High pressure coolant on Citizen sliding-head lathes has proven so successful in the field that, according to Citizen Machinery UK's managing director Geoff Bryant: "Almost 60 per cent of Citizens now sold are specified with its CoolBlaster II option. The take-up of this 2,000 psi programmable coolant supply system rises to almost 100 per cent when further machines are ordered solely due to the experience and the advantages gained." In fact, due to the type of work, materials machined, volume of swarf and tool life gains, nine out of every 10 Citizens with a 32 mm bar capacity now employ the CoolBlaster system.
Image: CoolBlaster provides high pressure coolant
Image: The CoolBlaster coolant tank sits under the machine
By far the governing factor is, Mr Bryant adds, the need for operational predictability and to maintain high levels of confidence when running unmanned. It is a point echoed by John Cable, managing director of C & M Precision in Maldon, Essex. His company's four, top-of-the-range Citizen M-Series machines have high specifications and each machine has the 2,000 psi CoolBlaster. "It has not only proven to be essential for the type of part we produce – but has been very rewarding, giving additional security, especially when running unmanned," Mr Cable offers.
C & M supplies connectors, brassware for bathrooms, custom car components, hydraulic fittings, special manifolds and valves, miniature railway model components and an own product of manual and electronic spice and herb grinders.
According to Mr Cable, on one regular brass component machined on a Citizen M32-V sliding head turn-mill centre which is 145 mm long, a hole 14 mm diameter has to be drilled from solid. "We can hit this with just one peck in eight seconds and have the total confidence to run this part totally unmanned, due to the performance of CoolBlaster," he says.
VALUABLE ASSET
Martin Barker, joint managing director of Rowan Precision, based in Witton (Birmingham), says: "It must be one of the most valuable assets in the company's machining portfolio."
Rowan is a successful sub-contractor producing components for medical, bespoke lighting, electronic, aerospace and defence customers. It machines difficult materials such as titanium, Polladium, Iridium and other high alloy steels where speeds and feeds are difficult to improve without tool costs being increased dramatically.
CoolBlaster was fitted to three of the company's latest Citizen 13-axis, M32 sliding-head machines. "Due to the difficult materials we often machine, being able to program the delivery nozzles to direct fluid where it is needed is very important. This is especially valuable when taking advantage of three tool simultaneous cutting on the M32. It ensures a positive control over swarf, giving highly predictable operations – especially for tool life.
"CoolBlaster gives us an enhanced capability and security of operation making production a very controlled routine. It is very rare we ever need to add a tool offset at the control," Mr Barker concludes.
Sub-contractor Unicut, which has customers in the medical, defence, brewing, fastening, aerospace, connector and automotive related sectors, machines a wide variety of materials including titanium, lots of stainless and alloy steels, which can pose a high risk for tool failure.
"We work to high levels of predictability on tooling to ensure surface finish and tolerances are maintained. High pressure coolant aids our ability to be consistent in size, tolerance and finish over a batch of parts which also helps the customer when the parts are eventually assembled," joint managing director Jason Nicholson explains. "The costs associated with premature tool failure far outweigh the cost of the tool; then you have to add the associated risk of damage to other tooling and back checking to find work that is no longer acceptable."
VERSATILITY
One of the most important elements of the Citizen system, maintains Mr Nicholson, is its versatility and the fact it is fully programmable from the CNC control. "This means it can be strategically controlled for important tools especially on internal features involving deep holes, U-drilling and the cleaning of the subspindle collets of any swarf to prevent misloading and damage to components. Flood coolant is fine to wash away swarf and general cutting because what you don't want is pressured coolant and swarf continuously blasting around the whole working area," he says.
Coolant management is also important he maintains, and with an effective filtration and swarf reclamation system, oil stays in top condition. Also the risk of coolant starvation is reduced, with swarf under full control, which otherwise can easily lead to tool burn-out.
At Renishaw, Wotton under Edge, Glos, each of the company's 12 Citizen M32-IIIs that carry up to 80 tools each are fitted with CoolBlaster to ensure swarf management and tool life predictability, especially when each machine is operational for at least four hours totally unmanned.
Roger Burleigh, production engineer, confirms the machine will maintain tolerances and surface finish all day in materials as diverse as EN31 to 174PH stainless steel. One particular threaded sleeve component, which uses 17 tools, of which seven are driven, has a tapped M1.6 hole where constant cleanliness of the hole is critical. Here, the 2,000 psi coolant supply ensures swarf is removed from the hole and that the tapping process is secure.
Another high pressure coolant system is available from 1st MTA. CoolJet, a typical lathe system (including replacement coolant joints in its turret, hoses, high pressure coolant nozzles, high pressure pump, coolant filtration and integrated electrical control) will cost in the region of £6,000-9,000.
This level of investment is likely to represent a payback period of perhaps less than six months, based on reduced tooling consumption and improved productivity. In extreme cases, where previously un-manageable chip control problems and tool damage issues are resolved through the HPC investment, this period can potentially be reduced to weeks or even shifts, rather than months.
At pressures of 1000-2000 psi, the coolant stream blasting over the tip of an insert or down the flutes of an end mill will virtually eliminate the risk of workpiece marking by chips. Its powerful flushing action minimises random tool failures from chip damage and results in greatly improved consistency of the machining process.
Most HPC systems are not specifically marketed as chip-breaking devices. However, a common by-product of their application is shorter, more manageable chips. This is attributed to two principal factors. First, the superior cooling and lubrication associated with HPC allows higher feed rates, without the rapid decline in tool life that would be expected with flood coolant methods. In addition, inserts with more aggressive chip-breaking geometries can be employed, without giving rise to mechanical or heat damage. And while some chips may not be broken up completely, they can often still be controlled through effective nozzling.
MANY-FOLD IMPROVEMENTS
The result is that, when applied to drilling operations, systems such as CoolJet offer up to a six-fold increase in productivity; single pass deep hole drilling, a 50-100 per cent uplift in surface speed through the use of solid carbide tooling; and between a two and four-fold boost in feed rates – all with improved surface finish and dimensional accuracy.
Typically, the most significant gains are achieved in high speed machining operations – where elevated temperatures are incurred or exotic materials are being worked. Nevertheless, other candidates for effective HPC use include customised or high value tooling applications, where tool cost is significant and so long life important; multi-spindle and transfer machine applications limited by drilling penetration rates; or operations susceptible to surface finish problems or scrap, due to chip packing or wrapping.
Of course, there are associated issues with the adoption of HPC. These include making sure that machine tool guarding is adequate – that the coolant does not foam and that any associated mist problem is dealt with – but the benefits of HPC are clear.
A typical production drilling example is given below:
Application: Drilling 0.5 in diameter x 1.5 in deep holes in grade 316 stainless steel
| Original Method | CoolJet Method |
| Tool Used | Coolant Drill – 200 psi | Coolant Drill – 1500 psi |
| Type | Cobalt Twist | Solid Carbide |
| Depth/length of cut | 1.5 in, with 0.6 in peck | 1.5 in, no peck |
| Feed Rate | 0.005 in/rev | 0.012 in/rev |
| Cutting Speed | 610 rpm | 1,150 rpm |
| Cutting time per part | 38 sec | 7 sec |
| Drill life | 200 components | 600 components |
In financial terms, the more than five-fold increase in throughput achieved by the CoolJet system represents a significant cost saving. In addition, the trebling of tool life will minimise replacement/setting downtime and tool refurbishment costs, providing substantial savings to more than offset the increased cost of solid carbide tooling.
In this second example, the only change to the original process is the replacement of standard flood coolant by a CoolJet high pressure ball delivery nozzle:
Application: Finish CNC turning of Titanium 6AL4V component
| Original Method | CoolJet Method |
| Tool Used | Sandvik 80 Diamond | Sandvik 80 Diamond |
| Insert and grade used | CNMG 431 – 45 psi | CNMG 431 – 1000 psi |
| Depth and length of cut | .012 in deep x .50 long | .012 in deep x .50 long |
| Feed Rate | 0.003 in/rev | 0.005 in/rev |
| Cutting Speed | 1,361 rpm | 2,722 rpm |
| Cutting time per part | 8 sec | 2.5 sec |
| Drill life | 500 components | 1,000 components |
In this case, cutting time is reduced by a factor of more than three and tool life is doubled.
Box item 1
Product developments in brief
• Fuchs UK's ECOCUT HFN 13 LE-UNI is a new, high performance cutting and grinding oil, recommended by leading grinding machine OEM's.
One of the claimed unique attributes of ECOCUT HFN 13 LE-UNI is that it can be used for all machining processes within gear and bearing production. This is said to be a huge benefit, which will allow users, in particular, gear manufacturers to rationalise to one cutting fluid.
The technology employed with ECOCUT HFN 13 LE-UNI allows users to use lower viscosity, low misting oils instead of conventional high viscosity milling and shaving oils. This has many advantages for users, including better cooling, consistent EP and anti-wear performance including lower drag out losses on material and chips. This will result in tangible cost savings including improved tool life, lower fluid consumption, reduced chip disposal costs and less contamination for cleaning processes.
Image: High performance cutting and grinding
• ExxonMobil's Mobilcut water-soluble cutting and grinding fluids offer long service life and reduce maintenance downtime, thereby increasing machine tool efficiency, availability and productivity. In addition, the fluids in service are easy to monitor and meet the latest Health and Safety regulations.
Easy to mix and multi-purpose in application, the latest additions to the Mobilcut line, under the Mobilcut 100, 200 and 300 series, respectively comprise milky emulsions, high performance micro-emulsions and fully synthetic fluids.
Mobilcut products are fully compatible with Mobil hydraulic and slideway oils, including the new Mobil DTE 10 Excel hydraulic oil and the new formulation Mobil Vactra Oil.
• Hirschmann Engineering UK has launched the Sludge Master GFS-1350-HYDRO-DSD filtration system. The Ebbco system is specifically for use on centerless and cylindrical grinders, the unit is able to remove particulates to below 10 microns, via an economical, media-free set-up, while use of Ebbco's 623 filter cartridges, filtration levels below 1 micron are possible.
Image: Sludgemaster
Box item 2
Coolblaster history
CoolBlaster was originally developed in the US by one of Citizen's distributors but, so effective was the system when used on Citizen machines (in the UK some 120 systems alone were fitted over a three-year period) that Citizen acquired the distributor. This was followed with investment to develop a more compact MK II version that has seen more than 80 per cent of all Citizen machines delivered to customers in America being CoolBlaster equipped.
The system is especially effective when deep hole drilling, which is a common requirement and can often be troublesome. Very often the parts machined have very small diameter holes and the materials tend to be difficult to cut which can pose problems with tool breakage and excessive wear. Not only does the high pressure coolant enable cycle times to be enhanced by eliminating or reducing the need for peck cycles to clear swarf from the hole, tool life is improved because coolant is presented right at the cutting edge.
The latest system is so compact, it will fit under the bar feed unit and is fully programmable with options of five or 10 independent line feeds able to deliver up to 24.5 litres/min – an increase of 25 per cent over the previous system. A five micron filter removes the minute swarf particles which further aids tool life and an on-board heat exchanger maintains the coolant at a constant temperature – a key point in creating high levels of machining consistently from part to part.
In addition, a booster pump giving 114 litre/min can be specified with a 25 micron filter, should users have the need for even higher demands. Apparently, in the US one customer even makes use of the high coolant pressure to re-cock a mechanical die head in-cycle.
First published in Machinery, January 2010
