Has MQL proven to extend tool life as well as the top rated water soluble flood coolants, in turning operations with carbide inserts on steel?
Yes, MQL can work well in turning applications. However there are some special considerations that need to be addressed. Since the cuttingedge of the tool is continuously in the cut, nozzle position is critical and more difficult. Carbide tools can work well, but it is largely determined by the relative size of the parts and the length of time in the cut. In many cases a multi-layer coating, such as TiAlN works even better
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 far too much air through the MQLnozzles 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!
Just as less is better with the air, closer is better with the nozzle. The longer the distance that the nozzle needs to spray, the more airflow is needed to carry aerosol and the higher the likelihood of an unwanted mist being generated. In closed machines, an extraction system can help with this. In open systems, putting the nozzle closer to the cut helps. The fluid output should be virtually invisible. If you see a mist spraying from an external nozzle, you will likely see fogging in the plant.
Unless you are working with very small chips, as in micro-cutting, trying to blow the chips away with air from the fluid delivery spray will only create a fog and use more fluid than is necessary. Use a separate chip removal approach, such as an air blow-off or a vacuum, to remove chips if needed.
On a Coolubricator or Serv-O-Spray system the amount of air that mixes with fluid at the nozzle tip can be adjusted with the air metering screw. Turn the metering screw counter-clockwise to increase the air flow and clockwise to decrease the air flow. A good initial setting is open about from ¼ to ½ of a turn.
Minimum Quantity Lubrication (MQL) is not the same as traditional flood coolant. In fact, it is very different. Many people new to MQL are used to a flood coolant mindset and have trouble making the distinctions:
- MQL does not use a coolant. Traditional flood coolant uses a circulated liquid designed for heat transmission to carry heat away from the interface of the cutting tool and the work piece.
- MQL uses a lubricant. With MQL, friction is reduced within the cutting tool/work piece interface through the use of a lubricant. Advanced lubricants such as Coolube reduce friction, and therefore heat, so well that there is no need to carry heat away using a coolant.
- Coolant uses a flood. For coolant to work, the interface must be flooded with coolant which must then have a place to go when it has done its job and absorbed the heat. This requires constant recirculation of gallons and gallons of coolant.
- MQL uses minimum quantities. Advanced MQL lubricants do their job so well that typically, only a few ounces are used during an 8 hour shift
- Coolant requires extra equipment. Because coolant is re-used until it is no longer viable, it requires equipment to recirculate and filter/clean it. Sump-side coalescers, skimmers, filters, sump vacs, and test kits are common equipment required for the use of coolant.
- MQL requires minimum equipment. With MQL, you need a quality applicator such as a Unist Coolubricator or Serv-O-Spray which has the ability to accurately dispense lubricant and to do it consistently. There is no need for any additional equipment.
- Flood coolant is not a sensitive process. Applying coolant is a simple process. As long as enough coolant is applied to flood the interface, it will work.
- MQL requires hitting a lubrication ‘sweet spot.’ With Minimum Quantity Lubrication, each cutting operation has an appropriate amount of lubricant or ‘sweet spot’ which must be hit to experience MQL‘s benefits. Luckily, adjusting your MQL applicator to hit the sweet spot is simple when you follow some basic guidelines.
- Coolant is anything but dry. Coolant tends to splash and get thrown from the interface. This can result in a mess with coolant coating equipment, parts, chips/swarf, and floors. Since coolant remains after the cutting process, it can create secondary messes during its filtration or disposal phases.
- MQL is near-dry. Such a small quantity of lubricant is applied in MQL that there is no mess to clean up. When applied properly, only a very thin film of lubricant remains on finished parts and chips/swarf are virtually dry meaning they can be recycled for greater profit. With MQL, your equipment and floors stay clean.
- Coolant requires disposal. Once coolant is no longer usable, it requires costly disposal
- MQL lubricants are consumed No excess MQL lubricant remains to require disposal or clean up.
- Coolant is cheap per gallon but an expensive process to maintain. When you consider the additional equipment required to utilize coolant, the increased housekeeping costs, and disposal costs, coolant quickly becomes an expensive proposition.
- MQL is an inexpensive process to maintain. MQL lubricants are more expensive than coolants per gallon. This may be true, but when you consider that only ounces are used per shift, you see that a gallon can go a long way. When you factor in the benefits of MQL in reduced housekeeping, cleaner parts, increased chip/swarf recycling values, healthier employees, and reduced equipment costs, MQLquickly becomes a less expensive proposition than coolant