Milling development prospects and challenges (2)


Combination of new square shoulder milling cutters

When developing a new square shoulder milling cutter, the key point is to combine the ability to create a high quality end surface with the shoulder surface. Some milling tools are capable of cutting high-level end faces or square shoulders, but no tool can simultaneously achieve both high precision and surface quality.

Since the industry is most concerned with production efficiency, it is necessary to combine the ability to perform fine end face and square shoulder milling with the high quality capability of performing high metal removal roughing processes. In some applications it is also required to combine roughing and finishing passes. The single cutting ability combines high metal removal rate with good shoulder surface quality, no compromise in performance, and improved functionality.

Although the cost of cutting tools is only a small fraction of the total production cost of all parts, many users put tool cost issues with tool inventory in a prominent position. The square insert provides four cutting edges and also provides the ability to have the best cutting edge for each insert. But the square blade means a 90° fillet and has a limited range of applications for the combination of capabilities required for the new efficient shoulder.

New challenges for milling tools

The square blade requirement also represents one of the challenges when developing new high performance milling tools with a true 90° lead angle. High precision and elimination of any associated tooling errors and high metal removal capabilities are required. In addition, the angular accuracy must be several times higher than existing tools.

By relying on the existing CoroMill solution and at the same time developing a new conceptual direction, a model for the new square shoulder milling platform was established. Recent developments in methods and metrics related to the manufacture of new milling tools have supported this.

In order to achieve the goal of combining roughing and finishing tools, and also to use square inserts, it is necessary to provide a new cutting edge that can simultaneously produce end faces and square shoulders. At this point, favorable cutting action and high finishing capability must be established.

In any multi-tooth milling tool, the wiper edge of the cutting edge plays a crucial role because it is the decisive factor in the generation of the end face. The wiper strip must be longer than the feed per revolution of the tool to ensure a good surface quality. One of the problems with the use of the wiper belt is that the cutting edge is too long to increase the cutting force, so it is prone to vibration trends and higher power consumption and higher cutting stability requirements. For CoroMill490, how to have the most suitable wiper belt without inherent disadvantages is a challenge.

Based on the tool's large enough forward rake angle for the insert and the sharp positive rake cutting edge on the insert, the solution has been fundamentally developed with a lightweight cutting tool design such as the CoroMill490. Cutting the apparent basic tool geometry also indicates that the blade will negatively enter the material, which means smoother and increased strength. Tool accuracy also contributes to the implementation of the solution and guarantees a favorable cutting action, especially for finishing. The successful development of the unique new blade wiper belt and tooling features is not only a key factor in ensuring the CoroMill490's capabilities, but also a key factor in achieving the best metal removal rate per unit of power consumption.

Wiping edge technology

This technology is a core part of the milling solution. Since the wiper technology was developed by Sandvik Coromant for turning, it was further developed for the CoroMill490 wiper belt and the insert cutting edge for square shoulder cutting. When cutting, a tool with multiple inserts can easily generate some tooling errors through the transitions produced by each blade land.

There is also the problem of tool skew. All tools have a certain program skew during cutting, and the use of conventional wiper strips often has a negative impact on the resulting surface due to the sharp transition edges.

The multi-arc wiper design of the CoroMill490 blade wiper belt compensates for tolerances and angular misalignment of the cut. This not only minimizes the tendency of any tooling error, but also improves the accuracy of the face and shoulder surfaces. Between the different shoulders on the shoulders or the surfaces created by the different blades on the end faces, it is now possible to achieve almost the same effect, which in the past required further finishing.

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