Casting process planning involves selection of the most appropriate casting process, and the various steps and parameters involved. Early process planning, preferably before freezing the final design of the cast part, combined with product-process compatibility analysis enables minor modifications to part design that can significantly reduce the overall cost.

Preliminary casting process planning involves deciding the methods, major operations and key parameters (quality checks) for each activity in casting production. Detailed casting process planning involves step-by-step work instructions related to individual operations specifying the sequence and duration of operations, equipment, and resources (material, energy and labour) required. Important activities in sand casting process include mould sand preparation, core sand preparation, moulding, core making, melting, pouring, shakeout, fettling and cleaning. Key parameters involved in these activities are outlined here.

Mould sand preparation and core sand preparation involve selecting the sand type and ingredients, mixing them in an appropriate proportion, processing, checking the resulting properties of the sand mix, and adding more ingredients (if necessary and possible). The ingredients and processing depend on the method (green sand, dry sand, sodium silicate, no bake, hot box, cold box, etc.). These affect sand properties such as permeability, green strength, dry strength, flowability and collapsibility. These in turn affect casting quality. For example, low green sand strength may lead to sand inclusions, and low permeability coupled with high moisture content may lead to blow holes.

Moulding involves compacting the moulding sand around a pattern. The mould layout (mould size and number of cavities per mould) must be decided to obtain an optimal sand to metal ratio: a high ratio leads to higher sand cost, whereas a low ratio may lead to solidification related problems. Process parameters related to moulding include compaction pressure and time, heating temperature (if necessary), and weight to be placed on the mould to prevent lifting of cope. Major quality checks include mould hardness and finish.

Core making involves compacting sand into a core box followed by some processing depending on the method. Key process parameters are heating temperature and curing time for hot box; drying temperature and curing time for cold box and no bake process; heating temperature and curing time for shell core; and gas quantity, blowing pressure and blowing time for sodium silicate core. Quality checks include surface finish and core hardness.

Melting activity involves furnace preparation and charging. Furnace preparation deals with furnace lining and preparation of coke bed (for cupola). Charging involves addition of metal ingots, scrap and alloying elements in the furnace to get the desired composition. Metal charge composition is the most important parameter in melting activity.

Pouring involves transfer of liquid metal from furnace to ladle and pouring into mould cavities. Key process parameters are pouring temperature, pouring time, pouring height and use of exothermic materials. This is perhaps the single most important activity affecting casting quality. Fast pouring leads to turbulence, causing higher oxidation, air entrapment and mould erosion; slow pouring coupled with low pouring temperature leads to poor fluidity, causing cold shuts and misruns.

Shakeout and cleaning operations begin after casting solidification, the time for which depends on the casting alloy, weight, geometry and process. Shakeout involves separating the sand from the casting. This is followed by fettling and cleaning. During fettling, the gating and feeding elements are removed from the casting by gas cutting or chipping. The casting is then cleaned by shot blasting, grinding, tumbling, sand blasting or hydro blasting to remove adhering sand particles and burrs. Key process parameters include as blast speed, water pressure and ball size depending on the equipment used and surface finish required.

There are two main approaches for process planning: generative and variant. Generative casting process planning involves automatic generation of process plan for a new part based on detailed manufacturing information stored in a database along with decision-making logic. The logic is however, difficult to evolve and implement in practice. Variant process planning uses group technology: the grouping of a new part is identified, based on which a standard process plan is retrieved and applied. The standard plan may not however, be suitable for the new part.