Canadian Plastics

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
________________________________________________________________________________
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
________________________________________________________________________________
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
________________________________________________________________________________
Hydraulic Oil (gal) 0 330
Savings/month $96.97
Calculation (Oil quantity x oil $ + $1,000 oil change) / 24
________________________________________________________________________________
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
________________________________________________________________________________
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.

Advertisement

Advertisement

Stories continue below

Print this page

Related Stories