A micro CNC milling machine is like any other, except that everything is scaled down. What is not scaled down however is the level of accuracy and precision you can achieve. So, how do you scale down your own milling techniques and ensure that you are successful and produce parts that are of the highest caliber?
Accuracy is a must with your micro CNC milling machine. As features begin with around 0.001 of an inch, you can easily see why accuracies of 0.0001 of an inch are required. To ensure this accuracy, you will need minimal runout. In fact, runout is akin to accuracy. What is required here to ensure levels of accuracy is that the cutting flute is placed exactly where it need to be along the rotating axis of the spindle. If you have too much runout, then some flutes will go on to do more work than others, and deeper cuts may be seen. This should not be allowed when micro milling, as the fragile cutters cannot tolerate a large chipload.
Micro CNC Milling Machine : Cutting Force and Care for Deflection
When you are using a micro milling machine, the smaller tools will deflect more easily, the forces being used being up to 20 times greater than with a traditional machine. To maximize rigidity, you should always use the shortest tools possible. You may also need to combine roughing and finishing in the same toolpath, as the toolpath may be too thin for separating the two processes.
To be successful with your micro milling machine you will also need to work with high spindle RPMS. This will ensure that you work with reasonable feedrates. The only way that you can increase machine speed is to use the highest rpms tolerable. As you cannot hear the cutter’s health, you will need to get your feeds and speeds correct the first time. If you fail to do so, tools can snap easily. As with everything, practice makes perfect.
Scaling down from a normal CNC milling machine or a CNC turning machine to a micro machine can feel like working with a toy. Remember as a child you had a toy garage or a toy ironing board? Everything was scaled down in your own little world to make you feel big. Well, when it comes to micro milling, everything is scaled down to make parts of the greatest accuracy.
Whether you are swapping over from a traditional machine to a micro machine, or you are adding a desktop machine to your operations, all the above points should be noted. With a micro machine, you will be able to achieve greater levels of accuracy and extremely high quality parts. But, like everything, there is a learning curve involved. You will not be able to feel your machine as it moves, making cuts. You need to fine tune your ear to adapt to your new machine, working with the greatest precision to become a true success.