RU1798139C - Method of controlling machine for belt grinding of strips - Google Patents

Abstract

Usage: metalworking, for use on grinding flocks for various purposes, mainly for grinding the surface of pain parts. long lengths, in particular strip hire. The essence of the invention lies in the fact that the load on the electric motor of the abrasive tool is continuously measured in the form of the active power Mw and the size of the workpiece Ht coming to the processing. In the invention, the invention relates to metalworking and is intended for use on grinding machines for various purposes, primarily for grinding the surface of long parts, in particular strip products. The purpose of the invention is to ensure uniform metal removal with a continuously changing part size and changing cutting properties of an abrasive tool. This is achieved by the fact that according to the method of controlling the grinding machine during continuous measurement of the load per m of supply of the workpiece to the abrasive tool, the moment of penetration of the abrasive tool into the part to a predetermined depth is determined, which is determined by the excess of the load by a predetermined amount over the idle load. At the moment of insertion, the part size Н0 and the position of the So-supply device are stored. Subsequently, depending on the size of the part in front of the machining center and on the degree of change in the cutting properties of the abrasive tool, the position of the supply device is changed, calculating it according to the t formula: St S0 + H0- Ht + K / о Niudt, where K is the coefficient of proportionality; t is the operating time of the abrasive tool. At; this the current part size is taken before | the processing center at a distance: L ДН (VA / Vy, where AN is the absolute value of the maximum allowable deviation of the part size from the nominal value; Beat, Vy is the speed of movement of the part and the feed device, respectively. 3 or. motor of the abrasive tool and size arriving at the workpiece, the workpiece is brought to the abrasive tool, the value of the load on the electric motor of the abrasive tool is stored, the working feed is turned on, the actual load is compared with the stored one at the moment when yes, the difference will become larger than the set one, which corresponds to the required depth of penetration of the abrasive tool into the part, i.e., the depth that is necessary for a given metal removal, the size of the s-s-hh) 00 Jk s o

Description

the workpiece and the position of the supply device, and subsequently, depending on the size of the part in front of the machining center and the degree of change in the cutting properties of the abrasive tool, the position of the supply device is changed, calculating it according to the mathematical dependence:

5.5d + But-H1 + K / o Nmdt, (1)

where So and But are, respectively, the position of the supply device and the size of the part stored at the time of cutting into the necessary

depth Ht is the current part size;

/ Nujdt - the value of the energy spent by an abrasive tool to remove the metal during the operation of the tool;

№ш - active power of the abrasive tool engine ;:

t is the operating time of the abrasive tool;

K-coefficient of proportionality. In this case, the current part size is taken in front of the treatment center at a distance determined by the formula:

-L-: days

vy

(2).

where L / d is the speed of movement of the part;

. Vy is the speed of movement of the supply device;

 And H is the absolute value of the maximum allowable deviation of the part size from the nominal value. .

In FIG. 1 shows a functional diagram of a device that implements the method; in Fig. 2 - the moment of cutting into the part; in FIG. 3 is a process for controlling the length of a belt sander.

The control method is as follows.

For a specific grinding process, empirically determine the load level on the electric motor of a new abrasive .. tool, in which the abrasive tool cuts into the part and removes the necessary layer of metal from the surface

details ..;:. ::

The workpiece is brought to the abrasive tool and the value of the load on the electric motor of the abrasive tool is stored, this load characterizes idling. After turning on the working feed, the abrasive tool comes closer to the part, and after cutting the abrasive tool into the part, the load begins to increase, At a time when the load exceeds the load level determined experimentally,

0

5

0

5

0

5

0

5

0

5

removal of metal from the part will correspond to what is necessary, and at this time the position of the supply device So and is stored; Part size H0. During grinding; all the time the value of the energy spent on metal removal is determined during the operation of the abrasive tool. The energy value is determined by integrating the value of the active power Ms of the abrasive tool electric motor t

Q / 0Nu, dt (3)

As the metal is removed, the cutting ability of the abrasive tool / decreases, and the value of the energy Q increases. If, ceteris paribus, the supply device is left in the same position, then with an increase in Q, the removal of metal from the part begins to decrease. Therefore, in order to compensate for the reduction in removal by reducing the cutting properties of the tool, it is necessary to move the part with the feed device towards the abrasive tool. The magnitude of this movement depends on the expended energy Q and the proportionality coefficient K; which is experienced for a particular type of part and type of abrasive tool.

During grinding, the feed device is set to St. which is determined by mathematical dependence.

When calculating St, the current part size Ht is taken in front of the machining center at the distance L This distance is determined by the formula (2).

(If you take the current part size directly in the pick-up area, then with large fluctuations in the size of the part, the supply device cannot be set to the desired position, that is, the position that is necessary at this size of the part due to its inertia. Therefore the current part size Ht is taken at a distance L from the machining center, i.e., with a lead.

The magnitude of the DN for each part arriving for processing is determined by the applicable standards and shows the maximum allowable deviation of the size of the raw part from the nominal value. The speed of movement of the device supplying part to the abrasive tool Vy and the speed of movement of the part A / d are constant for the particular type of workpiece. Taking into account the size of the part Ht in front of the machining center at a distance L allows the approach device to be maintained in a position that provides a constant depth of cut

abrasive tool into the pedal when changing its size, i.e. if the part size even changes by the LN value from the nominal value, the device under water will have time to be set in a new position by the time of approach to the treatment center of the part with a changed size.

The method is illustrated in Fig. J-3.

The device that implements the method includes a machine 1 with an abrasive tool rotation motor 2 and a device for supplying 3 parts to an abrasive tool, an engine load sensor 4, a storage device 5, an adder 6, an integration unit 7, a comparison unit 8, a storage device 9 and 10 , adder 11, delay blocks 12 and 13, position sensor 14 of the approach device, part size sensor 15, control unit 16 of the approach device, multiplication unit 17. The input of the load sensor 4 is connected to the motor 2, and the output is connected to the inputs of the adder 6 and remember his device 5, the output of which is connected to the inverted input of the adder 6. The output of the adder is connected to the b input of unit 7 and integrating comparing unit 8, the second input signal which is supplied a predetermined load value N3.

The output of the integration unit 7 is connected to the input of the side of the multiplication 17, to the second input of which a signal of the proportionality coefficient K is supplied, and its output is connected to the first output of the adder 11, the output of the comparison unit 8 is connected to the control inputs of the storage devices 9 and 10, the outputs of which are connected respectively to the second and third inputs of the adder 11, and the information inputs of the storage devices 9 and 10 are connected respectively to the output of the position sensor 14 and the output of the delay unit 12, to the control input of which a signal is supplied Beats

The input of the delay unit 12 and the first input of the delay unit 13 are connected to the output of the part size sensor 15, a value reference signal is supplied to the second input of the delay unit 13, and the output of this unit is connected to the inverse input of the adder 11, the output of which is connected to the first input of the control unit .sixteen. The second input of the control unit 16 is connected to the output of the position sensor 14, which is connected to the output of the supply device 3, and the output of the control unit 16; connected to the control input of the supply device.:

Consider the operation of the grinding machine from the moment it is put into operation using a device that implements the proposed method of controlling

nor with the example of a belt sander for grinding strip products.

After completing the preparatory operations, the abrasive belt rotation motor 2 is turned on, the power of which is measured by the active power sensor 4. In the initial state, there is no contact of the strip being processed and the abrasive belt, and at the output of the sensor 4 there is an idle power signal. After turning on the working feed from the logic unit (not shown in the diagram), the idle power recording signal Nxx is supplied to the storage device 5 and the supply of the sanding strip 19 via the feed device 3 to the rotating sanding belt 18 starts, and after cutting the sanding belt into the power strip consumed by engine 2 starts to increase and a signal appears at the output of adder 6 equal to the difference in apparent power and idle power of engine 2 (Nuj N-Nxx), i.e. power spent directly on material removal.

When the Mch value is N3, which indicates the necessary depth of cutting of the abrasive tape into the strip being processed, the comparison unit 8 is activated and its output signal is recorded information in the storage device 9 and 10. In this case, the position So of the supply device 3 is entered into the storage device 9, and in the storage device 10 records the value of the thickness of the strip H0 located at the processing center (Fig. 2).

During the movement of the processed strip 19, a metal layer e is removed from it (Figs. 2, 3). The thickness of the strip is measured by a sensor 15, which is installed at a certain distance from the treatment center, so portions of the strip with the measured thickness fall into the machine with a certain delay, therefore, in order to know the thickness of the strip in the treatment center, delay units 12 and 13 are used. Delay value depends on the distance between the measuring point and the treatment center and on the speed of the strip Ud. By setting the delay value of block 12 in proportion to a fixed constant speed of movement of a particular strip at its output, a signal of the strip thickness located in the processing center is generated. Thus, at the time of cutting to a predetermined depth in the storage device, the thickness of the strip located in the focus of processing Ho is fixed. Since for control purposes, this method uses a strip thickness located at a distance L from the treatment center,

depending on the value. the delay value of the block 13 is set and the value of the strip thickness Ht is supplied to the inverse input of the adder 11. The integration unit 7 integrates the value of the active power of the abrasive belt rotation motor, and multiplying this value by the proportionality coefficient K (found experimentally for various materials and types of abrasive belts) is performed in the multiplication unit 17 and a signal equal to the required value is received at its output moving the strip feed device toward the abrasive belt in order to compensate for the loss of cutting ability of the latter, i.e. to ensure the necessary removal of metal, all other conditions being equal. At the output of the adder 11, a signal is generated. Of the necessary position of the supply device St, which provides the necessary metal removal regardless of the degree of wear of the abrasive belt and the changing current strip thickness Ng (Fig. 3). In the control unit 16 of the supply device, the actual position of the supply device is compared 3 and the necessary St, and a command is generated to move the supply device in the necessary direction according to formula (1). .

By controlling the grinding machine according to this method, it is possible to obtain a high-quality surface of a steel strip by uniformly removing the surface layer of the metal, which contains various defects, non-metallic inclusions, etc. In this case, fluctuations in the thickness of the strip and current changes in the cutting properties of the abrasive tool do not affect the amount of removal. .

Consider the control according to the claimed method, a belt grinder for grinding strip products, the Machine processes Moving steel strips of infinite length, i.e. strips of several hundred meters are welded one after another at the entrance to the machine and form one side. The purpose of grinding is to remove from the surface of the strip a layer of metal whose value is constant along the entire length of the strip, while the amount of removal of metal should not depend on fluctuations in the thickness of the strip, on the degree of wear of the abrasive belt.

The operation diagram of the machine is shown in FIG. 2iZ.

In the grinding process, the moving steel strip 19 is pressed by the feed device 3 against the rotating abrasive belt 18, as a result, the metal d is removed from the surface of the strip.

After turning on the working feed5, the device 3 of the drive 3 begins to move and leads the moving strip 19 to the abrasive belt 18. From the moment of their contact, the abrasive tool starts cutting into the strip 19 and starts from the surface

10, the metal layer e is removed, and at the same time the power consumed by the rotation motor 2 of the abrasive belt 18 starts to increase. In this method, only the operating power is used, i.e. of

At full power, idle power is subtracted. For this machine, this type of machined strip with a new abrasive belt, it was experimentally established that when the power 0 reaches 36 kW, the amount of removal becomes equal to the set value of d 0.015 mm, therefore, when kW, the strip feed stops. The position So of the feed device 3 and thickness H0

5 of the processed strip 19 in the treatment center. If the supply device is left in this position, then with fluctuations in the incoming thickness. the processing center of the strip will fluctuate Nut power and amount of removal

0 d: An increase in thickness leads to an increase in the load on the abrasive belt and to an increase in removal 6, with a decrease in thickness the reverse process. Absolute .. The value of the maximum value deviates from the thickness of the nominal value for this type of steel strip is 2 mm. Therefore, grinding at a constant position of the supply device leads to an unstable removal rate

0 metal, to large fluctuations in the load of the abrasive tape, which leads to its premature failure.

To increase the machine, in order to take into account changes in the strip thickness, you can use the formula:

S, So + H0-Hoi ,. (4) where St is the required position of the supply device; . .

Hot - current strip thickness in the focus

0 processing ... -... Constantly detecting St and setting the inlet device 3 in this position, the influence of the Hot thickness on the amount of removal can be largely eliminated

55 overload abrasive tape. From the formula (4), it follows that the current thickness H0t is equal to the thickness Ho, then the supply device remains in the forward position. If the current Hot thickness has increased, for example by. 0.1

mm, then using the device to feed the strip must be allotted to 0.1 mm. When decreasing the thickness of the strip, it must be brought to the abrasive belt. But control of the position of the supply device on a real mill according to the formula (2) does not provide stability of the removal, since the speed of movement of the delivery device is not taken into account.

In this machine, the speed of movement of the feed device, 03 mm / s, the speed of the processed strip m / min 333.3 mm / s, so if the thickness of the Udin Hot changes for. 2 mm, then the feed device according to the formula (5) will be set in a new position for 66 s (g DN / Vy), and during this time a section of a strip of length L g х .66 sec - 333.3 mm / s will pass through the treatment center. 2222 mm. Thus, a section of a strip with a large thickness can leave the treatment center earlier than the supply device occupies the necessary position, which, in addition to increased removal, can lead to a break in the abrasive belt. A sharp decrease in the strip thickness can lead to the appearance of completely non-sandable sections of the strip

 To eliminate this phenomenon, it is necessary according to formula (4), instead of the current strip thickness in the treatment center Hot, use the current strip thickness H-t taken at a distance L from the treatment center. The value of L is determined by the formula (2);

The use of Ht for control purposes makes it possible to significantly eliminate the overload of the abrasive belt, to provide more stable metal removal by keeping the feed device in a position that provides a constant depth of cut of the abrasive tool into the strip.

For this machine: 333.3 mm / s

L en Vs

UU

0.2 mm.

0.03 mm

Therefore, if the thickness changes by the maximum value of the DN, then the supply device will have time to establish itself in a new position by the time of approach to the treatment center of the section with the changed thickness. Similar changes in strip thickness along the length are characteristic of hot rolled strips entering grinding machines in order to remove surface defects and non-metallic inclusions. Therefore, formula (4) takes the following form:

Si So + Ho-Ht ,. where Ht is the strip thickness at the distance LOT of the treatment center. As the metal is removed, the abrasive tool is worn. its cutting ability decreases .. These factors increase as the work performed by the abrasive tool increases, therefore, for the purpose of controlling, it is proposed to use formula (1). The proportionality coefficient K is determined o: by an irrigation method for a particular machine, material of the processed strip, type of abrasive belt. :

For this machine empirically obtained the following data:

- almost complete wear of the abrasive tape occurs when it is performed.

 t work Q / Q N.mdt 44.8 kWh. Determination; Q values were carried out by continuous integration of the active grinding power, until the tape- was completely worn out. . . ....-.

- when the abrasive belt performs work 0 to 44.8 kWh, the metal removal during grinding decreases from 0.015 mm to zero. Therefore, the coefficient K is calculated as follows ::.

 mm P PPP - mm

TO

 0,00035- 44 8 kWh u-uv kWh Consider a specific example of the use of formula (1). We take the initial position of the input device mm, the thickness of the strip at the time of cutting .8 mm and K OLO 0335 mm / kW h.

With a strip thickness at a distance of LOT of the machining chuck equal to 9 mm and work performed with an abrasive belt

 t; -.

Nyjdt 15KBT -h we calculate the necessary position of the supply device: mm +3.8 mm + 3.9 mm + mm

+0,000335

kW

-15kWh -7.905 mm.

At., 8mmi / o Nujdt 40 kWh:

 mm + 3.8 mm - 3.8 mm + mm

+0,000335

40 kWh 8.0134 mm.

kWh

Thus, the calculation formula is obtained on the basis of the analysis of the work of a belt sander for processing strip products. The proportionality coefficient K and the purpose of the grinding load providing the necessary material removal with a new belt are tested empirically by a specific grinding machine, the type of material being processed and the type of abrasive tool. . SUMMARY OF THE INVENTION A method for controlling a belt grinding machine for strip products, comprising measuring drive power

abrasive tool and thickness of the processed strip and installation of a device for supplying the processed strip to the abrasive tool in a position determined by taking into account the measured values, with the exception that, in order to improve the quality of the processed surface, the device for supplying the processed strip to ab active tool during processing is set to the position St, determined from the expression:

Si So + Ho-Ht + K / o

0

where So is the position of the supply device at the time of cutting the abrasive tool to a predetermined depth;

But-thickness of the strip at the time of cutting to a given depth:

Ht is the current value of the strip thickness:

Msh - active power drive of an abrasive tool;

t is the operating time of the abrasive tool;

K is the coefficient of proportionality.