Safety Hazards Material Processing Laboratory Room 232 HAZARD: Rotating Equipment / Machine Tools Be aware of pinch points and possible entanglement Personal Protective Equipment: Safety Goggles; Standing Shields, Sturdy Shoes No: Loose clothing; Neck Ties/Scarves; Jewelry (remove); Long Hair (tie back) HAZARD: Projectiles / Ejected Parts Articles in motion may dislodge and become airborne. HAZARD: Heating - Burn Personal Protective Equipment: Safety Goggles; Standing Shields Be aware of hot surfaces Personal Protective Equipment: Safety Goggles; High Temperature Gloves; Welding Apron, Welding Jacket, Boot Gauntlets, Face Shield HAZARD: Chemical - Burn / Fume Use Adequate Ventilation and/or Rated Fume Hood. Make note of Safety Shower and Eyewash Station Locations. Personal Protective Equipment: Safety Goggles; Chemically Rated Gloves; Chemically Rated Apron HAZARD: Electrical - Burn / Shock Care with electrical connections, particularly with grounding and not Using frayed electrical cords, can reduce hazard. Use GFCI receptacles near water. HAZARD: High Pressure Air-Fluid / Gas Cylinders / Vacuum Inspect before using any pressure / vacuum equipment. Gas cylinders must be secured at all times. Personal Protective Equipment: Safety Goggles; Standing Shields HAZARD: Water / Slip Hazard Clean any spills immediately.
EXPERIMENT # 3 COMPUTER NUMERICAL CONTROLLED MACHINING Goal: Objective: Equipment and Tools To learn computer numerical controlled (CNC) metal cutting approach To familiarize students with automated method of controlling the motions and actions of CNC cutting machine by series of programming codes and to design a sequence of operations. NASA II CNC milling machine, teletype printer, collet, vise, parallels, Vernier caliper. Materials: Duraluminum (2017) Each group of students has to complete all given by the Instructor problems, to learn suggested drawings, to design the sequence of operations, to write a program, if necessary, to make all computations, to cut the part and to give the answers to the Set of Questions. Group leader is responsible for distributing among students the responsibilities and producing the Data Sheet. A report has to be prepared according to the requirements of the General Instruction. LABORATORY ASSIGNMENT Your aim for this assignment is to learn how to design a sequence of operations, prepare a program and cut your part. To assure a more complete understanding of how to reach your goal be sure that each group of students must complete following assignments: 1. Learn the principles of computer numerical controlled(cnc) method and basic process flow; 2. Study suggested drawing; 3. Prepare a sequence of cutting operations; 4. Learn all directions of table & spindle motion of the NASA II CNC milling machine; 5. Compute all machining cycles time; 6. Prepare the manuscript; 7. Prepare the CNC program; 8. Learn to operate the tape preparation device - teletype printer; 9. Prepare the tape; 10.Learn to operate the CNC controller; 11. Learn other methods to communicate with the controller; 3-1
12.Execute your program without part cutting. Use Single Block Mode and Automatic Mode to check the CNC program; 13.Execute your program using Single Block Mode to perform 1/3 depth of cutting; 14.Execute your program using Automatic Mode to perform another 1/3 depth of cutting; 15.Finish your part by operating the cutting machine in Automatic Mode and cut your part to the full depth. ATTENTION All final steps of your assignments must be checked and approved by the Instructor. RULES FOR CLEAN UP: 1. All tools must be put in their proper place or returned to the Instructor. 2. All machinery must be cleaned and chips be swept into a pile near the aisle and placed in the proper receptacle. In carrying out your assignment, follow the sequence given below: WEEK I 1. Learn the principles of CNC programming; 2. Learn the Binary Code of Decimal System shown on Fig. 3-?; 3. Consider the suggested drawing for your group, Fig. 3-?; 4. Plan the sequence of operations. Fill your plan in the Data Sheet, Table 3-? ; 5. Calculate and fill in all required data in the form MACHINING DATA AND MACHINING CYCLE TIME, Table 3-? for your part with the help of the example in Table 3-?; 6. Prepare the manuscript in accordance with your sequence of operations for the movement of table and cutting tool. Use the Data Sheet on Fig. 3-?; 7. Prepare your CNC program using the form COMPUTER NUMERICAL CONTROL PROGRAM shown in Table 3-?; 8. Learn to operate the teletype printer and prepare the tape of your CNC program; 9. Prepare the duplicate of your tape by running it through tape duplicator; 10. Put all group member names on your program sheet, sign it and obtain the Instructor s approval. ATTENTION Your manuscript and CNC program must be checked and signed by the Instructor. 3-2
WEEK II 1. Obtain the duraluminum blank from the Instructor and install it in the vise with the assistance of the Instructor; 5. Learn the function and operation of the controller of NASA II CNC machine; 6. Learn different methods to upload and download CNC program into and from the controller; 7. Learn accuracy of the cutting machine; 8. Learn how to set reference origin points; 9. Select & establish your part origin points; 10. Compare your program with the program memorized by CNC controller; 11. Define the reason why machine is not able to execute the maximum accuracy; 12. Check the CNC program by executing without cutting the CNC program using Single Block and Automatic Mode and by lowering the table downward 5 turns; 13. Bring the table up by 4 turns of the crank, perform 1/3 depth cut of your part by execution of prepared CNC program in Single Block Mode ; 14. Execute your program and cut second 1/3 of the total depth using CNC program in Automatic Mode, bring the table up by half turn more; 15. Bring the table up to the initial height and execute the CNC program using Automatic Mode to perform full depth cutting process; 16. Take the duraluminum work out of the vise (after machine has come to a full stop). Examine the finished part. 17. Discuss the operation procedures, results, repeatability and alternatives; 18. How to perform your part in large quantities? 19. Clean the machine and working area around the machine. ATTENTION Goggles must be worn when machine is operating. 3-3
Fig. 3-1. Basic computer numerical controlled process flow. 3-4
Fig. 3-2. Binary numbers & binary coded decimals 3-5
CNC Program Entries and Command Codes: 1. Line Number Letter Address: N Range: N0 to N19999 2. Feed rate Letter Address: F Range: IPM ( inch per minute ): F2 to F320 in increments of 0.1 IPM MMPM ( mm per minute ): F5 to F812 in increments of 1 MMPM Note: If a value greater than 320 is given, the feed will be set at F320. 3. Tool Number Letter Address: T Range: T1 to T 24 4. Miscellaneous Function Code: M Maximum number of digits: 2 Functions relative to direct machine movements and actions. Code Before With After Modal Non-Modal Function M00 x x Program Stop M01 x x Optional Stop M03 x x Rotating Spindle M06 x x x Tool Change M25 x Z Axis Home M30 End of Program and Back to Beginning 3-6
TABLE 3-1 G - codes: Functions to perform a desired operation. G code Modal Non-Modal Function Note G00 x Rapid Traverse, point-to-point positioning G01 x Linear Interpolation Feed rate G02 x Circular Interpolation, Arc CW Feed rate & Index G03 x Circular Interpolation, Arc CCW Feed rate & Index G04 x Dwell G17 x XY Plane Index G18 x ZX Plane Index G19 x YZ Plane Index G30 x Cancel Mirror Image G31 x Reverses Programmed Direction of X axis Index G32 x Reverses Programmed Direction of Y axis Index G40 x Cutter Diameter Compensation OFF G41 x Cutter Compensation Left G42 x Cutter Compensation Right G70 x Select Inch Dimension System G71 x Select Metric Dimension System G72 x Transformation Off G73 x Transformation On G74 x Multi quadrant Circular Interpolation Cancel G75 x Multi quadrant Circular Interpolation G77 x Facing Cycle G78 x Pocket Mill Cycle G79 x Rough Bore Milling Cycle G80 x Fixed Cycle Cancel G81 x Drill Cycle G82 x Spot Facing Cycle G83 x Deep Hole Drilling Cycle G84 x Tapping Cycle G85 x Boring Cycle Cancel G86 x Boring Cycle G87 x Chip Breaking Deep Hole Drilling Cycle G89 x Boring Cycle G90 x Absolute Programming Mode G91 x Incremental Programming Mode G92 x Present Absolute Registers G99 x Deceleration Override for 2.8 IPM & above 3-7
Fig. 3-3. Part drawings 3-8
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SAMPLE: N/C PROGRAM FOR PLATE 3673653 N5G00G90X 1.000Y 1.000S1500T1M3 N10X0.500Y2.500Z0.050 N15G01Z-0.375F50 N20G00X1.000Y2.000Z0.050 N25G01Z-0.600F50 N30X2.000 N35G00X1.500Y2.000 N40G01Y1.000F50 N45G00X2.500Y0.500Z0.050 N50G01Z-0.600F50 N55G00X-1.000Y-1.000Z0.050M30 3-12
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SET OF QUESTIONS: 1. Explain the difference between Numerical Control & Computer Numerical Control. 2. What is the first step in preparing the program on N/C machine? 3. Convert the following Decimal numbers to Binary numbers: a) 23; b) 92; c) 147; d) 1897 4. Position the tool to cut the hole shown in the figure below, use 3 axis x,y,z motion. 5. Calculate the cutting speed and machining time for all your cutting operation and fill in the form called Machining Data & Machining Cycle Time, see Tab. 3-5 6. Write the instruction for positioning in absolute mode for spot drilling using the spot face cycle. The depth of drilling is 0.195 and the feed rate is 10 inch per minute. 7. Determine the decimal value of the following binary number: (1011) 2 = (?) 10 8. What do the following expressions mean? a) N100 G01 G 81 Z-1.50 F200 b) N55 G00 G91 X0Y0M3 9. Why is the air compressor needed with the Numerical Controlled Milling Machine NASA II? 3-17
SUGGESTED LITERATURE: 1. E. P. De Garmo, J. Temple Black, Ronald A. Kosher, Materials and Processes in Manufacturing, Macmillan, 8-th Edition, New York, 1997 2. L.E. Doyle, Manufacturing Processes and Materials for Engineers, Prentice-Hall, Inc., Third Edition, Englewood, 1980 3. S. Kalpakjian, Manufacturing Processes for Engineering Materials, Addison-Wesley Publishing Co., Reading, Massachusetts, 1990. 4. F.T. Farago, Handbook of Dimensional Measurement, Industrial Press, New York, 1978. 5. J. Pusztai, M. Sava, Computer Numerical Control, Reston Publishing Co., Inc., Reston, Virginia, 1985 6. R.Dubrovsky. Laboratory Manual, Engineering Materials & Processes, ME Department, NJIT, CAPCO, Oklahoma, 1998. 3-18