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Features of normalization of work on CNC machines. Rationing of work performed on machines with numerical control Rationing of technological operations with CNC

The use of machines with numerical program management(CNC) is one of the main directions of automation of metal cutting, allows you to free up a large number of versatile equipment, as well as improve product quality and working conditions for machine operators. The fundamental difference between these machines and conventional ones is that the processing program is set in mathematical form on a special program carrier.

The norm of time for operations performed on CNC machines when working on one machine consists of the norm of preparatory and final time and the norm of piece time:

The preparatory-final time is determined by the formula

T pz \u003d T pz1 + T pz2 + T pr.obr

The norm of piece time is calculated by the formula

T c. a \u003d T o + T mv,

The main (technological) time is calculated on the basis of cutting conditions, which are determined according to the General Machine Building Standards for time and cutting conditions for standardizing work performed on universal and multi-purpose machines with numerical control. According to these standards, the design and material of the cutting part of the tool is selected depending on the configuration of the workpiece, the stage of processing, the nature of the allowance to be removed, the material being processed, etc. It is preferable to use a tool equipped with hard alloy plates (if there are no technological or other restrictions on their use). Such limitations include, for example, interrupted machining of heat-resistant steels, machining of holes with small diameters, insufficient speed of rotation of the part, etc.

The depth of cut for each stage of processing is chosen in such a way as to ensure the elimination of machining errors and surface defects that appeared in the previous stages of processing, as well as to compensate for errors that occur at the current stage of processing.

The feed for each stage of processing is assigned taking into account the dimensions of the surface to be machined, the specified accuracy and roughness of the material being machined, and the depth of cut selected at the previous stage. The feed selected for the roughing and semi-finishing stages of processing is checked by the strength of the machine mechanism. If it does not meet these conditions, it is reduced to a value allowed by the strength of the machine mechanism. The feed selected for the finishing and finishing stages of processing is checked according to the condition for obtaining the required roughness. The smallest of the innings is finally chosen.

Cutting speed and power are selected according to previously defined tool parameters, depth of cut and feed.

The cutting mode at the roughing and semi-finishing stages is checked by the power and torque of the machine, taking into account its design features. The selected cutting mode must satisfy the following conditions:

N<= N э и 2М <= 2М ст,

Where	N	-	power required for cutting, kW;
	N e	-	effective power of the machine, kW;
	2M	-	double cutting torque, Nm;
	2M st	-	double torque on the machine spindle, allowed by the machine according to the strength of the mechanism or the power of the electric motor, Nm.

Double cutting torque is determined by the formula

If the selected mode does not meet the specified conditions, it is necessary to reduce the set cutting speed according to the value, allowable power or torque of the machine.

Auxiliary time associated with the execution of an operation on CNC machines provides for the implementation of a set of works:

related to the installation and removal of the part: "take and install the part", "align and fix"; "turn on and off the machine"; "unfasten, remove the part and put it in a container"; "clean the device from chips", "wipe the base surfaces with a napkin";
associated with the execution of operations that were not included during the cycle of automatic operation of the machine according to the program: "turn on and off the tape drive mechanism"; "set the given relative position of the part and the tool along the X, Y, Z coordinates and, if necessary, make adjustments"; "check the arrival of the tool or part at the point specified after processing"; "advance the punched tape to its original position."

In general, auxiliary time is determined by the formula

T in \u003d T v.y + T v.op + T v.meas,

Auxiliary time for control measurements is included in the piece time only if it is provided for by the technological process, and only when it cannot be blocked by the cycle time of the automatic operation of the machine.

Correction factor (K t in) for lead time manual auxiliary work, depending on the batch of machined parts, is determined from Table. 12.7.

Table 12.7. Correction factors for non-productive time depending on the size of the lot of workpieces in series production. Map #1

item number	Operative time (T c.a + T c) min., up to	Type of production
		Small-scale			Medium series
		Number of parts in a batch, pcs.
		6	10	16	25	40	63	100	160	250
1	4	1,52	1,40	1,32	1,23	1,15	1,07	1,00	0,93	0,87
2	8	1,40	1,32	1,23	1,15	1,07	1,10	0,93	0,87	0,81
3	30 or more	1,32	1,23	1,15	1,07	1,00	0,93	0,87	0,81	0,76
Index		A	b	V	G	d	e	and	h	And

Maintenance of the workplace includes the following

The main way to automate the processes of machining parts for small-scale and single-piece production is the use of machine tools with numerical control (CNC). CNC machines are semi-automatic or automatic, all moving parts of which perform working and auxiliary movements automatically according to a predetermined program. The structure of such a program includes technological commands and numerical values of the movements of the working bodies of the machine. The changeover of the CNC machine, including the change of the program, requires little time, so these machines are most suitable for automating small-scale production.

A feature of normalizing the operations of machining parts on CNC machines is that the main time (machine) and the time associated with the transition constitute a single value T a - the time of automatic operation of the machine according to the program compiled by the technologist-programmer, which consists of the main time of automatic operation of the machine T o.a and the auxiliary time of the machine according to the program T v.a i.e.

T a \u003d T o.a + T c.a;

T v.a \u003d T v.h.a + T oc t

where Li is the length of the path traveled by the tool or part in the feed direction during processing of the 1st technological section (taking into account the plunge and overrun); s m - minute feed in this area; i == 1, 2, ..., n - the number of technological processing sections; T v.h.a - time to perform automatic auxiliary moves (supply of a part or tools from the starting points to the processing zones and retraction, setting the tool to a size, changing the numerical value and direction of feed); T ost - time of technological pauses - stops of feed and rotation of the spindle for checking dimensions, inspection or tool change.

Auxiliary manual work time T in not overlapped by the time of automatic operation of the machine,

T in \u003d t set + t v.op + t counter,

where t mouth - auxiliary time for installation and removal of the part; t v.op - auxiliary time associated with the execution of the operation; t counter - auxiliary non-overlapping time for control measurements of the part.

Auxiliary time for installation and removal of parts weighing up to 3 kg on turning and drilling machines in a self-centering chuck or mandrel. is determined by the formula

t mouth \u003d aQ x

to determine the auxiliary time for insertion and removal of parts in centers or on the center arbor of a lathe

t mouth \u003d aQ x

to determine the auxiliary time for insertion and removal of parts in a self-centering or collet chuck on lathes and drilling machines

t mouth \u003d aD in x l y vy l

to determine the auxiliary time for the installation and removal of parts on the table or square of the drilling and milling machine

t mouth \u003d aQ x N y children + 0.4 (n b -2)

Coefficients and exponents for determining the auxiliary time for installing and removing parts in the vise of a drilling and milling machine

t mouth \u003d aQ x

Auxiliary time machine control. (turning, drilling and milling machines)

t v.op \u003d a + bSH o, Y o, Z o + sK + dl pl + aT a

Auxiliary time for control intentions.

t counter \u003d SkD z change L u

The preparatory-final time is determined

T p-z \u003d a + bn n + cP p + dP pp

After calculating T in, it is adjusted depending on the serial production. Correction factor

k c er \u003d 4.17 [(Ta + TV) n p + T p-z] -0.216,

where n p is the number of workpieces in the batch.

The preparatory-final time is defined as the sum of time: for organizational preparation; installation, preparation and removal of fixtures; setting up the machine and tools; trial run of the program. The main characteristics that determine the preparatory and final time are the type and main parameter of the machine, the number of tools used in the program, the correctors used in the operation, the type of fixture, the number of initial modes of operation of the machine.

The norm of piece time for the operation

T w \u003d (T a + T ser) (1 + (a obs + a ot.l) / 100].

The time for organizational and maintenance of the workplace, rest and personal needs,% of the operational time, is set depending on the main parameters of the machine and the part, the employment of the worker and the intensity of labor. It can be partially overlapped by the time of automatic operation of the machine; piece time in this case should be reduced by 3%.

Automation of the processing and auxiliary work on CNC machines creates the prerequisites for the simultaneous maintenance of several machines by the operator. The performance by the worker-operator of the functions of servicing the workplace on one of the machines usually leads to interruptions in the work of other serviced machines. The time for rest increases due to the higher intensity of labor in the conditions of multi-machine maintenance. The time of operational work in the norm of piece time increases due to the auxiliary time for transitions from machine to machine.

METHODOLOGICAL DEVELOPMENT ON THE DISCIPLINE

"TECHNOLOGY OF ENGINEERING"

Compiled teacher: Fazlova Z.M.

Introduction

The intensification of production, the successful introduction of the latest equipment and technology require the improvement of the organization of labor, production and management, which is possible only on the basis of technical regulation.

Labor rationing is the establishment of a measure of labor costs, ts of the total socially necessary costs of working time for the production of products of a certain consumer value for a given period of production and technical conditions. The most important tasks of labor rationing are the consistent improvement of the organization of labor and production, the reduction of the labor intensity of products, the maintenance of economically justified relationships between the growth of labor productivity and wages. Labor rationing should contribute to the active introduction of best practices, achievements of science and technology.

The methodological development “Rationing of work performed on machines with NC U” allows you to acquire the necessary skills to establish a reasonable time limit for performing a technological operation. It outlines the theoretical foundations for establishing time standards for a technological operation with CNC. The appendix contains the main machine-building labor standards.

REGULATION OF WORK, PERFORMED ON CNC MACHINES

The changeover of the CNC machine, including the change of the program, requires little time, so these machines are most suitable for automating small-scale production.

Time limit for performing operations on CNC machines Nvr consists of the norm of the preparatory and final time T pz and the norm of piece time T pcs:

(1)

T pcs \u003d (T c.a + T in K TV)
(2)

Where n - the number of parts in the manufactured batch;

T c.a - cycle time of automatic operation of the machine according to the program, min;

T in - auxiliary time, min;

K TV - correction factor for the time of performing manual auxiliary work, depending on the batch of workpieces;

and those, a org, a ex - time for technological and organizational maintenance of the workplace, for rest and personal needs during single-station service,% of the operational time.

The cycle time of the automatic operation of the machine according to the program is calculated by the formula

T c.a \u003d T o + T mv (3)

where T o - the main (technological) time for processing one part, min:

T o = (4)

L i - the length of the path traversed by the tool or part in the feed direction during the processing of the technological section (including infeed and overrun);

s m - minute feed in this technological area, mm/min;

Tmv - machine auxiliary time according to the program (for approaching and retracting a part or tool from the starting points to the processing zones, setting the tool to size, changing the tool, changing the feed value and direction, the time of technological pauses (stops), etc.), min.

Auxiliary time is defined as follows:

T in \u003d T v.y + T v.op + T v.meas (5)

where T v.y - time to install and remove the part, min;

T v.op - auxiliary time associated with the operation (not included in the control program), min;

T in. ism - auxiliary non-overlapping time for measurement, min.

Time limits for installing and removing a part are determined by types of fixtures depending on the types of machines and provide for the most common methods of installation, alignment and fastening of parts in universal and special clamps and fixtures.

Ancillary time associated with the operation, subdivided:

a) for auxiliary time associated with the operation, not included during the cycle of automatic operation of the machine according to the program;

b) machine-assisted time associated with the transition, included in the program, related to the automatic auxiliary operation of the machine.

The required dimensions of parts processed on CNC machines are provided by the design of the machine or cutting tool and the accuracy of their settings. Due to this time for control measurements should be included in the standard piece time only if it is provided for by the technological process, and it cannot be blocked by the cycle time of the automatic operation of the machine according to the program.

Workplace maintenance time is determined according to the standards and standard sizes of equipment, taking into account single-station and multi-station service as a percentage of the operational time.

Rest time and personal needs when servicing one machine by one worker, it is not allocated separately and is taken into account in the time for servicing the workplace.

Norms of preparatory and final time are designed for setting up CNC machines for processing parts according to embedded control programs and do not include additional programming directly at the workplace (except for machines equipped with operational program control systems).

Standards of piece time for dimensional setting of the cutting tool outside the machine are designed to standardize work on setting up a cutting tool for CNC machines, which is carried out by toolmakers outside the machine in a specially equipped room using special devices.

TYPICAL PROBLEM WITH SOLUTION

Initial data: detail - shaft (Fig. 1); material - steel 30G; surface precision 1,2,3 - IT10; surface roughness 1, 2 Ra5; 3 - Ra10.

Workpiece: production method - stamping (normal precision IT 16); surface condition - with a crust; weight 4.5 kg; surface treatment allowance: 1 - 6 mm; 2 - 4 mm; 3 - 5 mm.

Machine: model 16K20FZ. Passport data:

spindle speed P(rpm): 10; 18; 25; 35.5; 50; 71; 100; 140; 180; 200; 250; 280; 355; 500; 560; 630; 710; 800; 1000; 1400; 2000;

feed range s m (mm/min)

along the coordinate axis X- 0,05...2800;

along the coordinate axis z - 0,1...5600;

the greatest force allowed by the longitudinal feed mechanism is 8000 N, by the transverse feed mechanism - 3600 N;

main drive power - 11 kW;

regulation range of constant power electric motor speed - 1500...4500 rpm.

Operation: basing in the centers, with the leash on the surface.

1. Choice of stages of processing.

The necessary stages of processing are determined. To obtain the dimensions of a part corresponding to grade 10, it is necessary to process it from a workpiece of grade 16 in three stages: roughing, semi-finishing and finishing.

2. Choice of cutting depth.

The minimum required depth of cut for the semi-finishing and finishing stages of processing is determined (Appendix 5).

In the finishing stage for the surface 1, whose diameter corresponds to the size range 8...30 mm, recommended depth of cut t = 0.6 mm; surface 2, the diameter of which corresponds to the range of sizes 30...50 mm, t= 0.7mm; for surface 3, the diameter of which corresponds to the size interval 50...80 mm, t = 0.8 mm.

Similarly, in the semi-finishing stage for surface / it is recommended t = 1.0 mm; surface 2 - t - 1.3mm; for surface 3 - t = 1.5 mm.

Figure 1 - Shaft sketch and tool path

The depth of cut for the roughing stage of processing is determined based on the total allowance for machining and the sum of the depths of cut of the finishing and semi-finishing stages of processing: for surface 1 - t = 4.4mm; for surface 2 - t = 2.0mm; for surface 3 - t = 2.7 mm. The selected values are entered in table 1.

Table 1 - Definition of cutting mode

Cutting mode value	Surface treatment stage
	Draft	semi-finishing	Finishing

Depth of cut t, mm
Tabular feed s from, mm / rev
Accepted feed s pr, mm / rev
Tabular cutting speed V t, m/min
Corrected cutting speed V, m/min
Actual spindle speed n f, m/min
Actual cutting speed V f, m/min
Tabular cutting power N t, kW
Actual cutting power N, kW
Minute feed s m, mm/min

3. Tool selection.

On the machine 16K20FZ, cutters with a holder section of 25 x 25 mm are used, the plate thickness is 6.4 mm.

Based on the processing conditions, a trihedral shape of the plate with an angle at the top is taken
° hard alloy T15K6 for roughing and semi-finishing stages of processing and T30K4 - for the finishing stage (Appendix 3).

Standard durability period: T = 30 min.

4. Feed selection.

4.1. For the roughing stage of processing, the feed is selected according to adj. 3.

For surface 1 when turning parts with a diameter of up to 50 mm and a depth of cut t = 4.4 mm recommended feed s =0.35 mm/rev. For surfaces 2 and 3, respectively, the feed s from =0.45 mm/rev. is recommended. and s from =0.73 mm/rev.

App. 3 Feed correction factors are determined depending on the tool material TO s and = 1.1 and plate mounting method K sp = 1,0.

4.2. For the semi-finishing stage of processing, the feed values are determined by adj. 3 in the same way: for surfaces 1 And 2 s from =0.27 mm/rev., surfaces 3 s from =0.49 mm/rev.

Feed correction factors depending on tool material K s and = 1.1, method of fixing platinum K sp = 1.0.

App. 3 we determine the correction factors for the feed of the roughing and semi-finishing stages of processing for the changed processing conditions: depending on the section of the cutter holder TO s d = 1.0; cutting edge strength K s l = 1.05; mechanical properties of the processed material TO s and = 1.0; workpiece installation schemes TO at =0.90; workpiece surface conditions K s p =0.85; geometric parameters of the cutter K sp =0.95; machine stiffness K sj = 1,0.

The final feed of the roughing stage is determined by:

For surface 1

s pr1 \u003d 0.35 1.1 1.0 1.0 1.05 1.0 0.9 0.85 0.95 1.0 \u003d 0.29 mm / rev.;

For surface 2

s pr2 \u003d 0.45 1.1 1.0 1.0 1.05 1.0 0.9 0.85 0.95 1.0 \u003d 0.38 mm / rev.;

For surface 3

s pr3 \u003d 0.73 1.1 1.0 1.0 1.05 1.0 0.9 0.85 0.95 1.0 \u003d 0.61 mm / rev.

Similarly, the feed rate of the semi-finishing stage of processing is calculated:

for surfaces 1 And 2 s pr1.2 = 0.23 mm / rev.;

for surface 3 s pr3 = 0.41 mm/rev.

surface 1 s from1 \u003d 0.14 mm / rev.,

surface 2 s from2 \u003d 0.12 mm / rev.,

for surface 3 s from3 =0.22 mm/rev.

App. 3 correction factors are determined for the feed of the finishing stage of processing for changed conditions: depending on the mechanical properties of the material being processed TO s = 1.0; workpiece installation schemes TO at=0.9; tool nose radius K st = 1.0; workpiece accuracy quality l 4 = 1.0. The final feed of the finishing stage of processing is determined by:

surface 1 s pr \u003d 0.14 1.0 0.9 1.0 1.0 \u003d 0.13 mm / rev.,

surface 2 s p p \u003d 0.12 1.0 0.9 1.0 1.0 \u003d 0.11 mm / rev.,

For surface 3 s p p = 0.22 1.0 0.9 1.0 1.0 = 0.20 mm/rev

The calculated feed rates for the finishing stage of surface treatment are entered in Table. 1.

5. Choice of cutting speed.

At the roughing stage of processing of alloy steel with a crust with a depth of cut t = 4.4 mm and feed s pr \u003d 0.29 mm / rev. cutting speed for surface 1 V t = 149 m/min; with depth of cut t = 2.0 mm and feed s p p =0.38 mm/rev. surface cutting speed 2 V t \u003d 159 m / min; with depth of cut t \u003d 2.7 mm and feed s pr \u003d 0.61 mm / rev. cutting speed for surface 3 V t = 136 m/min.

App. 8, 9 correction factors are selected for the roughing stage of processing depending on the tool material: for the surface 1 TO in = 1.0, for surfaces 2 and 3 TO in =0,95.

The final cutting speed for the roughing stage will be:

surface 1 V 1 = 149 0.85 = 127 m/min;

surface 2 V 2 = 159 0.81 = 129 m/min;

surface 3 V 3 = 136 0.98 = 133 m/min.

5.2. At the semi-finishing stage of processing alloyed steel without skin with a depth of cut t up to 3.0 mm and feed s p p = 0.23 mm / rev. cutting speed for surfaces 1 And 2 - V T = 228m/min; with depth of cut t = 1.5 mm and feed s pr \u003d 0.41 mm / rev. cutting speed for surface 3 - V t = 185 m/min.

Correction factor for semi-finishing depending on tool material K v = 0,95.

App. 8, 9, the remaining correction factors for the cutting speed are selected during the roughing and semi-finishing stages of processing for the changed conditions:

depending on the material machinability group TO v With = 0,9;

type of processing K vo = 1,0;

machine stiffness K vo = 1,0;

mechanical properties of the processed material TO v m = 1.0; geometric parameters of the cutter:

for surfaces 1 And 2 K v f =0.95, for surface 3 K v f = 1.15; tool life TO v T = 1,0;

availability of cooling TO v and = 1,0.

Finally, the cutting speed at the roughing stage is determined by:

surface 1 And 2 V 1,2 = 228 0.81 = 185 m/min;

surface 3 V 3 = 185 0.98 = 181 m/min.

5.3. The cutting speed for the finishing stage of processing is determined by adj. 8, 9:

at t \u003d 0.6 mm and s p p \u003d 0.13 mm / rev. surface 1 V T =380 m/min;

at t \u003d 0.7 mm and s p p \u003d 0.11 mm / rev. surface 2 V T =327 m/min;

at t \u003d 0.8 mm and s p p \u003d 0.2 mm / rev. V T =300 m/min.

App. 8, 9, the correction factor for the cutting speed for the finishing stage of processing is determined depending on the tool material; K V n =0.8. Correction factors for the finishing stage numerically coincide with the coefficients for the roughing and semi-finishing stages.

General correction factor for cutting speed at the finishing stage of processing: K v = 0.68 - for surfaces 1 And 2; K v = 0.80 - for the surface 3.

Final cutting speed at the finishing stage:

surface 1 V 1 = 380 0.68 = 258 m/min;

surface 2 V 2 = 327 0.68 = 222 m/min;

surface 3 V 3 = 300 0.80 = 240 m/min.

Tabular and corrected cutting speed values are entered in table. 1.

5.4. Spindle speed by formula

At the rough stage of surface treatment 1

n = =1263 rpm

The rotational speed available on the machine is taken, n f = = 1000 rpm. Then the actual cutting speed is determined by the formula:

V f = = 97.4 m/min.

The calculation of the spindle speed, its adjustment according to the machine passport and the calculation of the actual cutting speed for other surfaces and processing stages are carried out similarly. The calculation results are summarized in Table. 1.

Since the 16K20FZ machine is equipped with an automatic gearbox, the accepted values of the spindle speeds are set directly in the control program. If the machine used has manual switching of the spindle speed, it is necessary to provide technological stops for switching in the control program or to set the smallest of the calculated speeds for all surfaces and processing stages.

5.5. After calculating the actual cutting speed for the finishing stage of machining, the feed is adjusted depending on the roughness of the machined surface.

App. 8, 9 for roughness no more Ra5 when processing structural steel with a cutting speed V f = 100 m/min with a cutter with a radius at the top r in = 1.0 mm, it is recommended to feed s from = 0.47 mm/rev.

App. 8, 9 correction factors for the feed, the roughness of the machined surface for the changed conditions are determined: depending on:

mechanical properties of the processed material To s =1,0;

tool material K s and = 1.0;

type of processing K s about =1,0;

the presence of cooling K s W =1.0.

The final maximum allowable roughness feed for the finishing stage of surface treatment 1 and 2 is determined by the formula

s o \u003d 0.47 1.0 1.0 1.0 1.0 \u003d 0.47 mm / rev.

Feeds for the finishing stage of surfaces 1 and 2, calculated above, do not exceed this value.

None of the calculated values exceeds the drive power of the main movement of the machine. Therefore, the established cutting mode in terms of power is feasible (the calculation is not given).

6. Definition of minute feed.

Minute feed formula

s m \u003d n f s o

At the roughing stage for surface 1

s m \u003d 1000 0.28 \u003d 280 mm / min.

The values of the minute feed for the remaining surfaces and processing stages are calculated similarly and are plotted in Table. 1.

7. Determining the time of automatic operation of the machine program.

The time of automatic operation of the machine according to the program for the general part.

For the I6VT2OFZ machine tool, the turret locking time Tif = 2 s and the time for turning the turret by one position Tip = 1.

The results of the calculation are given in table. 2.

8. Determination of the norm of piece time.

8.1. The norm of piece time is determined by the formula (2)

8.2. Auxiliary time consists of components, the choice of which is carried out according to the 1st part of the standards (formula (5)). Auxiliary time for installation and removal of the part T v.y = 0.37 min (app.12).

The auxiliary time associated with the operation, T v.op, includes the time to turn the machine on and off, to check the return of the tool to a given point after processing, to install and remove the shield that protects against splashing with emulsion (Appendix 12, 13):

T v.op \u003d 0.15 + 0.03 \u003d 0.15 min.

Auxiliary time and control measurements contains the time for two measurements with a one-sided limit bracket, four measurements with a caliper and one measurement with a simple shaped template (app. 18):

T in.out =(0.045+0.05)+(0.11+0.13+0.18+0.21)+0.13=0.855 min.

8.3. The time of automatic operation of the machine according to the program is calculated for each section of the tool trajectory and is summarized in Table. 2.

Table 2 - The time of automatic operation of the machine according to the program

Continuation of table 2

Section of the trajectory (position numbers of the tools of the previous and working positions)	Movement along the Z axis, mm	Travel along the X axis, mm	Length of the i-th section of the tool path	Minute supply on the i-th section	The main time of automatic operation of the machine according to the program	Machine-assisted time
Tool #2 - tool number 3
Tool #3 - tool no. 4

8.4. The final cycle time of the automatic operation of the machine according to the program

T c.a \u003d 2.743 + 0.645 \u003d 3.39 min.

8.5. Total auxiliary time

B \u003d 0.37 + 0.18 + 0.855 \u003d 1.405 min.

8.6. Time for organizational and maintenance of the workplace, rest and personal needs is 8% of the operational time (Appendix 16).

8.7. Finally, the norm of piece time:

T PC = (3.39+ 1.405) (1+0.08) = 5.18 min.

9. Preparatory and final time.

The preparatory-final time is determined by the formula

T pz \u003d T pz1 + T pz2 + T pz3 + T p. arr.

Time for organizational preparation: T pz1 = 13 min,

time to set up a machine, fixture, numerical control device

T pz2 = 4.0 + 1.2 + 0.4 + 0.8 + 0.8 + 1.0 + 1.2 + 1.2 + 2.5 + 0.3 = 13.4 min;

time for trial processing

T ex. arr \u003d 2.2 + 0.945 \u003d 3.145 min.

Total preparatory-final time

T pz = 13 + 13.4 + 3.145 = 29.545 min.

10. Part lot size

n= N/S,

where S is the number of launches per year.

For medium series production S = 12, therefore,

n = 5000/12=417.

11. Piece-calculation time

T pcs. to = T PC + T pz / n= 5.18 + 29.545/417 = 5.25 min.

The norm of time for performing operations on CNC machines when working on one machine (N VR) consists of the norm of preparatory and final time (T PZ) and the norm of piece time (T W)

where: T CA - the cycle time of the automatic operation of the machine according to the program, min;

T In - auxiliary time to perform the operation, min;

а those, a org, a ex - time for technical and organizational maintenance of the workplace, for rest and personal needs during single-station service, % of operational time;

K t in - correction factor for the time of manual auxiliary work, depending on the batch of workpieces.

The cycle time of automatic operation of the machine according to the program is determined by the formula:

where: T O - the main (technological) time for processing one part, min;

T MB - machine auxiliary processing time according to the program (for approaching and retracting a part or tool from the starting points to the processing zones; setting the tool to a size, changing tools, changing the magnitude and direction of feed, technological pauses, etc.), min.

The main processing time is:

where: L i - the length of the path traversed by the tool or part in the feed direction during processing of the i-th technological section (including infeed and overrun), mm;

S mi - minute feed in this technological section, mm/min.

The auxiliary time for the operation is defined as the sum of the times:

where: T V.U - time to install and remove the part manually or with a lift, min;

T V.OP - auxiliary time associated with the operation (not included in the control program), min;

T V.ISM - auxiliary non-overlapping time for measurements, min;

Machine auxiliary time associated with the transition, included in the program and related to the automatic auxiliary operation of the machine, providing for the supply of a part or tool from the starting point to the processing zone and withdrawal; setting the tool to the processing size; automatic tool change; turning the feed on and off; idle strokes during the transition from processing one surface to another; technological pauses provided for by a sharp change in the direction of feed, checking dimensions, for inspecting the tool and reinstalling or refastening the part, are included as constituent elements during the automatic operation of the machine and are not taken into account separately.

The preparatory and final time standards are designed for setting up CNC machines for processing parts according to the implemented control programs and do not include additional programming directly at the workplace (except for machines equipped with operational program control systems).

The norm of time for setting up the machine is presented as the time for receiving preparatory and final work for processing a batch of identical parts, regardless of the batch, and is determined by the formula:

where: T PZ - the norm of time for setting up and setting up the machine, min;

T PZ 1 - the norm of time for organizational training, min;

T PZ 2 - the norm of time for setting up a machine, fixture, tool, software devices, etc., min;

T PR.OBR - the rate of time for trial processing.

The time for preparatory and final work is set depending on the type and size group of equipment, as well as taking into account the features of the program control system, and is divided into time for organizational preparation; for setting up the machine, tool fixtures, software devices; for a trial pass through the program or trial machining of the part.

The scope of work for organizational training is common to all CNC machines, regardless of their group and model. Time for organizational preparation includes:

receipt of an order, drawing, technological documentation, software carrier, cutting, auxiliary and measuring tools, fixtures, blanks before the start and handing them over after the processing of a batch of parts at the workplace or in the tool pantry;

familiarization with the work, drawing, technological documentation, inspection of the workpiece;

master's instruction.

The composition of the work on setting up the machine, tools and fixtures includes methods of work of a setting nature, depending on the purpose of the machine and its design features:

installation and removal of fasteners;

installation and removal of the block or individual cutting tools;

setting the initial modes of operation of the machine;

installing the program carrier in the reader and removing it;

zero position adjustment, etc.

Features of normalization of work on CNC machines. Rationing of work performed on machines with numerical control Rationing of technological operations with CNC

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