In the processing of milling, how to select the appropriate CARBIDE END MILL and judge the wear of the milling cutter in time can not only effectively improve the processing efficiency, but also reduce the processing cost.
Basic Requirements for End Mill materials:
1. High hardness and wear resistance
At normal temperature, the cutting part of the material must have enough hardness to cut into the workpiece; with high wear resistance, the tool will not wear and prolong the service life.
2. Good heat resistance
The tool will generate a lot of heat during the cutting process, especially when the cutting speed is high, the temperature will be very high.
Therefore, the tool material should have good heat resistance, which can maintain high hardness even at high temperature, and has good heat resistance. The ability to continue cutting, this property with high temperature hardness, also known as hot hardness or red hardness.
3. High strength and good toughness
In the cutting process, the tool has to bear a large impact force, so the tool material must have high strength, otherwise it is easy to break and damage. Since the milling cutter is subject to impact and vibration, the material of the milling cutter should also have good toughness, so that it is not easy to chip and break.
Causes of milling cutter wear
The reasons for the wear of end mills are more complicated, but they can be roughly or mainly divided into two categories:
1. Mechanical wear
The wear caused by the severe friction between the chip and the rake face of the tool, the elastic deformation of the machined surface of the workpiece and the flank of the tool is called mechanical wear. When the cutting temperature is not too high, the mechanical abrasion caused by this friction is the main cause of tool wear.
2. Thermal wear
During cutting, due to the severe plastic deformation of the metal and the cutting heat generated by friction, the wear caused by the reduction of the hardness of the blade and the loss of cutting performance is called thermal wear.
In addition to the above two kinds of wear, there are the following kinds of wear:
Under high temperature and high pressure, there will be a bonding phenomenon between the tool and the workpiece material, and a part of the tool material will be taken away by the chips, causing the tool to be bonded and worn.
At higher temperatures, some elements in the tool material (such as tungsten, cobalt, titanium, etc.) will diffuse into the workpiece material, thereby changing the chemical composition of the surface layer of the cutting part of the tool, and reducing the strength and wear resistance of the tool , so that the tool produces diffusion wear.
For high-speed steel tools, at higher cutting temperatures, the metallographic structure of the surface of the tool will change, reducing the hardness and wear resistance, and phase change wear will occur. Each tooth of the milling cutter is a periodic intermittent cutting. The temperature of the tooth varies greatly from the idle stroke to the cutting. It can be said that each time it enters the cutting, it is subjected to a thermal shock. Carbide tools, under thermal shock, will generate a lot of stress inside the blade, and cause cracking, resulting in thermal cracking and wear of the tool. Since the milling cutter cuts intermittently, the cutting temperature is not as high as that in turning, and the main cause of tool wear is generally mechanical wear caused by mechanical friction.
How to recognize tool wear?
1. First, judge whether it is worn or not during processing. Mainly in the cutting process, listen to the sound. Suddenly, the sound of the tool during processing is not normal cutting. Of course, this requires experience accumulation.
2. Look at the processing. If there are intermittent irregular sparks during the processing, it means that the tool has been worn, and the tool can be changed in time according to the average life of the tool.
3. Look at the color of the iron filings. The color of the iron filings changes, indicating that the processing temperature has changed, which may be the tool wear.
4. Looking at the shape of the iron filings, there are serrated shapes on both sides of the iron filings, the iron filings are abnormally curled, and the iron filings become finer, which is obviously not the feeling of normal cutting, which proves that the tool has been worn.
5. Looking at the surface of the workpiece, there are bright traces, but the roughness and size have not changed much, which is actually the tool has been worn.
6. Listening to the sound, the machining vibration is aggravated, and the tool will produce abnormal noise when the tool is not fast. At this time, we should pay attention to avoid “knife sticking”, which will cause the workpiece to be scrapped.
7. Observe the machine tool load. If there is a significant incremental change, the tool may be worn.
8. When the tool is cut out, the workpiece has serious burrs, the roughness is reduced, the size of the workpiece changes and other obvious phenomena are also the criteria for determining tool wear.
In short, seeing, hearing, and touching, as long as you can sum up one point, you can judge whether the tool is worn or not.
Ways to avoid tool wear
1. Cutting edge wear
Improvement methods: increase the feed; reduce the cutting speed; use a more wear-resistant insert material; use a coated insert.
2. Crash
Improvement methods: use a material with better toughness; use a blade with a strengthened edge; check the rigidity of the process system; increase the main declination angle.
3. Thermal deformation
Improvement methods: reduce the cutting speed; reduce the feed; reduce the depth of cut; use a more hot-hardened material.
4. Deep cut damage
Improvement methods: change the main declination angle; strengthen the cutting edge; replace the blade material.
5. Hot crack
Improvement methods: use coolant correctly; reduce cutting speed; reduce feed; use coated inserts.
6. Dust accumulation
Improvement methods: increase cutting speed; increase feed; use coated inserts or cermet inserts; use coolant; make the cutting edge sharper.
7. Crescent wear
Improvements: reduce cutting speed; reduce feed; use coated inserts or cermet inserts; use coolant.
8. Fracture
Improvement method: use a material or geometry with better toughness; reduce the feed; reduce the depth of cut; check the rigidity of the process system.
If you want to find high hardness and wear resistant end mills, come to check our products:
End Mill Manufacturers and Suppliers – China End Mill Factory (mskcnctools.com)
Post time: Oct-24-2022
