DESIGNING A G CODE PROGRAMMING LANGUAGE FOR THE REFERENCE POINT SEVEN-SPEED SHAFT

Transcription

1 DESIGNING A G CODE PROGRAMMING LANGUAGE FOR THE REFERENCE POINT SEVEN-SPEED SHAFT PROFESSOR DOCTOR ENGINEER VALERIA VICTORIA IOVANOV, Technical College No. 2, Târgu-Jiu, miciovanova@yahoo.com Abstract: A CNC machine makes use of mathematics and various coordinate systems to understand and process the information it receives to determine what to move where and how fast. The most important function of any CNC machine is precise and rigorous control of the motion. All CNC equipment have two or more directions of motion, called axes. CNC machines are driven by computer controlled servo motors and generally guided by a stored program, the type of motion (fast, linear, circular ), the moving axes, the distances of motion and the speed of motion ( processing ) being programmable for most CNC machines.this paper proposes the design and implementation of a G code programming language for the reference point Seven-speed shaft, used in all fields, in the motion transmission systems. Keywords: CNC, traiectory, SINUMERIK The Programming of CNC machines Before starting writing any program, a CNC programmer must determine the zero position, i.e the origin of the coordinate system. Absolute and relative poistioning motions relative In the absolute positioning mode, all positioning endpoints are relative to the origin of the machine coordinate system. A motion of relative positioning considers that the start position (in which the tool is found prior to the start of the motion) is the origin towards which the positioning must be achieved. Using relative motion (or incremental, as it is sometimes called), the user can focus directly on the tool motion from the point where it is, without reporting all sizes to the absolute coordinate system. Programming with relative motion is very convenient at times, but it is more complex and difficult than absolute positioning method. 211 Fig. 1. Differences between the absolute and relative (incremental) positionings.

2 Fast, linear, circular motions. Interpolation. During a motion with linear interpolation, the machine controller will automatically calculate very precisely a very small number of motions for each axis separately, keeping the tool closer to the imaginary straight line between the two points. In many applications for CNC machines are required processing motions in the form of circles or arcs for making holes of various shapes, curved surfaces, contour milling, etc. These types of motions require circular interpolation. As with linear interpolation, the controller will do everything possible to achieve the real curve as closer to the ideal curve. Fig. 2. Tool trajectory for a linear interpolation movent in XY plane. Fig. 3. Practical achievement of circular interpolation motion Programming on NEF 400 The workstation A Shopturn workstation comprises a control panel, the automatic turning machine and the monitor. Fig. 4. The diagram which shows the workstation. 212

3 The lathe machine there can be used Shopturn on a turning with a single guiding, with 3 axea, a main shaft and an counter axe. The control- Shopturn functions on SINUMERIK vs The control panel makes the connection with Shopturn, thus with the machine. The coordinate system The position of the coordinate system, of the processing zero point and the work piece zero point. When a piece is processed on a lathe, it requires a rectangular coordinate system. This contains the three coordinate axes X, Y and Z which are parallel to the axes of the processing. The axis of the pivot Z, which can be rotated by any angle, is an axis of separate rotation and it is marked with C. Fig. 5. The positions of the coordinate system and the zero point of the work piece. The structure of NC languages. The functions of the letters used in CNC commands Letter Function A Rotation around axis X B Rotation around axis Y C Rotation around axis Z F Feed rate commands G Motion preparation commands l Circulating interpolation - offset axis X J Circular interpolation - offset for axis Y K Circular interpolation - offset for axis Z M Various commands N Number of the programme line R Radius of the arc S Tool rotation speed (main axe) 213

4 T Number of the tool X Data for axis X Y Data for axis Y Z Data for axis Z H Distance correction indicator (offset) of the tool length D Indicator of distance correction of the tool radius (diameter/2) O Number of the programme (identification of programmes)* * Ocasionally, letter O" is used for commands of the secondary axis. G and M commands Commands which begin with letter G sunt are used: - to set up the positioning mode, G90 absolute mode, G91 relative mode; - to indicate the type of motion, G00 - fast, G01 - linear, G02 - circular; - for other settings related to the tool s motion. Commands which begin with letter M are used for various functions, the most important being: - start/end tool rotation; -start/end liquid cooling; - comunication of the CNC machine with the external equipment by digital input/output: - special instructions for structuring CNC programmes. Other programmable functions S tool s rotation speed; T1,2 tool s case; m30 the code for ending the programme. f tool s progress; m3/m4 trigonometric/clockwise rotation of the work piece; d1 tool warehouse; x,z coordinate axes of NEF 400; Seven-speed shaft G code program The semi-finished product for Seven-speed shaft is made of steel, having a diameter of ø 32 crosscut on the lathe at a height of mm (strunjit frontal), and the gripping of the piece is made between the tops. T1 outer cutting tool with removable plate; T2 slot tool with removable plate; d1 number of the warehouse; TC(1) TOOL CHANGE command (decreases the totation time of the tool turret by choosing the shortest rotation); G0 positioning command code; G1 - command code for linear or inclined processing; G2 command code for processing inside an arc (for fillet radii, clockwise); 214

5 Fig. 6. Seven-speed shaft execution design. Program for the first grip T1 d1 TC(1) S800m4f0.2 G0 X30Z1 G1 Z-64.5 G1 X33Z-65.5 G0 X28 G1 Z-43 G1 X30.5Z-44 G0 X26 G1 Z-43.6 G0 X24 G1 X25Z-19 G1 Z-43.6 G0 X22 G0 X23Z1 G0 X20 G0 X21Z1 G0 X18 G0 X250Z150 m30 Program for the second grip T1 d1 TC(1) S800m4f0.2 G0 X30Z1 G1 Z-77 G1 X33Z-77.5 G0 X28 G1 Z-58 G1 X30.5Z-59 G0 X26 G1 Z-77.5 G0 X24 G1 Z-31.3 G1 X25Z-32.3 G1 Z-58.4 G0 X22 G1 Z-31.3 G0 X24Z1 G0 X20 G1 Z-30.3 G2 X21Z-31.3R1 G0 X150Z150 T2 d1 TC(1) S800m4f0.11 G0 X31Z-77.5 G1 X22.3 G0 X35 G0 Z G0 X31 G1 X22.3 G0 X27 G0 Z G1 X15.6 G0 X35 50Z150 m30 215

6 CONCLUSIONS The key to success for any numerically controlled machine is the understanding of the basic notions of the technology of splintering processing, combined with the correct programming in the machine s language and the suitable exploitation of the machine, paying a special attention to the periodical overhauling as well as to the rational exploitation of the machine. The project comprises the original section regarding the design and programming of a G code language for the reference point Seven-speed shaft. The productivity of such numerically controlled machines is very high and it is emphasized by the following: The automation of the process of gripping the part, which is hydraulic. The automatic removal of the span with the help of the conveyer which reduces significantly the auxiliary time due to the operation Speed and advance which are superior to normal turnings, the operation of adjusting the part not being necessary anymore and resulting in small basic times. High productivity about 250 pieces/shift, with an operator per shift, which involves an effective processing time of 3 minutes and 40 seconds. High quality, pieces which are made at the same size without rejects, the prime cost being very small. High precision guaranteed by the producer. High safety in exploitation. Very low power consumption. High reliability guaranteed for 25 years. This reference point for which the program is designed is used: - to support rotative machine parts (gears, pulleys, engine rotors, stocks) and transmit tortion moments to the machine parts they are connected to. REFERENCES [1] AutoTurn - SINUMERIK 840D/840Di/810D Siemens AG, [2] Graphic Programming System - Siemens AG, [3] Programming/Setup - Siemens AG, Edition [4] User Documentation - Siemens AG, Edition [5] Operator s Guide SINUMERIK 840D/840Di/810D, Siemens AG, [6] ManualTurn SINUMERIK 840D/840Di/810D, Siemens AG, [7] Description of Functions SINUMERIK 840D/840Di/810D, Siemens AG, [8] ShopTurn SINUMERIK 840D/840Di/810D, Siemens AG,