Cnc Machines

Triflow Concepts designs and manufactures exclusive taps, water filtration systems, and bathroom and kitchen accessories.
Two of the latest Citizen M32-V CNC sliding head mill-turn centres bring benefits to Triflow Concepts.

Two of the latest Citizen M32-V CNC sliding head turn-mill centres were installed at Triflow Concepts to reduce cycle times and increase quality of machined components.

‘Everything is manufactured in-house – including castings, full machining, finishing, plating and assembly,’ said Keith Liversage, plant manager at the company’s Wolverhampton site.

Two of the latest Citizen M32-V CNC sliding head mill-turn centres bring benefits to Triflow Concepts.

‘We have programmed 53 parts over four months and produced 98,000 components on four machine and 90,000 on the other,’ said engineering manager, Ajit Singh.

Two of the latest Citizen M32-V CNC sliding head mill-turn centres were installed mid-2008, which Liversage said were selected on merit.

‘The average cycle time for all 53 parts has fallen from 2.33 minutes to  0.66 minutes, giving an average saving of 1.67 minutes per part,’ she added.

‘In achieving this, these two machines have replaced four, 3-axis mill-turn centres that could rarely come near the cycle time, level of quality, speed of resetting and changeover they are now obtaining.

‘The brassware market is  competitive and they are fighting against a host of low-cost producers around the world keen to copy or provide a standard product,’ she said.

Liversage said that there were other important considerations in the decision to buy the Citizen machines.

Average changeovers take less than 45 minutes and these are predicted to reduce by half in the future.

‘Having selected Triflow taps, customers normally require the installation completed quickly so they cannot afford stoppages in production.’ she added that the company must reduce stockholding, work in progress and move towards a make-to-order initiative and this is where Citizen Machinery is helping achieve that aim.

‘The flexibility of the M32 means they have taken away restrictions on our design team who can now push the barriers of new concepts to take our company further away from run-of-the-mill brassware producer,’ said Liversage.

Previously, the three-axis mill-turn centres took between two and four hours to reset.

Once the first-off is approved there has rarely been any requirement to fine-tune offsets and from the first to last part our records show there’s been no deviations.

Commenting on quality achievement, Singh said that batch sizes are scheduled between 50 and 2,000 and each machine is always set to mid-limit.

she added that abrasive band grinding has been eliminated and such is the level of surface finish achieved, even on spherical knobs, connectors and handles, that polishing is reduced to light mopping allowing the machined profiles to be maintained.

Both Citizen M32-V mill-turn centres were bought with identical specifications.

Singh said that the level of flexibility through the 14-axis machines enables both front and back machining of a component using up to two tools simultaneously, which reduces cycle times.

Programmable gantry unloading provides flexibility in scheduling machine loading and ensures identical floor-to-floor times without any concern of damage or marking of components.

This is achieved by independent programming of tools mounted in the turret, gang toolpost and the fixed toolpost.

Adding to the enhanced flexibility for production is the inclusion of two Y-axis movements on the 10-station turret and vertical gang toolpost able to carry up to four turning tools and four driven tools and the fixed toolpost is able to carry two tools.

Programming is carried out by the Citizen Machinery CNC Wizard, enabling speedy program creation with each machining method explained with a clear description and diagram.

The all-driven turret is able to accommodate up to 40 tools using multiple toolholders – the latest development by Citizen.

Both machines are also set permanently with duplicated common tools to speed changeover.

Singh said this enabled him to generate and optimise each machining cycle off-line to achieve high orders of cycle time reduction and then use the DNC link to transfer program data to the machine control.

Typical of the type of brass components produced is a wall connector – pot filler out of 32mm bar.

This part previously took 3.25 minutes on a three-axis turn-mill centre against, which has been reduced to 1.02 minutes by the Citizen M32-V.

it’s then faced and the profile turned developing various grooves and radii.

The component is initially drilled through from solid with a 13.5mm drill then counterbored to 16mm diameter followed by the broaching of a 1/2in A/F hexagon.

The part is then faced and chamfered on the back followed by a boring operation to generate a thread, which is then screw cut to 1/2in NPT thread.

Two opposed keyways are milled using the C- and Z-axis and the profile finish turned before being parted-off ready for the subspindle.

‘The complete cycle is balanced and here the flexibility in programming and the ability to use a wide variety of tools means they can generate a faster cycle time,’ said Singh.

‘We have been able to rethink our production methods with a neat sheet of paper to generate new standards of quality right across our brass components,’ added Liversage.

Two CNC sliding-headstock lathes operated by Rodmatic are able to mill-turn components of medium to high complexity as quickly as the cam-type, six spindle automatics on site, Star has announced.

Brian Steatham, owner and managing director of Rodmatic, made the claim and added that the turned finish achieved using the Stars, mainly on stainless steel and steel components, is so good that subsequent grinding is frequently eliminated, lowering unit production cost.

A multi-spindle auto takes around two days to reset, so batch sizes above 30,000-off are needed to justify the time investment.

By contrast, sliding-head lathes can be set in a couple of hours, and so much smaller runs are economic.

Rodmatic has produced batches as low as seven-off on the Stars, although runs can be up to 5,000-off.

In this connection, Steatham has the following tip for precision-turned parts manufacturers: when producing larger batches on CNC sliding-head lathes, think of using form tools alongside single-point cutting tools to reduce cycle times.

Rodmatic often does just that, using its experience of wire-eroding and grinding form tools for the multi’s and transferring the technology to the sliding-head machines.

Reductions in cycle times are achieved, typically of around 30 per cent.

One component regularly produced, a profile-turned and bored steel shaft for a European customer in the fluid power sector, is machined in part by form tools in an overall cycle of 37s.

This is more than 38 per cent faster than the 60s it used to take by exclusively single-point cutting.

Tolerances of +/- 2.5 micron are routinely held on the sliding-head machines, which would be difficult to achieve on the multi’s.

Equipped with a 4m bar magazine and high-pressure coolant to allow long periods of unattended running, the first Star was a nine-axis SV-32 of 32mm bar capacity, installed mid-2007.

It was followed in 2008 by a similarly equipped seven-axis SR-20RIII for mill-turning parts up to 20mm diameter.

They joined three multi-axis CNC fixed-head lathes for producing larger components.

When asked why he did not continue down the route of fixed-head lathes to satisfy the market’s increasing demand for smaller size, high-accuracy mill-turned parts in lower volumes, Steatham said that, in his opinion, a sliding-head lathe is twice as fast as an ‘equivalent’ fixed-head lathe – in other words, one with a counter spindle and two turrets containing driven tooling.

He added: ‘Major factors slowing fixed-head lathes are their inability to cut with more than two tools simultaneously, and long turret-indexing times compared with the rapid infeed of gang and cross-working tools on sliding-head machines.’ He also likes the advanced mill-turning and simultaneous end-working capabilities of modern sliding-headstock lathes, as well as their traditional strength – that of producing shaft components accurately due to the support given by the guide bush at the point of cutting.

During machining trials against competitive sliding-head lathes, the Star machines were inherently faster.

In addition, Steatham felt that their extra weight and rigidity would allow the production of more accurate components.

Dennis Jones, managing director of DJJ, said the multi allowed the company to resume production of an automotive job previously lost to India.

DJJ Precision Engineering has revealed how an Index MS32C six-spindle multi from Geo Kingsbury Machine Tools has enabled the subcontractor to win back business from Asia.

Operations mainly involve turning outside diameters, thread-cutting also a small amount of prismatic machining to produce a hexagon on two end.

Machined from high-tensile steel bar (606M36), the component is a vehicle braking system shaft for a tier two automotive supplier in the UK.

Cycle time on the Index MS32C is 14s, which allowed Jones to manufacture the part for 29p – and the cost of the material & finishing – & win the contract.

The previous cycle time on a single-spindle, sliding-head lathe at the firm was over eight times longer at around 1min.

Another contract that DJJ hopes to win is for a complex hydraulic part that plays to the MS32C’s strengths, as it requires a lot of prismatic work including cross holes, a roller-burnished bore also a high surface finish all over.

it is not just large volumes that can be produced economically on the CNC multi, as setting is much faster than on elderly cam-type machines.

Irrespective of volumes machined, DJJ consignment stocks parts if necessary for scheduled delivery to its customers.

Component batches as low as 8,000-off are now feasible.

All have a full C-axis for use with driven tooling & are held at a constant temperature by refrigerated coolant.

Moreover, the quality & efficiency of machining is much better on the Index multi, as cutting feeds & speeds can be controlled independently at each of the three spindles.

With the market conditions driving down the batch sizes Reading based Rodmatic Hytek has developed fast-track machine changeover techniques for an automotive project.

Said managing director Brian Steatham: “We won this contract about a year ago which involved the production of 30 variants of piston rods in batches of up to 250 parts. Since then the number of types have grown by a third but lately certain batch sizes have dropped to as small as seven parts to meet prototype requirements. This change in supply, with growing demands on production for our CNC sliding head lathes from other customers, would have given us concern over scheduling, stock holding versus pricing and lost production due to the increased frequency of changeover and setting demands.”

Mr Steatham decided to call in an application engineer from the sliding head machine supplier Star Micronics GB to carefully look at all the processes on the nine-axis Star SV-32 and seven-axis SR-20 RIII machines. While minor operational changes were made, more important was the setting up of macro programming based on length/diameter ratios for the 40 different part variants.

The suspension rods are produced from chrome steel and range up to 16 mm diameter by 280 mm long. Each part has to be turned, threaded at each end and have flats milled in a single operational cycle. Already, Rodmatic had developed the process using form tools alongside single point turning and cut original cycle times by almost 30 percent. This development enabled output targets to be achieved that were double what could be produced on two recently installed fixed head lathes.

Said Mr Steatham: “We can now maximise the productivity from the 4m barfeed and change over within a few minutes. It has also enabled us to improve our minimal manned production between shifts and at night and respond to our customer within 24 hours when needed. As a result, we have worked closely with the customer to fast track prototypes and specials causing minimum disruption to our normal production schedules.”

http://www.engineeringcapacity.com/archive101/2009/july/sliding_head_turning/rodmatic_takes_the_fast_track

Mitsui Seiki USA has announced that several of its customers are cutting 10-14 class ring gears in low- to mid-volume applications on its CNC vertical and horizontal machining centres.

Traditionally, manual gear hobbers or CNC gear cutting machines are employed.

However, benefits are surfacing in certain applications, such as for aerospace and power generation, using highly precise machining centres.

In particular, Mitsui Seiki’s Vertex machine is suitable for ring gears up to 16in (41cm) and a special gear-making model incorporates a rotary trunnion table for the finish turning operations.

Mark Speier, sales engineer at Mitsui Seiki, said: ‘This machine can turn the gear faces, the final profile of the internal bore and generate the gear teeth.’ On one of its largest precision five-axis machining centres, the HU80A-5X, users are producing spiral bevel gears up to 35in.

Speier added: ‘One of the benefits of producing gears on that machine is that the relative gearboxes or gear cases, and even reduction gear boxes, can also be processed on this one machine.

‘The gear housing is a critically precise piece.

‘The accuracy of both parts has a direct correlation to the transmission performance over the life of the motor.

‘The end product reliability is a positive factor, too.

‘Further, the gear is mounted flat and then turned up 90 degrees – or another angle – so that the end mills can cut at the optimum attitude to the gear profile.

‘This results in excellent roughing efficiencies.

‘For finishing, ball nose end mills generate the final profile before heat treating,’ he said.

Mitsui Seiki’s initial foray into gear cutting involved cutting the gear teeth and roughing and semi-finishing operations prior to heat treating.

Now, by adding turning operations to the Vertex machine, accuracies have improved through the single setup for all operations, according to the company.

Mitsui Seiki anticipates that turning functionality will be available on the HU80A-5X in about six months.

Speier continued: ‘The traditional gear-cutting machines may run faster; however, [as a result of] the tooling economics, improved accuracy through one-setup machining and improved process control, the overall cost may be advantageous, especially in low-volume runs.

‘Plus, this application may enable our current gear-making customers to get more use out of their Mitsui Seiki five-axis machining centres,’ he said.

One of the key aspects to successful gear cutting on a Mitsui Seiki machining centre is software.

CNC Software, the developer of Mastercam, has generated the optimum toolpaths for spiral bevel gear cutting.

http://www.manufacturingtalk.com/news/mkh/mkh108.html