Problems in a CNC Surface Grinder

Posted on Dec 19, 2020

CNC Surface Grinder

Usually, precise mixing of the coolant in a CNC surface grinder is done by hand, with little regard to the accuracy of the mixture. Since the results are not so readily visible, this problem persists and goes undetected.

Undoubtedly, the most common problem for operators with water-soluble coolant for CNC surface grinders is concentration. It's not that toolmakers have ADHD, but rather, it's a case of too little or too much concentration in the coolant mixture. Commonly, the proper mixing of water-soluble coolant is omitted, leading to poor cutting or grinding performance. Rust, bad smells, possible pitting in the metal, and a poor finish are all signs of inadequate concentrate levels.

Each manufacturer has a specific mixing ratio for each type of coolant and each type of machining application. It is extremely important that you follow these recommendations as they were developed after extensive pre-marketing testing. Usually, precise mixing of the coolant in a CNC surface grinder is done by hand, with little regard to the accuracy of the mixture. Since the results are not so readily visible, this problem persists and goes undetected.

What Is Grinding All About?

Grinding is a less controlled process than other production areas due to the use of a metal removal wheel. A grinding wheel is a cutting material that deteriorates and changes constantly. In fact, it changes its grinding characteristics during grinding. The skillful hands of the miller grind with both sound and sight; listening to the wheels clash. Adjustments were made as needed to control the beast. The process of grinding can never be tamed, only controlled.

No low-cost entry into the grinding arena to meet high-precision tool manufacturing needs. Initial efforts to bring CNC into the surface grinding world were made at the lowest common denominator of technology and cost. Simple manual surface grinders are equipped with basic CNC control. The thinking revolved around the concept that a precision manual surface grinder must be of quality to grind the workpieces precisely and simply needed a basic CNC control to automate the movements. Unfortunately, it has become all too obvious that a precision manual surface grinder is just that - a precision when it is handled and a skilled grinder is constantly making adjustments to make a good part.

CNC Control to Precision Surface Grinding

The CNC control was not simple enough to be used for grinding tasks; Therefore, the first CNC grinding machines left a bad impression on the precision grinding community. They have proved inaccurate for maintenance-free precision grinding and too difficult to program surface grinding applications. Of course, there was some success and initial automation that got transferred to the grinding department, but most of them were relegated to coarse grinding and manufacturing jobs that fit within the limits of the grinding machines. This ineffective stage convinced us that the grinding department belongs to a skilled grinder.

Other technologies such as EDM and hard milling have taken over some of the processes previously performed on surface grinders. To minimize skilled labor costs, management often develops strategies to pull more work away from grinders, further marginalizing the grinding department. Often, the best way to machine a part is through sacrifice due to unreasonable process work.

:: Read More: Boost the Performance of Your Surface Grinder

How To Use Water Soluble Coolants For CNC Surface Grinder?

It’s recommended to use a refractometer to check water-soluble coolant because it's not enough just to guess and randomly add coolant. Take the time to understand that A precision CNC surface grinder requires a suitable coolant mixture and you will get better results.
Most CNC machining or CNC surface grinding operations require "replenishment" of coolant due to the evaporation or evacuation of fluid by the chips or parts. Air tubing is known to slowly lower the fluid level during a purging operation. This make-up coolant should be less concentrated than the starting fluid. It helps to maintain the correct concentration level with regard to evaporation water loss and drainage.

Symptoms of Incorrect Coolant Concentration

• Poor milling or grinding finish
• Shortened life of end mills, drill bits, and carbide inserts
• Glazing or loading of grinding wheels
• Machine tool corrosion
• Bad coolant odors
• Wasted money due to overly concentrated mixtures
• Reduced service life of the sump pump

How to Use Water-soluble Coolants on a CNC Surface Grinder

Oh, that smell! What is that unpleasant smell and where does it come from? How can I get rid of it? Why does some coolant smell? The reason why some CNC coolants have an unpleasant sulfur odor is because of anaerobic bacteria. The smell of rotten eggs can fill a room fairly quickly and in some cases make workers sick. These bacteria must be eliminated before the odor disappears.

How to Get Rid of CNC Machine Coolant Odors?

•Good housekeeping is essential
•Maintain correct coolant concentration levels
•Avoid or prevent contamination
•Keep the filters clean and do not allow coolant to accumulate in any areas
•Periodically clean the sump pump and entire machine

How to Mix Water-soluble Coolants?

Many, if not most, small tool and die making, mold making, or other precision machine shops mix coolant by hand. This can work if the correct amounts are mixed and the correct mixing procedures are followed. As with any industrial material, check with the manufacturer to find out how to thoroughly mix the concentrate. To be sure, check the concentration level with a refractometer. This can be done easily and the refractometer is inexpensive.

Also, leaving the coolant to an apprentice or unskilled worker creates problems. If a person is not properly trained, he or she will almost certainly get worse. In general, the oil should be added last, after adding water. It is also important to use chemically pure water otherwise the PH level may drop or contaminants may enter the coolant.

Even with a steep tradition of highly skilled, innovative tools and die makers, the grinding departments have been surprisingly resistant to CNC technology. The concept of skillful manual work of a grinder working on a hand grinder with frequent visits to the surface plate and optical comparator is alive and well in the United States, with every detail of a precision mold component carefully ground and individually qualified.

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