Relevant regulations for programming CNC machine tools

July 20, 2023

The core of the CNC machine tool is the numerical control device. This is actually a control computer. It is the main component of executing the computing function and commanding the CNC machine tool to carry out automatic processing. Over the years, with the development of technology, the functions of the CNC system have been continuously expanded, making it easier for people to use it. Therefore, learning the functions of the CNC system and clarifying its concept is an important part of the NC entry.

As we all know, the purpose of using CNC machine tools is to efficiently process qualified parts. The qualified parts must be products that meet the requirements of the drawings. How can the machine know the requirements of the drawings? This must be told by people. In what way, by what rules and conventions are people telling the machine tool? This requires the development of rules for the programming of numerically controlled machine tools. In other words, we must express the parts' drawing size, process route, cutting parameters, etc., with numerical and machine-readable codes that can be accepted by the CNC machine tool, and then make input media (such as perforated tapes, tapes, cards, etc.) according to the prescribed form of the code. ) Then input the information recorded on the input medium into the numerical control device so that the machine tool can be automatically controlled for processing.

This process from the part drawing to the input media is called CNC machine programming. The programming of CNC machine tools is divided into manual programming and automatic programming. The general steps of manual programming include process processing, coordinate calculation of the motion trajectory, filling in a procedure sheet, preparation of the input media, and program check. The automatic programming process is also carried out according to the above steps, but most of the work is done by a computer or an automatic programmer. According to different input methods, automatic programming is divided into three modes: language input, graphic input and voice input. Common programming languages include APT, SKC-1, and ZCX-1. In order for the machine tool to receive the programmed program, there must be corresponding regulations. These concepts are described separately below.

1, punch tape and code

There are two ways to read information from CNC machine tools: one is manual input mode; the other is automatic input mode. Therefore, there are two types of control media as the carrier of CNC machine tools: one is the punched tape, punched card, tape, disk, etc. when the input is automatic; the other is the keyboard, band switch, manual data input when the console is manually input ( MDI) and so on. Perforated belts are mechanically fixed code holes, are not easily affected by the environment (such as magnetic fields), easy to long-term preservation and reuse, and the program's storage capacity is large, so it is still the main commonly used information input method of many CNC machine tools.

2, block format

When programming a CNC machine tool, first determine the coordinate value based on the pulse equivalent of the machine tool, and then program the NC program according to its program segment format. The so-called program segment refers to the combination of the function "word" required to complete an action. "Word" is a set of code symbols representing a certain function. For example, X2500 is a word indicating that the X dimension is 2500; F20 is a word indicating that the feed rate is 20. The block format refers to the order and expression of each word in a block. There are three commonly used block formats, the fixed sequence block format, the fixed sequence block format with separators, and the word address block format. Since the program segment consists of the function "word", the following describes the common function words first, and then introduces the program segment format.

1) Common function words

In a program segment, in addition to the three-digit number (N×××) consisting of the address character N, the commonly used function words are: ready function word G; coordinate function word X, Y, Z; auxiliary function word M; feed function word F; spindle speed function word S and tool function word T, etc.

(1) Prepare the function word. The preparation function word is preceded by the address character G, followed by two digits (G00-G99). The provisions of the ISO 1056 standard for preparing function G are shown in Table 1. The standard in our country is JB3208-83, which stipulates that ISO1056-1975(E) is equivalent. These preparation functions include: specification of coordinate movement or positioning method; designation of interpolation method; selection of plane; designation of machining such as thread, tapping, fixed cycle, etc.; description of spindle or feedrate; tool offset or tool offset Designation etc. When designing a numerical control system for a machine tool, it is necessary to select a part of preparation functions that are compatible with the system in the G functions specified in the standard, as a basis for hardware design and programming. The "not specified" preparation function in the standard can be used as a special preparation function for the system if necessary.

Table 1 Provisions for preparation function G of the ISO standard

Code

Features

Instructions

Code

Features

Instructions

G00

Point positioning

G57

XY plane linear displacement

G01

Linear interpolation

G58

XZ plane linear displacement

G02

Clockwise arc interpolation

G59

YZ plane linear displacement

G03

Counterclockwise arc interpolation

G60

Accurate positioning (fine)

Positioning according to specified tolerances

G04

time out

Suspend for a period of time before executing this paragraph of procedure

G61

Accurate positioning (in)

Positioning according to specified tolerances

G05

Not specify

G62

Accurate positioning (rough)

According to the provisions of the larger tolerance positioning

G06

Parabolic interpolation

G63

Tapping

G07

Not specify

G64-G67

Not specify

G08

Automatic acceleration

G68

Internal corner tool offset

G09

Automatic deceleration

G69

Outer Corner Tool Offset

G10-G16

Not specify

G70-G79

Not specify

G17

Select XY plane

G80

Cancel canned cycle

Cancel the canned cycle of G81-G89

G18

Select ZX plane

G81

Drilling cycle

G19

Select YZ plane

G82

Drilling or reaming cycles

G20-G32

Not specify

G83

Drilling deep hole circulation

G33

Cutting pitch spiral pattern

G84

Tapping cycle

G34

Cutting increase pitch spiral pattern

G85

Boring cycle 1

G35

Cut Pitch Swirl

G86

Boring cycle 2

G36-G39

Not specify

G87

Boring cycle 3

G40

Cancel tool compensation

G88

Boring cycle 4

G41

Tool Compensation - Left

According to the direction of movement,

The tool is on the left side of the workpiece

G89

Boring cycle 5

G42

Tool Compensation - Right Side

According to the direction of movement,

The tool is on the right side of the workpiece

G90

Absolute value input method

G43

Positive compensation

The tool compensation value is added to the given coordinate value

G91

Incremental value input method

G44

Negative compensation

Tool offset value is subtracted from the given coordinate value

G92

Prefabricated

Modify size words

No movement

G45

Used for tool compensation

G93

Feed rate given by the countdown time

G46-G52

Used for tool compensation

G94

Feed rate (mm/min)

G53

Linear displacement function canceled

G95

Feed rate

(mm/r (spindle))

G54

X axis linear displacement

G96

Spindle constant speed

(m/min)

G55

Y-axis linear displacement

G97

Spindle speed

(r/min)

Cancel the designation of G96

G56

Z axis linear displacement

G98-G99

Not specify

(2) coordinate function word. The coordinate function word (also referred to as the dimension word) is used to set the displacement of each machine coordinate. It generally uses X, Y, Z, U, V, W, P, Q, R, A, B, C, D, E, etc., followed by the address character followed by "+" (positive) or " — (negative) and a series of digits. This number is generally expressed in units of system pulse equivalents and does not use a decimal point. When there are multiple size words in a block, they are generally arranged in the order of the above address characters.

(3) Feed function word. The feed function word is used to specify the speed of the tool relative to the workpiece motion. Its unit is generally mm/min. When the feed speed is related to the spindle speed, such as thread, tapping, etc., the unit used is mm/r. The feed function word is preceded by the address character "F" followed by a series of numeric codes. Specifically specify the following methods:

1 Three-digit code method: F followed by three digits, the first one is the integer bit of feedrate plus “3”, and the last two digits are the first two significant digits of the feedrate. For example, the feed rate of 1728mm/min is specified by F717; the feed rate of 15.25mm/min is specified by F515; the feed rate of 0.1537mm/min is specified by F315.

2 two-digit code method: For the two-digit code followed by F, specifies the speed table corresponding to 00-99, except for 00 and 99, when the number code increases from 01 to 98, the speed is increased in an equal relationship of. The 20th root of the scale factor is 10 ( ≈ 1.12), that is, the adjacent speed increases by about 12% from the previous speed. For example, F20 is 10 mm/min, F21 is 11.2 mm/min, F54 is 50 mm/min, and F55 is 560 mm/min. The comparison of the feed rate of F00-F99 is shown in Table 2.

Table 2 Two-digit digital feed rate comparison table mm/min

Code

speed

Code

speed

Code

speed

Code

speed

Code

speed

stop

10.0

100

1,000

10000

1.12

twenty one

11.2

112

1120

11200

1.25

twenty two

12.5

125

1250

12500

1.40

twenty three

14.0

140

1400

14000

1.60

twenty four

16.0

160

1600

16000

1.80

18.0

180

1800

18000

2.00

20.0

200

2000

20000

2.24

22.4

224

2240

22400

2.50

25.0

250

2500

25000

2.80

28.0

280

2800

28000

3.15

31.5

315

3150

31500

3.55

35.5

355

3550

35500

4.00

40.0

400

4000

40000

4.50

45.0

450

4500

45000

5.00

50.0

500

4500

50000

5.60

56.0

560

5600

56000

6.30

63.0

630

6300

63000

7.10

71.0

710

7100

71000

8.00

80.0

800

8000

80000

9.00

90.0

900

9000

high speed

3 One-digit code method: For numerically controlled machine tools with less speed limit, F can be followed by a digit, ie 0-9 to correspond to 10 preset speeds.

4 Direct designation method: Just like the coordinate displacement amount in the dimension word, the required feedrate is written directly after F in the predetermined unit.

(4) Spindle speed function word. The spindle speed function word is used to specify the spindle speed in r/min. It is prefixed by the address character S, followed by a string of digits. It can use the three-digit, two-digit, one-digit code method or direct designation method as the feed function word headed by F. The meaning of the numbers, the method of splitting the block, and the comparison table and feed function are common. Just change the unit to r/min.

(5) Tool function word. When the system has a tool change function, the tool function word is used to select the replaced tool. The tool function word is preceded by the address symbol T, followed by two digits, which represents the tool number.

(6) Auxiliary function word. The auxiliary function word is preceded by the address symbol M, followed by two digits (M00-M99). The provisions of the ISO 1056 standard for the auxiliary function M are shown in Table 3. This table is equivalent to the provisions of the Chinese standard JB3208-83 M function. These auxiliary functions include: specifying the spindle's steering and start and stop; specifying the system's coolant on and off; specifying the clamping and release of the machine; specifying the fixed line and angular displacement of the table, etc.; indicating that the program is stopped or the tape ends. . Some unspecified auxiliary functions in the standard can be selected for special purposes. When designing a machine tool numerical control system, it is necessary to select some of the auxiliary function codes required by the system in the M code specified in the standard as the basis for the relevant circuit design and future programming.

Table 3 Provisions of the ISO standard for auxiliary functions M

Code

Features

Instructions

Code

Features

Instructions

M00

Program stop

Spindle, coolant stop

M32-M35

Not specify

M01

Planned stop

Need button operation to confirm line feed

M36

Feed speed range 1

Do not stop gear shift range

M02

End of program

Spindle, coolant stop, machine reset

M37

Feed speed range 2

M03

Spindle rotates clockwise

Right-hand thread into the workpiece

M38

Spindle speed range 1

Do not stop gear variable speed range

M04

Spindle counterclockwise

Right-hand thread exits the workpiece

M39

Spindle speed range 2

M05

Spindle stop

Cooling fluid off

M40-M45

Not specify

Can be used for gear shifting

M06

Change knife

Manual or automatic tool change, excluding tool selection

M46-M47

Not specify

M07

Coolant No. 2 opens

M48

Cancel M49

M08

Coolant No. 1 open

M49

Manual speed correction fails

Return to programmed speed or feedrate

M09

Coolant stops

M50

Coolant No. 3 opens

M10

Clamping

Workbench, workpiece, fixture, spindle, etc.

M51

Coolant #4 on

M11

release

M52-M54

Not specify

M12

Not specify

M55

The tool is linearly displaced to a predetermined position 1

M13

Spindle rotates clockwise, coolant opens

M56

The tool is linearly displaced to the predetermined position 2

M14

The spindle rotates counterclockwise and the coolant opens

M57-M59

Not specify

M15

Positively moving fast

M60

Change workpiece

M16

Reverse fast

M61

Workpiece linear only to the predetermined position 1

M17-M18

Not specify

M62

The tool is linearly displaced to the predetermined position 2

M19

Spindle exact stop

Spindle slows down to a predetermined angle to stop

M63-70

Not specify

M20-M29

Not specify

M71

The workpiece rotates to a predetermined angle 1

M30

Tape end

Spindle coolant stop, machine reset, tape rewind, etc.

M72

The workpiece rotates to a predetermined angle 2

M31

Temporary failure of the interlock mechanism

M73-M99

Not specify

2) Block format

Different CNC machine tools stipulate different program segment formats depending on the number of functions, the complexity of the numerical control device, and whether the programming is simple and intuitive. If the format of the input program does not comply with the regulations, the CNC will report an error. Common segment formats include fixed sequence, fixed sequence with separator TAB, and word address format.

In the early days, due to the simplicity of numerical control devices, a block format called fixed sequence was specified, for example:

Programs compiled in this format have no address code for each word. The order of the words is the order of the addresses. The order of each word and the number of character lines are fixed (regardless of whether a certain word is needed or not), even if it matches the previous paragraph. Compared to certain words, they have to be rewritten and cannot be omitted. When the effective number of digits of a word is small, the required number of digits must be supplemented with "0" in the front. Therefore, the length of the perforated belt occupied by each program segment is constant. The control system of this format is simple, but the programming is not intuitive, the perforated belt is longer and the application is less.

Later, a fixed sequential segment format with the separator symbol TAB was produced. The basic form is the same as the above format except that the words are separated by a separator to indicate the order of the addresses. The above example can be written as:

Due to delimiters, unwanted words or words that are identical to the upper block can be omitted, but the corresponding delimiter must be retained (ie the number of delimiters in each block is equal). This format is better than the former one and is often used for numerically-functional devices such as wire-cutting machines and certain CNC milling machines. The "3B" or "4B" format commands used in CNC wire-cutting machine tools in China are typical fixed sequential formats with separate symbols. The general representation of its 3B format is:

BXBYBJGZ

Its specific meaning is as follows:

x coordinate value

Delimiter

y coordinate value

Delimiter

Count length

Counting direction

Processing instructions

The most commonly used at present is the word address block format (also called variable block format using address characters). Blocks expressed in this format, each word is preceded by an address code to identify the address, that is, as previously described by the letter and data of the various functional words, so for the unwanted words or with the previous section The same word can be omitted. Each word in a program segment can also be arranged out of order (but for programming convenience, often in a certain order). Although using this format to increase the address into the circuit, but the programming is intuitive and flexible, easy to check, can shorten the punch tape, widely used in car, milling and other CNC machine tools.

Program segments for word address formats can often be represented in general form. Such as:

N134 G01X — 32000Y + 47000F1020S1250 T16 M06 (1—1)

If formula (1-1) is written in the general form, it is:

N3G2X ± 23Y ± 23F4S4T2M2 (1 - 2)

In the formula