Custom CNC machining can be done in multiple ways. Two of the most common CNC machining services are CNC milling and CNC turning. These are both everyday processes in a machine shop. Both methods use a cutting tool in order to remove material from a solid workpiece. This will be done to create 3D products, which can also be done with online 3D printing. CNC milling and CNC turning are both seen as subtractive manufacturing methods. This is the case since they both remove material. There are some key differences between the two processes, as you can read down below.
The term turning refers to the part since it rotates about a central axis. The cutting tool will thus remain stationary and will not rotate. However, it will move. It namely moves in and out of the piece in order to create cuts. Turning is employed to create cylindrical items and derivatives of cylinders. Examples of these parts are shafts and balusters, but even baseball bats can be created with the help of CNC turning.
The workpiece will be held centered on a rotating spindle by a chuck. At the same time, a base secures the cutting tool so it is able to move along the axis and in or out radially. The rate of rotation of the piece will influence the feeds and speeds, just like the radial depth of the cut and the rate the tool moves along the axis.
CNC milling differs from CNC turning quite a bit. In milling operations, the cutting tool will rotate. The workpiece will be secured to the worktable and will thus not move at all essentially. The tool can move in the X, Y, or Z direction. Typically CNC milling is able to create more complex shapes than what is possible with the help of CNC turning. It could produce cylindrical products, but many other shapes are possible as well. In a CNC milling machine a chuck will be used to hold the tool in a rotating spindle.
The cutting tool will be moved to create patterns on the surface of the workpiece. Milling does have a major limitation. This is about whether or not the tool can access a cutting surface. Access can be improved by using thinner and longer tools, but these can deflect which could lead to a poor product.
Vertical milling is the type that is the most commonly used. This kind of milling machine consists of a vertically oriented spindle or cutting head. It holds and rotates the cutting tool against the piece that is being worked on. The cutting head is thus oriented vertically, so the other machine parts have to shift along one or more axes in order to move the material in the right place so the machine can milling properly. The spindle will then move up and down. This is needed to remove material, which the cutting head does by pressing against the workpiece.
A horizontal milling machine has a similar design. It also uses a spindle with a rotary cutting tool to remove material by pressing against the part. It does differ from vertical milling in multiple ways. The main difference is the spindle orientation, of course. A vertical milling machine uses a vertical spindle orientation, while the spindle of a horizontal mill is oriented horizontally. Besides that, the two machines vary based on the cutting tools they feature. Horizontal mills usually have shorter and thicker cutting tools, while the vertical mills use cutting tools that are long and thin. Horizontal mills will usually be more capable to perform deeper and heavier cuts due to this.