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The Process of a CNC Lathe

The cnc lathe is one of the most versatile pieces of equipment used in manual or CNC manufacturing. This results in the presence of a lathe in almost every shop. At its core, the lathe is a piece of equipment that rotates a workpiece on an axis and removes material with a variety of cutting tools perpendicular to the part. The process of a CNC lathe operates according to a program written and uploaded to the machine, allowing for highly precise and repeatable production.

We will look at some common operations, as well as some tips for the overall approach in the process.

How to Use a CNC Lathe

 There are several steps in understanding how to operate a lathe correctly. The computer-programmed aspect of the CNC lathe, as well as the complexities of this highly versatile machine, means that training and skill are required. With this overview, you will understand the basic mechanics.

  1.   Be sure the lathe is powered down. Safety always comes first.
  2.   The cutting tool is loaded first. This single-point cutting tool is held by bolts, the tool holder is typically attached to the tool post with a quick-release lever, and the tool post is mounted on the lathe machine with a T-bolt.
  3.   Load the part in the chuck securely. Since in many operations the part is in movement, both the design and tension of the chuck are important.
  4.   Check alignment and tolerances with the “learning eye”. This checks alignment to guarantee the program will run in sync.
  5.   Make adjustments, as needed, to the part placement to be sure the cutting tool will contact the part at “zero” for smooth, clean cuts.
  6.   Enter and execute the program.

 

Types of Lathe Operations

CNC Lathes were originally designed for metal fabrication only, using carbide bits, but are now used for a variety of materials and operations. The brief list describes only some of the turning capacities of the lathe.

Turning – This application reduces the workpiece diameter to the desired dimension. This overall dimension can be varied through step, taper, or other means, sometimes requiring multiple runs.

Grooving – This process creates a groove, or even cut, in the part. Wider grooves will require several passes to accomplish the finished dimension.

Threading – This produces a thread pattern by moving the outer edge of the piece along the tool which is set at a specified pitch and length, creating a spiral design in the finished piece.

Drilling – In this operation, the part is held fixed and a spinning drill tool removes material from the inside of a piece, set at a specific diameter and depth.

Boring and Reaming – These operations also move the cutting tool into a fixed part, either widening or changing the shape of the drilled hole.

Both vertical and horizontal lathes are available, where the part moves along only one axis. A swiss lathe sees movement in both the part and the cutting tool creating high accuracy and speed. And the 3-in-1 lathe machine, more common in smaller shops, introduces drilling or milling applications into the lathe. These are less accurate, but take up less floor space, and combine multiple processes on one machine.

Tips for Easier Operation

While lathe operation may seem fairly straightforward, the machine often performs the final precision work on a part. These tips will ease your lathe operations.

Offsets – Specific tools have precise axis offsets for precision cutting. Be sure to use them, and make note of different settings. Not only do these axes differ from manufacturer to manufacturer, but they can also differ minutely from individual tool to tool. For this reason, it’s important to be careful when setting the axis offset. Noting the correct offset for each tool (which may be slightly different from that recommended by the supplier) can affect accuracy.

Speed Control – Automation is one of the great benefits of CNC machining, and it can be tempting to allow a machine to run at a constant speed all the time. Taking over with manual speed control, however, can help with the accurate and successful machining of softer or difficult-to-machine materials.

Programming – Be sure you understand the program, especially if you’re using a program written by someone else. Be aware of the proper tooling and setup offsets and calibrations required. Programming is only as good as its operator, and vice versa. Making parts to specification the first time saves materials, time, and potential equipment damage.

Vibration & Noise – Both vibration and noise are indicators of a setup problem and will affect accuracy, and eventual tool or machine repair. Check workholding and material for proper speed of feed, level, lubrication, and machine component alignment. Be sure to perform regular maintenance See our blog on how to improve machine shop efficiency.

Lathe operations are the backbone of many CNC machine shops. From a simple bolt to a complicated 3-dimensional table leg, the process of a CNC lathe machine can produce some beautiful pieces along the simple X-Y axis. Understanding the basic process and types of turning and drilling operations available expands your creativity in product design in everything from aerospace to sports equipment.

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