When you cut or shear metal using a CNC machine, or rub two metal surfaces against each other at high speed, you will certainly generate higher temperatures. What should you do when you see smoke for the first time or an alarm goes off? Below we present tips and ways to prevent CNC tool overheating.
When does CNC tool overheating occur?
When in practice can you see that the CNC machine is overheating? In practice, if you see sparks or smoke, you may have caused unnecessary damage to the tool or the 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 signs of overheating can be seen long before the tool is damaged. Evaporation of coolant, black or discolored tools, and even unusual changes in gaps may indicate that there has been an excessive increase in temperature. If any of these signs appear and they do not occur during normal operation of the CNC machine, you should consider whether the equipment is being used correctly.
Dispose of coolants and chips
Coolant fluids not only cool down the processes of CNC machining. They also lubricate and remove impurities from cutting tools. Thanks to 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 machined object heats them up. You don't want your tools to be wrapped in a layer of hot metal. For this reason, quick chip removal also removes heat from the CNC cutting process. As a rule - coolant is not required, and compressed air is sufficient to reduce the working temperature of the CNC machine. Although it will not cool the tool as effectively as a fluid, it will provide better chip removal.
Overheating of CNC tools - Additional advice
Regardless of whether you use coolant or compressed air, consider the following issues in terms of cooling your CNC machine:
- A larger or any amount of coolant is not always required for cutting parts.
- Coolant is only required when cutting materials with low thermal conductivity, such as titanium and some steels.
- Coolant fluid may be required during the machining of larger recesses, as compressed air may not be sufficient to remove all chips.
- Remember to spray the coolant directly onto the tool, not the active part.
- Consistent delivery of coolant throughout the entire cutting process is important to avoid hot spots and sudden thermal shocks.
- Do not suddenly turn on the coolant while the tool is heating up! Wait for the tool to cool down first!
Choose the right tool
Cutting chips play a crucial role in removing heat from cutting tools. Cutting strategies that generate too few chips reduce the amount of heat removed from the machining process. Choosing the right tool for the geometry, size, number of grooves, and cutting length will help reduce potential temperature increases. For example, 2-flute end mills are ideal for removing material from soft, heat-conductive materials such as aluminum and copper. Unfortunately, they have less mass or heat capacity, which can cope with the heat generated by harder, less conductive materials. Tool wear and coatings are other important factors that have a real impact on changing the temperature to the disadvantage 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 buildup during steel milling may bind with other materials, such as aluminum, at typical cutting temperatures. Remember this, as it is an important factor affecting the correct temperature of a CNC machine.
It is necessary to determine the proper speed and feeds
The higher the speed of the tool moving 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 it turns out that CNC machines produce very fine chips. This is important because even a slight slowdown can reduce heat generation and extend tool life. The compromise, of course, is a slower material removal rate and longer processing time. However, remember that reducing the feed rate alone can have the opposite effect, as it reduces the size of the chip and the load - both key factors in removing heat from cutting operations. Poorly chosen chip clearance also means that the tool spends a little more time rubbing against the workpiece instead of cutting. Such a situation can lead to unnecessary tool heating and may cause material hardening.
CNC Tools- path
CNC turning tends to achieve consistent, predictable results in terms of chip size, tool heating, and material removal rate. Besides very simple tool paths, the material removal rate during milling is not constant. A traditional tool path for milling would use the tool's end at a constant feed rate. The result is a greater radial depth of cut, a smaller axial depth of cut, and a variable angle of engagement. This results in uneven tool wear and high thermal stresses of the moving parts of the tool. One machining strategy used to mitigate this effect is dynamic milling, which reduces the radial chip thickness (reduces the radial depth of cut) and maintains a constant angle of engagement. Another example is high-performance milling. It uses most of the axial cutting edge to maintain work and generate heat over a larger area. Both strategies shorten the contact time of each groove with the material, thus reducing the transfer of heat to the tool. Note, however, that in both strategies you will likely need to increase the feed rate to maintain appropriate thickness and chip load.
If you are having trouble maintaining the correct temperature of your CNC machine, you cannot ignore these issues. Prolonged unnecessary heating of the equipment can cause product damage or lead to device failure during operation. To avoid these problems, it is worth following the advice we have listed in this article. The information contained in it will certainly help solve problems resulting from the overheating of the CNC machine.