Mechanical Grinding: Everything you need to know

Mechanical Grinding: Everything you need to know

MECHANICAL GRINDING

By grinding we mean a process obtained on a piece by means of the abrasion exerted by a grindstonemade of abrasive material.

- grindstone, performing a fast rotary movement, removes a very moderate amount of material from the surface of the part to be machined with a very high level of precision.

- rectification is yes a very precise process, but also expensive; for this reason it is only recommended when you need to get one high degree of finish.

Rettifica Meccanica

The precision of a grinding job is such as to find application in many fields: it is used to make bearings, moulds, gears, measuring instruments, aeronautical elements and drive shafts and any situation in which the precision of the couplings is essential.

There are different types of grindstone depending on the material of which they are made up and of the type of processing for which they are used.

For example, the tangential grinding wheels, centerless and round of exteriors are disk-shaped. While the interior wheels they have the shape of cylinders joined to a shaft (tang) which allows coupling with the spindle.

Then there are the cup mole which take their name from their cylinder shape with the inside hollowed out, which resembles an overturned cup, and the bevelled, i.e. disc-shaped, wheels with two walls inclined to form a V, which are mainly used to make chamfers and grooves .

Wheels are made up of three elements, which combined in different ways allow you to create wheels of many different types: abrasive, agglomerating and pores (which is understood as empty space).

mole composition: abrasive

-abrasive it is formed by grains of very hard material which have the task of cutting and removing a part of the metal of the machined part. The size of the abrasive grains allows for different levels of surface finish to be obtained. A smaller grain size is clearly usually associated with a better finish.

mole composition: AGGLOMERANT

-clumping it is the substance intended to hold the small grains of abrasive together and let them emerge to allow contact with the part being worked on. There are binders of different strengths, the toughest allow you to work with less wear on the grinding wheel.

The hardness of the grinding wheel refers to the hardness of the agglomerating agent, therefore a softer grinding wheel can work harder materials because it has a higher exposure of abrasive. 

This increases the consumption of the grindstone and the need to dress it more frequently.
A harder wheel will remove more volume from the workpiece than the volume lost from the wheel, but will decrease the hardness of the workable material.

The most common Types of Grinding

There are many types of mechanical grinding.

They differ from each other mainly in three aspects:

  • the features of the worked surfaces;
  • The guy of machinery used;
  • The movement accomplished by the grindstone.

There are three most common types and they are cylindrical, plunge and flat grinding.

cylindrical grinding

rettifica cilindrica

cylindrical grinding takes place with the axis of rotation of the wheel parallel to that of the workpiece.
Through this type of grinding, it is possible to work only cylindrical or conical parts, internally or externally. By internal we mean when the wheel works the inside of a hole concentric to the piece itself, while we refer to the outside when the machining is carried out on the surface furthest from the centre.

Plunge grinding

rettifica a tuffo

plunge grinding like the cylindrical one occurs with the axis of the grinding wheel parallel to that of the piece to be worked, the relative movement of the grinding wheel is however a radial approach with respect to the piece. Also in this case the piece is in rotation therefore conical or cylindrical surfaces and shoulders are generally machined, for example the seats for the bearings.

FLAT GRINDING

rettifica in piano

In the end, the flat grinding, which instead works with the axis of rotation of the grinding wheel perpendicular to the movement of the worktable.

Contrary to the processes we have seen before, in this typology the piece is not placed in rotation: therefore flat surfaces are obtained with high surface finishes (flatness and roughness). Surface grinding can be carried out with the grinding wheel in two different positions with respect to the piece: tangential grinding which provides for tangent contact between the grinding wheel and the worked surface; face grinding which involves a face of the wheel lying on the work surface. In this case the axis of the grinding wheel is perpendicular to the movement of the table and also to the plane worked.

The grinding operations allow to obtain grooves, threads and profiles of various kinds, also thanks to the use of CNC machines.

PCM Stampi for its production it uses both cylindrical and flat grinding, as well as CNC profiles. With the use of specific grinding wheels we also grind hard metal.

 

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