Citizen
By switching from fixed head turn-milling using high specification machines to the use of two Citizen CNC sliding head turn-mill centres for parts up to 32 mm diameter, BGB Innovation, now recognised as one of the world leaders in the design, development and manufacture of slip rings and fibre optic rotary joints used mainly in wind turbines, underwater lighting systems and sewage treatment plants has saved in excess of £50,000 a year in production costs.
In addition with the Citizen installations, the company is now able to maintain micron tolerances under ‘one-hit’ production turning strategies for its ultra-precision high performance rotary joints. Used in fibre optic data transmission, these assemblies have proven to be vital in the latest generation equipment for use in the wind turbine industry around the world.
According to David Gilbert, Works Director: “The ability to cost-effectively machine to micron tolerances within a single cycle has enabled us to achieve critical line up of the fibre optic elements in our connectors used for the world-beating transmission of up to 1 GB of data. In addition, this production capability has paved the way for the recently launched Optilinc FORJ (Fibre Optic Rotary Joint) to be manufactured plus the next generation under development and patents registered for a more advanced system involving inductive transmission of power/signals without wires.
BGB installed its first Citizen, a top of the range M32-VIII in 2009 and subsequently a Citizen A20 VIIPL. Following significant levels of process and tooling development on the larger capacity machine BGB engineers found it was able to hold tolerances as tight as 3 µm on through bores as small as 2 mm over depths of 12.5 mm and in the same cycle hold tolerances of 4 µm on a 6 mm OD while maintaining a concentricity of 3µ TIR between the two. This particular Optilinc component made from 303 stainless steel was critical to enable the ultra-high speed transmission of data.
With future product development very firmly being production capability biased, before selecting the Citizen M32, BGB’s engineering team went through exhaustive trials to ensure the investment would meet the accuracy and repeatability requirements. However, consideration also had to be given to embrace more competitive production of smaller components in-house that were either made on fixed head machines or were previously sub-contracted covering the likes of risers, studs, spacers, rivets and a whole range of special fasteners.
Said Michael Gilbert, Lean Co-ordinator and who has responsibility for developing cost saving initiatives across all aspects of production: “At that time the Citizen M32 was the only sliding head machine that we had the confidence of meeting our future demands. Over the last three years our justification to purchase has been qualified as it has repeatedly delivered the levels of consistency and reliability that we required.”
From 2009 to the close of 2012 BGB Innovation has grown by over 20% a year to reach a turnover of £25 million for the Grantham based business. The company has three UK divisions which have an export ratio of 95%:- BGB Engineering that designs and manufactures complete slip ring packages for a number of applications but primarily for wind turbines to transmit data and power between, for instance, the hub and blades. Packages are also supplied for end blade pitch control as well as a range of brush holders and brushes. BGB Marine is responsible for the production of sophisticated underwater lighting, cameras and connectors and BGB Telemetry, encompasses wireless technologies of fibre optics, induction and capacitance.
“Our products are used in many rotary applications and in particular farming situations,” said James Tupper, responsible for marketing and IT, “with most products being installed in the likes of wind farms, sewage farms, waste water treatment and fish farms we are also involved in spin-off areas having 360 deg rotary powered applications such as revolving doors and packaging machinery.”
With such a consistent level of growth being achieved by the company the Citizen M32 became a key production unit with the capability to slash overall costs by 50 per cent against the fixed head turn-mill centre machines while also recouping subcontract costs, bring back total in-house control over deliveries, quality and support to meet the demands of final assembly.
With the Citizen installed batch sizes became far easier to control in-house with quantities varying between 200 and 10,000. Indeed, over 500,000 parts in stainless steel, brass, aluminium, copper and mild steel have been produced by the machine with the M32 maintaining a utilisation factor in excess of 75 per cent. In addition to service schedules, it has a record of only one single fault requiring a service call.
But most significant added Michael Gilbert: “Was in addition to normal production demands the high levels of flexibility and precision, means it was ideal for prototyping and small component development with the added guarantee that if the part was proven to meet design and development targets, we could always make it in a production sequence.”
By mid 2012 it became apparent that even by running extended shifts, selected parts run unmanned through the night and the continuous improvements created by the company’s lean manufacturing techniques, the production schedules were becoming overcrowded and spindle availability was being flagged up for action. So in October 2012 the decision was made to expand the sliding head capacity and a Citizen A20-VIIPL was installed to free up the turret based 80 tool M32 for the larger more complicated components.
The 7-axis Citizen A20 is powered by a 3.7 kW 8,000 revs/min main spindle motor with a 1.5 kW, 8,000 revs/min drive to the sub-spindle. It will accommodate seven turning tools with four tools for front end and eight tools for back end machining and three driven tool positions.
The BGB machine specification incorporates the optional long workpiece unit enabling parts up to 400 mm long to be machined that is ideal for producing the company’s longer threaded shaft riser components. The Citizen CoolBlaster high pressure coolant system is also included.
Said Mark Scoffins, CNC Team Leader: “We were surprised how the development of the A20 with greater rigidity of build, its faster processing times and lack of idle time in a cycle, plus the benefits of faster acceleration to 32 m/min rapid traverse and the ability to overlap tool applications made such a difference.”
He then gave an example of using the same proven speeds and feeds from the M32. “We were able to reduce the cycle time from 26 secs which we thought was very cost-efficient on the M32 to just 12 secs which is a massive leap in productivity.” Pulling up production data he then outlined that the new machine running through the first weeks of December up to Christmas and in the first week of January had recorded 30,000 individual cycles.”
Still ultimately privately owned BGB was originally set up in 1976 to produce stand-by power generators. In the early 90s developments evolving from its expertise in slip rings and brush gear enabled it to break into the early stages of wind power development which helped to rocket sales from £500,000 to the current £25 million.
BGB has recently gained planning permission to further extend the Grantham plant. Here two 25,000 ft2 temperature controlled production, cleanroom and assembly areas will be set up where the two Citizen’s will be relocated. As a result this will free up machine tool space on the shop floor, provide a more stable environment and create further enhancements to quality levels by helping to improve consistency.
Meanwhile, BGB Technology based in Richmond, Virginia USA has also selected Citizen as its machine choice for production of high tolerance products for the US market.