A kind of wear that tools are extremely prone to-groove wear

 

 

 

Look at the picture above, the blade under the magnifying glass

Other places are fine, but one position has worn out, and this position is always like a groove. This is the so-called groove wear.

 

 

 

 

 

What is going on here? In fact, the reason is very simple, that is work hardening.

 

It is during processing that cutting heat will be generated, and the temperature of this heat is quite high. At high temperatures, the workpiece will perform a heat treatment on the workpiece material in the processing area (especially when the coolant is insufficient). The result is that the surface of the workpiece becomes hard. This hardening phenomenon is called work hardening.

 

With this hardened layer, the workpiece will have two hardnesses, the surface is hard and the other is soft. It's like me, a clambered man, but in fact I have a soft heart.

 

So what happens when there are two hardness machining? The situation mentioned above will appear. Because one position of the blade is always used to process the hard skin, then this place will break first.

 

So what kind of materials are prone to this phenomenon?

Hardened material

Surface crust and oxide skin material

 

 

 

 

 

 

 

In another case, the more viscous material is also prone to work hardening. For example, stainless steel, heat-resistant alloy and other materials, if the machining allowance is large, and you do not consider the work hardening problem, the blade life will not be good.

 

So how to solve this problem? There are many solutions, it is too troublesome to change the tool! Qingfeng tells you a simple way: adjust the (Ap) cut depth in the processing parameters, that is, don't always let the blade touch the hardened skin in one place.

 

When processing, try to divide it into several layers of different depths to process, so that the contact position of the blade and the hardened layer is not the same position, so that the tool life is improved. For example, if you want to process 6mm deep, you can process 3mm in the first layer, 2mm in the second layer, and 1mm in the third layer, so that the 3m position of the blade will not always contact the hardened layer!

 

There is also a cutting method that gradually changes the depth of cut, which is more used in CNC milling, that is, steep cutting (the following figure is 1-2-3)

 

 

 

 

 

 

 

There is another point that needs to be mentioned. Sometimes the depth of cut (Ap) cannot be too shallow, especially when finishing.

 

It is also the old master’s saying ""cannot hold the knife", that is, the cutting depth is too shallow, the tool is grinding the part, instead of cutting the part normally, which causes the surface of the part to harden, the tool does not move, and the part chattering. So. When there is work hardening, the shallower the work, the better. The depth of cut must exceed the hardened layer.