An Engineers Guide to CNC Lathes

CNC Lathes, Engineers Guide -

An Engineers Guide to CNC Lathes

The lathe is one of the oldest manufacturing machines on Earth. The earliest versions date way back to the ancient Egyptians, who invented a two-person, bow-driven lathe around 1300 BC.  Lathe technology has been far from static, as evidenced by the sophisticated CNC Lathes of today.

This is an Engineers overview of the types, components, operations and applications of CNC Lathes.

Nevertheless, while there is no formal distinction between lathes and turning centers, the former term is often used to refer exclusively to simpler machines—those designed for turning operations alone. In contrast, the term ‘turning center’ usually denotes machines which integrate milling or drilling capabilities, or those with sub-spindles for performing secondary operations.

A CNC lathe just does turning; it’s a 2-axis lathe with X and Z axes and typically only one chuck. A CNC turning center has milling capability, or a second spindle plus milling capability, and so it might have a Y-axis as well.

 

This information is provided by 'engineering.com'

Headstock

The headstock houses the main spindle as well as the speed- and gear-changing mechanisms. The main spindle end often includes a Morse taper. In the early days of industrial lathes, the spindle was driven directly via a flat belt pulley. These days, it’s driven by an electric motor.

Bed

The lathe bed is a base connected to the headstock such that the carriage and tailstock move in parallel with the spindle access. This movement is facilitated by bedways, which restrain the carriage and tailstock in a set track.

Feedscrews and Leadscrews

The feedscrew is a long driveshaft that connects to a series of gears in the apron in order to drive the carriage along the Z-axis. The leadscrew has the same function but operates orthogonally to the feedscrew, moving the carriage along the X-axis.

Feedscrews and leadscrews are manufactured to either imperial or metric standards, which can cause compatibility issues between workpieces made on different lathes.

Carriage

The carriage holds the cutting tool and moves it longitudinally to the workpiece for turning operations or perpendicularly for facing operations. The carriage is composed of two castings: the top, or saddle, and the side, or apron.

Tailstock

The tailstock refers to the center mount which is positioned opposite to the headstock. In contrast to the headstock, the spindle in the tailstock—which can include a taper to hold drill bits, centers or other tooling—does not rotate. Instead, it travels longitudinally under the action of a leadscrew.

Turning Center Operations

There are many operations that can be performed on a lathe, and even more that can be performed on a turning center. Here are some of the most common:

Facing

Facing operations are used to produce flat surfaces on the end of a part.
Facing operations are used to produce flat surfaces on the end of a part.

Threading

Threading operations produce external or internal threads on a part.
Threading operations produce external or internal threads on a part.

Knurling

Knurling operations are used to produce a regularly shaped roughness on cylindrical surfaces.
Knurling operations are used to produce a regularly shaped roughness on cylindrical surfaces.

Drilling

One of the most basic operations, drilling is used to generate holes in workpieces.

Boring

Boring involves enlarging a hole or cavity to produce circular, internal grooves.
Boring involves enlarging a hole or cavity to produce circular, internal grooves.

Reaming

Reaming operations involve sizing and finishing existing holes.
Reaming operations involve sizing and finishing existing holes.

Taper Turning

In taper turning, the diameter of the workpiece is gradually reduced over the length of the part.
In taper turning, the diameter of the workpiece is gradually reduced over the length of the part.

 

Turning Center Configurations

You have essentially two different types of CNC machining centers: the traditional, horizontal type that’s been around for quite some time, and then you have the vertical type, which spins the part like a top instead of spinning it like a car tire.

Horizontal probably makes up 60 or 70 percent of the market because it’s been around longer—every machinist learned on a horizontal lathe.”

Horizontal Turning vs. Vertical Turning

CNC turning centers come in either horizontal or vertical configurations. There are also inverted vertical turning centers, which reverse the position of the spindle and the chuck. All three machine types generally consist of the same basic components (i.e., headstock, carriage, etc.), but differ in their orientation. Deciding whether to opt for a horizontal, vertical or inverted vertical lathe depends on a host of factors, but there are some rules of thumb that can help you make the decision.

The advantage with a horizontal lathe is that gravity pulls the chips away from the part.

 


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