Metalworking Fluid Troubleshooting Guide

Here are quick tips for solving the problems with your shop's most significant liquid asset.

Article From: 3/3/2009 Modern Machine Shop

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Take good care of your coolant. Here's how.

Metalworking fluids have seen so many technology advances that, among other improvements, the “Monday morning odor” is probably a thing of the past in many facilities.

Indeed, as a component of the metalworking process, the fluid is as finely engineered as almost any machine, tooling or control components that is also vital to making the part. This sophistication makes it all the more valuable to keep the performance of the cutting fluid high. Proper maintenance is key to this.

Mike Pelham, a chemist involved in machining and grinding fluid development for International Chemical Company, compiled the troubleshooting table below. It addresses both common and not-so-common factors that can affect coolant performance. In a way, this table is an investment guide, helping shops to realize the highest rate of return from their most significant “liquid asset.”

PROBLEM	POTENTIAL CAUSES	SOLUTIONS
CORROSION	Too Weak Concentration	Adjust and maintain concentration as recommended by coolant manufacturer.
	Poor Water Quality/Corrosive Ion Buildup from Water	Use better quality water such as deionized, reverse osmosis or softened water.
	High Temperature/Humidity	Reduce temperature and humidity and/or use a supplementary rust preventative.
	Contamination	Identify and eliminate contaminants that promote corrosion, such as heat treating salts.
	Corrosive Atmosphere	Identify and vent corrosive fumes out of problem area. Could be from heat treat or propane forklift truck exhaust.
	Part Handling/Storage	Use clean, plastic dividers to allow parts to dry and remain separate. For extended storage, use a supplementary rust preventative
POOR TOOL LIFE	Too Weak Concentration	Adjust and maintain concentration as recommended by coolant manufacturer.
	Water Quality	Hard water (greater than 200 ppm Total Hardness) can promote mix instability in metalworking fluids and lead to loss of tool or wheel life.
	Changes	Verify that no changes have been made to the coolant, tooling or material you are working with.
	Contamination	Identify and eliminate or minimize contaminants that promote loss of tool or wheel life, such as high levels of hydraulic or way oils, floor cleaners or other coolants.
FOAM	Too Strong Concentrate	Adjust and maintain concentration as recommended by coolant manufacturer.
	Type of Operation	Some operations, such as high-speed milling or surface grinding, can promote foam. Work with your coolant supplier to implement the product properly suited for your operation.
	Contamination	Look upstream from operation. What chemical or lubricant has been in contact with the part, and how does this impact foam?
	Water Quality	Soft water (less than 100 ppm Total Hardness) can promote foam in some metalworking coolants.
	Coolant Level Low	Keep the sump full in order to maximize fluid retention time in sump and allow the air to come out of the mix.
	Mechanical Problems	Check the fluid delivery, filtration system, and fluid return systems for mechanical problems and repair them. Kinks in the hoses or small pinholes may allow air to be pulled into the system.
COOLANT INSTABILITY	Water Quality	Hard water (greater than 200 ppm Total Hardness) can promote an unstable mixture. Technology exists to prevent this, particularly in synthetic products.
	Contamination	Identify and eliminate or minimize contaminants that promote coolant instability. These may include tramp oils, way lubricants or chemicals from a previous process.
	Concentration	Adjust and maintain concentration as recommended by coolant manufacturer
TACKINESS/ STICKINESS/ GOOEYNESS	Quality of Water	Hard water (greater than 200 ppm Total Hardness) can create tackiness in certain coolants. Your coolant supplier can provide coolants with blended additives that naturally soften the water.
	Delivery	Some machining centers may have “blind” areas where coolant in not in continous contact. With heat and time the water will evaporate, leaving a film that will cause chips to cling. A daily flush of the area with coolant will reduce this problem.
	Contamination	Identify and eliminate or minimize contaminants that promote coolant instability. These may include tramp oils, way lubricants or chemicals from a previous process.
POOR SURFACE FINISH	Concentration	Adjust and maintain concentration as recommended by manufacturer.
	Coolant Instability	When coolants become unstable (see “Coolant Instability” below), the additives can be depleted and lead to more rapid tool wear. This is common for older soluble oil formulations. Newer synthetic formulations do not have this problem.
	Changes	Verify that no changes have been made to the coolant, tooling or material you are working with.
RANCIDITY	Concentration	Adjust and maintain concentration as recommended by coolant manufacturer.
	Circulation	Keep it moving. Circulating the tank will assist with sump life.
	Tramp Oil	Tramp oil can promote microbial growth, especially in soluble oil formulations. Implement preventative maintenance practices to minimize tramp oil. This will improve coolant life and minimize waste.
	Contamination	If adding water manually, use clean buckets. Minimize tramp oil and use oil skimmers.
	Micro-Biological Activity	If concentration and other factors are not the cause, then the use of a tank-side biocide may be necessary. Advancements in coolant technology have minimized this. If your coolant requires this, contact the manufacturer. A machine cleaner may be necessary to eliminate bacteria or fungus.