New retrofit systems make it possible to quickly, easily and cost effectively transform the standard external-coolant live tooling heads on turning machine turrets into those with through-tool-coolant capability. And shops that have done the retrofit are experiencing longer tool life, more efficient chip control and less heat generation.
These retrofit systems also increase overall productivity by allowing for faster machining speeds and feeds as well as shorter cycle times. Plus, they eliminate the high initial cost of dedicated through-coolant heads along with the required routine maintenance (O-rings and lubrication) and complete system rebuilds typically needed every other year.
With respect to increased machine production, through-the-tool coolant is much more efficient than external flood coolant, which is both messy and time consuming. With each tool change, shops must interrupt machining operations to readjust flood coolant nozzles and, often times, getting the spray close to the cut zone proves impossible.
Coolant-through tooling keeps coolant pinpointed at the cutting tool’s edge and precisely in the cut zone to evacuate chips and reduce heat, which ultimately shortens part machining cycle times. For example, through-the-tool coolant capability eliminates time-consuming pecking operations to pull chips out of a hole and relieves built-up heat when drilling deep holes.
Shops can also drill holes quicker in one continuous feed. And, because through-tool coolant controls heat better, it is possible to machine parts at much higher speeds and feeds without the risk of excessive heat generation or premature tool wear.
Maintenance-free retrofit systems often entail few components and install within minutes. Current systems, however, require holders with internally threaded regular ER-type nuts. Fortunately though, about 50% of the manufacturing market already uses these types of holders in straight and angled live heads on turning machine turrets.
Regardless of the retrofit through-the-tool-coolant system type, any standard ER collet should work, and common collet sizes usually range from ER 16 through ER 40. The systems should handle maximum cutting speeds up to 6000 rpm and deliver coolant pressures as high as 300 psi. Currently, special high-pressure systems that work with externally threaded nuts are in development to potentially handle coolant pressures up to 1000 psi.
All retrofittable units incorporate some type of coolant-inducing technology. For instance, one system uses special clamping nuts that induce a tooling head’s external coolant supply into the collet holder cavity. Because this system brings the coolant in through the collet cavity, it prevents coolant from seeping back into the live tooling head’s internal compartment. Such seepage causes many of the maintenance issues associated with dedicated through-coolant heads.
The special clamping nuts eliminate the need for gaskets or O-rings, creating a virtually maintenance-free solution. Instead, the nuts use the coolant as a seal and bearing. During operation, machine tool coolant fills a small gap between the system’s rotating component and a mating stationary nut. Once the gap is full, a liquid bearing forms and reduces friction and dissipates heat caused by system rotation. It also maintains lower operating temperatures to preserve internal components.
Because the special nuts use coolant as a bearing, a machine tool’s coolant must be switched on and flowing prior to starting a cutting tool’s rotation in the live head. Basically any level of coolant pressure will work as long as the coolant is filtered, and the flow is strong, consistent and maintained. Also, there can be no loss of pressure during system operation.
Shops that would benefit greatly from retrofittable alternatives are those using live heads and wanting to easily and cost effectively incorporate through-the-tool coolant into their operations. Within a few minutes, these shops can add such capability and bypass the maintenance and rebuild fees often associated with dedicated through-coolant heads.
This article was first published in the June 2015 edition of Manufacturing Engineering magazine.
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