The motion track of plane grinding can be divided into two types: the motion track of manual grinding and the motion track of mechanical grinding. Among them, the motion track of manual grinding includes: linear reciprocating, swinging linear, spiral and "8" form; The movement track of mechanical grinding includes: epicycloid, hypocycloid, rectilinear reciprocating, sinusoidal and irregular circular (spiral) forms.

Epicycloid

Flat grinding plate

When a rolling circle rolls along a straight line, the locus formed by any point on the circumference of the rolling circle is called a cycloid.

The so-called epicycloid is the locus formed by any point on the circumference of the rolling circle when the rolling circle T is pure rolling along the outer side of another base circle.

Epicycloid can also be divided into two kinds of long spoke epicycloids, which are formed at the inner and outer sides of the rolling circle according to the locus. The locus formed by a point outside the rolling circle is called a long spoke epicycloid, and the locus formed by a point inside the rolling circle is called a short spoke epicycloid.

There are many kinds of machine tools to realize the epicycloid grinding track. The processing path of this kind of grinder is a short epicycloid, which is particularly suitable for rough grinding of large size workpieces. Because this kind of grinding track can make the moving direction of the workpiece change regularly, with small change amplitude and smooth turning angle, the machining accuracy of the workpiece is high.

Shaded Flat

The epicycloid locus makes the workpiece move at a high speed at the outer edge of the lapping tool, and compensates the internal and external differences caused by different radii, so that the lapping tool is worn evenly. In addition, the workpiece moves for a long time at the outer edge of the lapping tool, and it basically does not do autobiography, thus forming a strong directivity of the workpiece's grinding track.

In order to avoid the premature periodic repetition of the grinding track, according to the derivation and analysis of the epicycloid diagram, the ratio of the radius of the rolling circle r to the radius of the base circle R should be an irrational number, so that the grinding track can not be repeated, but in practice, the infinitely circular decimals are selected to meet the requirements.

Hypocycloid type

Coloring disc

The hypocycloid is the locus formed by any point on the circumference of the rolling circle when the rolling circle rolls along the inner side of another base circle.

Like epicycloid, hypocycloid also has long and short spokes.

The machine tool structures for obtaining the hypocycloid grinding track are also various, but the mechanisms are relatively complex, and the commonly used mechanisms are planetary gear type, tri eccentric type, etc.

The hypocycloid track makes the workpiece move at a high speed on the inner ring of the lapping tool, while the workpiece moves at almost zero speed on the outer ring, which makes the inner ring wear much and is not conducive to maintaining the flatness of the lapping tool. In addition, the workpiece itself is constantly turning and turning around, resulting in a large amount of grinding around the edges, which is not conducive to obtaining high geometric accuracy of the workpiece, and is generally used for rough grinding.

Straight reciprocating

Cast iron grinding plate

Linear grinding is widely used in manual grinding or mechanical grinding. The motion of linear reciprocating grinding track is relatively simple, but there are many opportunities for abrasive grains to re cut, which deepens the cut marks, which is extremely unfavorable to the guarantee of grinding accuracy. For example. It is difficult to make the workpiece surface finish above ▽ 13b, so the surface finish can only reach ▽ 13 when the original 3894 belt type grinder is used to grind the gauge block in a straight reciprocating manner.

In the process of manual linear reciprocating grinding, the workpiece with small size is ground by hand; If the size is too small, the lamination method is used for grinding, that is, the lamination is stuck on the auxiliary cushion block with the same accuracy, and the auxiliary cushion block is pressed by hand for grinding; For workpieces with long size and complex shape, the auxiliary fixture is often used to clamp the workpieces, and the auxiliary fixture is pressed by hand for grinding.

Sinusoidal ('8' form)

This motion track is a combination of longitudinal and transverse simultaneous motion, and its motion is related to variable wavelength, vibration amplitude A and frequency f. With the difference of the wavelength and the amplitude ratio K, the angle of the reticle tilt will change.

Sinusoidal grinding path is widely used in manual grinding and mechanical grinding. For example, the correction and sanding of the grinding plate, the grinding of the ice skate blade, the grinding of the micrometer and the gauge block, etc.

There are many kinds of machine tool mechanisms to realize the sinusoidal grinding path, for example, the synthesis of cam motion is one of them.

Irregular ring line type (spiral type)

Manual grinding plate

The formation of the grinding track is irregular. Because the spoke plate is sleeved on the non concentric moving axis, when the grinding pressure increases, the circular path of the workpiece on the surface of the lapping tool is intensified; When the grinding pressure decreases, the torus is pulled apart one by one, just like the torus shown when the spring spiral ring is pulled apart and pressed down on a plane.

In the process of making irregular circular path, the moving direction of the workpiece is constantly changing. This kind of trajectory is very beneficial to ensure the uniformity of the workpiece size, but it is not suitable for processing workpieces with large size and too large ratio of length to width of the area to be lapped. In manual grinding, this track is often used to trim various grinders.

Because the grinding track is irregular and should not be repeated, and the structure of the grinder to realize the grinding track is simple, the grinding track is widely used.