Development of a control program for a CNC machine. Development of a control program for a machine tool with numerical control
Companies producing CNC systems adhere to the ISO standard, but often allow deviations. This is due to the "weakness" of the microcomputer in the implementation of multi-parametric technological commands (for example, changing tools). Therefore, when compiling programs for a specific CNC system, it is necessary to focus on the "User's Manual", which is included in the documentation set for the programming machine.
The ISO-7bit code defines a character as a seven-bit binary number. If the number of holes on the punched tape that define the bits of this character is odd, then the DPD (data preparation device) automatically complements the encoding of this character with a hole on the eighth track - a parity bit. For the EIA code (America, Japan), the eighth track is the control for the odd number of holes.
In the UE, the movement is programmed, defined by the coordinate axes X, Y, Z, or rotation around them, respectively, A, B, C (for example, the rotation of the machine table). Letters U, V, W define the secondary movement functions, parallel to the X, Y and Z axes respectively.
UE is a sequence of numbered sentences called frames. The frame number is a label by which you can find the required frame in order to edit it or start the NC from this frame. When constructing the UE, only the information that changes with respect to the previous part of the program is recorded in the frames.
The frame is made up of words. Each word has an address (one of the Latin letters) and a decimal number. Decimal number is written in a word according to the word format. AT modern systems numbers are usually written with a decimal point, however, it is necessary to clarify the number format according to the user's instructions for a particular machine (there are CNC systems where the word format is determined by a parameter stored in the CNC RAM).
At the end of the block, the LF character (carriage return) is written. For example: N10 G90 X10,2 Z-100 (LF) In block no. 10, a movement is defined in the absolute reference system (G90), to a point with coordinates (10.2, -100). The LF character can only be seen on punched tape, it is invisible on the display. It is also not affixed to the listing of the UE.
Words in NC blocks can be entered in any sequence, the CNC will first process the commands of the technological functions S, F, T, M and then the preparatory G, with the performance of dimensional movements.
Modulo UE control.
As noted earlier, the ISO-7bit code assumes when encoding characters, even number holes in punched tape. If we consider the character code as a binary number, then according to the ISO standard, it must contain an even number of ones. This property guarantees checking against a single error (loss of one bit or one extra bit). Therefore, some systems use more reliable appearance modulo control.
The data preparation device (PDD) when recording UE frames automatically calculates the checksums for each frame and divides them by 10, determining the remainder of the addition (mod) to a multiple of 10. This addition will be the checksum (0....9) for the frame and the UPD will be written automatically after the “end of frame” (LF) character. The CNC, when reading NC blocks, also calculates the padding for each block and compares them with the paddings on the program medium. If these values do not match, it causes an error message on the program medium. The checksum is equal to the sum of the numeric codes of all characters, including the "end of frame" (LF) character. The character code is a binary number, for example code N 1001110| 2=78| ten
Fragments of NC for a CNC machine
Preparatory Functions G
Attention: The command functions of the NC are not given for a specific CNC model, but are their generalized forms for developing programs in the course and graduation design. Functions with address G, called preparatory functions, determine the mode and operating conditions of the CNC machine. They are coded G00 to G99. 4
G00 Positioning. Move to the programmed point at rapid traverse.
G01 Linear interpolation. Moving in a straight line at fast feed.
G02 Clockwise circular interpolation Movement along a circular arc in a clockwise direction when viewed from the positive direction of an axis perpendicular to the plane of motion.
G03 Circular interpolation counterclockwise Movement along an arc of a circle counterclockwise when viewed from the positive direction of an axis perpendicular to the plane of motion.
G04 Pause. Initializes the delay in the execution time of the NC.
G17 G18 G19 Selection of the circular interpolation plane. Specifying the plane XY - G17, XZ - G18, YZ - G19 when programming the movement along the circular arc and compensation for the cutter diameter.
G25 Program repeat Multiple repetition of a group of NC blocks.
G41 G42 Cutter diameter compensation left and right. Used to shift the toolpath of the cutter center relative to the contour being machined.
G60 Fine positioning Move at rapid traverse, approaching a position from one direction.
G81 … G89 Canned cycles. The movements of typical surfaces of parts are programmed.
G80 Canned cycle cancel. Cancels canned cycles
G81 G89 G90 Absolute dimension. Programming of coordinates in absolute reference system.
G91 Incremental size. Programming of coordinates in relative reference system.
G92 Coordinate system setting. Determines the origin of the coordinate system relative to the specified position of the working bodies of the machine.
G94 G95 Determine the unit of feed value
G94 - mm/min
G95 - mm/rev G96 Constant cutting speed. Programming processing with a constant cutting speed.
G98 G99 Define properties in canned cycles. Set the return point after running G81 89
Auxiliary functions M
M00 Technological stop. After executing the command, the program is stopped. Continuation of work - pressing the "Start" key.
M01 Stop with confirmation. The M01 command is executed, provided that the corresponding key on the control panel is pressed.
M02 M30 Program end. End of program block. The command to complete the processing of this UE. There can be several programs on a program carrier (magnetic tape, punched tape). This command actually means "end of tape".
M03 M04 Spindle rotation. The direction of spindle rotation is clockwise. The direction of spindle rotation is counterclockwise.
M05 Spindle stop Causes spindle stop, turns off cooling. M06 Tool change. Puts in the working position the tool, the number of which is determined by the address T.
M08 M09 Coolant supply. Turns on cooling. Turns off cooling.
M19 Oriented spindle stop. Causes the spindle to stop at the specified angular position.
M17 End of subroutine. M20 Communication with an external device. It can set the transfer of control to an industrial robot, initialize the operation of a transport and storage device, etc.
M41 M42 M43 Spindle speed range. Sets the spindle speed range number.
It should be noted that a number of functions, such as "absolute reference system - G90", the dimension of the feed value (G94, G95), diameter compensation (G40) and others, are automatically set when preparing the machine for operation (turning on the power supply). They are called "default functions" and their initial state is specified in the "User's Instructions".
Under address F, the feed value is programmed, and S is the value for the spindle speed. The address letter H determines the corrector number for the length, and D for the diameter.
Development control program for a machine with a numerical program management
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MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION
MOSCOW STATE TECHNICAL UNIVERSITY MAMI Faculty: "Mechanical and technological" Department: "Automated machine tools and tools" COURSE WORK by discipline Programmed processing on CNC and SAP machines Development of a control program for a machine tool with numerical control Moscow 2011 Doing Technological preparation control program 1 Selection of process equipment 2 Selecting the CNC system 3 Sketch of the workpiece, justification of the method for its production 4 Tool selection 5 Technological route for processing the part 6 Purpose of processing modes Mathematical preparation of the control program 1 Coding 2 Control program Work Conclusions Bibliography coding machine detail software control 2. Introduction
At present, mechanical engineering has been widely developed. Its development is in the direction of a significant increase in product quality, reduction of processing time on new machines due to technical improvements. The modern level of development of mechanical engineering imposes the following requirements on metal-cutting equipment: high level of automation; ensuring high productivity, accuracy and quality manufactured products; reliability of the equipment; high mobility is currently due to the rapid change of production facilities. The first three requirements led to the need to create specialized and special automatic machines, and on their basis automatic lines, workshops, factories. The fourth task, the most typical for pilot and small-scale production, is solved by means of CNC machines. The process of controlling a CNC machine is presented as a process of transferring and converting information from a drawing to a finished part. The main function of a person in this process is to convert the information contained in the drawing of the part into a control program understandable by the CNC, which will allow you to control the machine directly in such a way as to obtain a finished part corresponding to the drawing. This course project will consider the main stages of the development of the control program: technological preparation of the program, and mathematical preparation. To do this, based on the drawing, the parts will be selected: workpiece, CNC system, technological equipment. 3. Technological preparation of the control program
3.1 Selection of process equipment
To process this part, select lathe with CNC model 16K20F3T02. This machine is designed for turning parts of bodies of revolution with stepped and curvilinear profiles in one or more working moves in a closed semi-automatic cycle. In addition, depending on the capabilities of the CNC machine, various threads can be cut on the machine. The machine is used for machining parts from piece blanks with a clamp in a mechanized chuck and, if necessary, clamping by a center installed in the tailstock quill with mechanized movement of the quill. Specifications machine: Parameter nameParameter valueMaximum diameter of the workpiece: above the bed above the support 400 mm 220 mmDiameter of the bar passing through the hole50 mmNumber of tools6Number of spindle speeds12Spindle speed limits20-2500 min -1Limits of working feeds: longitudinal transverse 3-700 mm/min 3-500 mm/min Rapid travel speed: longitudinal transverse 4800 mm/min 2400 mm/min Movement resolution: longitudinal transverse 0.01 mm 0.005 mm 3.2 Selecting the CNC system
CNC device - part of the CNC system is designed to issue control actions executive body machine in accordance with the control program. Numerical control (GOST 20523-80) of the machine - control of the processing of the workpiece on the machine according to the control program, in which the data is specified in digital form. There are CNC: -contour; -positional; position-contour (combined); adaptive. With positional control (F2), the movement of the working bodies of the machine occurs in given points, and the trajectory of movement is not specified. Such systems allow processing only rectilinear surfaces. With contour control (F3), the movement of the working bodies of the machine occurs along a given trajectory and at a given speed to obtain the required processing contour. Such systems provide work on complex contours, including curvilinear ones. Combined CNC systems work on control points (nodal) and on complex trajectories. Adaptive CNC machine provides automatic adaptation of the processing of the workpiece to changing processing conditions according to certain criteria. The item covered in this term paper, has a curved surface (fillet), therefore, the first CNC system will not be used here. It is possible to use the last three CNC systems. From an economic point of view, it is advisable in this case to use a contour or combined CNC, because. they are less expensive than the others and at the same time provide the necessary processing accuracy. In this course project, the CNC system "Electronics NTs-31" was chosen, which has a modular structure that allows you to increase the number of controlled coordinates and is intended mainly for controlling CNC lathes with feed servo drives and pulse feedback sensors. The device provides contour control with linear-circular interpolation. The control program can be entered either directly from the remote control (keyboard) or from an electronic memory cassette. 3.3 Sketch of the workpiece, justification of the method of its production
In this course work, we conditionally accept the type of production of the part in question as small-scale. Therefore, a bar with a diameter of 95 mm of simple long products (round profile) was chosen as a workpiece for the part. general purpose from steel 45 GOST 1050-74 with hardness HB=207…215. General-purpose simple profiles are used for the manufacture of smooth and stepped shafts, machine tools with a diameter of not more than 50 mm, bushings with a diameter of not more than 25 mm, levers, wedges, flanges. At the harvesting operation, the bushing is cut into a size of 155 mm, then it is cut into a size of 145 mm on a milling and centering machine, and center holes are simultaneously made here. Since when installing the part in the centers, the design and technological base are combined, and the error in the axial direction is small, it can be neglected. The drawing of the workpiece after the milling and centering operation is shown in Figure 1. Figure 1 - drawing of the workpiece 3.4 Tool selection
Tool T1 To process the main surfaces for roughing and finishing, we select the right through cutter with mechanical fastening of the DNMG110408 insert made of GC1525 carbide and a clamp of increased rigidity (Fig. 2). Figure 2 - right through cutter K r b, mmf 1, mmh, mmh 1, mml 1, mml 3, mm γλ s Reference plate93 02025202012530,2-60-70DNMG110408 Tool T2 Picture 3 - prefabricated cutting tool l a , mma r , mmb, mmf 1, mmh, mmh 1, mml 1, mml 3, mm Reference plate4102020,7202012527N151.2-400-30 Tool T3 To drill a given hole, we select a GC1220 carbide drill for drilling for M10 threads with a cylindrical shank (Fig. 4). Figure 4 - drill D c , mmdm m , mmD 21max, mml 2, mml 4, mml 6, mm91211,810228,444 Tool T4 To drill a given hole, we select a GC1220 carbide drill with a cylindrical shank (Fig. 5). D c , mmdm m , mml 2, mml 4, mml 6, mm20201315079 Tool T5 For execution internal thread M 10x1 choose a tap GOST 3266-81 from high-speed steel with helical grooves (Fig. 5). Figure 5 - Tap 3.5 Technological processing route
The technological route for processing a part must contain the name and sequence of transitions, a list of surfaces processed at the transition, and the number of the tool used. Operation 010
Procurement. Rental. Cut off the workpiece Ø 95 mm to size 155 mm, make center holes up to Ø 8 mm. Operation 020
Milling and centering. Mill the ends to a size of 145 mm. Operation 030
Turning: set the workpiece in the front leading and rear rotary centers. Set A Transition 1 Tool T1 Sharpen in advance: · cone Ø 30 mm to Ø 40 · Ø 40 · cone Ø 40 mm to Ø 6 0 mm from length 60 mm to length 75 mm from the end of the workpiece · Ø 60 · Ø 60 mm to Ø 70 along an arc with a radius of 15 mm from a length of 85 mm from the end of the workpiece · Ø 70 · Ø 70 mm to Ø 80 mm at a length of 120 mm from the end of the workpiece · Ø 80 mm to Ø 90 · Ø 90 Leave a finishing allowance of 0.5 mm per side Transition 2 Tool T1 Sharpen finally on transition 1: · cone Ø 30 mm to Ø 40 mm up to a length of 30 mm from the end of the workpiece · Ø 40 mm from a length of 30 mm to a length of 30 mm from the end of the workpiece · cone Ø 40 mm to Ø 60 mm from length 60 mm to length 75 mm from the end of the workpiece · Ø 60 mm from length 75 mm to length 85 mm from the end of the workpiece · Ø 60 mm to Ø 70 along an arc with a radius of 15 mm from a length of 85 mm from the end of the workpiece · Ø 70 mm from length 100 mm to length 120 mm from the end of the workpiece · Ø 70 mm to Ø 80 mm at a length of 120 mm from the end face of the workpiece · Ø 80 mm to Ø 90 mm along an arc with a radius of 15 mm from the length from the length of 120 mm from the end of the workpiece · Ø 90 mm from length 135 mm to length 145 mm from the end of the workpiece Transition 3 Tool T2 · Sharpen a rectangular groove 10 mm wide from a diameter of 40 to a diameter of 30 mm at a distance of 50 mm from the end of the workpiece. Set B Transition 1 Tool T3 · Drill a hole Ø 9 40 mm deep. Transition 2 Tool T4 · Drill hole with Ø 9 to Ø 20 to a depth of 15 mm. Transition 3 Tool T5 · Cut the thread with an M10 tap ×1 to a depth of 30 mm. Operation 040
Flushing. Operation 050
Thermal. Operation 060
Grinding. Operation 070
Control. 3.6 Purpose of processing modes
Set A Transition 1 - rough turning Tool T1 2.The depth of cut during preliminary turning of steel with a through cutter with a carbide plate is chosen t = 2.5 mm. .When turning steel and cutting depth t = 2.5 mm, we select the feed S = 0.6 mm / rev. . .Cutting speed With v To MV = 0.8 (Table 4 p. 263) To PV = 0.8 (Table 5 p. 263) To IV = 1 (Table 6 p. 263) 6.The number of revolutions of the spindle. 7.Cutting force. where: C R (Table 9 p. 264) 8.cutting power. Transition 2 - fine turning Tool T1 .Determining the stroke length L = 145 mm. 2.The depth of cut during the preliminary turning of steel with a through cutter with a hard-alloy plate is chosen t = 0.5 mm. .When turning steel and cutting depth t = 0.5 mm, we select the feed S = 0.3 mm / rev. .Tool life T = 60 min. .Cutting speed With v = 350, x = 0.15, y = 0.35, m = 0.2 (Table 17 p. 269) KMV = 0.8 (Table 4 p. 263) To PV = 0.8 (Table 5 p. 263) To IV = 1 (Table 6 p. 263) 6.The number of revolutions of the spindle. 7.Cutting force. where: C R \u003d 300, x \u003d 1, y \u003d 0.75, n \u003d -0.15 (Table 22 p. 273) (Table 9 p. 264) 8.cutting power. Transition 3 - grooving Tool T2 .Determining the stroke length L = 10 mm. 2.When grooving, the depth of cut is equal to the length of the cutter blade .When turning steel and cutting depth t = 4 mm, we select the feed S = 0.1 mm / rev. 4.Tool life T = 45 min. .Cutting speed