Solid carbide end mills have played an increasingly important role in replacing traditional EDM processes. Especially when machining narrow and deep workpiece parts, small-diameter ball-end mills and rounded corner end mills have become the mainstream choice. Through optimized design and coating technology, these tools not only effectively reduce cutting resistance, but also greatly improve machining efficiency and tool life, especially in deep cutting of high-hardness materials.
Solid Carbide End Mills
Cutting Performance of Carbide Milling Cutters
In recent years, the trend of replacing previous EDM with cutting has become increasingly obvious, and this demand has gradually shifted to cutting narrow and deep parts on workpieces. When using end mills to deep cut such narrow and deep parts, the mainstream tool suitable is a small-diameter ball-end mill. However, when using small-diameter ball-end mills for efficient deep cutting, the following problems will occur (i.e., problems with replacing EDM with cutting).
- Cutting resistance is easy to increase.
- It is difficult to increase the cutting speed in the center (the top center edge is easily damaged.
- There is a theoretical cutting residue (the radial cutting amount of the tool cannot be too large).
When using a small diameter end mill for deep cutting, if the cutting resistance at the front end of the tool cutting edge is too large, vibration will occur and it will not be possible to process under efficient cutting conditions, thus affecting the processing efficiency. From the perspective of cutting resistance, a comparison between a ball end mill and an R angle end mill shows that the latter has a smaller cutting edge contact area and a relatively smaller cutting resistance.
In addition, when performing contour cutting, a ball end mill has a theoretical cutting residue, especially the end chisel edge with a low cutting speed is easily damaged. However, a rounded end mill can usually form a certain cutting surface during processing, so it has the advantage of stable and reliable processing.
In order to further improve the processing efficiency, an inverted taper design is adopted. This design can prevent the peripheral edge from contacting the cut material due to the bending of the tool during the cutting process, thereby achieving stable processing. In addition, the tool coating adopts TH (TiSiN) hard coating with high hardness and high heat and wear resistance, which is very suitable for direct deep cutting of high hardness materials.
Examples of End Mill Processing Molds
Example of Efficient Groove Processing
In order to process grooves efficiently, it is necessary to increase the pitch in the XY direction to a certain extent. However, if a ball end mill is used for processing, the center edge that cannot increase the cutting speed will be subjected to a large load and the cutting conditions have to be reduced.
From the results of processing grooves with a ball end mill, it can be seen that if the set XY pitch is increased, the degree of damage at the center edge will also increase; if the set XY pitch is reduced and the cutting conditions are reduced, although the center edge is not damaged, the wear of the front center chisel edge increases. From the results of processing grooves with a deep-cutting rounded end mill, it can be seen that not only is the cutting stable, but the wear is reduced, and the groove processing effect on high-hardness (about 50HRC) hot die forging steel workpieces is good.
In this processing example, compared with a ball end mill, the processing time required for the new rounded end mill is shortened by about 1/4, and the processing cost is reduced by more than half.
Deep Cutting of High-hardness Materials
From the results of machining SKD11 cold-working die steel (60HRC) with a long-necked end mill, it can be seen that the peripheral cutting edge of the ball-end end mill is greatly damaged; while the SAMHO tool deep-machining rounded end mill is not damaged, only uniformly worn. It can be inferred that due to the large contact length of the cutting edge of the ball-end end mill, the cutting resistance is also large, and the peripheral cutting edge with high cutting speed is easily damaged. This is the same as the above case, and the rounded end mill has obvious advantages.
From the comparison of the rounded end mill of SAMHO tools and the rounded end mills of other companies under the same processing conditions, it can be seen that the rounded end mills produced by other companies do not adopt the inverted cone design, and the processing effect of high-hardness materials exceeding 60HRC is not ideal. The new generation of deep-cutting rounded end mills of SAMHO tools adopts a unique design of anterior oblique shape, and the peripheral cutting edge is point contact cutting. Even when machining high-hardness materials with the straight cutting method, the cutting resistance is very small and the processing state is stable.
From the processing examples of SAMHO deep-cutting rounded corner end mills, it can be seen that this tool has excellent performance, especially when deep cutting high-hardness materials. In short, by giving full play to the role of rounded corner end mills, grooves can be directly processed on heat-treated and quenched materials. Since the processing process is shortened, the processing cost can be greatly reduced. Experiments have shown that the processing efficiency of using rounded corner end mills can be increased by more than 5 times, and the processing cost can be reduced by 35%.
Indexable Corner Radius End Mill for High Feed Roughing
Multi-edge High-feed Rounded Corner End Mill
The mold industry generally adopts a small cutting depth and high feed cutting method to achieve efficient processing, but market demand requires further improvement of processing efficiency. In response to this need, SAMHO Tools has developed multi-cutting edge tools and coatings that can withstand high cutting speeds under high feed conditions.
The design concept of multi-edge high-feed rounded corner tools is to reduce the cutting edge size within a limited tool outer diameter based on the previous number of blades design method, but without reducing the edge strength. The main cutting edge radius of the high-feed rounded corner end mill is set to R8. Compared with circular blades with the same radius of R8, it has the same edge strength, but minimizes the blade area to achieve multi-edge. In the past, blades with an outer diameter of φ32 all had 2 blades, while multi-edge high-feed rounded corner end mills have up to 5 blades, which is 2.5 times higher than previous products.
Characteristics of High-feed Cutting Tools
In the past, indexable cutting tools used for rough machining were generally equipped with round blades. On the surface, they seemed to be able to achieve a large cutting depth and remove a large amount of material at a time. However, since the contact length between the cutting edge and the material being machined is greater than that of a straight-edge blade, the cutting resistance increases, making it difficult to achieve high-feed cutting. In addition, the round blade is subjected to radial force in machining situations where the tool overhang is long, which can easily cause the tool to bend and vibrate.
The cutting edge of a multi-blade high-feed rounded corner end mill is designed at the bottom of the tool’s rotary axis, so the cutting resistance mainly acts in the axial direction, that is, even if the multi-blade high-feed rounded corner end mill has a long overhang, it is not easy to vibrate, and stable machining can be achieved. At the same time, by miniaturizing the blade, the cutting edge length is significantly shorter than that of previous high-feed cutting tools, reducing the cutting resistance, and thus effectively controlling the cutting force through multi-blade.
Advantages of Small Cutting Depth and Large Feed Processing
Small cutting depth and large feed processing is the application condition of large feed tools. Its advantages are large material removal rate and high processing efficiency. Compared with high-efficiency processing with large cutting depth, high-efficiency and fast feed processing can be performed within the maximum feed limit of the machine tool table when the cutting depth is reduced.
When circular blades are used to increase the cutting depth to improve processing efficiency, a significant cutting residue will be left on the workpiece after processing, which will increase the processing load of the subsequent finishing tool. Although the roughing efficiency is very high, it will reduce the processing efficiency of subsequent processes. In contrast, when small cutting depth and large feed processing are used, the roughing residue is reduced and closer to the final finishing shape, thereby reducing the load of the finishing tool in the subsequent process, so that the efficiency of roughing and finishing can be improved at the same time, and efficient processing can be achieved stably and reliably.
Super Lubricious HG Coating
As mentioned above, while improving the cutting edge shape and increasing the number of cutting edges to improve machining efficiency, if the tool rotation speed can be increased, the cutting speed and feed speed can be increased, the machining efficiency can be further improved. However, when the cutting speed is higher than the current cutting speed, the current tool coating is not able to withstand the high temperature and pressure generated by cutting.
Therefore, we have re-recognized the impact of small cutting depth and high feed cutting on the cutting edge and determined the performance required for high-speed cutting: lubrication performance that can suppress the friction between the chips and the tool generated by high feed cutting even at high temperatures. For this reason, Samho Tools has successfully developed a series of titanium compound coatings with extremely strong lubricity. This new performance HG coating that can be used for efficient machining can effectively reduce crater wear and flank wear, and effectively prevent edge adhesion.
HG Coating with Low Friction Coefficient, High Hardness and High Toughness
HG coating adds self-lubricating materials to titanium and aluminum compounds, and can use cutting heat to form a thin oxide layer on the coating surface. This oxide layer can improve lubrication performance, control the rise in cutting temperature, and at the same time reduce the affinity between the cutting edge and the workpiece being processed, suppressing the adhesion of the cutting edge. The hardness of HG coating is comparable to that of TiSiN coating with the highest hardness. High hardness can prevent cutting edge wear in high-speed and high-efficiency machining environments, greatly extending the service life of the tool.
Ceramic hard coatings are difficult to effectively prevent thermal cracking caused by intermittent cutting that is unique to milling, but HG coatings have high chipping resistance due to their greatly improved toughness. It can be seen that JHG coating is a new generation of coatings that have lubricity, wear resistance, and chipping resistance. Under the premise of the same number of blades and service life, it increases the cutting speed by 40% compared with previous coatings.
Example of High-speed Cutting of Multi-blade, High-feed Rounded End Mills
Use multi-blade high-feed rounded end mills and HG coated inserts in the latest CNC machining center machine tools (cutting feed speed can reach up to 50m/min). The high-speed CNC machining centers used for machining are not yet widely used at home and abroad. Compared with the currently commonly used high-speed CNC machining centers with cutting feed speeds of 10 to 20m/min, the machining efficiency can be increased by 2.5 to 5 times. The new generation of multi-edge high-feed radius end mills can maximize the functions of existing high-speed CNC machine tools.
Solid carbide end mills and indexable radius end mills have significantly improved cutting performance and processing efficiency through precision design and advanced coating technology. Whether in deep cutting of high-hardness materials or in roughing applications with small cutting depth and high feed, these tools have demonstrated their unique advantages and brought more efficient and stable processing solutions to the mold industry.
