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WANNER INTERNATIONAL

EMO September 2007

High pressure coolant systems incorporating Hydra-Cell seal-less pumps are contributingto success stories at UK users of Star sliding head machines

Performing under pressureTHE metalworking industry broadly accepts theadvantages of delivering coolant to the cutting tool or thegrinding wheel at high pressure. The potential forimprovements in swarf control, cutting data, tool life, workpiece quality and productivity when upgrading from a lowpressure (eg 10 bar) system to a high pressure system is welldocumented. But there is more to it than exchanging a lowpressure coolant pump for one that will perform atpressures of 70 bar or higher.

Bob Hunt, managing director of Star Micronics GBgives special attention to this aspect of cutting efficiency.Four years ago he invited Warwick-based coolant systemspecialists Pumps & Equipment to re-evaluate hiscompany’s high pressure coolant requirements on Starsliding head lathes and mill-turning centres. The companywas already providing high pressure coolant delivery on itsmachines, but the system had limitations.

Among the issues evaluated were the need to work atoptimum speed and feed rates, maximise up-time,maximise tool life, remove swarf from the cutting area andminimise the size of swarf produced. Following appraisal,development and prototyping, Pumps & Equipmentoffered a complete customised high pressure coolant(HPC) system meeting all the criteria - with the assuranceof reliably consistent performance through time. Designedas a ‘plug and go’ package, it incorporates power unit,controls, pipework, fittings and purpose-designed spraynozzles. A productive working relationship ensued, Pumps& Equipment is now a fully integrated supplier to StarMicronics GB, and the HPC system as it evolved hascontributed to some outstanding application achievements.

One of the key components in Star’s current system is

the high pressure pump. Many HPC systems on machinetools use screw or piston-type, or centrifugal pumps - allintrinsically vulnerable as they incorporate dynamic seals(always subject to wear) and are designed with narrowclearances between static and moving surfaces. Theirmanufacturers therefore require that the pump is protectedby fine filtration. The HPC system previously offered onStar machines in the UK used piston pumps rated at 140bar, protected by filtration down to 5microns. However,filtration levels are expressed nominally. In reality a ‘5micron’ filter may pass much larger particles, dependingon their shape. There is potential, confirmed in the field,for premature pump failure, as well as a gradual decline offlow and pressure performance as seals begin to wear.

Pumps & Equipment was confident its chosen HPCpumps - from the Hydra-Cell range of seal-less pumpsmanufactured by Wanner - would extend the lifeexpectancy of Star’s coolant systems, and also that flowsand pressures could be sustained at optimum level. In theabsence of seals there can be no loss of performancethrough seal wear. ‘Seal-less design is one reason for ourconfidence in Hydra-Cell reliability,’ says P&E director LeeBott. ‘The pump is tolerant of particles if there’s a filterproblem and can handle any type of coolant from neat oilto low-lubricity emulsions.’ He also cites positivedisplacement and smooth low-pulse output, with multiplehydraulically-balanced (stress-free) diaphragms in a singlehead. Other factors are robust construction, simple build(easy maintenance), ability to run dry without damage,and high efficiency with consequent low powerconsumption. Not least important, flow at any pressure isdirectly proportional to motor speed - a linear relationshipthat makes the Hydra-Cell very easy to control

Automotive plants in the USA, Japan, Germany, Italy,France and India are among major users of machine toolcoolant systems incorporating Hydra-Cell pumps. For Starmachines fitted out in the UK, Pumps & Equipmentcurrently supply G10 and G04 models - conservativelyemployed by P&E for this application in 70 bar and 140 barHPC systems. Users of these machines have seen notableadvances in productivity, efficiency and cost reduction.

At B&D Patterns, a leading supplier of aero engine pipeassemblies to Rolls Royce, Star lathes with 140 bar highpressure coolant revolutionised stainless steel componentproduction. Time savings of 25% or more were achieved onsome components, previously produced on fixed headlathes without HPC. And UK sub-contractor DKWEngineering (where ‘HPC greatly assists machining ofstainless steel’) was able to replace with new, more complexwork, business previously lost to Chinese competition. 15%of turnover is now in direct exports - to China.HHAALLLL66:: SSttaanndd JJ6611www.wannerint.com

Users of Star machinesreport notable advances inproductivity, efficiency andcost reduction as aconsequence of HPCsystems

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