MANUFACTURING PROCESS - CASTING TERMS

CASTING TERMS

1. FLASK: A METAL OR WOOD FRAME, WITHOUT FIXED TOP OR BOTTOM, IN WHICH THE MOLD IS FORMED. DEPENDING UPON THE POSITION OF THE FLASK IN THE MOLDING STRUCTURE, IT IS REFERRED TO BY VARIOUS NAMES SUCH AS DRAG – LOWER MOLDING FLASK, COPE – UPPER MOLDING FLASK, CHEEK – INTERMEDIATE MOLDING FLASK USED IN THREE PIECE MOLDING.
2. PATTERN: IT IS THE REPLICA OF THE FINAL OBJECT TO BE MADE. THE MOLD CAVITY IS MADE WITH THE HELP OF PATTERN.
3. PARTING LINE: THIS IS THE DIVIDING LINE BETWEEN THE TWO MOLDING FLASKS THAT MAKES UP THE MOLD.
4. MOLDING SAND: SAND, WHICH BINDS STRONGLY WITHOUT LOSING ITS PERMEABILITY TO AIR OR GASES. IT IS A MIXTURE OF SILICA SAND, CLAY, AND MOISTURE IN APPROPRIATE PROPORTIONS.
5. FACING SAND: THE SMALL AMOUNT OF CARBONACEOUS MATERIAL SPRINKLED ON THE INNER SURFACE OF THE MOLD CAVITY TO GIVE A BETTER SURFACE FINISH TO THE CASTINGS.
6. CORE: A SEPARATE PART OF THE MOLD, MADE OF SAND AND GENERALLY BAKED, WHICH IS USED TO CREATE OPENINGS AND VARIOUS SHAPED CAVITIES IN THE CASTINGS.
7. POURING BASIN: A SMALL FUNNEL SHAPED CAVITY AT THE TOP OF THE MOLD INTO WHICH THE MOLTEN METAL IS POURED.
8. SPRUE: THE PASSAGE THROUGH WHICH THE MOLTEN METAL, FROM THE POURING BASIN, REACHES THE MOLD CAVITY. IN MANY CASES IT CONTROLS THE FLOW OF METAL INTO THE MOLD.
9. RUNNER: THE CHANNEL THROUGH WHICH THE MOLTEN METAL IS CARRIED FROM THE SPRUE TO THE GATE.
10. GATE: A CHANNEL THROUGH WHICH THE MOLTEN METAL ENTERS THE MOLD CAVITY.
11. CHAPLETS: CHAPLETS ARE USED TO SUPPORT THE CORES INSIDE THE MOLD CAVITY TO TAKE CARE OF ITS OWN WEIGHT AND OVERCOME THE METALLOSTATIC FORCE.
12. RISER: A COLUMN OF MOLTEN METAL PLACED IN THE MOLD TO FEED THE CASTINGS AS IT SHRINKS AND SOLIDIFIES. ALSO KNOWN AS “FEED HEAD”.
13. VENT: SMALL OPENING IN THE MOLD TO FACILITATE ESCAPE OF AIR AND GASES.

STEPS IN MAKING SAND CASTINGS

THERE ARE SIX BASIC STEPS IN MAKING SAND CASTINGS:

1. PATTERNMAKING
2. CORE MAKING
3. MOLDING
4. MELTING AND POURING
5. CLEANING

PATTERN MAKING

THE PATTERN IS A PHYSICAL MODEL OF THE CASTING USED TO MAKE THE MOLD. THE MOLD IS MADE BY PACKING SOME READILY FORMED AGGREGATE MATERIAL, SUCH AS MOLDING SAND, AROUND THE PATTERN. WHEN THE PATTERN IS WITHDRAWN, ITS IMPRINT PROVIDES THE MOLD CAVITY, WHICH IS ULTIMATELY FILLED WITH METAL TO BECOME THE CASTING. IF THE CASTING IS TO BE HOLLOW, AS IN THE CASE OF PIPE FITTINGS, ADDITIONAL PATTERNS, REFERRED TO AS CORES, ARE USED TO FORM THESE CAVITIES.

CORE MAKING

CORES ARE FORMS, USUALLY MADE OF SAND, WHICH ARE PLACED INTO A MOLD CAVITY TO FORM THE INTERIOR SURFACES OF CASTINGS. THUS THE VOID SPACE BETWEEN THE CORE AND MOLD-CAVITY SURFACE IS WHAT EVENTUALLY BECOMES THE CASTING.

MOLDING

MOLDING CONSISTS OF ALL OPERATIONS NECESSARY TO PREPARE A MOLD FOR RECEIVING MOLTEN METAL. MOLDING USUALLY INVOLVES PLACING A MOLDING AGGREGATE AROUND A PATTERN HELD WITH A SUPPORTING FRAME, WITHDRAWING THE PATTERN TO LEAVE THE MOLD CAVITY, SETTING THE CORES IN THE MOLD CAVITY AND FINISHING AND CLOSING THE MOLD.

MELTING AND POURING

THE PREPARATION OF MOLTEN METAL FOR CASTING IS REFERRED TO SIMPLY AS MELTING. MELTING IS USUALLY DONE IN A SPECIFICALLY DESIGNATED AREA OF THE FOUNDRY, AND THE MOLTEN METAL IS TRANSFERRED TO THE POURING AREA WHERE THE MOLDS ARE FILLED.

CLEANING

CLEANING REFERS TO ALL OPERATIONS NECESSARY TO THE REMOVAL OF SAND, SCALE, AND EXCESS METAL FROM THE CASTING. BURNED-ON SAND AND SCALE ARE REMOVED TO IMPROVED THE SURFACE APPEARANCE OF THE CASTING. EXCESS METAL, IN THE FORM OF FINS, WIRES, PARTING LINE FINS, AND GATES, IS REMOVED. INSPECTION OF THE CASTING FOR DEFECTS AND GENERAL QUALITY IS PERFORMED. 

References :- www.nptel.iitm.ac.in