MONITORING THE COOLANT LINES A WAY TO REDUCE PRODUCTION COSTS
With the advent of the modern high-speed CNC machines, the need for maintaining optimum concentrations of cutting fluids in machining operations has become essential. Higher feed rates, deeper cuts, better accuracy, reduced power consumption, and longer tool & insert life are all benefits from using the appropriate cutting fluid at the proper concentration.
Some of the water-miscible cutting fluids are actually emulsions, that is, suspensions of oil droplets in water. The oil is emulsified by blending it with an emulsifying agent. With the addition of water, this will combine the lubricating properties of the oil with the cooling properties of water. Too much water results in a loss of lubrication, which can result in damaged cutting inserts, tools or parts. Too much oil can result in a higher cutting temperature that causes damage to parts, inserts, or tools, as well as the higher costs for the oil itself.
Some of these cutting fluids are actually solutions, organic or inorganic compounds that have been dissolved in water. These are of two types: surface-active fluids and inactive fluids. Some of the water-miscible cutting fluids are combinations of emulsions and chemical fluids that produce oil droplets of a much smaller size by using higher emulsifier and surface-active agent contents
Over time, these cutting fluid mixtures are lost by transport on the chips and parts, from the machining feed lines through vaporization of the fluid into the air, evaporation of the water, and spills during the cutting process. These events result in a change in concentration in the remaining fluids contained in the sump. The change in concentration can cause damaged and broken inserts and cutting heads, poorly finished surfaces on machined parts, and loss of accuracy.
While a single machine may not see a large effect from this problem within a short time frame, multiple machines and extended time periods will have a multiplying effect that can result in costs totaling thousands of dollars. Major manufacturers and producers of machined products have a great interest in eliminating or at least controlling these costs.
Establishing a good, efficient ratio of coolant to water has been a rather crude process in the past. Many machine shops have traditionally relied upon a rule-of-thumb measurement by adding a certain amount of the cutting oil to a given amount of water, and simply adding more of this mixture to top off the holding tank as time goes by.
Monitoring has also been haphazard, done at various intervals using guesstimation techniques or hand refractometers. This process requires detailing an individual to actually take the samples from the sump, place them in a hand refractometer, read the refractometer, and record the results. If the coolant concentration is off, arrangements must then be made to add enough coolant or water to bring the mixture back to the required concentration. All of this takes time, resulting in a commensurate loss of production.
The inline process refractometer was developed to solve this monitoring problem. Inline process refractometers monitor a solution continuously, providing an output that can be taken to a PC or PLC for automatic monitoring and control of the concentrations.
Several companies have developed refractometers over the last several years to monitor process lines containing moving solutions, but most are unable to monitor water-miscible fluids due to the emulsive characteristics of these cutting fluids. This problem was recently addressed by James Corbett, President of AFAB Enterprises of Eustis, Florida.
I knew that we could produce a refractometer capable of handling fluids unreadable by most of the refractometers on the market, and at a price far cheaper than any of them,” said Corbett. “The prices of most of these inline refractometers was far above what most machine shops could afford.”
Corbett, who has been involved in refractometer design for some 30 years, has several patents for his work. He developed the PR-111 in its original configuration approximately 4 years ago, and began taking orders for the unit only relatively recently.
“We have now been producing the PR-111 Inline Process Refractometer for three years, and have many successful applications in machining environments,” he explains. “Research and development of the PR-111 has continued, with improvements in the unit being added as experience dictates. We have been working with several manufacturers of machining coolants to produce an accurate and reliable instrument capable of handling the potential tramp oil fouling and coating problems that have affected most inline refractometers.”
AFAB Enterprises has recently made the PR-111 much more responsive to temperature changes, reducing the time it takes for the sensor to react to changes in the fluid characteristics. A high-pressure directed-flow adapter has been developed that reduces the amount of coating build-up on the sensor, thereby reducing or eliminating a problem common to many refractometers in the machining applications.
The PR-111 utilizes a third “backscatter” photocell to eliminate the error generated by light reflected from suspended solids with a solution or emulsion, allowing this refractometer to effectively monitor most cutting fluids in use today. The third cell is a unique feature of the PR-111 that allows it to monitor many machining coolants which much more expensive instruments have been unable to read.
The PR-111 is calibrated by the skilled team of technicians and engineers at AFAB Enterprises to meet the specifications of each individual customer, and is temperature compensated. Mounting adapters for the sensor probe are customized to fit the coolant lines of the particular customer’s facility, and the console of the PR-111 is encased in a NEMA-4 enclosure to protect it from environmental hazards such as dust, water, and etc. The probe can be mounted up to 600 feet away from the console using an 8-lead shielded cable, and optional industrial connectors at both the probe and console ends allow for easy installations.
The unit is CE certified, and comes with a one-year warranty and guaranteed 5% accuracy. By adding the optional SM-2 Smart Meter, the customer can get guaranteed 1% accuracy and a digital readout. The unit provides a 4-20 mA output that can easily be run to most of the available computerized control systems. Power supplies can be selected from 24 VDC for mobile monitoring units and 110VAC and 220VAC for permanent installations.
if your machining operation is experiencing problems maintaining consistent levels of lubrication., an inline process refractometer is the likely “solution for your solutions”. You can count on an inline refractometer to reduce or eliminate damaged equipment, rising material costs, and production downtime.