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Keeping cool under pressure

Developed primarily for the aerospace industry, high pressure coolant (HPC) systems can offer a host of benefits for a range of machining applications. Katherine Crichton writes.
WITH the ability to reach temperatures of over 1000°C, things can get a little hot when maching materials such as titanium and other heat resistant super alloys.
With twice the elasticity of steel, titanium is often used in applications that require flexible materials that won't crack or rupture - such as aerospace, automotive and medical sectors - but the many qualities that make it appealing, also contributes it to being one of the most difficult materials to machine.
Often a poor thermal conductor, the heat generated when cutting titanium often doesn't dissipate through the part but concentrates in the cutting area, leading to premature tool wear and poor surface finish.

Cutting fluid plays a crucial part in controlling cutting zone temperature, but traditional flood coolant systems can fail to make the cut when machining thermal resistant materials.

However recent technology developments in the application of ultra-high pressure coolants (HPC) has helped to overcome many of the issues involved with cutting 'exotic' materials.

Paul Fowler, MD at Dimac Tooling, says high pressure coolant application, typically at 70-140bar (1000-2000psi), provides an accurate, high velocity jet stream which ensures the coolant actually penetrates the heat barrier created by cutting at high speeds.

"With traditional 'flood' or low pressure coolant systems, even though it appears as if they are flooding the cutting area with fluid, typically there's so much heat generated at the cutting face, the coolant evaporates before the cooling and lubricating effects of the fluid gets down to the friction zone between cutting edge and the workplace," Fowler told Manufacturers' Monthly.

"HPC technology, using properly designed coolant nozzles and tool sealing systems, performs these functions to a degree unobtainable with flood coolant."

According to Fowler, some of the benefits of effectively applying HPC include a dramatic decrease in cycle time due to increased cutting speeds and feed rates (50-80% depending on application), as well as extended tool life.

"Another key benefit of using HPC is the proven ability to better predict tool life, which is essential in applications where tool failure could result in major productivity loses, such those in high volume, heavily automated applications," he said.

As well as an improved capacity to cut exotic materials, Fowler says using HPC allows formerly 'specialised' processes, such as deep hole drilling, to be performed on CNC mills and lathes, with "impressive results".

"In drilling applications, when the depth of the hole is more than 2x the diameter of the tool, the benefit of using HPC kicks in. When drilling down 30mm with a 1mm diameter hole (so depth is 30x diameter) then it would be imperative to use a HPC system to ensure the coolant reaches the friction zone and to eject chips," he said.

In the zone
As well as extended tool life, the application of HPC can also provide superior chip control and major cutting tool manufacturers are now developing standard tooling solutions designed to harness the full benefits of using HPC.

Sandvik Coromant has developed a standard tooling system designed to channel HP coolant through the tool to accurately penetrate the heat affected zone.

Mark McGuinness, Sales Support Applications Engineer, says the company's high-pressure coolant tooling, combined with the Coromant Capto coupling, will reduce the temperature in the cut, providing superior chip control even at lower pressures (from 10bar).

"The controlled direction of the coolant jets aimed directly at the heat affected zone though the tool produces a hydraulic wedge between the top surface of the insert and the underside of the chip, lifting the chips away and reducing temperature in the cutting area.

"Because of the effective cooling of the cutting area, the tooling can be pushed harder due to higher feed rates and this enables optimum use of the chip breaker, which results in tighter chip breaking leading to efficient chip evacuation.

"The force required to lift the chip varies depending upon the material, feed rate, entry angle and depth of cut."
McGuiness says the improved chip control as a result of HPC systems is a major benefit in high volume applications utilising robots and automatic component changing.

"Sometimes turning or drilling applications produce stringy swarf that can be wrapped around the workpiece or cutting tool which can make it difficult for robotic handling or when using multi-task machines, swarf gathering around the tool can prevent automatic tool changing," he said.

While HPC systems can be used in a range of machine tools including vertical turning lathes (VTL), multi-task machines and turning centres, Fowler advises it is important to ensure the machine tool is set up to handle HPC, as retrofitting high pressure capabilities onto existing systems can be quite cost prohibitive.

"It is also important to have the appropriate sized pump and coolant tank to provide the flow and volume required to maintain the required coolant pressure," Fowler suggests. "These systems need to be particularly well guarded with no open areas as coolant at this kind of pressure will be going everywhere," McGuinness explained.

"When HPC systems are in operation it can be difficult to see what's happening so it is important to ensure you have that reliability in the cutting tool," he added.

While modern machine tools often come with a flood coolant system as standard, buying a machine with HPC capabilities will come at a price premium, but Fowler asks machine tool users to at least "consider the technology" as ROI can often be measured in months or even weeks, rather than years.

"Depending on the level of system sophistication and type of machine (mill or lathe) prices for machine tools fitted with HPC capabilities start from around $10,000 to $35,000," he said.

"However don't just focus on the capital investment, but rather on the reduced downtime and increased tool life that can be achieved with using this technology - it's not just a doubling of capability - it's an exponential improvement," he said.


McGuinness echoes these sentiments and says with HPC systems now available that offer even higher pressures (up to 1000bar), machinists can enjoy even more productivity, reliability and security when cutting and milling.

DR Driil

Foremost Dual Rotary drills feature two rotary drives, including a unique lower rotary drive that is used to advance steel casing through unconsolidated overburden such as sand, gravel, glacial till and boulders. The lower drive feeds and rotates the casing independently of the top drive. The casing is held securely in the lower drive by a set of power-operated jaws. A carbide-studded casing shoe, welded to the casing bottom, cuts through the overburden. Once the desired casing depth is reached, the DR continues drilling open-hole like a conventional top drive drill. There is no need to trip out or change tools when transitioning to open-hole drilling.
The independent rotary top drive simultaneously handles a drill string, which can be equipped with a down-the-hole hammer, tri-cone or drag bit. Cuttings are typically evacuated with air, but Foremost DR drills can also be configured with pumps for mud or flooded reverse circulation drilling.
The upper and lower rotary drives feed independently on separate hydraulic cylinders. This means that the bit position can vary in relation to the casing shoe. In most situations, the bit is advanced slightly ahead of the casing for best penetration rates. In heaving formations, or at times when it is desirable to obtain a clean sample of the formation, the casing can be advanced ahead of the drill bit.
Over the years, the Dual Rotary method has proven very effective for advancing steel casing in difficult unconsolidated overburden. In addition to the primary benefit of effective penetration, the rotation of the casing results in very straight holes and casing can be easily extracted using the lower drive, which is useful in well abandonment applications and for exposing well screens.

Foremost Drills Model Line Up

Foremost Drills Model Line Up

The DR-12 is a light, yet powerful PTO rig popular among domestic water well contractors drilling in moderate to severe overburden. It will handle casing up to 12" (305 mm) in diameter, and has been field tested to depths beyond 550 ft (168 m) for a typical 6" (152 mm) cased well.

The DR-12 is available with an optional pipe tub, single pipe loader arm and telescopic casing jib. The configuration accommodates diverse site conditions.

DR-12

Foremost Dual Rotary (DR) drills have long been known amongst water well drillers for outstanding performance in unconsolidated overburden and water-bearing formations. But open-hole drilling speed is also critical to your profitability. That's why the DR-12W is designed to drill fast in any formation.

It has features like a carousel, pipe tub, rod spinner and draw works winch for quick handling and tripping in open-hole applications. And, when the going gets tough, the DR-12W is equipped with out unique lower rotary drive - just like all Foremost DR rigs - that allows you to simultaneously drill and advance steel casing without special down-hole tools.

DR-24

The DR-24 will set casing up to 24" (610 mm) in diameter. This model is commonly used for domestic and municipal wells, and construction applications such as foundation piling projects and holes for hydraulic elevator jacks.
The DR-24 is available in PTO or deck engine configurations and can be mounted on a truck, trailer or self-propelled tracked carrier.

DR-24HD

The DR-24HD ('heavy-duty') features a heavy-duty gear driven lower drive, which generates two and a half times the torque of the standard DR-24. The DR-24HD is also configured with a heavy-duty mast to withstand the additional torque and larger hoist cylinders for increased pullback capabilities.

The DR-24HD is most commonly used in deep, large diameter applications such as municipal/industrial wells and mine de-watering.

DR-40 handles

The DR-40 handles casing up to 40" (1,000 mm) in diameter. The DR-40 excels in large diameter construction and industrial water well applications.
Standard configurations include tracked undercarriage or crane carrier with deck engine and on-board air compressor.

DR-610C

The DR-610C is a unique hydraulic foundation piling drill that incorporates Foremost's proven Dual Rotary technology to simultaneously drill and advance steel casing in difficult formations. It also provides added flexibility for continuous flight and kelly auger drilling applications.
The DR-610C is designed to set steel casing up to 24" (610 mm) in diameter and has a long stoke via a rack and pinion system. The standard configuration is crawler-mounted, providing 360 degree rotation to quickly load drill pipe and casing from any angle. The DR-610C can also be fitted to other carrier configurations as well.

Foremost Industries LP
Corporate Head Office/Investor Relations
1225 64th Avenue N.E.
Calgary, Alberta, Canada
T2E 8P9
Worldwide Tel: 1-403-295-5800
Canada/U.S.A.: 1-800-661-9190
Fax: 1-403-295-5810

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