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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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.

 

 

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