Guitar interchangeable gears. Replacement Gear Selection Methods Guitar Replacement Gear Repair
transcript
1 FEDERAL STATE BUDGETARY EDUCATIONAL INSTITUTION OF HIGHER EDUCATION "VOLGOGRAD STATE TECHNICAL UNIVERSITY" KAMYSHINSKY TECHNOLOGICAL INSTITUTE (BRANCH) OF THE FEDERAL STATE BUDGETARY EDUCATIONAL INSTITUTION OF HIGHER EDUCATION "VOLGOGRAD STATE TECHNICAL UNIVERSITY" Department "ENGINEERING TECHNOLOGY AND APPLIED MECHANICS" METHODS OF SELECTION OF REPLACEMENT GEARS Guidelines to perform laboratory and practical work on the course "Metal-cutting machines" and " Technological equipment» Volgograd 206
2 UDC 62906(0758) М 54 METHODS OF SELECTION OF REPLACEMENT GEARS: guidelines for the implementation of laboratory and practical work on the course "Metal-cutting machines" and "Technological equipment" / Compiled by N.I. Nikiforov; VolgGTU Volgograd, s Descriptions are given various methods selection of gears in guitars Designed for students studying in the direction of "Design and technological support engineering industries"and specialty SPO "Technology of Mechanical Engineering" Il 2 Table 4 Bibliography: 4 titles Reviewer: Ph.D.
3 General information about guitars with interchangeable wheels A guitar is a mechanism with interchangeable gears designed to step change the gear ratio of the calculated kinematic chain They are mainly used in rarely retuned chains with a large range and the number of gear ratios of the tuning chain of the calculated chain These mechanisms are simple in design The main disadvantage of guitars is the complexity of tuning Guitars are one, two, less often three-pair In gearboxes, usually single-pair guitars are used In the vast majority of cases, either a single-pair or two-pair guitar is sufficient to obtain the required feed values Two-pair guitars of interchangeable wheels can be made with a constant and variable distance between the axes of the wheels They are used in machine tools for high-volume production with rare tuning They are compact, simplify the structure and design of the drive Two-pair guitars with adjustable distance between the axles have a movable intermediate shaft and make it possible to engage gears with any number of teeth, which makes it possible to adjust the gear ratio with a high degree of accuracy. Fig. Two-pair guitar with interchangeable gears 3
4 General series of teeth numbers z for turning milling backing General series of teeth numbers z for turning milling backing Sets of interchangeable wheels for groups of machines (recommended) gear-cutting gear-cutting Distance A between the driving shaft (wheels a) and the driven 2 (wheels d) is unchanged On the driven shaft freely the slope of the guitar is planted 3 In the slope there are radial and arc grooves In the radial groove, the axis of 4 wheels b and c is attached By moving the axis along the groove, you can change the distance B between wheels c and d Due to the presence of an arc groove in the slope, it is possible to change the distance C between wheels a and c b, turning the incline on the shaft 2 In the required position, the inclination is fixed with a bolt 5 2 Selection of the number of teeth of interchangeable gears The task of selecting interchangeable gears is to determine the number of teeth of these wheels to ensure the required gear ratio Each guitar of the machine is equipped with a certain set of interchangeable wheels (table) Quantity wheels in the set and their number of teeth are different and are determined by the possible variety of gear ratios that are required to be carried out during the operation of the machine, as well as the degree of accuracy with which the selection of gear ratios is required Table Normal sets of replacement gears for machines of various types machine groups (recommended)
6 All methods for selecting replacement gears can be divided into exact and approximate. Let's consider several methods for selecting the number of teeth of replaceable wheels are decomposed into simple factors After factorization, the first ratio of factors is taken and the numerator and denominator of this ratio are multiplied by the same number to obtain numbers in the numerator and denominator equal to the number of teeth of the wheels in the set. Similarly, they do the second ratio of factors (for a two-pair guitar ) and with the third (for a three-pair) Consider the example i a b c d, 63 a 36, b 20, c 30, d 63 (The factors in parentheses are indicated by which we multiply the numerator and denominator) 22 The method of continued fractions The ratio a / b of any integers can be expressed as a continued fraction: a a b a2 a3 a4 an, an where a, a2, a3, a4, a n ; an - quotients of division performed as follows: first a is divided by b, it turns out a, then b is divided by the remainder of the first division, it turns out a2 and so on, each previous remainder is divided by the next until the remainder is zero 6
7 In the continued fraction thus obtained, a is the roughest approximation; more precisely the approximation a a2 a ; adding each subsequent term a2 a2 of the fraction gives a more accurate approximation. First, they stop at some term of this fraction and determine the gear ratio, decomposing it into factors and select the wheels according to the first method we have considered. After selecting the wheels, check the tuning error. If it goes beyond the permissible error, then they again calculate, taking a larger number of terms of a continued fraction. Example Select gears for a gear ratio, 765 Let's turn the number, 765 into a continued fraction, for this you need to divide the numerator by the denominator, we get the first quotient and the first remainder, 765: \u003d (private) 765 (th remainder), then divide the denominator by the -th remainder: 765 = 8 (2nd quotient), (2nd remainder) Divide the first remainder by the second remainder 765: = (3rd quotient) 5885 (3rd remainder) Divide the second remainder by the third remainder: 5885 = 7 (4th quotient) 5835 (4th remainder) Divide the third remainder by the fourth remainder 5885: 5835 = (5th quotient) 50 (5th remainder) Divide the fourth remainder to the fifth remainder 5835: 50 = 6 (6th quotient) 35 (6th remainder) , all members are discarded and the fraction interrupted in this way is converted into an ordinary one: 9); 2) 8 8 7
8 To get the next suitable fraction, you need to multiply the numerator and denominator of the previous suitable fraction by the denominator of the last term of the interrupted fraction and add the numerator to the numerator of the product, and the denominator of the second previous suitable fraction to the denominator of the product 3) (9) 0 8 (8) 9 4) ( 0 7) (9 7)) (79) (6)) (89 6) (70 6) Thus, a series of convergent fractions is obtained: ; ; ; ; ; For the selection of interchangeable gears, you can use any suitable fraction, but since each subsequent fraction will be closer to the value of the continued fraction, then taking the next suitable fraction, the selection error will be less. 25.4; and 25, 4 are replaced by approximate values (Table 2), which make it possible with sufficient accuracy 25.4 8
9 get gear ratios This method is used, for example, on screw-cutting lathes when cutting inch threads in the absence of a set of wheels with the number of teeth z=27 Example 2 Select replacement gears for cutting inch threads with the number of threads per inch k=0 screw-cutting lathe with a screw pitch Pxv = 6 mm and a constant gear ratio i post We solve this example using table 2: a c Pp 25, b d i post Pxv in determining the setup error 25.4 Table 2 Table of replacement values; 25.4; and 25, 4 25.4 25.4 25.0 0, 0.2 0.4 0.23 0. 0 0.45 0.2 0.6 0, Note In brackets inaccuracies of linear movement are indicated in millimeters per m of length 24 The logarithmic method is based on finding the logarithm of the gear ratio (if the gear ratio has the form of an improper fraction, take the logarithm of the value, 9
10 inverse gear ratio) and according to the corresponding table VASHishkov determine the number of teeth of replaceable gears. This method is based on the principle of logarithm of the gear ratio and gives the gears of the heel set with a very small error. The gear ratio of the gears a c of the guitar i after logarithm is b d lg i lg ac lg bd a c For example, for gear ratio i 2.76; b d lg 2.76=0.425 lg i a c b d gear ratios is less than one, so for i you need to take the logarithm of the reciprocal of the gear ratio: 0
11 i i t abl Selection of the number of teeth of the wheels on a slide rule The edge of the slide rule engine is set against the number corresponding to the gear ratio By moving the sight find the risks that match on the engine and on the ruler The risks must correspond to integers that give the value of the gear ratio when divided Then select the number of teeth interchangeable gears, for example, by the method of decomposition into prime factors:, 885 i 0.629 3 Leaving the engine in the resulting position, move the sight until the risks on the engine and on the ruler match Then i 0, This method of selection and wheels when cutting threads as a rule, it cannot be used, since its accuracy is usually not high. to gear ratios The given gear ratio in the form of a simple proper fraction, inconvenient for conversion, must first be converted to a decimal fraction with six decimal places. If the fraction is incorrect, then it is necessary to divide its denominator by the numerator to get a decimal fraction less than one they find a decimal fraction equal to or closest to it, and next to it a simple fraction corresponding to it. Having received a simple fraction, then the number of teeth of interchangeable wheels is selected in the usual way
12 Table 4 Fragment of the MVSandakov table 0, For example, i, from where 0, i From the MVSandakov table we have 0, Due to the fact that the gear ratio before converting to a decimal fraction has the numerator and denominator swapped, the approximate number does the same Then i Selected wheels available in a set for gear-cutting machines If it is not possible to select the necessary gears, then another nearest value is taken from the table (for example, see the fragment of the table 0.64340 or another) 27 Knappe method This method is based on the fact that the numerator and denominator of fractions, close to one, you can add (or subtract) an equal number of units without significantly changing the value of the fraction Let i Divide this fraction, we get Then we can write: i We got a factor in the form of a fraction close to one 335 Using the above rule, we can write:
13 i We have obtained a fraction that is easily decomposed into factors Now, using the previously considered method, we will select gears: (5) i (5) This method is recommended to be used in the absence of tables specifically designed for selecting interchangeable wheels. It is also convenient when selecting three-pair guitars. 3 Determining the error settings When using approximate methods for selecting interchangeable gears, it is especially important to correctly estimate the error with which the exact gear ratio is replaced by an approximate one. Knowing the setting error, you can determine its effect on the accuracy of the workpiece. required i gear ratios: i i Relative error is the ratio of the absolute error to the required gear ratio: i The kinematic chain setting error will be equal to: P L, where L is the length of movement carried out by the adjustable kinematic chain For example, when threading, this will be the thread pitch t p ; when setting up the differential chain of a gear hobbing machine, such a movement will be an additional rotation of the workpiece by a certain arc 3
14 Guitar gear engagement conditions After selecting the number of teeth of the guitar wheels that satisfy the required gear ratio accuracy, it is necessary to check the possibility of installing them in the guitar, taking into account the dimensions of the guitar body and the distance between the axes of the first and last wheels Let us denote a, b, c, d the number of replaceable teeth wheels (Fig. 2), D is the diameter of the gear shafts, mm; m - wheel module, mm; hr tooth head height, mm To be able to install wheels a and b, it is necessary that the sum of their radii is greater than the radius of wheel c, plus the tooth head of wheel c, plus the radius of the shaft of wheel a Similarly, to install wheels c and d, it is necessary that the sum of their radii was greater than the radius of the wheel b, plus the head of the wheel teeth b, plus the radius of the wheel shaft d The above can be written as inequalities: D D ra rb rc hr ; rc rd rb hr 2 2
15 For most guitars, the diameter of the wheels is constructively taken equal to D 3 m Height of the head of the teeth h r m Then the inequalities can be written as follows: a m b m c 2 m 3 m ; c m d m b 2 m 3 m, from which we obtain the adhesion conditions: a b c 5 and c d b 5 22 If the condition is not met, then it is necessary to swap the gears in the numerator or denominator and check them for adhesion again. If in this case the adhesion conditions are not met, then it is necessary to repeat the calculation of the number of teeth, taking other additional factors. Textbook for engineering colleges - M: Mechanical engineering, s, illustration 2 Petrukha PG Technology for processing structural materials: Textbook for universities M: graduate School, s, ill 3 Sandakov M V et al Tables for the selection of gears: Handbook 6th ed., add M V Sandakov V D Wegner M: Mechanical Engineering, s ill 4 Fundamentals of machine tool science: Lab work / Comp: VA Vanin, VKh Fidarov, VK Luchkin Tambov: Publishing House of Tambgos Technological University, p. 5
16 Compiled by: Nikolai Ivanovich Nikiforov METHODS OF SELECTION OF INTERCHANGEABLE GEARS Guidelines for the implementation of laboratory and practical work on the course "Metal-cutting machines" and "Technological equipment" Edited by the author Templan 206 g, pos 5K Signed for printing g Format / 6 Sheet paper Offset printing Conv. print 0.93 Uch-izdl 0.7 Circulation 00 copies Order Volgograd State Technical University, Volgograd, Lenina pr., 28, building Printed in KTI, Kamyshin, Lenina st., 5 6
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With gear cone and ring gear (Norton cone).
II cap wheel Z0 can be alternately engaged with the wheels mounted on the shaft I.
I- drive shaft; II- driven shaft
When moving the housing along the shaft II cap wheel Z0 can be alternately engaged with the wheels mounted on the shaft I.
I- drive shaft;
II- driven shaft
The transmission of movement from the driving to the driven shaft is carried out through a gear wheel 2 spinning on your finger 5 lever 4 , Which can
rise or fall, thereby the wheel 2 or engages with the wheel 3 or breaks up with him.
Flaws:
1. Low efficiency, because an intermediate link is constantly involved in the work.
2. More complex design.
3. Under the action of the expansion force that occurs in the gearing, the mechanism may open, so additional devices are required to fix the lever.
4. The mechanism is used to transmit small torques.
5. Low rigidity.
It is used in screw-cutting lathes. Up to 12 gears can be placed in one row.
At TO transfer required K + 2 wheels.
Guitar- a machine tool designed to change the feed rate. Interchangeable wheel guitars make it possible to tune the pitch to any degree of precision.
a, b, c, d- number of teeth of replaceable wheels.
For correct selection replacement wheels, it is necessary to fulfill the adhesion condition.
a + b > c + 22- must be carried out
c + d > a + 22 simultaneously.
Each guitar is supplied with a specific set of interchangeable gears.
Replacement wheels are selected in various ways. The easiest way factorization.
The adhesion condition is satisfied
The device of a two-pair guitar with interchangeable wheels.
Axes 1 and 2 have a fixed position. Intermediate wheels b and c are fixed on the pivot arm. Radial and arc grooves which allow you to install gears with different numbers of teeth i = a/b∙c/d
To a metal-cutting machine, sets of interchangeable wheels are usually given. Sets are heeled (multiples of 5) and even (multiples of 4).
The first selection method is to reduce the gear ratio to a simple fraction. Then the numerator and denominator are decomposed into simple factors and multiplied by constant numbers, so that in the end it corresponds to the numbers of gears in the set
1 = 9/8=3∙3/4∙2 = 3∙(15)/4∙ (15) ∙3∙ (20) / 2∙ (20)
Adhesion condition.
Second method - the method of continued fractions. The ratio of two integers A and B can be represented as a continued fraction
.
where a 0, a 1, a 2 ... and n -1, a n - quotients from division, obtained as follows: first divide A by B, it turns out a 0, then B divide by the remainder of the first division, etc., t .e. The previous remainder is divisible by the next until the last remainder is 0.
Example: 223/137= A/B.
The third digit of the second row is obtained: the first digit of the first is multiplied by 2 the digit of the second row and the first digit of the second is added. The fourth digit of the second row is obtained by multiplying the second digit of the first row by the third digit of the second row and adding the second digit of the second row.
Replacement wheel guitars are selected with varying degrees of precision.
Lathe chucks
According to the number of jaws, the cartridges are divided into two-, three-, four-jaw. Two- and three-jaw chucks are self-centering, four-jaw chucks are usually made with independent jaw movement and less often self-centering.
Accessories and fixtures for lathes
A very common way of processing parts on lathes is machining in centers. A clamp is put on the workpiece, which is installed in the centers of the machine, which rests against the faceplate leash. The faceplate rotates with the machine spindle and rotates the workpiece through the collar.
The designs of the most common centers are shown in the figure.
2) the middle center is used when trimming the ends, when the center should not interfere with the exit of the cutter;
3) the center with a ball is used when it is necessary to grind the cone and shift the axis of the part from the axis of the machine;
4) reverse cone - when processing a small diameter and there is nowhere to make a center hole. They just make a conical chamfer.
clamps
Serve to report the rotation of the part installed in the centers.
Clamps come with a straight and curved end that fits into the groove of the driving chuck. Clamps are made with one screw and two (with high cutting forces) there are self-tightening clamps.
Driver chucks are a disc with 4 slots and a threaded hole for screwing onto the end of the spindle.
Movable and fixed rests
Steady rests are used as additional supports when processing non-rigid shafts. Are used universal fixed or movable steady rests with sliding cams and special, designed to process certain parts.
Methods for processing conical surfaces
Guitar- a machine tool designed to change the feed rate. Interchangeable wheel guitars make it possible to tune the pitch to any degree of precision.
a, b, c, d- number of teeth of replaceable wheels.
For the correct selection of replacement wheels, it is necessary to fulfill the adhesion condition.
a + b > c + 22- must be carried out
c + d > a + 22 simultaneously.
Each guitar is supplied with a specific set of interchangeable gears.
Replacement wheels are selected in various ways. The easiest way factorization.
The adhesion condition is satisfied
Reversing mechanisms
Used to change direction. They have different designs.
With movable blocks and intermediate 2. C various types interchangeable clutches and intermediate wheel. wheel.
Conical snaffle.
Maltese mechanism.
It is used for periodic rotation of the working bodies of the machine at the required angle.
With continuous rotation of the crank 1
finger 2
periodically enters the grooves of the Maltese disc 3
and turns it around α
.
Ratchet mechanism.
Serves to convert continuous rotational motion into intermittent and to rotate to the desired angle.
| |
Rocket mechanism.
With continuous rotation of the crank disk 1 finger 2 informs backstage 3 reciprocating rotational movement, and the wings through the finger 4 informs the working body 5 reciprocating motion.
It is used in gear shaping machines.
Crank mechanism.
Serves to convert rotational motion into reciprocating motion.
| |
It is used in slotting and cross-planing machines.
This mechanism provides good smoothness of movement of the working body of the machine, however, it has an uneven speed of the working stroke.
Cam mechanisms.
Serve to convert rotational motion into translational.
They are mainly used in automatic machines.
1 - disc cam
2 -finger
3
- spring for constant finger contact
with the working surface of the cam.
blocking mechanisms.
Designed to prevent the simultaneous activation of several mechanisms, the joint operation of which is unacceptable
A) 
b) 
Figure, a - the neutral position in which you can turn on or the handle 1 or handle 2 .
Figure, b - handle 1 turned on and the handle 2 blocked
Safety devices
Serve to protect the machine from overloads. They are divided into electrical, hydraulic and mechanical or combined. Electrical safety devices and safety clutches are especially widely used. Of the mechanical safety devices, the most common are shear pins and keys, falling worms.
travel limiters.
They are installed so that the moving part of the machine does not reach a dangerous end position. Sled 2
when meeting with a hard stop 1
stops and the friction clutch 3
starts to wobble. This continues until the motor is turned off or the slide is moved away from the stop.
Brake devices.
They are used to stop or slow down the movement of individual machine mechanisms.
After turning off the machine, the individual mechanisms move by inertia. This time is called run-out time.
To reduce the run-out time, various braking devices are installed on the high-speed shafts of machine tools.
Braking can 
carried out by mechanical, electrical and pneumatic means.
The main types of mechanical brakes are band and shoe brakes.
Pulley- cast iron, ribbon- asbestos copper.
When the machine is turned off, the tape 2 pressed against the pulley 1 and due to the force of friction braking is provided.
Shoe brake pads 1
And 6
connected by a common thread 3
, the length of which can be adjusted with a rail 2
, thus setting the necessary clearance between the pads and the pulley 7
for non-working position. During braking, the pads are pulled together by traction 4
from the drive mechanism 5
.
Movement summation mechanisms.
planetary transmissions.
planetary called rack and pinion, in which part of the gears (satellites) moves with their axes relative to the central wheel along with the carrier.
The link on which gears with movable axles are mounted is called carrier.
Satellite- this is a gear wheel with a movable axis of rotation, which simultaneously rotates around its axis and moves along with the planet carrier.
Planetary gear with cylindrical wheels.
M1 And M2- engines
I- central axis
II- movable axle
III- carrier
Z1 And Z4- central wheels
Z2 And Z3- satellites.
When turned on M1, Z1 rotates Z2. Z2 rolls around Z1 and at the same time Z3 rolls around the immovable Z4, the carrier receives a certain amount of motion. If you additionally include M2, through the worm gear begins to rotate Z4, which rotates Z3 hence the carrier is reported additional movement.
Planetary gears with bevel gears
(differential mechanisms).
For these gears of three links, any two can be leading, and the third can be driven. The differential consists of central wheels Z1 And Z4, satellites Z2 And Z3 and drove 1 . Typically a gear Z4 rotates at a higher frequency, and the wheel Z1- with less. Wheel spin Z1 transmitted from the worm pair 2 .
Couplings serve for permanent or periodic connection of two coaxial shafts and for transferring rotation from one shaft to another.
Distinguish couplings permanent , serving for the permanent connection of the shafts; coupling connecting and disconnecting shafts during operation; safety , preventing accidents in case of sudden excess of loads; overrunning clutches that transmit rotation in one direction only.
Permanent couplings.
They are used in cases where it is necessary to connect two shafts that do not separate during operation. In this case, the shafts can be connected rigidly or with the help of elastic elements.
Couplings
They are used for periodic connection of shafts, for example, in the drive of the main movement or the feed drive of machine tools.
Machine tools often use cam clutches in the form of disks with end teeth-cams and gear clutches.
Gears mounted on a shaft I are in constant engagement with the gears mounted on the driven shafts II And III. Shaft connection II And III to the leader, produced by couplings KM1 And KM2
1 - gear wheel
2
- bushing pressed into the hole
gear wheel
3 - shaft
4 - retaining ring
5 - cam crown
6 - claw clutch
Depending on the accuracy of the manufacture of the cams, precise and inaccurate cam clutches are distinguished. For precise couplings, the torque is transmitted by several cams, for inaccurate couplings, by one cam.
disadvantage clutches is that with large differences in the speeds of rotation of the driving and driven elements, the clutches cannot be turned on.
Friction clutches.
They have the same purpose as the cam ones. Friction clutches can be switched on at any difference in the speeds of rotation of the clutch elements. With them, during overloads, the driven link can slip and thereby prevent an accident. The presence of several friction surfaces makes it possible to transmit significant torques at relatively low pressures on the friction surfaces of the disks.
Mechanical and electrical friction clutches are used. Of the electric friction clutches, electromagnetic clutches have found wide application.
Safety couplings.
Are intended for protection of mechanisms of the machine from failures at overloads. For couplings (Fig. a, b), the safety link is a pin 1 , the cross section of which is calculated depending on the transmitted torque. When overloaded, this pin is cut off, the corresponding kinematic chain is broken and thus prevents damage to machine parts.
Overtaking clutch.
Designed to transmit torque during rotation of the kinematic chain links in a given direction and to disconnect the links during rotation in reverse direction, as well as to communicate two different movements to the shaft (slow - working and fast - auxiliary), which are carried out along two separate kinematic chains. The overrunning clutch allows you to turn on the high-speed chain without turning off the working movement chains.
Ratchet mechanisms (Fig. a) and a roller-type clutch (Fig. b) can be used as an overtaking clutch.
Shaft 2 rotates from the shaft 1 through bevel wheels Z3/Z4 and ratchet mechanism (wheel Z4 loosely seated on the shaft 2 ). If you simultaneously turn on the high speed chain through the gear Z1/Z2, then the shaft 2 together with ratchet wheel 4 will rotate faster than the gear Z4 and doggy 3 will slip.
1
- frame
2 - ring
3 - video clip
4 - pin
5 - spring
If the leading part is a ring 2 , then when rotating counterclockwise, the rollers are carried away by friction into the narrow part of the recess and are wedged by the ring and the clutch housing. In this case, the corpus 1 and the associated shaft will rotate with the angular velocity of the ring 2 . If, with the continued movement of the ring 2 counterclockwise shaft and housing 1 report movement along another kinematic chain, directed in the same direction, but having a speed greater than the speed of the ring 2 , then the rollers will move to the wide part of the recess and the clutch will be disengaged. At the same time, the details 1 And 2 each will rotate at its own speed.
Any of the details can be the leading element 1 And 2 . If the body is leading, the clutch engages when it rotates clockwise or when the body, rotating in this direction, is ahead of the ring.
Methodology of kinematic adjustment of metal-cutting machines.
Kinematic adjustment of the machine is to coordinate the movements of the executive bodies. The setup procedure is the same for most machines and does not depend on their complexity. For example, consider setting up a screw-cutting lathe for threading.
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To cut a thread on a workpiece 1 , it is necessary to inform the caliper 3 with a cutter 2 longitudinal feed along the axis of the workpiece, coordinated with the spindle speed 5 . Therefore, it is necessary to calculate two kinematic chains: high-speed (chain of the main movement) and threading.
Consider the kinematic chain of the main movement. Spindle 5 with blank 1 receives rotation from the electric motor through a belt drive and three pairs of gears. The spindle speed is calculated by the formula
Where V- cutting speed, m/min (selected from the cutting mode guide)
d- workpiece diameter, mm.
Let us compose the equation of the kinematic chain from the electric motor to the spindle, provided that the spindle must rotate with a frequency
Where n- frequency of rotation of the motor shaft, min -1;
0,985 - coefficient taking into account belt slip.
The equation can be represented in general view:
Where i post- constant gear ratio characterizing the chain,
i cm- replaceable gear ratio of the adjustment mechanism.
In the considered kinematic chain, all quantities are known, with the exception of the replaceable wheels a - b, which are the adjustment mechanism.
Substituting numerical values, we get
Let's define the value
Let's define the wheels A And b and thus we will adjust the circuit of the main movement. Then we proceed to the adjustment of the kinematic chain of the feed movement or the threading chain. Cutter 2 , mounted on a caliper 3 , receives movement from the lead screw 4 , which is driven by a spindle 5 through a pair of spur gears, two pairs of bevel gears and interchangeable gears c-d And e-f.
Let us compose the equation of the kinematic balance, based on the condition that in one revolution of the spindle the cutter will move along the axis of the workpiece by the step value pp cut thread
In general, this equation will look like this:
Where pp- thread pitch; Rx.v.- Lead screw pitch
In the circuit under consideration
Picking up replacement wheels c-d, e-f, we will adjust the supply chain. When kinematic adjustment of machines is necessary:
1. Find out the nature of the movement of the working bodies and their consistency;
2. Identify all kinematic chains of the machine;
3. Compose the equation of the kinematic chain connecting the working bodies of the machine in pairs;
4. Determine the gear ratios of the adjustment mechanism and select replacement gears or other adjustment elements in accordance with them.
Example. Set up the machine according to the following data: n = 240 min -1 ; PP = 4 mm; A=B=80
Checking the adhesion condition
CNC machines
Program control (PU) is a set of commands that ensure the functioning of the working bodies of the machine in a given sequence. Without exception, all machines with PU work according to the program. In some cases, the program is in the memory of the working body, in others it is set using material analogues (reference part, copier or cams). The manufacture of material analogues and the readjustment of such machines require high qualifications and a lot of time, so such machines are used in large-scale production.
IN small-scale production, which takes up to 80%, machines with PU are widely used in which the program is recorded on a program carrier, which is used as punched tape, a magnetic disk, a programmable controller.
On program media, the program can be recorded in encoded and decoded form. The production of the program and the readjustment of the machines does not require high qualifications and does not take much time.
Machine tools with PU are classified in the same way as manual machines.
In the designation of machine models with PU, the following letters are written after the numbers:
C- machines with cyclic program control (CPU)
F- machine tools with numerical control (CNC)
T- machines with operating system CNC.
In machines with CPU technological information is recorded on the program carrier, and geometric information is set using adjustable stops. Installation and alignment of stops during setup takes a lot of time, so CNC machines are used in large-scale production.
In CNC machines, all information is recorded on the program carrier.
In machines with an operational CNC system, information is typed by the operator directly at the workplace using a keyboard located on a mini computer.
Cyclic software control.
Cycling system program control(CPU) called such a program control system in which the machine cycle, processing modes and tool change are fully or partially programmed, and the amount of movement of the working bodies is set using pre-adjustable stops.
Machine cycle- this is a set of all movements necessary for processing workpieces and performed in a certain sequence.
Turret turning, turning and copying, copy milling, diamond boring and other machines are equipped with the CNC system. CPU systems are used in automatic lines using a computer for the day of diagnostics and planning of the line, as well as for controlling industrial robots.
Functional diagram of the CPU system. 
The scheme includes: cycle programmer, automation scheme, actuator and device feedback.
The cycle programmer consists of a program setting block 1 and a step-by-step program input block 7 . From a program job block 1 information enters the automation circuit, consisting of a machine cycle control circuit 2 and circuits for converting control signals 6 . The automation circuit coordinates the actions of the cycle programmer with the executive elements of the machine and the feedback sensor, and can perform a number of logical functions. The automation circuit in CPU systems is most often built on electromagnetic relays. From the block 2 the signals are sent to the actuator, which ensures the processing of the commands specified by the program.
The executive device consists from executive elements 3 (drives, couplings, etc.) and working parts of the machine 4 (caliper, pumps, tables, turrets). The working bodies work out the program stage, and the sensor 5 controls the end of mining and gives a command to the block 7 through the block 6 to switch to the next program step.
cycle programmers.
They consist of a program task block and a step-by-step program input block. The program task unit memorizes and enters the complete program into the system, the stage-by-stage program input unit is designed for sequential reading of the program stages and entering them into the system for processing.
The most common electrical type programmer is plug panel. The program on the plug-in panel is set manually, the machine is idle during this period. An overlay paper template can be used for safe and quick programming. The template is applied to the plug-in panel, and the plugs are inserted into the sockets through the holes in the template. Punched in accordance with the program.
A common mechanical type programmer are cam commanders And perforated tape programmers.
Cam controllers- these are programmers of a mechanical type with a kinematic program assignment. Into the nests of the drum 2 command device lay balls or pins 1 , which, when rotated, act on electrical contacts or limit switches 3 , including the chains of the relevant executive bodies. The drum is driven by a ratchet mechanism with an electromagnet or a stepper motor.
Programmers with punched tapes or punched cards used for large amounts of information. The program is read either electromechanically or by photocells.
The most convenient are universal CPU systems built using microelectronics. These systems include programmable controllers.
Programmable controller is a sequential control logic machine created on the basis of computer technology, relay contactless automation and CPU equipment. They are reliable, durable, have small dimensions, provide the ability to quickly change the program, and are easily specialized depending on the specific processing.
Programmable controller (PC) consists of a central processing unit 1 (control device), read-only memory 2 , input 3 and weekend 4 devices and scanner 5 (pulse generator). A software panel can be connected to the controller 6 (program loader) containing decade switches and keys. The program is entered sequentially by pressing the key with the designation of logical elements. In write mode, the program is written to the device 2 and remembered in it. Scanner in operation 5 alternately connects to the processor 1 input and output devices. In processor 1, according to the program, the specified logical operations are performed. Displays, magnetic cassette drives, printers that record the state of equipment, the cost of main and auxiliary time, emergency situations, etc. can be connected to the controllers.
Computer numerical control.
Classification of CNC systems.
CNC system (CNC)- a set of device methods that provide CNC machines.
CNC device (CNC)- a component of the control system that issues commands to perform a specific action.
CNCs are distinguished by the following features:
I. By appointment
1. (F1)- machines with digital indication and presetting of coordinates;
2. Positional and rectangular (F2)- allow you to automatically set the working bodies to the position specified by the machine control program, and during the movement of the working body, processing is not carried out.
3. Contour (continuous) (FZ)- provide automatic movement of the working body along an arbitrary trajectory with a contour speed specified by the machine control program. The processing path is provided by the joint and interconnected movement of several actuators.
4. Combined (universal) (F4)- provide processing of complex profiles of parts in several coordinates at the same time, accurate positioning of accelerated movements.
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