Technically speaking, lathing (decolletage) designates a manufacturing field where revolving parts (screw, bolt, axis, etc.) are machined by removing material from metal bars with a spindle.
The parts are machined in small, moderate or large series on conventional automatic cam or CNC lathes. They are machined one after another in the bar, the objective being to reach a high precision and productivity. Also, generally, the goal is to produce the least possible amount of chips.
As a general rule, the thus-machined parts undergo subsequent operations (mechanical, thermal or chemical) before being used in the realization of sub-assemblies.
Mechanically speaking, dressing is an operation which consists of machining flat surfaces on a machine tool equipped with a spindle dedicated to this application. On a lathe, dressing corresponds to the tool moving along an axis perpendicular to the part’s axis of rotation.
Electro-erosion, also called EDM (Electrical Discharge Machining), is a machining process which consists of removing material from a part by using electrical discharges.
Machining by sparking is also talked about. This technique is characterised by its ability to machine all electrical conductor materials (metals, alloys, carbides, graphites, etc.) regardless of their hardness. To machine by electro-erosion, four elements are necessary :
- an electrode
- a part
- a dielectric (electric insulating liquid)
There are three types of machining by electro-erosion :
- electro-erosion by driving-in in which an electrode of a shape complementary to the shape to be machined is driven in the part ;
- electro-erosion by wire, where a conductor wire animated by a planar and angular movement cuts a part according to an adjusted surface ;
- rapid drilling, which uses a tubular electrode to drill very hard materials.
Electro-erosion is particularly adapted to the realization of mould imprints for injection. It is also used to obtain a granite-like surface condition (due to sparking). Surface conditions close to mirror polished finishes are possible by lowering the current intensity to a few tenths of an ampere.
Milling is a manufacturing process. It is characterised by the recourse to a machine tool : the mill. The classically used tool is the mill carried by a spindle.
In milling, the material removed as chips results from the combination of two movements: the rotation of the cutting tool placed on a spindle, on the one hand, and the moving forward of the part to be machined, on the other.
The mill is particularly adapted to the machining of prismatic parts and also allows, if equipped with a computer numerical control (CNC) capability, realizing any type of shape, even complex.
Artwork, craftwork or industrial work using cutting or digging, with a sharp instrument or a mordant, to make a printing element, in relief or in hollow, intended for reproducing an image or text by printing or stamping.
Drilling is a machining process which consists of making a hole in a part. This one can pass right through the part or not emerge from it. In the latter case it is called a recessed hole.
This hole can be made by a drill on a spindle, a drill bit on a crankshaft, cut out between a punch and a die, laser, electro-erosion, ultrasonic device, etc.
It can be used to pass a part (a shaft, a tube), a fluid, or be threaded to receive a screw.
Grinding is a mechanical process for machining a flat or cylindrical surface to improve the part’s surface condition. Growing production, quality and efficiency requirements can be optimised by an appropriate grinding. For these processes, a sophisticated machine and a high-performance spindle are necessary.
Cutting is a machining operation intended to remove material by using a spindle or a cutting tool. The essential application is the cutting of gearings.
Turning is a machining process for removing material with a spindle to obtain cylindrically and/or conically shaped parts. The part to be machined is fastened in a clamp, a mandrel or between tips.
In turning, the cutting movement is obtained by rotating the part fastened between the jaws of a mandrel or in a specific clamp, while the advancing movement is obtained by moving the spindle. These two combined movements allow removing material in the form of chips.
A lathe is used to manufacture mainly revolving parts even though some machines can realize very complex forms (lathing centers).