Precision Depends on Details

In the field of high-precision cutting, the Corner Radius End Mill is a commonly used tool type. It combines the rigidity of a flat-bottomed milling cutter with the anti-chipping ability of a ball-end cutter and is one of the indispensable tools in mold, aviation, and precision parts processing.

However, even the best quality tools, if used improperly, are difficult to achieve ideal processing results, and may even accelerate tool wear, damage the workpiece surface, and affect production efficiency.

This article will take you from the perspective of a front-line processing engineer to help you avoid several common "invisible traps" when using corner-end mills.

1. Radius Selection Matters

When choosing a milling cutter, many engineers only focus on the tool diameter, but ignore the value of the corner radius. 

In fact, the corner radius (R) directly affects the processing path and the corner root cleaning effect:

Corner radius is too large → It is easy to produce "residual material" problems due to insufficient root cleaning;

The corner radius is too small → Although it can improve accuracy, it reduces the strength of the cutter head and is easy to break the edge.

When cleaning the corners of the mold cavity and contour, pre-analyze the internal fillet size of the product and select an R-value slightly smaller than the workpiece corner radius to ensure that it can clean the corners without compromising rigidity.

2. Tune Parameters for Radius Tools

Experienced programming engineers know that for the same diameter, different cutter types have different responses to feed, speed, and cutting depth.

Because of its rounded transition of corners, the rounded corner cutter can effectively reduce stress concentration during processing and is suitable for higher-side milling depths (Ae). However, if the parameters of the flat-bottom cutter are blindly applied, the following problems are likely to occur:

1. Tool vibration;

2. Workpiece size tolerance;

3. Severe local wear of the cutter head.

According to the actual corner radius used, reasonably adjust the following parameters:

3. Choose Coating for the Heat

In high-speed machining (HSM) or carbide machining, the coating on the tool surface plays a key role. Many users only look at the tool's appearance and ignore whether the coating type is suitable for their application conditions.

For example:

1. TiAlN coating is suitable for dry cutting and hard material processing. It can withstand high temperatures but not oxidation resistance;

2. AlCrN coating has excellent oxidation resistance and is suitable for wet cutting or stainless steel processing;

3. DLC coating is specifically used for aluminum or high-viscosity materials to reduce built-up edges.

Confirm that the tool coating you use matches the processing material/method. Choosing the wrong coating = the beginning of a high-temperature disaster.

4. Control Tool Overhang

Although rounded milling cutters are less likely to break than flat cutters, long overhang cutters are more likely to vibrate and resonate during high-speed processing, affecting tool life.

Too long overhang will lead to:

1. Reduced tool rigidity;

2. Processing size drift;

3. Deterioration of surface roughness;

4. Abnormal tool wear.

Preferentially use rounded corner cutters with extended neck (neck relief) design, and try to control the overhang ratio ≤3D (3 times the tool diameter). If necessary, use a vibration-damping tool holder or hydraulic chuck to enhance clamping stability.

5. Don't Skip Rough-to-Finish Strategy

In order to pursue processing efficiency, many factories use a rounded corner end mill "from rough to fine in one cut", which is a great challenge to the tool, especially when processing hard steel parts.

This practice can easily lead to:

1. The temperature of the cutter head rises suddenly;

2. The tool is scrapped midway;

3. Thermal deformation/dimensional deviation of the workpiece.

Suggestions:

Use different tools for rough, semi-finish, and fine processing in stages;

Retain 0.2~0.5mm margin for the last rounded corner cutter to fine-tune;

Use dedicated CAM software to achieve reasonable step distance and tool path planning.

Smart Use = Longer Tool Life

A high-performance rounded corner milling cutter is of course inseparable from high-quality materials and processes, but the professionalism of its use is the key to its life and performance.

Choose the right corner radius, match the right cutting parameters, match the right fixture, and execute the processing strategy according to the process. These small details of each step will show great value in long-term operation.

Don't let your tools pay for you.

If you would like to learn more about the performance data, coating types, or selection suggestions of our customized Corner Radius End Mills, please feel free to contact our technical support team.