In this article we'll introduce the basic concepts and applications of CNC turning centers and CNC lathe machining.
The lathe is one of the oldest manufacturing technologies on the planet; in fact, the earliest version of it dates back to the Egyptians around 1300 B.C. The technology has grown exponentially, becoming more and more advanced with each decade, and today lathes are used to make everything from artisan wooden bowls to large parts for heavy machinery.
Turning Center Basics
First, here are some basic definitions.
Lathe: A lathe is a machine that shapes material by rotating a drive that holds the workpiece being machined against a cutting tool that can be switched to get the proper cut.
Turning: Turning is the act of cutting a part on a lathe.
Tooling: The tool is the cutting mechanism that is fixed to the machine to build the part.
Turning Center: A turning center is a lathe with computer numerical control (CNC).
Spindle Box: The spindle box holds the workpiece, powers the various parts of the machine, and rotates the spindle.
Carriage: The carriage supports the tool, guides the tool and feeds it close to the workpiece.
Lathe and CNC Turning Center
Although they look similar, horizontal CNC turning centers are an evolutionary leap from the CNC lathes of the past. By definition, a lathe is a 2-axis machine. Once lathes evolved to include 3, 4 and 5 axis capabilities, they became known as turning centers. While there is no formal distinction, lathes are often used to refer to simpler machines, such as those that typically use only the X and Z axes to perform turning operations. Turning centers, on the other hand, may integrate milling, drilling and sub-spindle functions and include the Y-axis. Today, these terms are used interchangeably.
To some extent, CNC turning centers are less complex to operate than lathes because they are fully computer controlled and can move all axes simultaneously with high precision.
Turning Center Operation
A conventional lathe rotates the material while the cutting tool gently takes the material away to form a circle. There are many operations that can be performed on a lathe, but there are many more that can be performed on a turning center. Additional axes allow cutting in corners. Tools on conventional 2-axis lathes can only adjust the diameter of the workpiece. They cannot corner or cut in. A multi-axis turning center can move the tool to make corner cuts. This feature removes material that is beyond the reach of traditional 2-axis lathes.
Turning centers easily drill, bore and ream holes. These operations occur in the center of the workpiece axis as the workpiece rotates. There are also dynamic tooling features that perform these operations on the workpiece while it is stationary. The tool drills and finishes holes wherever the specifications require. This feature eliminates the need to perform additional steps at different stations.
Knurling creates a natural grip for the tool. Some machined parts, especially tools, require the user to grip them well. Smooth machined surfaces make them slippery. Knurling presses the pattern into the surface, making it easy to handle. Socket wrenches and other metal tools often have knurled handles. It's easy to cut tapers using more than two shafts. Think of this like sharpening a pencil. Performing this function requires an option that is not available for CNC lathe machining. The taper makes the most sense at the end of the piece, but the technique can be applied anywhere along the length of the piece.
Turning center threads reduces machining time. On a conventional lathe, threading is a separate step; the operator needs to remove it and apply the thread at a different station. This step takes time and adds an unnecessary risk factor. Precision threading locks the part in place and can save significant time.
The finish provides a clean edge and trims the piece to the correct length. The piece usually starts with a rough cut stock. As part of the machining process, the turning center can face rough edges. It can also trim the workpiece to the desired size.
Horizontal Machining Center Applications
Horizontal machining centers can be used in almost every industry because of their functionality and efficiency. Since tool change is automatic, it eliminates costly setup and machining time. Instead of moving the part to another station, the turning center can switch tools. Computer programs drive tool changes, often without the intervention of the machine operator. Choosing between horizontal and vertical turning centersThere are many options regarding which machine is best for you. In the final analysis, make sure the company you use for contract manufacturing work is equipped with a variety of CNC machines.
No one machine can do it all. Machine capabilities, part size and tooling requirements all play a role in machine selection, and this is usually something your outsourced manufacturing supplier will look at closely. For horizontal and vertical machining, the main difference is the orientation of the spindle. Vertical milling uses a fixed spindle and is an excellent choice for projects that require working primarily on one side, such as sinker dies and large metal plates. The internal structure of vertical milling is usually less complex than that of horizontal milling. Instead of using a fixed spindle, horizontal milling uses a cutting head mounted on a horizontal mandrel.
Gravity also comes into play. In a horizontal machine, gravity causes the metal chips to fall to the bed below, thus keeping the part clean during the cutting process. The same part in a vertical turning center may be difficult to remove chips from, especially if the top has a bowl-shaped indentation. This indentation keeps chips in place throughout the turning process.
The horizontal machining center is the center that is most easily understood by everyone. It looks and operates much like a lathe, accommodating a wide range of material types and sizes. Everything within reach of the operator is within reach. Many can be set up to handle automatic bar feeders. Gravity helps keep the cutting area clean, but can also cause problems if the stock is too thin and sags. Conventional vertical turning centers use gravity to their advantage. The weight of the item helps hold the part in place on the headstock. Depending on the application, chip removal may be an issue.