xiehe model

At Xiehe, we consider the machinability of different features during the part design process. Some designs are easier to make than others when machining parts, examples of simple design parts with shallow cavities and large features.

How to correctly machine undercuts in parts

Undercut

An undercut is a recessed feature in a part. Standard cutting tools, such as end mills, cannot create undercuts. We need to make these functions with the help of specialized tools. This is because some surfaces of the undercut are not directly accessible from overhead. The process of designing an undercut part is a challenging task. In addition, such parts are difficult to manufacture, thus incurring additional costs, and machining specific undercut standards that are difficult for us to achieve. Many undercuts exist where one part of the workpiece overhangs the other, so there are gaps that are inaccessible to normal conventional tools. Such tools include three-axis milling machines and routers.

Special tools for undercutting

Making simple undercuts requires tools such as cutters and slot cutters. These special tools have unique shapes that allow them to undercut where traditional tools cannot. Both special tool tools feature wider tips and narrow shafts. The tip of the slotted cutter is flatter compared to the rounder tip of the cutter. This makes the latter ideal for machining curved shapes. Our machinists use the distance between the shaft edge and the outer tip to determine the overhang distance for machining CNC parts.

One challenge with using these special tools is that most CAM software lack the algorithms needed to support them. One workaround is to use manual G-codes or to operate the mill manually.

Unique cuts in undercutting

T-slot

A T-slot tool consists of a connected flat horizontal blade and vertical shaft. This allows the tool to plunge into the workpiece and cut horizontally in either direction. So a T-shaped undercut is created. This cutting tool is available in different width standards and can produce undercuts in sizes from 3mm to 35mm.

Undercut processing skills

Working with CNC professionals

Manufacturing the parts you need is a lot easier when you work with a CNC specialist machining company. Professional firms usually have enough expertise, experience and the right tools to handle the toughest tasks. Whenever you are unsure about an undercut design, seek professional guidance to help optimize the design. This will ensure the highest quality of undercut standards and reduce the risk of errors.

Avoid custom tools

Custom tools take time to make and add to the cost of the project. Since they are only a one-time tool, it is best to avoid them by designing standard sized undercut features. We needed a custom tool to cut 15's dovetails, as no stool like this existed. However, for a standard 45 cut, it makes the process easier.

If possible, avoid undercut machining of CNC parts

In the design process of parts, undercuts should be avoided as much as possible. Undercuts are difficult to handle and require special tools to make. Therefore, it is more cost-effective and efficient not to include them in the design. An example of a design that does not require an undercut is designing a workpiece with tool space to use standard machining from the back. This avoids difficult undercuts from the front.

Shallow undercut design

The shallower the undercut design, the better. Most undercutting tools have a vertical shaft attached to the blade. This limits the depth the tool can reach. Deeper designs may also affect tool stability because the vertical axis will be longer. This can lead to increased tool vibration, which reduces tool accuracy. Also, the tool may be damaged. Therefore, it is important to create a design with a depth suitable for most undercutting tools.