Worth knowing

Flood cooling, be it with water or oil, is still the most frequently used method for cooling and lubricating workpieces during the machining process. However, high costs are incurred here for maintaining the cooling lubricant and problems arise due to health risks. In addition, the striking, for example of an emulsion, onto the tool cutting edge causes a proper temperature shock with a minimum temperature. When the tool cutting edge re-enters the workpiece, the cutting edge temperature then increases again to its highest level. The consequence is increased variation in stress to the tool and the coating and an uneven surface appearance. When the oil is filtered, the development of micro-sludge can lead to increased wear. Moreover, additives used to improve the lubricating products harbour risks to health and the environment.

Pure dry machining in turn means extreme tool technology requirements. The temperature level is relatively even here, but is far above that in flood cooling. For some large-scale production applications, dry machining is definitely state of the art and makes perfect sense. On the other hand, this machining technology is not really universally applicable, but instead requires many special solutions with, for example, a large amount of energy and cooling needed for the spindle and machine. As a further example, only a handful of machine manufacturers worldwide supply the required machine stability for effective hard turning.

Residue free lubrication with UNILUBE

With UNILUBE residue free lubrication, for an optimal application using the UNILUBE nozzle technology, the lubricant particles get between the tool and workpiece as a permanent and constantly renewed micro-lubrication layer. In the case of this minimal lubricating technology, the consumption is less than 0.5 ml per hour and nozzle. Furthermore, the evaporation energy leads to reduced resistance with less heat building up. The lubrication layer thus also provides an even, ultra-thin separating layer between the tool and the chip. You can imagine this like a drop of water that jumps around on a hot stove due to the vapour generated. Similarly the evaporating lubricant medium reduces the resistance between the tool and chip and achieves good removal. This creates stable temperature conditions on the tool and workpiece. Due to the increased feed rate and cutting speed, the heat still generated from cutting goes into the chips and is dissipated. Altogether, the heat developed here is much lower than with pure dry machining, and if you consider the effective cutting edge, this is even the case compared to flood cooling.

If the amount of lubricant is set too low, the generated film will tear off, thereby reaching the sphere of pure dry machining. This leads to an increase in temperature, resistance and wear. In practice, this is seldom or never the case, when using UNILUBE lubricating systems. On the contrary, users who are familiar with flood cooling tend to set the system parameters much too fully. The result is fogging and wet workpieces. Our advice is therefore always: “Please set lower.”

Less is more

If the lubricant consumption is set too high, this increases the resistance between the reactants due the development of disruptive and inhibiting fluid cushions and, besides higher temperatures in the tool’s working area, also generates microcavitations in the tool cutting edge and the workpiece. In the case of high surface quality standards, as required by the optical industry for example, this can lead to increased wear or scrap in case of doubt. If the delivery rate is increased further (e.g. minimal quantity sprayers), you get into the area of flood cooling (see above) with wet workpieces, sticky machines and unsatisfactory machining results. Only a constant micro-dosing with repeat accuracy, as is guaranteed with the UNILUBE ECOLUBE “μ“ minimal lubrication system, can prevent irregularities in the machining result, and do so with all the ecological and economical benefits.