Managing chips and fluid is vital to maximizing machine tool output
Some of the most impressive sights at industrial trade shows are big machine tools cutting away at large parts while being sprayed with coolant. To keep those machine tools operating at peak output requires a less glamorous part of manufacturing: the systems that help manufacturers remove chips and recycle fluid.
The products these companies produce include filtration and recycling systems, conveyors and centrifuges. Among the factors that such equipment has to deal with are environmental regulations and changes in the machine tool industry, where machines cut parts more precisely and perform more tasks.
“The focus of coolant recycling systems is to recover the coolant to meet the requirements specified by the machine tool manufacturer,” said James D. West, general manager of Sanborn Technologies’ North American filtration division (Walpole, MA).
There is “almost always a tradeoff between recycling equipment costs and what is considered ‘clean enough,’” he said. “Technology has advanced to a point where we can provide recycled coolant with the same specifications as new coolant. The challenge has been how to achieve the best results at a lower capital cost.”
One part of the equation is the need for precision cutting. That, in turn, affects other steps in the process.
“The demand for high-precision parts is growing in multiple industries, especially in the medical industry,” said Neb Petrovic, director of machine tool products at Mayfran International Inc. (Cleveland).
“In order to achieve this, high-precision tools are required to machine the parts within tolerance,” he said. “The coolant quality is a critical component for maintaining the high level of precision. In order to clean the coolant properly, high-end separator conveyors are required to remove the fine particles from the coolant.”
Removing chips from coolant “is important so that tolerances of the parts and tool life can be maintained,” said Darrell Milton, market manager, metals recycling for Eriez (Erie, PA).
“Chips that recirculate in the coolant can score or pit expensive parts as well as cause premature damage to machine tool and grinding wheels,” Milton said in a written statement. “With large dollar machine tool investments, demands from aerospace and medical manufacturers and others to maintain critical tolerances and eliminate potential damage to expensive components, precision is essential.”
Coolant formulas have also changed, including vegetable-based fluids instead of traditional oil-based ones.
“New coolants can be very challenging for us,” Friedrich Bitterwolf, director of engineering at Jorgensen Conveyors Inc. (Mequon, WI), said in a written statement.
He said coolant “can have physical impact on our conveyor and filtration systems,” and the company focuses “on making sure that our component materials are compatible with the coolant chemistry.”
For example, he said, “We have made stainless steel tanks for many years with zinc-coated parts inside.” However, “the introduction of a new coolant generated a reaction with the two metals and the liquid coolant. We had to suddenly change the materials of our product to accommodate the use of this coolant.”
What follows is a look at the strategy of some companies.
Machining Precision Parts
Sanborn Technologies’ lineup of products includes filtration systems and centrifuges. The company’s equipment is designed to remove fine solids and tramp oil.
West said in his more than 30 years in the industry, “the core technologies have not changed. We can improve some designs and features, but the core technologies are the same. What has changed is how to process coolant to achieve a cleaner recycled product, at a higher throughput and at a lower cost per gallon.”
Machine tool makers “are the real drivers in this selection process,” West said. “They are the ones that examine quality and performance of the coolant and specify requirements for coolants that are used in their equipment.”
According to West, the problem is getting the end user of the machine tools to also invest in recycling systems.
“What is happening out in the field is a lack in understanding in the value of coolant recycling,” he said. “I am amazed, on a regular basis, by how many machining operations still employ no coolant recycling programs at all. And this is not just small shops, but major manufacturing operations as well…It is much easier to spend operating cash than get capital expenditures approved for ‘nonproductive’ equipment.”
Manufacturing precision parts, he said, “requires more control over coolant quality. This, in turn, requires better performing coolant recycling systems. The problem is convincing the customer it is worth the additional capital investment.”
West said the Sanborn products most affected by environmental regulations are its ultrafiltration (UF) systems, which are “primarily used for disposing of spent coolants, compressor blow-down and other similar oil wastewater streams.
“As the cost for disposing of oil wastewater increases, equipment that can reduce disposal volumes by 95% or more become more in demand,” he said. “There has also been an increased demand for our UF systems in the recycling of mop water and wastewater from floor scrubbers.
“From our perspective, the next step in recycling systems is for manufacturers to recognize the need and value for installing coolant recycling systems in their facilities.”
‘Higher Up Times’
Mayfran products include shredders for chip processing, conveyors to move chips and filter systems.
Environmental regulations and the cost of coolant replacement have “driven the industry to prolong the life of the coolant,” Petrovic said. “Some cutting fluids are considered hazardous waste and have special disposal regulations. The costs to dispose of these fluids can be high so extending the life of the cutting fluid is financially beneficial.”
Changes in machine tools has spurred evolution in systems to manage chips and fluids, Petrovic said.
“The days of machines cutting a specific part for the entire life of the machine are decreasing,” he said. “In order for companies to maximize profits, the machine tools need higher up times so they can cut various materials and produce multiple parts.
“Cutting different materials on the same machine means that a better general-purpose separator is required to properly remove the various materials from the coolant.”
Mayfran has developed a general-purpose separator called ConSep Flex. It includes a chip conveyor to remove larger particles and a media drum filter to clean coolant. A magnetic bed was added to the separator. The company said conveyor designs are changing to deal with newer, harder materials.
“Conveyor construction now often includes the use of harder and abrasion-resistant material in order to extend the life of the conveyor,” he said. Challenges posed by new materials are growing, he said.
“Machining of carbon fiber composite materials is increasing,” Petrovic said. “The chips that are produced are unlike most other commonly machined materials like cast iron, aluminum and steel. These composite materials are nonferrous so magnetic conveyors cannot be used to separate” the material from coolant.
“Traditional media-style drum filters are not an efficient solution,” he said. “The new proven solution is utilizing a deep-bed gravity paper filter to permanently remove these small particles. The deep bed allows coolant to accumulate in the conveyor and a ‘filter cake’ on the paper is produced. The formation of this filter cake increases the filtration level, which allows the conveyor to remove a high volume of very small particles.”
Eriez designs and manufactures magnetic separation, metal detection and other equipment for metalworking industries, according to its website.
The company has introduced its Superfiltration technology, which Milton said “recovers particles down to 3 μm, which means a cleaner oil, in many cases cleaner than new oil.” Also, he said, “The use of variable frequency drives to match coolant demand from the pumps offers energy savings that can be measured over a period of time. We now also minimize the use of filter aids by developing and manufacturing machines that are more efficient in their operation.
“Eriez equipment removes chips from the coolant and oils but can also maintain coolant or oil temperatures.” Maintaining a set temperature is important, he said, because “temperature fluctuations in the coolant or oil will have a negative effect on the tolerances of the parts being machined.”
Need for Flexibility
Jorgensen’s products include conveyors, coolant filtration and material handling equipment.
Regulations spur “our customers to reduce the amount of coolant they dispose of,” Bitterwolf said in the written statement. “The best way to extend coolant life is through proper filtration.”
One of Jorgensen’s offerings is EcoFilter, which offers primary chip removal and secondary filtering of coolant. The company said its Vacuum Media Filter removes fine chips and grinding sludge. The company said its filtration systems are used in various CNC grinding, metalcutting and composite machining operations.
“Our product solutions are designed such that they can readily and cost-effectively be modified in the field,” Bitterwolf said. “Our systems in the future have to be more flexible, so they can grow with the demand.”
More changes may come in the future, he said.
“There is not enough standardization in machine tools and filtration equipment,” Bitterwolf said. “The end users would like to see a standardized interface. Right now it’s very complicated for end users to update their filtration system when needed. Sometimes their system has to be completely changed out and they cannot keep any of the parts.”
PRAB (Kalamazoo, MI) produces automated systems for processing metal turnings and recovering cutting fluids.
“PRAB has integrated our chip and fluid treatment systems to provide a complete machine shop recycling system,” said Mike Hook, the company’s national sales manager.
The company said its wringer and centrifuge systems remove up to 98% of spent metalworking fluids from chips. Coolant is collected in a holding tank under the wringer. A separator removes tramp oils and provides clean fluid that can be reused, according to PRAB.
“The cleanliness of the coolant plays a significant role in tool life and surface finish,” Hook said. “By recycling the cutting fluids on a regular schedule, PRAB customers have witnessed up to 200% improvement in tool life.”