kega 022Žu-4/2017 implementation of on-line education in

KEGA 022ŽU-4/2017 Implementation of on-line education in the

area of precise technologies with an impact

on educational process to increase skills and

flexibility of students of engineering fields of study

KEGA 022ŽU-4/2017 Implementation of on-line education in the area of precise technologies with an impact

on educational process to increase skills and flexibility of students of engineering fields of study

- developed doc. Ing. Dana Stančeková, PhD.

Honing is the process of mass-cutting micro-cutting of material with

thousands of abrasive grains of precisely undefined shapes and

geometry, firmly held in the binder, for heavy soaking and cooling

with process fluid. The workpiece surface is in constant contact with

the tool, resulting in a periodic change in the direction of the

rectilinear axial movement with simultaneous rotation of the tool or

workpiece..

During honing, the quality of the surface of the machined surface, most commonly of the inner cylindrical

surfaces, is increased by the cutting action of the fine abrasive grinding stones (bars) which are attached

to the honing head. Honing can be cast iron, non-ferrous metals, hardened and non-hardened materials,

hard coatings and many other materials in dimensional ranges ranging in diameter from 1 to 750 mm and

up to 24 m in length. In addition to internal honing, the outer cylindrical surfaces are rarely honed.

Honing is used in practice when finishing hydraulic, brake and pneumatic cylinders, cylinders of

combustion engines, drums, bushes, spindle bearings, etc.




Honing is essentially grinding at a low speed. It is largely used as a finishing operation in the machining of

holes (internal honing), but the outer cylindrical surfaces (external honing) can also be honed. In the internal

honing, the hole wall is wiped with honing stones clamped in the honing head. The stones are pressed to the

machined area at a pressure of 0.2 to 1.4 MPa and perform a movement of the rotating and axial movement,

i.e., a substantially reciprocating, helical movement so that the grain paths overlap.

The workpiece is firmly clamped on the table of honors when honing the walls of holes. With increasing

material picking, the diameter of the engraving circle of the stones must be increased. It performs both rotary

and axial external sweep the movement of the workpiece and the head is mounted on the table of the hunt.

According to the required accuracy and roughness, the inner and outer cylindrical faces are channeled one or

more successively with two honing heads. By honing, material is picked at low wear of honing stones, great

geometric precision of machined surfaces, uniformity of dimensions in narrow tolerances (serial production)

and excellent surface quality. By honing, the accuracy of the dimension of holes or outer cylindrical diameters

in the IT3 to IT6 precision class, surface quality up to Ra = 0.08 μm and high accuracy of geometric shape

(circularity, cylindricality) is achieved. Honing can be used to finish holes with a diameter of 2 to 1,000 mm

and lengthsup to 10 m.

Honing can be machined hardened and non-hardened steels, cast

iron, colored and light metals, SK, graphite, glass and others. When

honing, it works 100 to 1000 times more abrasive grains than

grinding. Their cutting speed is 50 - 100 times smaller and tool

pressure 6-10 times lower than when grinding. The average cutting

temperature is 8-10 times lower than when grinding.

The depth of the deformed layer ranges from 0.006 to 0.002 mm.

The depth of amorphous (the process of the affected and

deteriorated layer) is only about 0.0005 mm




Honing has several advantages over grinding:

✓ greater accuracy of dimension and shape,

✓ higher surface quality,

✓ higher labor productivity,

✓ the ability to remove conicity and other shape deviations from previous

operations,

✓ smaller auxiliary times for setting up components,

✓ maintaining the perpendicularity of the axis of the orifice on its

perpendicular plane,

✓ reducing the accuracy and surface quality requirements of previous

operations,

✓ low surface waviness,

✓ very small amorphous layer,

✓ lower demands on precision and stiffness of the machine, the possibility

of trouble-free machining of thin-walled parts.

However, honing has some drawbacks to grinding:

❖ it is not possible to improve the position of the honed hole axis, the price,

❖ when honing tough materials, the pores of the honing stones are quickly

poured through the chips, thus decreasing labor productivity.

Honovanie guľových plôch




Under honing, we can understand that it is a low speed grinding of the

fine grinding tool of the honing tool with intense use of cutting fluids. In

the honing of the inner holes, the honing stones perform a helical

movement consisting of a rotary movement of the honing head with a

velocity vc and a sliding movement in the direction of the hc speed

axis.

On the surface, characteristic cross-marks, which bring an angle of 2a

to each other, appear. Angle value α is recommended in the range of

20° to 55° at higher angles, a lower surface roughness is obtained.

a - the stroke and movement of the honing head,

b - kinematics of the movement of the honing tool,

D

l

lh

l1

l2

2α

v

vo

va

I

II

III

‐ diameter of honing head,

‐ stroke length,

‐ length of stones on heads,

‐ lower course of honing stones,

‐ the upper course of honing stones,

‐ angle of crossing of honing tracks,

‐ the resulting cutting speed of honing,

‐ perimeter speed of honing,

‐ axial speed of honing,

‐ the initial position of the head in the upper position,

‐ the position of the head in the lower position,

‐ final position of the head after one twin stroke,

‐ shift of stones to one double-twin, difference

between positions I and III




Honing stones are pressed to a machined surface with a constant pressure of 10 -100 N.cm-2. Cutting

speed 15 - 30 m.min-1, peripheral speed of rotation is 20 to 50 m.min-1. Low pressure and low cutting

speed ensure that the surface temperature does not exceed 100 °C.

At the beginning of the honing process, the peaks and waviness of the surface are sharpened. As the

space increases, the pressure on the surface and thus the amount of material removed will be reduced. It

is known from practice that by increasing or decreasing the pitch of the tool traverse, reduce the volume

of material being removed. The magnitude of this angle also affects some other characteristics. In

addition, it is known that increasing the working speed will improve surface quality.

In order to ensure desirable surface quality and productivity, cutting liquids are always used for cutting,

most commonly using petroleum with oil or oleic acid. Cutting fluids in the process take away heat,

reduce cutting forces and resistances, but in particular remove particles of abrasives, chips and binder

from the pores.




Honing stones are pressed to a machined surface with a constant pressure of 10 -100 N.cm-2. Cutting

speed 15 - 30 m.min-1, peripheral speed of rotation is 20 to 50 m.min-1. Low pressure and low cutting

speed ensure that the surface temperature does not exceed 100 °C.

At the beginning of the honing process, the peaks and waviness of the surface are sharpened. As the

space increases, the pressure on the surface and thus the amount of material removed will be

reduced. It is known from practice that by increasing or decreasing the pitch of the tool traverse,

reduce the volume of material being removed. The magnitude of this angle also affects some other

characteristics. In addition, it is known that increasing the working speed will improve surface quality.

In order to ensure desirable surface quality and productivity, cutting liquids are always used for

cutting, most commonly using petroleum with oil or oleic acid. Cutting fluids in the process take away

heat, reduce cutting forces and resistances, but in particular remove particles of abrasives, chips and

binder from the pores.




One of the basic and typical features for honing is its specific

tools. The honing tool consists of a honing head, which is positioned and

fastened (mechanically or by gluing) the honing stone along its

circumference. Honing stone is a prismatic body with width and thickness

dimensions according to the size of the honing head (diameter of the honed

hole) and its length depends on the length of the hole. The amount of stones

clamped in the head varied according to the work specification.




One of the basic and typical features for honing is its specific tools. In the past, monopolies of honing

heads with interchangeable honing stones were formed - the amount of stones clamped in the head

varied according to the work specifications. These were cylindrical shaped heads with the possibility of

clamping of block honed stones with a square or rectangular cross section.

The clamping and construction of the honing head also affected the honing dimension. The honeycomb

mechanism is usually the product of the manufacturer and includes improvements and features

characteristic of its production line, so it is not entirely possible to talk about the general types of

honeycomb mechanics. Therefore, at least a wide-ranging division for better performance of traditional

honors:

a) Fixed clamping heads

- simpler design

- when adjusting the dimension, the tool must be completely dismantled

- elimination of errors in the clamping mechanism

b) Honing heads with springs / springs

- more complicated construction

- the spring springs ensure a constant pressure of the stones on the machined surface

- adjustment of the spring has been influenced by the honing dimension

c) Hydraulic honing heads

- prototype, little used

- a complex mechanism

- precise control of pressure and dimension

- occurrence of mechanical disorders

Honing tools




Such "classic" honing heads are still used today on various principles

and with different types or numbers of honing stones. In addition,

however, other types of instruments such as the so-called " spiky honing

thumbs, likewise using swapping stones, or increasingly used honing

brushes in dozens or hundreds of different designs. Such a variation of

tools is caused both by a constant attempt at a qualitative development

of honors and at the same time a commercial competitive struggle.




Honey stones mounted around the perimeter of the honing head

are used as honing tools. Their choice depends on the type of

machined material. For pre-honing, segments with a grain size

of 8 to 16 and a fine honing of 3 to 4 are designed. The honing

heads are swingable and can be adjusted to the desired size

and diameter to a certain extent.

The composition of the stones is similar to that of the grinding

wheels. However, it is necessary to provide self-shrinkage even

at low pressures. The grain must be broken and burst.

Common honing stones are corundum (Al2O3), grain size 120,

140, 320, 400, 500, medium to higher porosity with medium to

harder binding. Similar carbocorundic honing stones (SiC) are

also available. New types of honing materials are diamond and

cubic boron nitride.




In this way, the ovality, conicity and waviness of the holes

can be corrected, but not the position of the hole axis, since

the honing spindle with the spindle joins the joint. Honest all

kinds of materials, including glass and plastic. He works

mostly on two operations - pre-honing and honoring purely.

Processed liquids are always used, using their cooling,

lubrication and cleansing properties. Kerosene, a mixture of

petroleum and mineral oil or oil are used. The higher the

viscosity of the oil, the less roughness is achieved, but it is at

the expense of performance.

Unrundheit Krümmung Konizität Tonnenform Vorweite Welligkeit Untermaß

Spôsob opráv pri honovaní




Vertical honors (Figure 21) are produced as single-woven or multi-woven. The spindle

drive is from the electric motor via a stepped gearbox. Direct reciprocating

displacement is hydraulic. The working cycle is controlled either manually or

automatically. Automatic machines are equipped with active control to prevent the

required hole size from being exceeded.

Horizontal honors are designed to finish holes in longer parts and occur in two

variations. The embodiment of FIG. and is intended for honing the rotating

workpieces clamped by one end in the chuck, the other end being guided by the

restraint. The tool performs a straightforward motion. These machines are built for

holes with a diameter of 50 to 750 mm and a tool lift of up to 3 m. The embodiment of

FIG. b is used for honing non-rotating workpieces. The tool spindle performs all

movements, similar to vertical machines.




Vertical

Horizontally

Honovaí dvoj vretenový




Honovanie hláv válcov

Honovanie valcov motora




THANK YOU FOR ATTENTION

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