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When you are cutting or shearing metal with a CNC machine, or rubbing two metal surfaces at high speed against each other, you are bound to generate higher temperatures. What should you do when you first see smoke or an alarm goes off? Here are tips and tricks for overheating CNC tools.

When does a CNC machine overheat?

When can you see in practice that your CNC machine is overheating? In practice, if you see sparks or smoke, you may have caused unnecessary damage to your tool or workpiece. Even brief exposure to excessive heat is enough to soften the tool material and damage the cutting edge. It is worth noting that quite often the signs of overheating can be seen long before the tool is damaged. Evaporation of coolant, black or discolored tools, and even unusual changes in spacing can all indicate that excessive heat has occurred. If any of these signs appear, and they don’t occur with normal CNC machine operation, consider whether the equipment is being used properly. 

Drain coolants and chips 

Liquid coolants don’t just cool CNC machining processes. They also lubricate and remove debris from cutting tools. Through this process, the tool cuts through the old material and works properly. Waste or chips also have a high temperature. Bending, cutting and shearing these small pieces of metal from the workpiece heats them up. You don’t want your tools to be wrapped in a layer of hot metal. For this reason, fast chip evacuation also removes heat from the CNC machine cutting process. As a general rule – coolant is not required, and compressed air is sufficient to reduce the operating temperature of the CNC machine. Granted, this will not cool the tool as effectively as liquid, but it will provide better chip evacuation.

Additional advice  – CNC Machine

Whether you use coolant or compressed air consider the following when cooling your CNC machine: 

  • Do not suddenly apply coolant while the tool is heating up! Wait for the tool to cool down first!
  • More or any amount of coolant is not always required to cut parts.
  • Remember to spray coolant directly on the tool and not on the active part.
  • Consistent coolant application throughout the cutting process is important to avoid hot spots and sudden thermal shocks. 
  • Coolant is only required when cutting materials with low thermal conductivity, such as titanium and some steels.
  • Liquid coolant may be required when machining larger cavities because compressed air may not be enough to remove all the chips.

Choose the right tool 

Cutting chips play a key role in removing heat from cutting tools. Cutting strategies that generate too few chips reduce the amount of heat removed from the machining process. Selecting the right tool for the geometry, size, number of grooves and length of cut will help reduce the potential temperature rise. For example, 2-blade finger cutters are ideal for removing material from soft, heat-conducting materials such as aluminum and copper. Unfortunately, it has less mass or heat capacity to handle the heat generated by harder, less conductive materials. Tool wear and coating wear are other important factors that have a real impact on changing the temperature to the detriment of the CNC machine. Worn or damaged tools cut less efficiently and generate more heat than new tools. Tool coatings are often optimized for specific materials. Make sure you know what materials your tool can handle. Coatings designed to reduce friction and heat build-up when milling steel can bind to other materials, such as aluminum, at typical cutting temperatures. Keep this in mind as it is an important factor in proper CNC machine temperatures. 

The correct speed and feed rate must be determined 

The higher the speed of the tool is moved relative to the part, the more heat is generated, so choosing a lower speed should generate less heat. This applies to spindle speed, especially if you find that CNC machines produce very fine chips. This is important because even a slight slowdown can reduce heat generation and extend tool life. The trade-off, of course, is lower material removal rates and longer machining times. Remember, however, that only reducing the feed rate can have the opposite effect because it reduces chip size and load – both key factors in removing heat from a cutting operation. Poor chip clearance also means that the tool spends a little more time rubbing against the workpiece instead of cutting. This situation can lead to unnecessary heat in the tool and can cause the material to harden.

CNC Tooling – Path

CNC (computer numerical control) turning tends to produce consistent, predictable results in terms of chip size, tool heating, and material removal rates. Except for very simple toolpaths, material removal rates during milling are not constant. A traditional milling toolpath would use the end of the tool at a constant feed rate. The result is a larger radial depth of cut, a smaller axial depth of cut, and a variable angle of application. This results in uneven tool wear and high thermal stresses on the moving parts of the tool. One machining strategy used to reduce this effect is dynamic milling, which reduces the radial chip thickness (reduces the radial depth of cut) and maintains a constant angle of apposition. High-performance milling is another example. It uses most of the axial cutting edge to hold the work and generate heat over a larger area. Both strategies reduce the contact time between each groove and the material, thus reducing heat transfer to the tool. Note, however, that with both strategies you will likely need to increase your feed rate to maintain adequate chip thickness and load. If you’re having trouble keeping your CNC machine at the right temperature, it can’t be ignored. Prolonged unnecessary heating of the equipment can damage the product or cause the machine to fail during operation. To avoid these problems, it is a good idea to follow the tips that we have listed in this article. The information in it will help you solve the problems caused by overheating of CNC machines.