by Kip Hanson
Still struggling with bird nests? It might be time for a different toolholder and a different pump.
Making chips is only part of the machining battle. It’s the size and shape of them that often spells success. Without chip control, part quality and tool life suffer, and it’s practically impossible to develop a repeatable process. Furthermore, long stringy chips are dangerous, leading to cut fingers or worse. The good news is, there’s no reason to settle for wads of chips wrapped around tools and coolant lines or having to stop the machine to remove stringers before they can jam up the chip conveyor. Provided you use a modern toolholder, appropriate feeds and speeds and sufficient coolant pressure, even the gnarliest metals are easily tamed.
Keep calm and blast away
Let’s start with the last of these—coolant pressure. Ron Parker, national product manager for high pressure coolant systems at LNS North America, explains that the traditional low pressure approach to cutting fluid delivery is unacceptable, providing little to no lubrication in the cutting area, extreme and inconsistent temperatures, and inefficient chip removal. “Flood coolant typically turns to super-heated steam before it can reach the tip of the cutting tool,” he says. “The result is poor tool life and even damage to the workpiece.”
At pressures of 1,000 psi (70 bar) or higher, however, cutting fluids can reach the work zone and are forced into the area between the cutter and workpiece. Not only does this increase lubrication where it’s needed most, but the lower temperatures eliminate the “steam effect” while also shortening the chip’s shear zone, which helps to break them up. Chip evacuation becomes easier, tool life improves and grows more predictable, and feeds and speeds can generally be raised, leading to higher productivity.
To this end, LNS offers a variety of high pressure coolant (HPC) systems, including variable and fixed volume pumps, filtration units, high performance chillers, and more. Which to purchase depends on factors such as:
The type of application (milling, turning, or drilling)
Available spindle horsepower (coolant needs increase in direct proportion to the machine’s metal removal capabilities)
And orifice size (a smaller hole means a less powerful pump can be used, but at the expense of coolant volume).
“There’s a lot to consider when sizing a system, which is why LNS Chipblaster has an entire engineering and applications staff dedicated to high-pressure coolant technology,” Parker says.
Use the force
“Apart from better chip control, we’ve seen a substantial improvement in tool life and productivity—up to 150 per cent in some cases.” That’s according to Abhay Chaubal, product manager for North America at Seco Tools LLC, who isn’t referring to HPC per se, but rather Seco’s JETI (Jetstream Integrated) system when used in conjunction with HPC.
“We recommend at least 300 psi to be effective, with 1,000 psi more than sufficient for most applications,” he says. “However, even with the low-pressure pump that comes standard on most machine tools, precision coolant delivery provides a host of benefits. These include less built-up edge (BUE), as well as reduced flank wear, chipping, and deformation.”
Jetstream delivers coolant through the tool block directly to the work zone in two directions— through the insert clamp up top, and via an integrated port directly underneath. Provided the block is designed for JETI coolant delivery, there’s no need for additional plumbing, although Chaubal is quick to note that adapting a non-JETI holder for Jetstream coolant is no big deal.
“The JETI tooling system dramatically reduces setup time,” he adds. “This is why we introduced a wide range of quick-change tooling for Swiss-style CNC lathes earlier this year, bolstering our existing Jetstream product lineup. Each provides a best of both worlds solution in terms of chip control and productivity.”
Ashok Guruswamy, product manager for Grip/Turn products at Iscar Tools Canada, agrees on the importance of precision HPC delivery, but says the best place to start is with the company’s JetCut High Pressure Tooling technology, noting that effective and efficient cooling can mean the difference between profit and loss:
It improved tool life from one to three pieces during a heavy, interrupted cut in a groove-turn application on a 300M forging (a type of 4340 steel), resulting in a 26 per cent cycle time reduction and overall cost savings of 20 per cent.
When parting aluminum, JetCut helped to maintain surface roughness and straightness from the first part to the last, and also improved tool life from 2500 to 3000 pieces. Here again, there was a 32 per cent reduction in cycle time and a 26 per cent cost saving.
When boring holes 6 x D in gummy, low-carbon steel, it helped to clear chips from around the cutting zone, eliminating friction between the tool and workpiece. Surface roughness and tolerance were improved as well, leading to a 30 per cent shorter cycle time and a cost saving of 27 per cent.
“The new JeT-R-Turn design uses a hollow rigid clamp, which allows Jet-Cut High Pressure coolant to reach the cutting edge without any obstacles or need for coolant tubes,” says Iscar’s Guruswamy. “This is a strong and reliable clamping mechanism that provides excellent performance even during heavy and interrupted cuts, extending tool life while also ensuring repeatable insert locating.” SMT