Effect of Feed Rate and Cutting Speed on Cutting Temperature

Cutting speed is the distance covered by the tool surface during the cutting process and it depends upon the types of materials and tools being used for the machining process. If the material being machined is harder, then the cutting speeds will be lower. The cutting speed for aluminum is higher compared to brass, bronze, and cast iron. The tensile strength of Titanium is higher than Aluminum, so the cutting speeds of titanium are less as compared to aluminum. The cutting speed for aluminum is 122-305 meters per minute and 400-1000 surface feet per minute while for titanium 25-55 surface feet per minute.

How the cutting temperature are effected by feed rate and cutting speed

The important parameters like feed rate and cutting speed are applied during the machining processes of different alloys. The change of these parameters also results in a temperature change. With the increase in cutting speed and feed rate, the cutting temperature also increases which affects the tool life and quality of the final product. At higher cutting speeds, the heat conduction will be less and the temperature will rise. While in the case of feed rate, with the increase in feed rate thicker chips are formed which results in the reduction of heat transfer due to which temperature rises. The main portion of the heat is carried away through the chips while the remaining heat is transferred into the tool and workpiece surface.

The cutting temperature is measured by attaching the thermocouple to the end of the cutting tool with the help of a clamp and the reading can be seen using the digital thermometer. In the case of the carbide cutting tool, the temperature at the tip increases with the increase in cutting speed e.g the temperature at cutting speed of 160 m/min is 108.9 oC while at 240 m/min it is 137.7 oC. In the case of AISI 304 steel the cutting temperature increases roughly from 730 oC to 1000 oC with the increase of cutting speed from 60 m/min to 190 m/min (at a fixed feed rate of 0.1 mm/rev).

The cutting temperature also increases with the increase in feed rate. For instance, in the case of AISI 304 steel the cutting temperature increases roughly from 730 oC to 820 oC with the increase of feed rate from 0.1 mm/rev to 0.3 mm/rev (at a fixed cutting speed of 190 m/min).

However, it is experimentally proven that cutting speed has more influence on temperature generation than the compared to change in feed rate.

The main aim of the machining is to produce workpieces of high quality and a good surface finish. There are different sources of heat generation during the machining processes such as the deformation of the workpiece in the shear plane and the friction between the cutting tool and the workpiece. The heat distributed in the shear plane is higher as compared During the turning processes, these sources result in the generation of high temperature which may affect the life of the cutting tool. The quality of the final product can be changed due to the thermal effects on the cutting tools

There are numerous drawbacks of the rise in the temperature during the machining process such as the increase in tool wear, dimensional changes in the workpiece, and thermal damage to the surface of the final machined product.

How to avoid over-heating during the machining processes?

In the case of high-speed machining technology, the cutting speeds and feed rates are higher. So, in order to maintain the temperature in these types of cases, the cooling processes are improved. There are different methods to manage the heat generated during the machining processes e.g by utilizing proper coolant methods and introducing the chillers in the existing cooling system. In cutting tool machining applications, High-Efficiency Milling, Chip Thinning Awareness, use of suitable coolant, and Chip climbing are important factors to be considered for better management of heat generation.

High-Efficiency Milling (HEM) is used to manage heat generation by removing the large amounts of material in pocketing and roughing applications. By using HEM, heat doesn’t build on one specific portion instead it spreads evenly across the whole cutting tool which enhances the tool life.

By preferring climb milling instead of conventional milling, the heat generation at the tool surface will also reduce. In the case of climb milling, chip formation starts with the larger thickness and gradually reduces. This greater chip thickness results in the transfer of heat generated to the chip instead of the tool used which results in the enhancement of tool life.

The proper use of coolant also reduces the increase of temperature during the machining processes. Different coolants can be used to avoid over-heating during the machining process e.g synthetic or semi-synthetic, compressed air-based, water-based, and oil-based (straight and soluble oil). The sliding out of the chip (formed during machining) is eased by the proper use of coolant which avoids the re-cutting.

Conclusion

To summarize, heat is generated during the different machining processes which depend upon the different parameters like cutting speed and feed rates. As the feed rates and cutting speeds increase the heat generated during the machining process also increases. This excessive amount of heat is required to be controlled for better life of the cutting tools and good quality of the final workpiece. This will also help to produce a greater number of products in less time by increasing the cutting speeds and feed rates. This over-heating can be controlled by modifying the machining process or using the proper coolant to transfer heat out instead of the cutting tool.

One way to avoid over-heating is to spread the heat generated throughout the surface instead of heating in a specific portion. All these methods enhance the life of the tool and the quality of the products in the case of cutting tool applications.