed in a 2min cycle.”

The BNE-51SY6, which has been developed for single-cycle machining, can cut with three tools simultaneously —overlapping at both ends of a workpiece when needed.

Contributing to the machine’s performance is the high level of rigidity provided by a 7.8-tonne bed, box-way slides, a 15kW main spindle and a 7.5kW secondary spindle (both with a maximum speed of 5,000rev/min) — and 12-station all-driven turrets.

Moreover, Davturn says the 2.2kW drive to these tools (delivering 25Nm of torque and speeds of up to 6,000rev/min) has enabled cross-machined features to be produced with optimum effectiveness, and the capabilities of the new BNE machine have helped the company to win a contract involving 1,000 parts a month for windscreen-wiper sub-assemblies for the railway industry.

In conclusion, Mr Birley said: “Investing in the Miyano means we are now ‘riding high’. Following the machine installation, we have won a contract involving a six-part series of hydraulic valve sleeves — complete with spools — between 16 and 30mm in diameter and made from 440-C stainless steel.

“We can machine the largest of these in under 5min; the most complex has 11 grooves in the outside diameter and 50 5mm-diameter holes pitch-drilled from the grooves into the bore, which itself has a 0.05mm tolerance.

“Because we can simultaneously gang-drill the holes using both turrets — and fully deburr in-cycle — we are achieving a capability that we could never have even dreamt about before.”

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