Technology that employs a variable-speed hydraulic pump rather than throttling to meet varying cycle demands.
Die casting is a common method of light metal processing that is used to produce accurately dimensioned, sharply defined metal parts. Most die casting machines use a hydraulic system to perform process work. Pressure and flow rate demands on the hydraulic system vary significantly throughout the cycle or time required for the repetitive sequence of mold closing, toggle lock, idle, shot, hold, mold open and idle. Many older systems are greatly oversized to meet the peak hydraulic demand at any point. These systems operate inefficiently because there is no way to limit the hydraulic capacity during periods of low demand. Fluid is typically throttled to lower pressures and excess fluid flow is routed directly back to the system reservoir, wasting energy and increasing the thermal load on the cooling system.
Adjustable speed drive (ASD) retrofits can improve the efficiency of older die casting machines currently in use. An ASD allows the speed of the pump motor to be varied, changing the pump output to suit the cycle demands. This minimizes the amount of wasted energy without affecting other process parameters.
For a die casting machine with constant displacement pumps, energy savings are typically 22% to 45% of pre-retrofit energy consumption. A study of four die casting machines that were retrofitted with ASD control indicated an average savings of 35.2%. Savings increase when multiple pump motors are deployed and cycle times are long. If variable displacement pumps are used for the baseline scenario, energy savings are generally less than 20% of pre-retrofit energy use. Processes with cycle times below 15 seconds should not be considered for an ASD retrofit.
Status:
Baseline Description: Die Casting Machine with Constant Displacement Pump driven by 75 hp Motor Baseline Energy Use: 151710 kWh per year per unit
The baseline energy use assumes a 75 hp hydraulic constant speed hydraulic motor that is 64% loaded on average and that is in a plant that runs for 2 shift/5 days per week (4000 operating hours total per year). For a die casting machine with constant displacement pumps, energy savings are estimated at 22% to 45% of pre-retrofit energy consumption. A study of four die casting machines that were retrofitted with ASD control indicated an average savings of 35.2%
"Typical" Savings: 35% Energy Savings Reliability: 3 - Limited Assessment
Energy Use of an Emerging Technology is based upon the following algorithm. Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Lawrence Ambs, 06/20/2005. Improving the Efficiency of Die Casting Machine Hydraulic Systems with the Retrofit of Adjustable Frequency Drives University of Massachusetts
Foundry, 04/04/2012. Energy-Efficient Diecasting Machine Foundry Magazine
Kenneth Korane, 06/14/2012. Energy-Efficient Hydraulics Slash Operating Costs Machine Design.com
Al Presher, 02/21/2011. New Variable Speed Pump Design Reduces Energy Use Moog Design News – Fluid Power/Power Transmission