塑料制品模具设计英文文献和中文翻译(2)
( Psi ) 48-55 (7000-8000) 62-82 (9000-12000) 4 Impact Strength Izod J/mm 0.01-0.018 0.05 -- 0.1 5 Hardness Rockwell R 124-R 128 R 108-R 120 6 Machining Qualities Fair to Good Excellent 7 Melting point 2400 C 2200 C Impact test of knob – After manufacturing impact test of both knobs were performed to find impact strength. The specimen prepared and machine used for impact test is shown in fig.4(A) and 4(B). FIG. 4 IMPACT TEST OF KNOBS (A) Test specimen (B) Impact testing machine Procedure for impact test 1. With the pendulum locked in the state of rest position, grip the test specimen firmly in vice of the impact testing machine. 2. Locate and lock the striking hammer in its topmost striking position. 3. With the help of trigger, the pendulum is released so that the pendulum while striking will knock the specimen and break it. 4. The used energy used to break the specimen was noted from graduated scale of machine into table-3. The difference between initial and final readings represents the residual energy in the pendulum. IV. Results & Tables Table -2 OBSERVATION TABLE Sr. No. Parameter Existing Process Modified Process 1 Material of knob Phenolics (Bakelite) Polyamide – 6 (Nylon – 6) 2 Density (gm / cm3) 1.3 1.13 3 Manufacturing Process Compression Molding Injection Molding 4 Weight of knob 29 gms 25 gms 5 Material cost Rs/kg 45 50 6 Rejection rate 5 % 8 % 7 Flash loss & scrap 6.7 gm /knob NIL due to Recyclable 8 Material required / knob 35.7 gms 25 gms 9 Material cost Rs/knob 1.6065 1.25 10 Die cost for 100000 pieces Rs 30000 12000 11 Molding time (Sec.) 165 30 12 Down time (Sec.) 50 60 13 Cycle time (Sec.) 215 90 14 Electricity consumption 3.5 KWH 2.1 KWH 15 Rate of electricity Rs. 8.5 / KWH Rs. 8.5 / KWH 16 Electricity cost Rs / knob 1.7767 0.4462 17 Labor cost @ Rs 200 / 8 hr. (Rs/knob) 1.4930 0.6250 18 Finishing cost (Rs/knob) 0.01594 NIL 19 Total cost (Rs/Knob) 5.19214 2.3212 20 No. of pieces produced / Hr 16.74 40 Table-3 OBSERVATION TABLE OF IMPACT TEST Sr. No Material Initial impact energy (Joule) Energy used in air & machine friction (Joule) Energy used to break the specimen (Joule) Energy absorbed by specimen (Joule) Residual Energy after impact (Joule) 1 Bakelite 17 0.675 1.55 0.875 15.45 2 Nylon-6 17 0.675 4.1 3.425 12.9 3 Steel 17 0.675 5.8 5.125 11.2 Different parameters observed from the experiment are represented in Fig-5. 35.72502040WEIGHT (Gms)Bakelite Nylon-6Material Consumption 3.52.1024KWHBakelite Nylon-6Electricity Consumption 215900100200300TIME (Sec)Bakelite Nylon-6Cycle Time 16.74400.0020.0040.00UNITSBakelite Nylon-6Production Rate / Hr 5.192.320.005.0010.00RupeesBakelite Nylon-6Cost 0.8753.4255.1250246JOULEBakelite Nylon-6 steelImpact energy absorbed Fig-5 Result analysis V. Conclusion From observation tables and fig-5 we can concluded following main points of research work : 1. By changing product material from Bakelite to Nylon-6, material consumption per knob was reduced from 35.7 gms to 25 gms. So 30% plastic raw material was saved. By using Nylon-6 material and in injection molding process knob can be produced with zero scrap because all the wastage can be recycled and reused due to a thermoplast material. 2. Weight of knob can be reduced from 29 gms to 25 gms due to less density of Nylon-6 material. 3. In injection molding electricity consumption per hour is 3 KWH which is less than 3.5 KWH in compression molding process. During the manufacturing it was not necessary to continuously heat the raw material in barrel, it was equipped with thermostat which remained 30% time off. Hence net electricity consumption was reduced upto 40% compare to compression molding. 4. Cycle time was reduced from 215 sec/knob to 90 sec/knob. Due to this production rate per hour was increased from 16.74 knobs/hour of Bakelite knob to 40 knobs per hour of Nylon-6. Hence productivity was increased by 138.94 %. Material productivity is increased from 62.24 % to 80%. 5. Production cost of Nylon-6 knob was reduced upto Rs 2.87/knob. So production cost was reduced by 55.29%. 6. It was observed in impact test that impact strength of knob was improved by 3.91 times. That means less damage of machine tool lever handle knob in operation. 7. Surface finish of Nylon-6 knob was glossy and this glossy look will remain long lasting. Unlike Bakelite knob no additional surface finish process was required.