Application of macro instruction in NC machining o

2022-05-25
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Application of macro instruction in NC machining of railway axle

the development direction of high-speed and heavy load railway transportation in China has higher and higher requirements for the quality of railway axle. Therefore, the production technology and equipment requirements of railway axles are constantly improving. Our factory is one of the main bases for axle production of CSR group. After many technical transformations, the axle machining production line is gradually adopting NC equipment. At present, NC machine tools account for more than 50%. With its good processing stability and high flexibility, CNC machine tools have greatly improved the overall quality of axles in our factory. However, in recent years, there are many problem axles through NC machining, including RD2, RE2A, rd3a, axles exported to Vietnam, Indonesia and other countries. Most of these problems are caused by improper economic losses due to knife planting or out of tolerance of size. Therefore, it is of certain significance to analyze and explore the methods to avoid the problem axis in NC machining

1. Cause analysis of problem axle in NC machining

(1) the influence of programming and operation habits. NC machine tool operators generally have a certain manual programming ability. The preparation of axle NC program is not complicated in both process and numerical calculation, so it is easy to use. However, bad programming habits or some differences in machine tool operation often lead to misoperation. If in actual programming, G50 command is used to set the coordinate system, which is executed first, and then directly operated to start the program of automatically establishing the coordinate system with return parameters (establishing the workpiece coordinate system after tool repair), misoperation will occur during operation. This is due to the tool compensation offset on the set value of G50 in this program, rather than the relative return parameter automatic coordinate system in the original program. It is not uncommon to see a product scrapped because of its different production habits

(2) the influence of equipment failure. Even though the reliability of CNC machine tool is high, it will fail without paying attention to strengthening maintenance, especially hidden failure. Generally, NC machine tools must return to zero (i.e. return to the reference point position) when starting up. Return parameter fault is one of the common faults of machine tools. The position error caused by returning to the reference point can only be found during machining. If the back parameter is used to automatically establish the setting and standard system, the tool compensation is used to set the workpiece coordinate system for programming, and the back parameter position error occurs in the machine tool, the workpiece tool planting accident is difficult to avoid. It also happens from time to time in the production of our factory. This is also the reason why the absolute encoder is gradually adopted for the coordinate axis of NC equipment, so that Guohao Exhibition (Shanghai) Co., Ltd. of machine tool does not need to return to the operation

(3) the influence of trial processing and operator level. Our factory produces many kinds of axles and different production batch sizes. NC programming often needs to be prepared manually on site. Therefore, there are errors in program entry. Due to the operator's low level or overconfidence, misoperation occurs from time to time in program debugging and operation

2. Preparation of general program based on macro instruction

(1) examples of general NC program of axle (RD2, re2, etc.) the geometry of railway axle is generally the same. Therefore, from the perspective of programming, we can use variables, make use of the repeatability of the same operation of macro program and the arithmetic and logic operation function of macro instruction to prepare NC general program and discuss the way to avoid problem axle through the method of program control. Based on the above analysis, in the actual production, we took the axle body processing as an example to make a programming attempt, and took the RD2 truck axle body processing task as an example (as shown in Figure 1)

the CNC machine tools of our factory are mainly FANUC-OTD system. Due to the early version of the system, there is no operator key on the panel; At the same time, the site does not have the means to communicate with the computer, so only class a macro programs can be applied, that is, macro programs can be compiled in G65 hxx p#xx q#xx r#xx or G65 hxx p#xx qxx RXX input format. The H code in the instruction is the basic instruction to realize arithmetic and logic operations (such as H01 assignment, h02-h05 addition, subtraction, multiplication and division, etc.); P. "XX" after Q and R address refers to micron value; "#xx" is the variable number. Figure 2 is a schematic diagram of the super route, and the example program is as follows

O1111; Main program (RD2)

N10 M43 * (spindle gear 3)

N20 Mo3 *

N30 M98 o9990 *

N40 M98 o9995 *

N50 t0212 *

N60 M98 o9997 *

N70 t0414 *

n8o M98 o9998 *

N90 t0111 *

N100 M98 o9999 *

n110 M98 o9990 *

N120 M30

o9990; Initialization subroutine (cancel offset, tool compensation and cycle, etc.)

N10 G18 t0000 * N30 C40 *

N20 C54 g80 G99 * N40 M99 *

o9995; Position check and coordinate system establishment subroutine

n05 M98 o9990 *

N10 G65 H3 Pressure transmission: pneumatic 01 p#120 q#5041 * (with workpiece coordinate value)

N20 C65 H01 p#121 q#5042 *

1 general ball screw N30 G65 H01 p

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