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Knowledge of CNC machining programming

Nov 16,20

Knowledge of CNC machining programming

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 machine tool is a kind of digital information, control of machine tool according to the given trajectory, automatic machining of electromechanical integration equipment, after half a century of development, numerical control machine tool is an important symbol of modern manufacturing, the manufacturing industry in our country, the application of CNC machine tools is becoming more and more widely, is a reflection of an enterprise comprehensive strength.

Numerical control lathe is the abbreviation of digital program control lathe, it sets the characteristics of universal lathe, precision lathe with high machining precision and special lathe with high machining efficiency in a suit, it is a kind of NUMERICAL control machine tool with the largest domestic usage and the widest coverage.To learn CNC lathe theory and operation, it is necessary to study hard, from plane geometry, trigonometric function, mechanical drawing, ordinary lathe technology and operation and other aspects of a good foundation.Another name for CNC machining is computer gong.The daily work of a machining center is dependent on computer programs.CNC machining center itself is an automatic machine controlled by a program.So for processing center, programming is very important, it directly affects the quality and efficiency of processing.
Commonly used software
  1. UG
  2. Unigraphics is a set of 3D parametric software developed by Unigraphics Solution, which integrates THE functions of CAD, CAM and CAE. It is the most advanced computer-aided design, analysis and manufacturing high-end software, which is used in aerospace, automobile, ship, general machinery and electronics and other industrial fields.
  3. UG software in the CAM field is a leading position, produced in the United States McDonnell Douglas aircraft Corporation, aircraft parts CNC machining programming tool of choice.
UG advantages
Provide reliable and accurate tool path
Can be directly on the surface and solid processing
Good user interface, customers can also design the interface of various processing methods, easy to design combination of high efficiency tool path
Complete tool library
Processing parameter library management function
Includes two - to five-axis milling, lathe milling, wire cutting
Management of large tool library
Solid analog cutting
General use after processor and other functions
High speed milling function
CAM custom templates

Ro/E is
PTC software is the world's most popular 3D CAD/CAM (computer-aided design and manufacturing) system.Widely used in electronics, machinery, mold, industrial design and toys and other civil industries.With parts design, product assembly, mold development, NUMERICAL control processing, modeling design and other functions.
Pro/E is widely used in enterprises in south China. It is a common practice to adopt PRO-E in design modeling and MASTERCAM and CIMATRON in programming.
[Differences and connections between M00, M01, M02 and M03]
M00 is an unconditional pause instruction for a program.Program execution to this feed stop, spindle stop.To restart the program, it is necessary to JOG back first, press CW (spindle forward rotation) to START the spindle, and then return to AUTO state, and press START key to START the program.
M01 is a program selective pause instruction.Before the program is executed, the OPSTOP key on the control panel must be opened to execute. After execution, the effect is the same as M00. Restart the program as above.M00 and M01 are often used for sizing or chip removal during machining.
M02 master program end instruction.Execute this command, feed stop, spindle stop, coolant close.But the program cursor stops at the end of the program.
M30 master program end instruction.Unlike M02, the cursor returns the program header, regardless of whether there are any other segments after M30.
[Address D and H have the same meaning]
Tool compensation parameter D and H have the same function and can be exchanged arbitrarily. They all represent the address name of the compensation register in the NUMERICAL control system, but the specific compensation value is how much, the key is determined by the compensation number address after them.However, in the machining center, in order to prevent errors, the general artificial stipulated H for the tool length compensation address, compensation number from 1 to 20, D for the tool radius compensation address, compensation number from 21 (20 knives of the knife library).
[Pause instruction]
G04X (U) _/P_ refers to the tool pause time (feed stops, spindle does not stop), and the value after address P or X is the pause time.The value after X should be numbered with a decimal point, or it should be counted as one thousandth of the value, in seconds (s). The value after P should not be numbered with a decimal point, in milliseconds (ms).
However, in some hole processing instructions (such as G82, G88 and G89), in order to ensure the precision roughness of the hole bottom, a pause time is required when the tool reaches the hole bottom. At this time, it can only be represented by address P; if it is represented by address X, the control system deems X to be the X-axis coordinate value for execution.
[Circular interpolation Instruction]
In the XY plane, the format is as follows: G02/G03X_Y_I_K_F_ or G02/G03X_Y_R_F_, where X and Y are the end coordinates of the arc, I and J are the incremental values on the X and Y axes from the beginning of the arc to the center of the circle, R is the radius of the arc, and F is the feed.
When arc cutting, note that Q ≤180°, R is positive;Q >180°, R is negative;The designation of I and K can also be specified by R. When both are specified at the same time, R instruction takes precedence and I and K are invalid.R cannot do round cutting, but can only be programmed with I, J and K, because there are an infinite number of circles with the same radius passing through the same point.When I and K are zero, it can be omitted;No matter G90 or G91, I, J and K are programmed according to relative coordinates.Circular interpolation, do not use the knife command G41/G42.
[Mirror command]
Mirror machining instructions M21, M22, M23.When only the X or Y axis is mirrored, the cutting order (forward and reverse milling), the cutter filling direction, and the circular interpolation turn will all be contrary to the actual program.When the X axis and Y axis are mirrored at the same time, the cutting order, the cutting direction and the circular interpolation turn remain unchanged.
Note: After using the mirror instruction, you must cancel with M23 to avoid affecting subsequent programs.In G90 mode, the use of mirror or cancel instruction must be returned to the origin of the workpiece coordinate system to use.Otherwise, the NUMERICAL control system can not calculate the following motion trajectory, will appear random knife phenomenon.In this case, the manual origin return operation must be performed to solve the problem.Spindle steering does not change with mirror commands.
[Program for changing Knives]
In the machining center, knife change is inevitable.However, there is a fixed tool change point when the machine tool leaves the factory. If it is not in the tool change position, the tool cannot be changed. Moreover, before the tool change, the tool repair and cycle must be cancelled, the spindle stops, and the coolant closes.There are a lot of conditions, if each manual tool change before, to ensure these conditions, not only error prone and low efficiency, so we can compile a tool change program to save, then use M98 call can complete the knife change action at one time.
Taking PMC-10V20 processing center as an example, the procedure is as follows:
O2002;(Program name)
G80G40G49;(Cancel fixed cycle and knife repair)
M05;(Spindle stops)
M09;(Coolant closed)
G91G30Z0;(Z-axis returns to the second origin, namely the knife change point)
[Program for changing Knives]
In the machining center, knife change is inevitable.However, there is a fixed tool change point when the machine tool leaves the factory. If it is not in the tool change position, the tool cannot be changed. Moreover, before the tool change, the tool repair and cycle must be cancelled, the spindle stops, and the coolant closes.There are a lot of conditions, if each manual tool change before, to ensure these conditions, not only error prone and low efficiency, so we can compile a tool change program to save, then use M98 call can complete the knife change action at one time.
Taking PMC-10V20 processing center as an example, the procedure is as follows:
O2002;(Program name)
G80G40G49;(Cancel fixed cycle and knife repair)
M05;(Spindle stops)
M09;(Coolant closed)
G91G30Z0;(Z-axis returns to the second origin, namely the knife change point)
M06;(in)
M99;(End of subroutine)
M06;(in)
M99;(End of subroutine)