Turning ups the temperature

Proper cooling is essential in turning operations, especially for exotic materials

High pressure coolant can be effective in breaking chips and, in cases when it is difficult to break chips and the chip formed is long and curled.

Cooling is essential to the machining world, where appropriate coolant use can significantly increase insert life and reduce manufacturing costs. Changes in chip shape, and the resulting temperature increase, impede the machining process.

In the last few years new cooling options for cutting tools have enjoyed a surge in popularity and enthusiasm as if they had never existed before. Machine manufacturers throughout the world have invested time and resources to develop technology that can supply coolant at high pressures, and today all new machines are supplied with a high-pressure coolant option.

Manufacturers in industries such as aerospace, automotive, and large-part production appreciate the advantage of supplying coolant directly to the cutting edge. These companies typically only order machines with high-pressure coolant capabilities of at a minimum 70 bar and up to 300 bar. Mass production manufacturers also benefit from the integration of high-pressure coolant into their processes.

Heat is the enemy

One of the most serious enemies of carbide inserts is the high temperature of the materials that results from the machining process. Temperatures vary depending both on the properties of the metal that is being machined and on environmental work conditions. The average temperature during machining can range from 300 to 900 degrees C.

As the temperature rises, the lifespan of the inserts is shortened. Increased wear can damage workpiece quality and negatively affect machining properties. The heat generated between the insert and the workpiece also can cause a change in chip shape and plastic deformation of the insert.

High-pressure coolant -- starting at 70 bar -- can be effective in breaking chips. In cases when it is difficult to break chips and the chip form is long and curled, coolant applied correctly and under high pressure can solve this problem.

Judicious application of coolant can prevent the workpiece materials from deformation and can act as a protectant for the machine. In many cases, effective and efficient cooling actually can mean the difference between profit and loss.

Machining exotics

Cooling has a major influence on machining exotic materials such as INCONEL®, titanium, HASTELLOY®, and MONEL®, which are all used in the aerospace industry. These workpiece materials are difficult to machine because they have a very high nickel content and possess a tendency to stick to cutter edges because of their elastic, sticky, and ductile properties. These are reasons that parts for the aerospace industry are extremely expensive. Machining these types of materials without coolant is almost impossible, because the high temperatures and stickiness cause instantaneous wear and premature failure of carbide inserts.

In addition to reducing temperatures for exotic metals, the use of coolant creates a shielded area between the insert and the workpiece material, preventing material from sticking to the cutting edge, which is a major factor in premature failure for inserts.

In groove-turn operations, it is particularly important to select the right grade for chipbreaking. An incorrect grade or chipbreaker choice can spell disaster for a manufacturer. In addition, cooling has a significant effect on chipbreaking effectiveness, and correct coolant application can mean the difference between success and failure.

After researching and studying the influence of coolant on its inserts, Iscar developed an integrated external and internal tools that deliver coolant directly to the cutting edge, including the JetCut range.

After researching and studying the influence of coolant on its inserts, Iscar applied this knowledge to new cooling technologies for turning operations. Integrated external and internal tools that deliver coolant directly to the cutting edge have succeeded in increasing tool life and improving productivity, and even at pressures as low as 10 or 20 bar, the advantages of directing coolant flow straight at the cutting edge can be seen in the reduction of temperature during machining.

Manufacturers engaging in high-volume machining have noted a substantial increase in tool life and productivity after integrating higher-pressure, directed tools that pinpoint coolant directly to the cutting zone. When the temperature is lowered, tool life increases, and cutting conditions such as speeds and feeds can be increased.

Manufacturers that work with exotic materials such as INCONEL, titanium, and stainless steels also have managed to achieve higher productivity by incorporating these types of tools. Pinpointing high-pressure coolant straight onto the cutting zone prevents a sticky edge from occurring, consequently extending tool life.

Rafi Ravoach is director of product management, non-rotating tools for Iscar Tools, 2100 Bristol Circle, Oakville, Ont. L6H 5R3, 905-829-9000, www.iscar.ca.