1. Factors that affect CNC machining part temperature
1. Natural Climate
According to the laws of thermodynamics, objects adapt to ambient temperature. That is to say, the hotter a room is, the hotter the objects in that room will be. Because of this, machines used in extreme heat environments run at temperatures above recommended or “normal” temperatures.
If your operation is in a naturally hot environment, you need to take extra measures to ensure that your CNC machine runs at the recommended temperature.
2. Ongoing Environment
Best practice suggests positioning your CNC machine frame as far as possible from other heat sources such as a heat-treating oven. For example, when planning the layout of a new factory, place the machine shop as far from the boiler or steam room as possible.
As your machine runs, it already has two sources of heat: natural climate heat and machining process heat. Process heat is the heat generated by the machine itself while in operation. These two sources are unavoidable although they can be mitigated and controlled. Positioning your CNC machine far from other heat sources eliminates a third heat source from adding to the heat gain of the CNC machining environment.
3. The Machining Tool
The temperature of the machining tool plays an integral part in the machining process. If the tool overheats, it leads to problems such as thermal deformation and thermal expansion which lead to diminished machining accuracy. Overheating of the tool also leads to a shorter tool life thereby increasing the cost of running the machining operation. In other words, tool hardness decreases with increasing temperature.
Common materials for machine tools include Tungsten Carbide and High-Speed Steel. Tungsten carbide maintains a sharp cutting edge longer than High-Speed -Steel, it produces a better finish, and can cut harder materials. Tungsten also withstands higher temperatures and therefore can achieve faster cutting speeds than steel. Faster cutting speeds reduce production time.
4. Material Properties
The type of material or material properties of the workpiece has an effect on the temperature generated in the machining environment. The harder a material is, the more energy is required to machine it or remove material from it.
The more energy required, the higher the temperature generated at that point if other parameters such as feed rate are kept constant. Following this observation, it is important to consider material properties when selecting materials.
The heat generated at the tool-workpiece is able to produce in the workpiece effects similar to heat treating. Stainless steel is a material that is prone to work hardening during the machining process.
There are different types of heat-treating processes such as annealing and hardening that can be done to a material to give it specific characteristics. Heat treatment processes are done to change metal alloy/ alloy steel physical properties such as hardness, toughness, tensile strength, and ductility.
However, hard materials are more difficult to machine thus some heat treatment processes are best done after machining.
An advantage of machining before heat treatment is that sourcing material is easier. Heat-treated profiles are more common than non-heat-treated profiles. Pre-treated materials also hold tighter tolerances better than non-treated materials.
An advantage of heat treating after machining is that you can choose which method of treatment you want to use in order to obtain your desired characteristics.
