Learn about Near Dry Machining

Near dry machining can be described in three ways:

  1. Minimum Quantity Lubrication (MQL)
  2. Micro-Fluidisation. (MF)
  3. Near Dry Machining. (NDM)

They all mean the same thing and this technology is now available through Unist Australia P/L. Near Dry Machining (NDM) techniques can be applied to almost any metal cutting or metal working application where you are cutting, sawing, milling, drilling, boring, reaming, bending, tapping only your imagination is the limiting factor…other ideas are automatic screw machines, CNC turning, vertical and horizontal with or without coolant fed turrets, CNC milling with or without coolant fed spinals, Rotary index machines, sanders and transfer machines, not to mention roll forming, band saws and circular saws mandrel bending machines. Almost all materials and process can benefit from this technology, the more difficult and challenging the better the results.

This technology can we well applied to both fixed and portable machining operations.

Is MQL a viable alternative to dry and wet machining?

Yes, this concept applies to virtually all metalworking processes on metals, many plastics and composites. The use of minute applications of primarily vegetable oil-based lubricants in metal working operations can reduce heat generation, speed up production, improve surface finish, improve tool life and reduce housekeeping while eliminating the collecting, treating and disposal considerations associated with flood coolants. The high strength microscopic lubricating film on the tool reduces friction, thus reducing heat generation and subsequently the need to remove heat. Not only will you be able to maintain your current cutting speeds and feeds, in many cases we can improve this whilst at the same time eliminating your machine coolant, cutting oil, cutting fluid which create such a mess and contribute to 10-15% of manufacturing costs.

Is it a popular choice amongst manufacturers?

With the growing awareness of the stringent laws regarding workers health and safety in the work place, not to mention the litigation that companies can find themselves in when it comes to complying with the rules and regulations of the Environmental Protection Authorities (EPA) companies are looking for new ways to clean up the work place. Minimum Quantity Lubrication (MQL) is the answer to a huge range machining problems that currently use traditional flood coolant systems, Unist Australia offers the complete solution for (MQL)supplying both the applicators and the high grade vegetable fluids to complete the job. Unist also offers educational material and field trials in order to prove the point that MQL is the way forward.

What are the benefits of MQL to manufacturers?

Some of the more obvious benefits of (MQL) include:

  • Elimination of air borne particles
  • Improved tool life.
  • Less housekeeping.
  • Increased chip value.
  • Increased production speeds and feeds.
  • No employee health concerns.
  • No machine coolant testing.
  • No machine coolant filtering.
  • No metal cutting coolant disposal costs.
  • No fluid oxidation (stickiness).
  • The low cost of using a high grade Vegetable.
  • No need for high pressure systems.

Each of the above have cost savings allocated to them and a progressive customer will recognise their own costs and savings that can be made in relation to their particular operations.

Lubricating fluids can amount to approx. 16% of the cost of an average job – how can MQL make savings in this costly area of manufacturing?

By employing minimum quantity lubrication (MQL) with the correct cutting fluid and the correct application of that fluid MQL can yield the lowest net manufacturing costs. Utilizing Unist oil mist, lubrication spray, lubrication system, oil lubrication system products along with their Coolube 2210 or 2210EP (EP extra pressure) we can revolutionise your metal cutting processes.

What environmental benefits can be seen with MQL?

A recent case study shows that coolant cost were reduced by 97% by a company that drills 3,200 holes per day and punches an additional 20,000 holes per day, and this was just the start of the savings for this company.

This company produced packages designed for field erection with bolted connection instead of weld-ments. Using common twist drills in a horizontal CNC drill and a 4-station punching machine to accomplish the hole making task, the shop employed soluble oil flood coolant for the drill and spot lubrication/coolant for the punching operation. Additional machining coolant was flooded onto the steel and aluminium being cut on the operation’s Peddinghaus saw.

The EPA compliant disposal costs for the coolant, plus the costs associated with cleaning of the coolant sumps on a weekly basis, leveraged the cost upwards. Because of the heat and humidity, cleaning the sumps was essential to control bacterial growth and resulting problems, such as odour and dermatitis cases.

Can MQL positively impact tool life?

A recent project in the Hunter Valley had to drill and ream 73mm diameter holes on site using a Climax drilling unit. Typical twist drills were replaced by Amec spade drills, incorporating Thu-the tool lubrication powered by a Unist Tornado unit. Typical tool life was extended by up to 300%.

Through what method is MQL dispersed into the cutting area?

Normally, the equipment for applying these lubricants is composed of small, air-operated, adjustable, positive displacement lubricant pumps often referred too as mist lubrication systems, oil mist systems, automatic lubricator system and the like. The cycle rate of the pumps is normally adjustable by either a pulse generator or an electrical repeat cycle time delay operating a solenoid valve. A normal approximate output per nozzle is about 1 drop every 10 seconds (0.2ml/Min), at which rate a litre would last about 100 hours.

Compressed air is used to operate the pumps and break up the lubricant and carry it to its point of application. On-Off controls can be electrical, pneumatic or manual in most cases.

Existing NC and CNC controls can operate these systems.

These applicators are most commonly mounted in electrical style enclosures, but in some cases an enclosure is not required. Although most systems are sold with small, gravity feed reservoirs, many can be remotely supplied by a centralized reservoir of any size including pressure tanks and/or pumps.

The use of positive displacement pumps for fluid metering offers various advantages:

  • Unaffected by viscosity variations (due to temperature change or fluid composition).
  • The nozzle length is not practically affected.
  • A system may have multiple nozzles, all with independent controls for cycling and/or on/off actuation.
  • The lubricant output will be repeatable and consistent.
  • Various on-off controls may be used.

Reliable, consistent and controllable applications equipment is critical for obtaining optimum results. Applying too much lubricant is detrimental, may result in unnecessary clean up and smoking (even fire), and will impede the friction reduction phenomenon.

What are the current limitations of the technology to overcome?

I think the only limitations are where to apply this technology in people’s minds, although I believe that in some machining instances there are limitations of how much heat can be removed from the cutting area using NDM. When this is the case may be flood coolant systems still have a role to play.

What applications are MQL best suited to?

Anywhere metal, plastic, or ceramics are being machined, be the metals ferrous or non-ferrous it doesn’t matter, if the machining is portable or fixed neither does it matter.

Where flood coolant systems are used, causing OH&S and environmental issues.

Where tool life is a substantial cost to the operation.

What advice would you give manufacturers looking to implement MQL in their operation?

Examine the current methods and question all the associate cost of that process.

This question is covered by the earlier question of What benefits can a manufacturer obtain by implementing MQL.

How to choose a suitable high quality vegetable fluid to implement MQL

BY PRICE. Price per unit quantity has some bearing; however, the ratio of the amount consumed to work performed is critical. A more expensive fluid used in lesser quantities could be the most cost effective.

BY COLOUR. The natural, pure, colours are a pale yellow to colourless. Adding any colouring contaminates the natural product, reducing its effectiveness. Since blue is the least contaminating colour it is often used by many suppliers. A more deep yellow colour could indicate that sulphur has been added to increase pressure properties

BY FRICTION TESTS. Although friction tests have some value, if performance in a machining operation is the objective, testing it in that operation is the only valid test. Friction test results may have little or no value in fluid machining performance characteristics

BY SMELL. Most all vegetable fluids are almost odourless at room temperature. More commonly, an undesirable odour can be generated when the fluids become hot. Since normally they have a very high flash point, they can get extremely hot before burning and emit an undesirable odour

BY FEEL. Commonly, rubbing some fluid between the fingers is used to evaluate the “slipperiness” of a fluid. This has no bearing on what is transpiring at the interface of a warm cutting tool and the work piece.

BY SHELF LIFE. A truly pure vegetable product will have an infinite shelf life. Additives intended to increase performance and/or reduce cost could cause degradation of shelf life

BY ENVIRONMENT REQUIREMENTS. Vegetable fluids are almost always very environmentally friendly in their neat state. Normally they are non-toxic and biodegradable. Once they are applied, they can “break-down”, and possibly react with the machined material and its chips, creating less desirable properties. Often if the fluid is atomized excessively, airborne particles can result which may cause irritation. This normally results from excess fluid and/or excess atomizing air

BY COMPATIBILITY WITH PAINT, SUBSEQUENT PROCESSING, ETC. Most fluids require viton seal materials. Some fluids are compatible with pre-painted stock, but may have negative side effects. Some fluids can ruin anodizing fluids. Some fluids can become tacky causing chips to adhere to each other, the tool and machine. This same property can cause a varnish type residue to form which is not soluble in any other fluid

BY RELIABILITY OF SOURCE. Most companies have many products available at differing prices. Check with your supplier on the properties of their products. Most often “You get what you pay for.” A cheaper product may not be the most cost effective option.

BY PERFORMANCE. There is no better way than trying the fluid in the actual application of its intended use. Many fluids will initially give similar results. Many fluids will expose oxidation or polarization problems only after exposure to heat and pressure. The most notable evidence of negative properties is “stickiness” which could eventually build into a hard varnish residue, creating unlimited problems. The less pure and normally less costly fluids fall into this category.

BY VISCOSITY. Vegetable products are known for their good “viscosity index”– that is viscosity changes very little with a temperature change. Viscosity at room temperature really tells very little about the effectiveness of a lubricant at the interface of a cutter and the work piece, the true behaviour of a lubricant under such pressures is not predictable and is best determined by experimentation. Penetration – or the ability of a fluid to migrate into the heat zone is a key to fluid effectiveness.

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