Standardization of adjustment work on CNC machines. Methodology for rationing certain types of work. Time spent setting up the machine

METHODOLOGICAL DEVELOPMENT ON DISCIPLINE

"TECHNOLOGY OF MECHANICAL ENGINEERING"

Compiled by teacher: Fazlova Z.M.

Introduction

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

Labor rationing is the establishment of a measure of labor costs, i.e. the total socially necessary expenditure 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 standardization are the consistent improvement of the organization of labor and production, reducing the labor intensity of products, and maintaining economically sound relationships between the growth of labor productivity and wages. Labor standardization should contribute to the active implementation of advanced experience, achievements of science and technology.

The methodological development “Rationing of work performed on machines with a state of emergency” allows you to acquire the necessary skills in establishing a reasonable standard of time for performing a technological operation. It outlines the theoretical basis for establishing time standards for a CNC technological operation. The appendix contains basic mechanical engineering labor standards.

RATING OF WORKS, PERFORMED ON CNC MACHINES

The main way to automate the processes of mechanical processing of parts for small-scale and individual production is the use of computer numerical control (CNC) machines. CNC machines are semi-automatic or automatic, all moving parts of which perform both working and auxiliary movements automatically according to a pre-established program. It includes technological commands and numerical values ​​of the movements of the working parts of the machine.

Resetting a CNC machine, including changing the program, requires little time, so these machines are most suitable for automating small-scale production.

Standard time for performing operations on CNC machines N BP consists of the norm of preparatory and final time T pz and the norm of piece time T pcs:

(1)

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

Where n - 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 parts being processed;

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

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

T c.a = T o + T mv (3)

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

T o = (4)

L i is the length of the path traversed by a tool or part in the feed direction when processing a technological section (taking into account plunge-in and overtravel);

s m - minute feed in a given technological section, mm/min;

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

Auxiliary time is determined as follows:

T in = T in.u + T in.op + T in.meas (5)

where Tv.u is the time for installing and removing the part, min;

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

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

Time standards for installing and removing parts are determined by types of devices 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 devices.

Additional time associated with surgery subdivided:

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

b) machine-auxiliary 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 ensured by the design of the machine or cutting tool and the accuracy of their adjustment. Due to this time for control measurements should be included in the piece time standard only if it is provided for by the technological process, and it cannot be covered by the cycle time of the automatic operation of the machine according to the program.

Time for workplace maintenance determined by standards and standard sizes of equipment, taking into account single-machine and multi-machine maintenance as a percentage of operational time.

Time for rest 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.

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

Norms of piece time for dimensional adjustment of cutting tools outside the machine are intended to standardize work on setting up cutting tools for CNC machines, which is carried out by toolmakers outside the machine in a specially equipped room using special instruments.

TYPICAL PROBLEM WITH SOLUTION

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

Blank: production method - stamping (usual accuracy IT 16); surface condition - with crust; weight 4.5 kg; allowance for surface treatment: 1 - 6 mm; 2 - 4 mm; 3 - 5 mm.

Machine: model 16K20FZ. Passport details:

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

main movement drive power - 11 kW;

the range of regulation of the rotation speed of a constant power electric motor is 1500...4500 rpm.

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

1. Selection of processing stages.

The necessary processing stages are determined. To obtain the dimensions of a part corresponding to quality 10, from a workpiece of quality 16, it is necessary to carry out processing in three stages: rough, semi-finish and finishing.

2. Selecting the cutting depth.

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

During the finishing stage of surface treatment 1, the diameter of which corresponds to the size range 8...30 mm, the recommended cutting depth t = 0.6 mm; for surface 2, the diameter of which corresponds to the size range 30...50 mm, t= 0.7 mm; for surface 3, the diameter of which corresponds to the size range 50...80 mm, t = 0.8 mm.

Similarly, at the semi-finish stage of surface treatment / recommended t = 1.0 mm; for surface 2 - t - 1.3 mm; for surface 3 - t = 1.5 mm.

Figure 1 - Sketch of the shaft and tool path

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

Table 1 - Determination of cutting mode

Cutting mode size

Surface treatment stage

Draft

Semi-finish

Finishing

Depth of cut t, mm

Table feed s from, mm/rev

Accepted feed s pr, mm/rev

Table cutting speed V t, m/min

Adjusted cutting speed V, m/min

Actual spindle speed n f, m/min

Actual cutting speed Vf, m/min

Table cutting power N t, kW

Actual cutting power N, kW

Minute feed s m, mm/min

3. Selecting a tool.

The 16K20FZ machine uses cutters with a holder section of 25 x 25 mm, plate thickness 6.4 mm.

Based on the processing conditions, a triangular plate shape with an apex angle is adopted
° from hard alloy T15K6 for roughing and semi-finishing stages of processing and T30K4 - for 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 depth of cut t = 4.4 mm recommended feed s from =0.35 mm/rev. For surfaces 2 and 3, respectively, feed s from =0.45 mm/rev is recommended. and s from =0.73 mm/rev.

According to adj. 3 correction factors for feed are determined depending on the tool material TO s and = 1.1 and method of plate fastening K sp = 1,0.

4.2. For the semi-finishing stage of processing, feed values ​​are determined according to 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.

Correction factors for feed depending on tool material K s and = 1.1, method of platinum fastening K sp = 1.0.

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

    The final feed rate of the roughing stage of processing is determined by:

For surface 1

s pr1 =0.35·1.1·1.0·1.0·1.05·1.0·0.9·0.85·0.95·1.0 = 0.29 mm/rev. ;

For surface 2

s pr2 =0.45·1.1·1.0·1.0·1.05·1.0·0.9·0.85·0.95·1.0 = 0.38 mm/rev. ;

For surface 3

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

The feed rate of the semi-finishing stage of processing is calculated similarly:

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

for surface 3 s pr3 = 0.41 mm/rev.

    for surface 1 s from1 =0.14 mm/rev.,

    for surface 2 s from2 =0.12 mm/rev.,

    for surface 3 s from3 =0.22 mm/rev.

According to adj. 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 diagrams TO at=0.9; cutter tip radius K st = 1.0; quality of precision of the workpiece l 4 = 1.0. The final feed rate of the finishing stage of processing is determined by:

    for surface 1 s pr = 0.14 1.0 0.9 1.0 1.0 = 0.13 mm/rev.,

    for surface 2 s p p = 0.12 1.0 0.9 1.0 1.0 = 0.11 mm/rev.,

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

The calculated feed values ​​for the finishing stage of surface treatment are entered in the table. 1.

5. Choice of cutting speed.

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

According to adj. 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 of processing will be:

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

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

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

5.2. At the semi-finishing stage of processing alloy steel without skin with cutting depth 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 cutting depth t = 1.5 mm and feed s pr =0.41mm/rev. cutting speed for surface 3 - V t = 185 m/min.

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

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

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

type of processing K vo = 1,0;

machine rigidity 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; durability period of the cutting part TO v T = 1,0;

availability of cooling TO v and = 1,0.

The final cutting speed during the roughing stage of processing is determined by:

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

    for 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 = 0.6 mm and s p p = 0.13 mm/rev. for surface 1 V T =380 m/min;

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

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

According to adj. 8, 9, the correction factor for the cutting speed is determined for the finishing stage of processing depending on the tool material; K V n =0.8. Correction coefficients for the finishing stage are numerically the same as the coefficients for the roughing and semi-finishing stages.

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

The final cutting speed at the finishing stage:

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

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

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

The tabulated and corrected cutting speed values ​​are entered into the table. 1.

5.4. Spindle speed according to the formula

During the roughing stage of surface treatment 1

n = =1263 rpm

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

V f = = 97.4 m/min.

Calculation of the spindle rotation speed, its adjustment according to the machine passport and 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 spindle speed values ​​are set directly in the control program. If the machine used has manual switching of the spindle rotation speed, the control program must provide technological stops for switching or set the lowest calculated rotation speed 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.

According to adj. 8, 9 to obtain roughness no more Ra5 When processing structural steel with a cutting speed Vf = 100 m/min with a cutter with a tip radius r in = 1.0 mm, a feed s of = 0.47 mm/rev is recommended.

According to adj. 8, 9, correction factors for feed and machined surface roughness are determined for changed conditions: depending on:

mechanical properties of the processed material K s =1.0;

instrumental material K s u = 1.0;

type of processing K s o =1.0;

presence of cooling K s w =1.0.

Finally, the maximum permissible roughness feed for the finishing stage of processing surfaces 1 and 2 is determined by the formula

s o =0.47·1.0·1.0·1.0·1.0=0.47 mm/rev.

The feeds for the finishing stage of processing 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. Consequently, the established cutting power mode is feasible (calculation is not given).

6. Determination of minute feed.

Minute feed according to the formula

s m = n f s o

During the roughing stage of processing for surface 1

s m = 1000 · 0.28 = 280 mm/min.

The minute feed values ​​for other surfaces and processing stages are calculated similarly and are plotted in the table. 1.

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

Time of automatic operation of the machine according to the general program.

For the I6VT2OFZ machine tool, the turret head fixation time Tif = 2 s and the turret head rotation time by one position T ip = 1.

The calculation results are given in table. 2.

8. Determination of the norm of piece time.

8.1. The rate of piece time is determined by 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 Тв.у = 0.37 min (Appendix 12).

Auxiliary time associated with the operation, Tv.op, contains the time for turning on and off the machine, for checking the return of the tool to a given point after processing, for installing and removing the shield that protects against splashing with emulsion (Appendix 12, 13):

T v.op = 0.15+0.03=0.15 min.

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

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

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

Table 2 – Time of automatic operation of the machine according to the program

Continuation of Table 2

Trajectory section (numbers of tool positions of the previous and working positions)

Travel along the Z axis, mm

X-axis travel, mm

Length of the i-th section of the tool path

Minute feed in the i-th section

The main time of automatic operation of the machine according to the program

Machine-auxiliary time

Tool No. 2 –

tool no. 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 = 2.743 + 0.645 = 3.39 min.

8.5. Total auxiliary time

B =0.37+0.18+0.855 = 1.405 min.

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

8.7. The final rate of piece time:

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

9. Preparatory and final time.

The preparatory and final time is determined by the formula

T pz = T pz1 + T pz2 + T pz3 + T p.obra.

Time for organizational preparation: T pz1 = 13 min,

time to set up a machine, device, 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 of the part

T arr = 2.2 + 0.945 = 3.145 min.

General preparatory and final time

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

10. Parts 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.k = T PC + T pz / n= 5.18+29.545/417 = 5.25 min.

Let's consider what the process of standardizing adjustment work on CNC machines is and why it is needed.

When developing complex processes for processing workpieces for CNC machines and the programs that control them, the main criterion is the standard time for manufacturing parts. Without it, it is impossible to calculate the salary for machine operators, to calculate such indicators as labor productivity and equipment load factor.

Start of the process

Typically, workers need to spend additional time on the procedure for approaching and retracting, changing modes, and changing tools. Therefore, the duration of the setup period is also taken into account as part of the time costs for processing parts. Labor standardization begins with timing in the operating conditions of the machine. Using a stopwatch, the time required to install one part on the machine and then remove it is recorded.

Minutes are spent on maintenance of the place of work, the immediate needs of the operator. When working on a rotary lathe (single-column), it takes 14 minutes, and on a two-column machine - 16 minutes.

What is included in workplace maintenance?

The machine maintenance process includes:

  • organizational measures - inspection of the machine, warming it up, testing of equipment: running in the hydraulic system and CNC. It takes some time to complete the task (work order, drawing, software) and receive instructions and tools from the master; present the first sample of the part received to the quality control department, lubricate and clean the machine during the shift, clean the work area after its completion. The constant time costs for performing a set of organizational works on rotary turning equipment, in accordance with the standards, are 12 minutes. When additional maintenance efforts are required, an appropriate amendment is introduced;
  • technical measures - replacing a tool that has become dull; adjustment of machines throughout the shift and setup. There are other mandatory tasks: during the working process, chips must be constantly removed from the cutting or turning zones.

Time spent setting up the machine

The documents reflecting labor standards define the time for setting up equipment, depending on its design. If processing is performed on, the standards for installing and removing cutting tools are taken as the basis for the calculation.

When it is necessary to correct the positions of tools processing test parts, the period of processing the part is included in the duration of the preparatory stage.

Standards for setting up and maintaining automatic lathes are an important standard standard. They are included in the total time for the production of one part and, accordingly, they form the economic indicators of the employee and production as a whole.

Collections of normative documents

Standardizers of plants and factories where numerically and program controlled machines are used use the standards laid down in the documents when calculating working time:

  • Unified Tariff and Qualification Directory of Works;
  • All-Russian classifier of workers' professions;
  • Unified qualification directory for positions of managers and specialists;
  • Collections of labor standards for work performed to set up programmable equipment.

IMPORTANT! All this normative literature is basic for managers of all levels and personnel structures.

Without it, it is impossible to determine the time to complete certain amounts of work, the number of specialists that need to be involved, and the time standards used in the development of maps for technological processes.

Setup cards

For a machine of a certain type, a strictly standardized duration of production adjustment operations is developed and an adjustment map is assigned to it. When developing, many factors are taken into account in order to obtain the final picture.

The time limit allocated to the machine operator provides for:

  • specifics of the procedure for diagnosing the machine fleet;
  • availability of several setup mode options;
  • compliance with service requirements.

In order to determine the labor intensity rate (unit of measurement - man-hours or man-minutes) of any work, take into account the time during which one part is processed on a given machine. The standardizer also operates with the concept of a piece time standard, which determines the total time in accordance with the types of work.

Accordingly, the total time is divided into main and auxiliary segments, office maintenance activities; transitions between machines during multi-machine maintenance; monitoring the work process; pauses caused by equipment operation.

The Institute of Labor has the results of standardization for equipment of milling and drilling-boring groups; lathes and automatic lines are provided with standards.

IMPORTANT! Knowing the standards, managers determine the worker’s degree of employment (his work intensity is calculated), distribute work zones and set the optimal work pace.


Multi-machine maintenance - approaches to timing

In factories with a high degree of automation, multi-machine maintenance of CNC machines is practiced (forms of labor organization - in teams, units and individually). Accordingly, service areas are assigned.

Multi-machine maintenance includes time spent on:

  • preheating of equipment at idle speed, if this is provided for in the operating instructions for turning equipment;
  • work according to the machine control program with workplace maintenance;
  • installation of workpieces, removal of parts and quality control;
  • meeting the personal needs of the operator;
  • loss of the planned plan;
  • performing the preparatory and final stage of work;

Multi-machine labor is classified according to work; zones, types and systems; functions performed by a multi-machine operator.

Machine maintenance systems and methods

Enterprises practice a cyclic maintenance system - at workplaces and production lines for machines that have an equal or similar length of time during which the part is processed. She is characterized by a constant flow of demands. Non-cyclical is that the operator immediately goes to service the machine where the automatic operation mode has ended. It is characterized by occasional service requirements.

Other methods are also possible:

  • sentry - a worker monitors the entire machine park assigned to him, simultaneously determining the need for maintenance. With priority, the priority in service is determined by the operator, based on the cost of the parts being processed.
  • route, it involves walking around a group of machines along a predetermined route.

Servicing several machines with the same or different duration of workpiece processing operations has its own nuances. However, all of them are subject to standardization during the careful development of the production process.

Conclusion

On CNC machines, to standardize adjustment work, you need to take into account many nuances when calculating the duration of various operations.

When determining the final processing time of a part on one machine (we are talking about turning or), the standards are calculated for the entire machine park.

The use of computer numerical control (CNC) machines is one of the main directions in the automation of metal cutting, which makes it possible to free up a large number of universal equipment, as well as improve the quality of products and the working conditions of machine operators. The fundamental difference between these machines and conventional ones is that the processing program is specified in mathematical form on a special program medium.

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

Preparatory and final time is determined by the formula

T pz = T pz1 + T pz2 + T pr.obra

The rate of piece time is calculated using the formula


T c. a = T o + T mv,


The main (technological) time is calculated based on the cutting modes, which are determined according to the General Machine-Building Standards for time and cutting modes for rationing 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 being 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, intermittent processing of heat-resistant steels, processing of small-diameter holes, insufficient rotation speed of the part, etc.

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

The feed rate for each processing stage is assigned taking into account the dimensions of the surface being processed, the specified accuracy and roughness of the material being processed, and the cutting depth selected at the previous stage. The feed rate selected for the roughing and semi-finishing stages of processing is checked based on the strength of the machine mechanism. If it does not satisfy these conditions, it is reduced to a value acceptable by the strength of the machine mechanism. The feed selected for the finishing and finishing stages of processing is checked to ensure that the required roughness is obtained. The smaller of the innings is finally selected.

Cutting speed and power are selected in accordance with previously determined tool parameters, cutting depth 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, permissible 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, permissible power or torque of the machine.

Auxiliary time associated with performing an operation on CNC machines involves performing a set of works:

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

In general, auxiliary time is determined by the formula

T in = T in.u + T in.op + T in.meas.

Auxiliary time for control measurements is included in the standard piece time only if it is provided for by the technological process, and only when it cannot be covered 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 processed parts, is determined from the table. 12.7.

Table 12.7. Correction factors for auxiliary time depending on the size of the batch of processed parts in mass production. Card No. 1
Item no. Operating time (T c.a + T c) min., up to Type of production
Small-scale Medium production
Number of parts in the 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 involves the following:

When developing a technological process for processing parts and control programs for CNC machines, one of the main criteria for assessing the perfection of the selected process or its optimization is the standard of time spent on processing a part or a batch of parts. It is also the basis for determining the salary of a machine operator, calculating the equipment load factor and determining its productivity.

The estimated time limit (min) for processing one part (labor intensity) is determined from well-known formulas:

piece time T piece = T o + T m.v + T v.u + T obs,

piece-calculation time

The total value of the operation time with all movements can be conventionally called the tape time T l = T o + T m.v,

where T o is the total technological time for the entire transition operation, min; T m.v - element-by-element sum of machine auxiliary time for processing a given surface (approaches, outlets, switching, turns, tool changes, etc.), taken from the machine passport depending on its technical data and dimensions, min.

The values ​​of these two components of the processing time norm are determined by the technologist-programmer when developing a control program recorded on punched tape.

The value of T l is almost easily checked when the machine is running using a stopwatch as the time from the start of processing in the automatic mode of starting the belt until the end of processing the part according to the program.

Thus, we obtain: operational time T op = T l + T v.u;

piece time T piece = T l + T v.u + T obs,

where Tv.u is the time for installing the part on the machine and removing it from the machine, taken depending on the mass of the workpiece, min;

T obs = T op *a%/100 - time for workplace maintenance, personal needs and operator rest (taken as a percentage of operational time), min. For single-column turning-boring machines, a = 13% is taken, i.e. T obs = 0.13 T op, and for two-column T obs = 0.15 T op; then T pcs = T op X (1 + a%/100) min.

Scope of works for servicing the workplace.

1. Organizational maintenance - inspection, warming up and running-in of the CNC device and the hydraulic system of the machine, testing of equipment; receiving a tool from a master or service technician; lubricating and cleaning the machine during the shift, as well as cleaning the machine and workplace at the end of work; Submission of a trial part to the Quality Control Department.

2. Maintenance - changing dull tools; input of tool length compensation; adjustment and adjustment of the machine during the shift; removal of chips from the cutting zone during operation.

If the number of parts obtained from one processed workpiece on a rotary lathe exceeds one and is equal to q, then when determining T pcs it is necessary to divide T op by the number of parts obtained q.

T p.z - preparatory and final time (determined for the entire batch of parts Pz launched into processing). It consists of two parts.

1. Costs for a set of organizational works that are carried out constantly: the machine operator receives a work order (work order, drawing, software) at the beginning of the work and submits them at the end of the work; instructing a foreman or service technician; installation of the working parts of the machine and the clamping device in the initial (zero) position; installation of the program carrier - punched paper tape into the reading device.

For all this work, the standards for rotary lathes allow 12 minutes. If the design features of a machine tool or CNC system require, in addition to those listed, additional work, then their duration is determined experimentally and statistically and an appropriate correction is introduced.

2. Time spent on adjustment work, depending on the design features of the CNC machine. For example, for single-column CNC lathes the following time standards are accepted: for installing four cams on the machine faceplate or removing them - 6 minutes; to install the device on the machine faceplate manually - 7 minutes, using a lift - 10 minutes; installation of one cutting tool in the tool holder takes 1.5 minutes, removal of it - 0.5 minutes; it takes 4 minutes to install one tool holder in the turret head, and 1.5 minutes to remove it; to install the cross member and calipers to the zero position at the beginning of work - 9 minutes.

If the adjustment of the position of the tools is carried out when processing a trial part, then the time for processing the trial part is also included in the preparatory and final time.

Calculation of time standards when processing parts on CNC machines Discipline: “Design of technological processes for modern multi-purpose machines” Completed by a student of group M 03 -721 -1 Pinegin S.N.

Time standards are intended for technical regulation of work performed on universal and multi-purpose machines with computer numerical control (CNC). The standard time (standard piece-calculation time, Tsht-k) for performing operations on CNC machines when working on one machine NVR consists of the standard preparatory-final time Tpz and the standard piece time Tsht and is determined by formula (1): , (1 ) where n is the number of parts in the launch batch.

The rate of piece time is determined by the formula (2): , (2) where Ttsa is the cycle time of the automatic operation of the machine according to the program, min; , (3) where To is the main (technological) time for processing one part, min;

, (4) where Li is the length of the path traversed by a tool or part in the feed direction when processing the i-th technological section (taking into account plunge-in and overtravel), mm; Smi – minute feed in a given technological section, mm/min; i =1, 2, …, n – number of technological processing sections; Тмв – machine auxiliary time (for bringing the tool part from the starting points to the processing zones and removal; setting the tool to size, changing the tool, changing the values ​​and direction of feed, time of technological pauses, etc.), min;

, (5) , (6) where L is the length of the path (or trajectory) traversed by the tool or part in the feed direction, mm; l 1, l 2, l 3 – length of approach, plunge and overtravel of the tool, respectively, mm. The value of L is determined based on the parameters of the part trajectory. Thus, when processing parts of a part with the tool moving along two coordinates, the length L is determined by the formula (7), (7)

where Δх, Δу – increments of the corresponding coordinates in a given processing area. When moving the tool along a circular arc, the length L is determined by formula (8) or (9), (9) where R is the radius of the circular arc, mm; a is the length of the chord of the circular arc, mm; φ – central angle based on the end points of the circular arc, rad; Tmv. and – machine auxiliary time for automatic tool change, min; Tmv. x – machine-auxiliary time for performing automatic auxiliary moves and technological pauses, min.

For machines with turret heads, the time is TMV. and can be determined by the formula (10), (10) where Type is the time of rotation of the turret head by one position, min; Кп – the number of positions by which it is necessary to rotate the turret to install the required tool; Typhoid – time of fixation of the turret head, min. For machines with contour control systems, the time is TMV. x can be determined by formula (11), (11)

where Lxxj is the length of the path of the jth section of the automatic auxiliary move, mm; j=1, 2, …, t – number of sections of automatic auxiliary moves; Smu – rapid traverse minute feed. For machines with positional and universal (contour-positional) machine control systems, in which processing programming is carried out using standard cycles, analytically, time Tmv. x is difficult to determine due to the fact that specific machines, depending on their setup, have significant variations in the values ​​of Sмхх and Lхх (associated with positioning settings). For a more accurate determination of the time TMB. x on these machines it is recommended to carry out preliminary timing in order to determine the actual time TMB. x when moving the table or tool a measured distance in the direction of different coordinates.

In the case when standardization is carried out for an already designed technological process and there is a control program, time Tts. and is determined by direct timing of the part processing cycle. Auxiliary time for an operation is calculated using the formula (12), (12)

where is TV. y – time for installing and removing the part manually or with a lift, min; TV op – auxiliary time associated with the operation (not included in the control program), min; TV meas – auxiliary non-overlapping time for measurements, min; Ktv - correction factor for the time of performing manual auxiliary work, depending on the batch of processed parts; ateh, aorg, aotl – time for technological and organizational maintenance of the workplace, for rest and personal needs during single-machine maintenance, percentage of operational time.

Standards for auxiliary time for installation and removal of TV parts. They are given by type of fixture, regardless of the type of machine, and provide for the most common methods of installation, alignment and fastening of parts in universal and special clamping fixtures. The main factors influencing the installation and removal time of a part are the mass of the part, the method of installing and fastening the workpiece, the nature and accuracy of the alignment.

Time standards for installing and removing parts provide for the following work: - when installing and removing manually: take and install the part, align and secure; turn the machine on and off; unfasten and remove the part, place it in a container; clean the device from shavings, wipe the base surfaces with a napkin; - when installing and removing with an overhead crane: call the crane; rig the part; transport the part to the machine; install the part, align and secure; turn the machine on and off; unpin part; call the tap; rig the part; remove from the machine and transport it to a storage location; rig the part; clean the devices or table surface from shavings, wipe the base surfaces with a napkin.

When installing and removing a part with a lift at a machine (or group of machines), they perform the same work as when removing a part with an overhead crane, with the exception of calling the crane. When installed in special devices, auxiliary time is defined as the sum of time: for installation and removal of one part; for installation and removal of each subsequent part more than one in multi-place devices; to secure the part, taking into account the number of clamps; to clean the device from chips and wipe the base surfaces with a napkin. In the case of using robots, manipulators and satellite tables for installation and removal of parts, the auxiliary time is determined taking into account their design features.

Standards for auxiliary time associated with the TV operation. op. . Auxiliary time associated with the operation, not included during the automatic operation cycle of the machine according to the program, provides for the following work: turn on and off the tape drive mechanism; establish the specified relative position of the part and the tool along the coordinates X, Y, Z and, if necessary, make adjustments; open and close the cover of the tape drive mechanism, rewind and insert the tape into the reading device; advance the punched paper tape to its original position; check the arrival of the tool part at the specified point after processing; install the emulsion splash guard and remove it.

Machine-auxiliary time associated with the transition, included in the program and related to the automatic auxiliary operation of the machine, provides for: supply of the tool part from the starting point to the processing zone and removal; setting the tool to the processing size; automatic tool change; turning on the feed; idling when switching from processing one surface to another; technological pauses provided for when there is a sudden change in the direction of feed, to check dimensions, inspect the tool and reinstall or re-fasten the part. The machine-auxiliary time associated with the transition is determined from the passport data of the machines and is included as constituent elements during the automatic operation of the machine.

Standards for auxiliary time for control measurements of TV. change . The required dimensions of parts processed on numerically controlled machines are provided in an automatic processing cycle. In this regard, the time for control measurements (after completion of work according to the program) should be included in the standard piece time only if it is provided for by the technological process and taking into account the necessary frequency of such measurements during the work process, and only in cases where it cannot be covered by the cycle time of the automatic operation of the machine according to the program.

Time standards for servicing a workplace. Time for workplace maintenance is given by type and size of equipment, taking into account single-machine and multi-machine maintenance as a percentage of operational time. Technological maintenance of the workplace involves performing the following work: - changing a tool (or a block with a tool) due to its dullness; - adjustment and adjustment of the machine during operation (changing the tool correction value); - sweeping and periodic cleaning of chips during work (except for sweeping chips from the base surfaces of installation devices, the time for which is taken into account in the auxiliary time for installing and removing the part).

Organizational maintenance of the workplace includes work on caring for main and auxiliary equipment, technological and organizational equipment, containers related to the work shift as a whole: - inspection and testing of equipment during work; - laying out tools at the beginning and cleaning them at the end of the shift; - lubrication and cleaning of the machine during the shift; - cleaning the machine and workplace at the end of the shift.

Time standards for rest and personal needs. Time for rest and personal needs for the conditions of servicing one machine by one worker is not separately allocated and is taken into account in the time for servicing the workplace. For multi-machine maintenance, time for breaks for rest and personal needs is provided, depending on the characteristics of the work.

Standards for preparatory and final time. The standard time for setting up a machine is presented as the time for preparatory and final work to process a batch of identical parts, regardless of the batch, and is determined by the formula (13), (13) where Тпз is the standard time for setting up and tuning the machine, min; Тпз 1 – standard time for organizational preparation, min; Тпз 2 – standard time for setting up a machine, device, tool, software devices, min; Etc. arr – time standard for trial processing.

The time for preparatory and final work is set depending on the type and size of the equipment, as well as taking into account the features of the program control system. The scope of work on organizational preparation is common to all CNC machines, regardless of their group and model. The time for organizational preparation includes: - receiving an order, drawing, technological documentation, software, cutting, auxiliary and control tools, fixtures, blanks before the start and handing them over after finishing the processing of a batch of parts at the workplace or in the tool storeroom; - familiarization with the work, drawing, technological documentation, inspection of the workpiece; - instructions from the master.

In a brigade form of labor organization, when workpieces are transferred between shifts, organizational preparation takes into account only the time for familiarization with the work, drawing, technological documentation, inspection of workpieces and instructing the foreman. The work on setting up the machine, tools and devices includes adjustment work methods, depending on the purpose of the machine and design features: installation and removal of fastening devices; installation and removal of a block or individual cutting tools; setting the initial operating modes of the machine; installing the software into the reading device and removing it; zero position adjustment, etc.

The time for trial processing of parts on machines of the turning and turret groups includes the time spent processing the part according to the program and auxiliary time for performing additional techniques associated with measuring the part, calculating correction, entering correction values ​​into the CNC system, and auxiliary time for techniques for controlling the machine and CNC system. The time for trial processing of parts on machines of rotary, milling, boring groups, multi-tasking machines includes time spent on processing parts using the test chip method and auxiliary time for performing additional techniques related to measuring the part, calculating the correction value, entering correction values ​​into the CNC system, and auxiliary time for techniques for controlling the machine and the CNC system.

To calculate the main time, it is necessary to determine the cutting modes for processing each surface of the part. They are determined according to general machine-building standards: - General machine-building standards for time and cutting modes for rationing work performed on universal and multi-purpose machines with numerical control. Part 2 – Standards for cutting conditions. – M.: Economics, 1990. - Metal cutting modes: reference book / Ed. Yu. V. Baranovsky. – 3rd ed. , processed and additional – M.: Mechanical Engineering, 1972. – 407 p. - Handbook of mechanical engineering technologist. In 2 vols. T. 2 / Pod. ed. A. G. Kosilova and others – 5th ed. , rev. – M.: Mechanical Engineering, 2003. – 944 p. , ill.

An example of calculating time standards To calculate time standards, we present the initial data: drawing of the “Roller” part, workpiece material steel 45 GOST 1050-88, batch of parts 100 pcs, workpiece – round rolled steel with a diameter of 125 x 54. We will carry out the calculation in three cases: 1. 1) Processing on two CNC machines - a lathe (16 K 20 F 3) and a milling machine (6 R 13 RF 3). Two necks with a diameter of 30 h 12 are processed on a CNC lathe with the ends trimmed. The operation involves reinstalling the workpiece in a self-centering chuck with a pneumatic clamp. On a CNC milling machine, a 4 x 10 groove and 4 holes with a diameter of 16 mm are processed in a self-centering prismatic vice with a pneumatic clamp. 2) Machining on a 5-axis turning machining center. Processing takes place in a self-centering chuck with a pneumatic clamp in one operation with reinstallation of the workpiece. The same transitions are performed as on conventional CNC machines - turning, milling and drilling.

3) Machining on a machining center with a sub-spindle. Processing takes place in a self-centering chuck with a pneumatic clamp in one operation with reinstallation of the workpiece. Such OCs have two chucks with pneumatic clamping and two tool heads. The role of the second chuck is played by the counter spindle, which reinstalls the workpiece and in which further processing of the workpiece takes place. The workpiece processing cycle is as follows: the workpiece is installed and secured in the chuck; they turn a neck with a diameter of 30 h 12 with trimming the end; The tool is automatically changed by turning the turret; drilling 4 holes with a diameter of 16 mm; the first turret goes back to the starting point; the counter spindle turns on and is automatically brought to the chuck, which continues to rotate at a given frequency; the counter spindle accelerates to the chuck rotation speed and automatically clamps the workpiece; the chuck automatically opens its jaws and the counter-spindle with the workpiece moves to its specified starting point; the second turret head is brought in and turns the neck with a diameter of 30 h 12 with trimming the end; automatic tool change and milling of a 4 x 10 groove is carried out; withdrawal of the turret to the starting point and switching off of the counter-spindle.

Main time To The main time for all three cases is calculated according to general machine-building standards and taken as a constant value, i.e. To = const. The main time for turning, milling and drilling operations can be found from tables and empirical dependencies. The main time is determined by the formula. As a result, we get: min; min.

Тмв – machine-auxiliary time (for supplying the tool part from the starting points to the processing zones and removal; changing the tool), min. We determine it based on machine data sheets and processing technology. min; min. Ttsa – cycle time of automatic operation of the machine according to the program, min. We determine min by the formula;

ateh, aorg, aotl – time for technological and organizational maintenance of the workplace, for rest and personal needs during single-machine maintenance, percentage of operational time. For CNC and OC machines, this value is 14% of the operating time.

Auxiliary time TV Auxiliary time for an operation is calculated using the formula Standards for auxiliary time for installation and removal of part TV. y . For the first case, the auxiliary time for installation and removal is determined for two operations depending on the type of device, the method of installation and fastening of the part and the weight of the part. During the turning operation, the workpiece is mounted in a self-centering chuck with a pneumatic clamp, and during the milling operation, in a self-centering prismatic vice with a pneumatic clamp. During the turning operation, the workpiece is repositioned. min; min. When processing on a turning center, the workpiece is installed in a chuck with a pneumatic clamp with one reinstallation of the workpiece. min.

When processing on an OC with a counter spindle, the workpiece is installed in a chuck with pneumatic clamping with one reinstallation of the workpiece using automatic installation of the workpiece in the counter spindle. min. Standards for auxiliary time associated with the TV operation. op. . min; min. Standards for auxiliary time for control measurements of TV. change . In all 3 cases it is equal to 0. The time for control measurements (after completion of work according to the program) should be included in the standard piece time only if this is provided for by the technological process and taking into account the necessary frequency of such measurements during the work process, and only in those cases , when it cannot be covered by the cycle time of the automatic operation of the machine according to the program.

Auxiliary time TV min; min. Ktv - correction factor for the time of performing manual auxiliary work, depending on the batch of parts being processed.

The norm of piece time is determined by the formula min; min. Standards for preparatory and final time. where Тпз – standard time for setting up and setting up the machine, min; Тпз 1 – standard time for organizational preparation, min; Тпз 2 – standard time for setting up a machine, device, tool, software devices, min; Etc. arr – time standard for trial processing.

min; min. The standard time (standard piece-calculation time, Tsht-k) for performing operations on CNC machines when working on one machine NVR consists of the standard preparatory-final time Tpz and the standard piece time Tsht and is determined by the formula