The tale of the tape: All-electric vs. hydraulic
Canadian Plastics
According to manufacturers, electric injection molding machines are more efficient. But how much more efficient? The following table compares operating costs for molding a 430 gram part made of polyst...
According to manufacturers, electric injection molding machines are more efficient. But how much more efficient? The following table compares operating costs for molding a 430 gram part made of polystyrene on an Ube Machinery Inc. 720 ton electric versus a 720 ton hydraulic machine. The comparison makes assumptions about electricity costs and operating conditions. The calculation can be customized for a molder’s operation by substituting specific values for machine and operating conditions. Savings vary according to the size (tonnage) of the machine. Ube estimates the average pay-off time for an all-electric machine to be about three to five years.
COST SAVINGS COMPARISON*
720 ton electric | 720 ton hydraulic | |||
Electricity Consumption | 13.4 | 57.6 | ||
(kwh) | ||||
Savings/month | $1,166.88 | |||
Calculation | (Hyd-Elec.)kw x 20 hr. x 22 days x elec. cost/kw | |||
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Cycle Time (sec) | 30.1 | 32.8 | ||
Reduction rate | 8.2% | |||
Savings/month | $1,195.24 | |||
Calculation | Machine Only Charge ($/hr) x reduction % x 20 hr. x 22 days | |||
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Cooling Water (gal/min) | 2.65 | 47.55 | ||
Savings/month | $118.54 | |||
Calculation | (Hyd-Elec.) x 60 x 20 hr. x 22 days x water $/gal | |||
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Hydraulic Oil (gal) | 0 | 330 | ||
Savings/month | $96.97 | |||
Calculation | (Oil quantity x oil $ + $1,000 oil change) / 24 | |||
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Scrap Rate (%) | 0.5 | 1.5 | ||
Savings/month | $145.20 | |||
Calculation | Machine Only Charge $/hr. x (Hyd. Scrap – Elec. Scrap ) x 20 hr. x 22 days | |||
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Production Start Up (shots) | 10 | 30 | ||
Saving month | $484.00 | |||
Calculation | Machine Only Charge $/hr./60 (1 min/shot) x 20 shots x 2 times x 22 days | |||
Monthly Savings | $3,206.53 | |||
Yearly Savings | $38,478.32 | |||
ASSUMED OPERATING CONDITIONS
Machine Only Charge ($/hr.) | $33 | |
Work hours/day | 20 | |
Work days/month | 22 | |
Price per shot | $0.27 | |
Water cost (G) | $0.0001 | |
Electricity cost (kwh) | $0.06 | |
Hydraulic Oil (G) | $4.00 | |
*Figures based on Michigan rates in U.S. dollars provided by Ube Machinery Inc.