What is the Difference Between CNC Milling and Turning?

CNC Milling and Turning: Which is Best for Your Machined Parts?

Since the rise of computers, CNC machining has steadily replaced manual milling, resulting in higher quality parts with tighter tolerances. Now, manufacturing companies use various computerized machining processes to create parts out of raw materials. Some of the most common processes include CNC milling and turning.

Both CNC milling and turning produce accurate, repeatable parts using a cutting tool. However, there are key differences between the two that you should take into consideration before starting work on any machined part project.

At Aztalan, we strive for flawless precision machining and can help you navigate the manufacturing process for your machined parts. Learn more about our capabilities or talk to one of our helpful team members for more information.

CNC Milling Overview

CNC milling involves removing material from a workpiece using rotating multi-point cutting tools and computerized controls. The machine moves around the X, Y, and Z axes and intermittently cuts the part while the workpiece is stationary. CNC milling machines have high accuracy and precision, and can meet tolerances as tight as +/- 0.004mm.

This process is much faster than CNC turning and is thus more suitable for large production runs. CNC milling can produce simple and complex shapes ranging from rings to automotive and aerospace parts with complex geometries.

Stages of the CNC Milling Process

The first step in the CNC milling process is to create a 2D or 3D CAD model using CAD/CAM software. This allows you to specify exact dimensions and tolerance requirements.

The next step is to convert the CAD model into a CNC program. The code will automate the cutting sequence, toolpath, machine tool speed, and workpiece movement necessary to fabricate your part.

The final step is to execute the milling operation. During this phase, a machinist will insert the workpiece into the CNC machine, attach the cutting tools, and download the code you create. The machine will then be able to operate on its own, cutting your desired piece.

Types of CNC Milling

There are three common CNC milling operations: face milling, plain milling, and angular milling. During face milling, the rotating axis of the cutting tool is perpendicular to the surface of the workpiece, which creates a flat surface.

For plain milling, the axis of the cutting tool is parallel to the workpiece, which is suited to producing plain, horizontal surfaces. 

The angular milling process involves the axis of the cutting tool at an angle to the surface of the workpiece. This is suited for making certain features like grooves, serration, and chamfer.

CNC Turning Overview

During the CNC turning process, bars of material are held in a chuck and rotated while a feeding tool removes material until the desired shape is achieved. Unlike in CNC milling, the cutting tool remains in continuous contact with the workpiece. 

CNC turning is more suitable for prototyping and smaller production runs due to the slower speed. CNC turning is best for producing shapes that have axial symmetry, which may include cones, cylinders, disks, or a combination of these shapes.

Stages of the CNC Turning Process

Like CNC milling, the first step of the CNC turning process is to make a 2D or 3D CAD model of your part using CAD/CAM software. 

Then, you must determine the cutting speed and feed rate of the operation. A professional should map these out as inaccurate estimations can cause an uneven finish or damage to the workpiece.

The third step of the process is to ready the machine and let the computerized program create your desired shape.

When to Use CNC Milling Over CNC Turning

Both CNC milling and turning are suitable for metals like aluminum, steel, brass, copper, and titanium, as well as various thermoplastics. The main difference lies in their rotational properties. Milling forces the cutting tool to rotate while turning forces the workpiece to rotate.

Ultimately, the decision to use CNC milling or turning will depend on the shape you’re trying to produce. If your design is axially symmetric, CNC turning could be the right choice for your particular part. However, if your parts are too large, heavy, non-symmetrical, or have complex geometries, you may consider CNC milling.

Work with Aztalan for Your Machined Part Needs

Aztalan’s talented staff of experienced engineers, CNC machinists, and assemblers share a passion and pride in our organization’s skill and workmanship. We offer various services to suit your needs, including CNC milling, turning, and Swiss turning, soldering and brazing, engineering support, ultrasonic cleaning, and assembly.

We regularly reinvest to provide our workforce with the latest CNC machining tools and technology, meaning you can expect high-quality parts when you work with us. We also invest in the best manufacturing software, which integrates all aspects of the manufacturing process, from order entry and scheduling to real-time monitoring of machine performance.

Our ISO 13485 and ISO 9001:2015 certifications demonstrate our commitment to quality. Every employee contributes to our quality system, and the state of Wisconsin has acknowledged our quality standards by recognizing us as a Certified Precision Machine Shop.

Get Started on Your CNC Milling and Turning Operations Today

Ready to learn more about CNC milling and turning and what’s right for your business? Contact our team or request a quote today.