Month: June 2014

Chip removal in MQL is different than in flood cooling. In some ways it is harder; there is no fluid to wash chips away from the cut. In other ways it is better because dry chips typically move more easily and cleanly than wet ones. Fast and complete removal of chips and metal dust from the workspace is important. Hot chips in contact with the tool or the work piece will increase the heat at that point. Chip accumulation and residues in the work area (e.g. on the work pieces and machining equipment) should be avoided as much as possible.

A good option for chip evacuation is an air blow-off. Compressed air can be used to blow the chips away from the work area. Pulsed air often works well for this and also minimizes air consumption. When using an air blow-off, consideration should be given to the emissions and metal dust that will also be blown. The use of an emission system can help alleviate any issues associated with this. It is also import to ensure you are not blowing the chips back into the cut. A separate air blow-off nozzle is recommended, not the nozzle that delivers the MQL fluid. Except in cases where the chips are very small or very fine, such as in micromachining, the air volume needed to move the chips is much higher than that needed to deliver the fluid. Trying to use one nozzle for both tasks will likely end up doing neither very well.

Although commonly called a mist system, machining with minimum quantity lubrication has been shown to produce fewer emissions than flood cooling. It is, in fact, a low-emission process. Unfortunately, when starting with MQL, many shops think that more is better so they blast as much air as possible through the MQL nozzles and literally create a fog or mist of lubricant in the air. This is not MQL! A properly adjusted MQL system uses just enough air velocity to drive the lubricant to the tool, not enough to drive it around the block!

MQL has fewer emissions and is safer than standard flood coolant. Numerous studies measured the exposure of machine operators working around and inside of the machine as well as the more static levels just at the machine’s control panel. In the main study, which was conducted by the German government, the baseline was done using flood coolants. MQL was found to never have higher levels for aerosols, and the concentrations in more than 95% of the areas were less than half of the flood coolant baseline values.