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Vacuum Pumps and Accessories Vacuum Pumps and Accessories WWW.MIDLANDTECHNOLOGIES.COM Vacuum-Assist Die Casting WHY VACUUM-ASSIST The two leading causes for rejection of high pressure castings are poor fill and excessive porosity. Vacuum-assist is an effective tool to combat both poor fill and air porosity when casting aluminum, zinc, magnesium or brass parts that are difficult to fill or have low porosity requirements. DIFFICULT TO FILL LOW POROSITY REQUIREMENTS Thin walls or ribs Pressure sensitive components Sharp angles Structural castings Standing posts Cosmetic parts VACUUM-ASSIST AS A PRODUCTION PROCESS Incorporating vacuum-assist when first quoting a part can help to maximize job profitability and minimize potential loss by ensuring proper air and gas evacuation from the start. PROMOTE AVOID Higher casting yields High fallout rates due to porosity or poor fill Faster job completion with less press time Downtime while troubleshooting More efficient casting processes Resources spent troubleshooting VACUUM-ASSIST AS A CORRECTIVE PROCESS Vacuum-assist can be a highly effective remediation tool when a casting presents unacceptable or undesirable fallout rates due to poor fill or excessive air and gas porosity. Midland Technologies provides the service of reviewing specific casting porosity and fill issues to evaluate applicability of vacuum-assist. GETTING STARTED WITH VACUUM-ASSIST STEP 1: Complete and submit a Vacuum Block Sizing Form (found on our website). If available, please send us a 3D model of the part and shot. If you have an existing casting with porosity or fill issues, please include a picture of the problem where possible. STEP 2: Midland will calculate the required evacuation area for the casting and then recommend the correct Valve-Less Vacuum Blocks. If it is an existing casting, Midland will first evaluate the casting issue to determine if vacuum-assist is likely to help. STEP 3: Provide a 3D layout of the die with a purchase order for the recommended Valve-Less Vacuum Blocks. Midland will provide you with a recommended vacuum block exit runner layout to help ensure optimal function. C2 MIDLAND TECHNOLOGIES, INC. Vacuum-Assist Die Casting BASIC PRINCIPLE OF VACUUM-ASSIST CASTING Vacuum-assist operates by means of a pressure differential. A vacuum pump creates a vacuum atmosphere within a receiver tank that will contain less matter than the ambient atmosphere. The volume of air that is present within the cavity and shot sleeve (VC) will move to fill the lower pressure receiver tank at a theoretical maximum speed (vs) of 340 m/s. The exit flow rate of air (Rv) from the die is limited by the smallest area of the exit orifice (A) in the mold set. If the volumetric flow rate of air is assumed to be constant, then the time required to evacuate the cavity (te) can be approximated as: When utilizing Valve-Less Vacuum Blocks, the pathway between the vacuum receiver tank and the die is governed by a solenoid valve. The solenoid valve is opened using a PLC, limit switch or timer when the pour hole of the shot sleeve is covered by the plunger. Valve-Less Vacuum Blocks allow the pathway to remain open throughout solidification to simplify process planning. SIZING VACUUM PUMPS AND RECEIVER TaNKS Correctly sizing vacuum pumps and receiver tanks for specific applications is critical to proper function. Vacuum pumps generate the vacuum level within a defined volume that is the receiver tank. Vacuum level is measured in relation to ambient atmospheric pressure and reported in units such as Torr, inches of mercury (“Hg), Pascals (Pa) or millibar (mb). The critical feature of the pump is the speed at which it can evacuate a volume of air down to a particular vacuum level as measured by average cubic feet per minute. If the pump is too small, it will not be able to achieve sufficient vacuum within the shot cycle. If the tank is too small, it will not provide a sufficient reservoir to evacuate air from the cavity. Midland Technologies can calculate the required pump and tank size for your specific casting application. CHECKLIST WHEN UTILIZING VACUUM __ Vacuum pump is properly sized for the casting application __ Correct size and quantity of vacuum blocks provide sufficient area for evacuation __ Proper vacuum block runner design from the cavity to manage velocity __ Vacuum blocks are correctly installed in the die __ Proper filtration between the press and the vacuum pump __ Proper maintenance is performed on vacuum blocks, pump, filters and hoses __ Floor operators understand how to turn the vacuum process on and off (763) 428-4229 | MIDLANDTECHNOLOGIES.COM C3 Vacuum-Assist Casting Process with Valve-Less Blocks THE ADvaNTAGE OF vaCUUM-ASSIST DIE CASTING WITH VALVE-LESS VACUUM BLOCKS IS SIMPLICITY! Filters STEP 1 – Pre-INJECTION Closed • Solenoid is closed 1.0” or 1.5” dia. hose x 15’ • Vacuum pump evacuates the receiver tank down to vacuum level • Die is in the closed position Filters STEP 2 – EvaCUATION OF CavITY/INJECTION • Injection begins Open 1.0” or 1.5” dia. • Solenoid on vacuum system opens when plunger tip hose x 15’ covers pour hole • Air evacuates from the sleeve and cavity through the vacuum block Slowing down the slow shot can increase time for air evacuation Filters Open STEP 3 – SOLIDIFICATION 1.0” or 1.5” dia. Hose x 15’ • Cavity fill and solidification Vacuum can remain on throughout solidification for process simplicity and to ensure maximum evacuation STEP 4 – CASTING EJECTION/RECOVERY Filters • Solidification complete Closed 1.0” or 1.5” dia. • Solenoid on vacuum system closes Hose x 15’ • Die opens and casting is ejected • Vacuum pump recovers vacuum level in receiver tank as necessary • Cycle repeats C4 MIDLAND TECHNOLOGIES, INC. Vacuum Pump Sizing Form MIDLAND WILL PROVIDE A RECOMMENDED VACUUM SYSTEM WHEN THE INFORMATION BELOW IS SUPPLIED. VISIT WWW.MIDLANDTECHNOLOGIES.COM TO FILL OUT AND SUBMIT THE FORM BELOW ONLINE. Contact Name: _____________________________________________ Title: _____________________________________________________ Company: _________________________________________________ Phone: ___________________________________________________ Email: ____________________________________________________ Number of machines that will be connected to the system: _________________________ Anticipated number of machines that will be connected to the system in the future:_______ Tonnage of all presses to be connected: _____________________________________ Pump motor voltage required:_____________________________________________ SIMPLICITY & RELIABILITY (763) 428-4229 | MIDLANDTECHNOLOGIES.COM C5 Portable System Configuration MIDLAND CAN SUPPLY A RANGE OF PORTABLE vaCUUM SYSTEMS IN vaRIOUS CONFIGURATIONS AND SIZES FOR DIFFERENT CASTING APPLICATIONS. FL-0016 FL0016 Media Filter Vacuum Vacuum Prefilter Vacuum Gauge Gauge VacuumGauge Gauge(Optional) (Optional) FL-0803 KnockdownFL0803 Manual Valve 1” ID Hose x 10’ Solenoid Filter 1” or 1.5” ID Hose x 15’ Vacuum Pump Vacuum Solenoid Filter Vacuum Pump Valve VacuumGauge Valve Gauge ** Connect Air **Connect Air ReceiveReceiver r forfor Air Air Assist Assist 1” or 1.5” ID 1.0" I.D. or 1.5" Dia. Hose x 15' Use 1" NPT Tee Hose x 15’ if usingUse 1” 2 NPT or moreTee Vacuumif using 2 Block or mores Valve-Less vacuum blocks Vacuum Block Valve-Less Vacuum Block C6 MIDLAND TECHNOLOGIES, INC. Pump Sizes and Configurations PORTABLE AND CENTRAL vaCUUM SYSTEMS ARE avaILABLE IN THE FOLLOWING SIZES AND CONFIGURATIONS. MIDLAND CAN HELP YOU TO SELECT THE PUMP SIZE APPROPRIATE FOR YOUR CASTING APPLICATIONS. CONFIGURATION OPTIONS Horizontal Tank Mounted* - One pump mounted horizontally on receiver tank Vertical Tank Mounted - One pump mounted on a vertical standing receiver tank Tank Mounted Duplex - Two pumps mounted on a horizontal receiver tank *Horizontal tank mounted is the standard configuration for Midland vacuum systems PORTABLE Systems – OIL-SEALED, ROTARY vaNE PUMPS CENTRAL Systems – DRY CLAW vaCUUM PUMPS Pumps are available with 208, 230 or 460 volt starters Oil-sealed, rotary vane pumps can be ordered customized to be H2O cooled (763) 428-4229 | MIDLANDTECHNOLOGIES.COM C7 Troubleshooting POOR CavITY FILL OR CONTINUED POROSITY Poor cavity fill or continued porosity can result from a variety of process and engineering factors. In the case of vacuum-assist die casting, poor cavity fill or continued porosity can result when there exists a blockage or failure to achieve an open flow path between the cavity and the vacuum tank. This can result in a failure to evacuate the cavity. Note that significant die leakage can also introduce enough air to overcome the ability of the vacuum pump to achieve sufficient vacuum levels. When troubleshooting, it is recommended to first ascertain the level of vacuum being achieved in the die cavity for reference. This can be done by placing a rubber mat over the pour hole of the sleeve while the die is in the closed condition. Slit the rubber mat and place a vacuum gauge within the slit. Turn the vacuum pump on, ensure the tank is at vacuum pressure, and activate the system by opening the solenoid. Check the vacuum gauge at the pour hole to determine if an effective vacuum level has been obtained through the cavity. BLOCKAGE IN HOSES AND FILTERS Excessive velocity as alloy exits the cavity and reaches the Valve-Less Vacuum Blocks can result in metal passing through the block and into the vacuum hose. If the quantity of metal is excessive, it may be necessary to install a filter close to the block. This will require regular cleaning of the filter so as to maintain a free outflow of air from the cavity. Alternatively, the hose can be disconnected and cleaned out as necessary. The optimal solution is a review of exit gating and vacuum block runners, and redesign as necessary to manage metal velocity. Midland can offer technical assistance in this area. FaILURE TO ACHIEVE EXPECTED VACUUM LEVEL AT PUMP If the vacuum pump is not achieving the expected level of vacuum within the receiver tank, check to ensure that all drain valves are closed.
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