The filtering cycle is completely automatic, triggered by a signal from an automatic ladler or the operator. A large supply of mesh filter fabric is continuously fed to the machine from a supply coil. A large filter coil can provide for hours of operation without human operator assistance. As the filtering cloth exits the machine, the amount of slag, dross, and other impurities can be seen in the dross “biscuit” captured by the fabric.
Fiberglass mesh fabric is an effective, proven, and inexpensive material that can be used for the filtration of non-ferrous metals whose temperatures do not exceed approximately 1350 degrees Fahrenheit or 732 degrees Celsius.
The degree of filtration is determined by the particular mesh size or openings in the fabric and the total working area of the filter. Some experimentation may be necessary at first to determine the correct mesh size for the particular foundry or application, since each foundry can have different amounts of dross or impurities inherent to their metal. The mesh size will also affect the flow rate of the metal through the machine. For example, if a very small mesh size is selected and themetal to be filtered contains a large amount of dross, the filter will collect the dross and impurities and the flow rate will decrease. When the filtration requirements dictate a small mesh size, a larger working (or “active”) area may be required to maintain an adequate flow rate.
Fabric Selection Chart
|Fiberglass Mesh Code||# Holes / Sq. In.||Hole Size(Sq. In.)||% Open Area||Typical Aluminum Flow Rate (lb / second / Sq. In.)
Alloy 380 at 1300F (1350F)
|FL & FP 36||81||.008||48.2||.46 – .91|
|FL & FP 40||144||.0031||39.1||.46 – .91|
|FP 43||182||.002||33.3||.23-.36 (.37-.48)|
|FP 55||289||.0013||37||.30 (.26-.37)|
The Alum-A-Filter is a heavy duty machine built to last in the harsh molten metal environment. The primary fabrication is comprised of steel and aluminum used in combination to provide high strength and maintain a light weight. All operating components are easy to access and replace as necessary.
The standard unit is a fixed position unit that would be placed directly over the pouring orifice. Options include swivel mounting, powered swivel, and any other necessary mechanical configuration to suit your exact needs.
The pouring basin and directing basin for the Alum-A-Filter are comprised of heavy iron castings precision machined on the seal surface to prevent run-outs. Each basin is also fitted with dual electric cartridge heaters to maintain a constant cup temperature (+/- 2 degrees F), ensuring that the metal is not chilled in the basins. A digital temperature controller and thermocouple mounted directly to the pouring cup monitor and control the basin temperature for accurate control.
The primary control for this unit is an Allen-Bradley MicroLogic-1000 PLC Processor. The PLC controls all functionality and timing of the unit. A three line DTAM display allows operator interface to the timing settings to adjust the machine to the applications exact needs. Wherever possible, Allen Bradley components have been used for their high quality and broad availability.
The pouring basin heating elements are controlled by a high accuracy digital temperature controller for precise basin temperature control. Each element circuit is fitted with a power status indicator. This allows convenient trouble shooting of elements if there is a burned out element or other process problem.
Both the filter cloth advance and pouring cup actuation are controlled by pneumatic devices, a high torque air motor and a short stroke, high-temperature cylinder for basin control. Pneumatic units are used for their simplicity and ruggedness. Dual air solenoid valves located in the primary control enclosure operate these devices. Each function is fully speed adjustable.
Die Casting– Metal filtration can be performed directly at the charge port of a shot tube on cold chamber die casting machines.
Permanent Mold Casting– The filter machine can be easily adapted to fit many permanent mold casting operations and provide automatic metal filtration for each pour.
Ingot and Pigging Operations– The machine can be positioned over the moving molds of a pigging line to filter metal going into each mold.
Sand Casting– The filter machine is easily adapted to mount over a pouring line of a automated green sand or no-bake molding machine. The only critical feature of this usage is that the sprue be consistently located.
Description of Operational Process
- Machine awaits entry of molten metal from ladler or operator
- Once metal is poured, a timer engages holding the machine long enough for the slag biscuit to partially solidify
- The pouring cup raises, freeing itself from the fabric
- The indexing air motor indexes the filtering fabric
- The pouring cup lowers and the machine awaits the next cycle