Casting Metal Yield
Calculate the metal yield of a casting process, η = (part mass ÷ total poured mass) × 100%, dividing the finished part mass by the total poured metal (part + risers + runners + spills). The result, in %, measures the metal utilization efficiency: the rest (runners, risers, flash) is remelted, but consumes energy and adds cost. Typical yields range from 50 to 80%, depending on the part and gating complexity. Maximizing yield (well-sized risers, optimized gating) cuts energy and remelting costs. Enter the part mass and the total poured mass.
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Casting metal yield
Not all the metal poured into a mould ends up as a usable casting. A good share solidifies in the feeding runners, in the risers (feeders), in the pouring cup and as flash — material that has to be cut off, separated and remelted. Metal yield measures that efficiency: η = (casting mass ÷ total poured mass) × 100%. A yield of 70% means that, for every 100 kg of metal melted and poured, only 70 kg become castings and 30 kg go back to the furnace. That return stream is not lost material (the metal is recycled in house), but it carries a real cost: the energy spent melting the extra metal, furnace wear, the labour of cutting and handling, and cycle time. Maximising yield is therefore a central economic goal in the foundry. Typical yields range from 50% to 80%, depending on complexity: simple, compact castings with little feeding demand reach high yields; complex castings with many heavy sections that call for large risers sit at the low end. Strategies to raise yield include sizing risers by modulus (neither larger nor smaller than needed), using exothermic or insulating risers (which stay liquid longer with less volume), optimising the gating system, and running solidification simulation to place the feeding precisely. There is a balance to strike: trimming risers beyond reason in pursuit of yield causes shrinkage cavities and scrap, which wipes out the gain. Enter the casting mass and the total poured mass.
Related Tools
Gate Area
Calculate the gating channel section area, A = Q ÷ v, dividing the desired metal flow rate Q by the metal velocity v. The result, in the consistent area unit (cm²), is the cross-section the sprue (or gate) must have to deliver the needed flow at the calculated velocity. It is the application of the continuity equation to the casting gating system. Correctly sizing the areas of the system's elements (basin, sprue, runner, gates) controls the flow rate, velocity and flow regime of the metal, avoiding turbulence and ensuring proper filling. The ratios between the areas define the system type (pressurized or unpressurized). Enter the flow rate and the velocity.
Pouring Velocity
Calculate the molten metal velocity at the base of the sprue by Torricelli's equation, v = √(2·g·h), from the metal column height h (m) and gravity g. The result, in m/s, is the velocity at which the metal enters the gating system by gravity, starting from the pouring basin height. It is the basis of gating system design: the velocity sets the flow rate (with the section area) and the flow regime. Velocities too high cause turbulence (air aspiration, oxidation, erosion); hence gating systems are designed to control and slow the flow. Enter the metal column height.
Casting Cooling Modulus
Calculate the cooling modulus (or geometric modulus) of a casting, M = V ÷ A, dividing the volume V by the surface area A in contact with the mold. The result, in cm (length unit), is the parameter governing solidification speed: the larger the modulus, the slower the solidification (Chvorinov's rule says the time is proportional to the modulus squared). It is the basis of riser sizing in foundry — the modulus rule requires the riser modulus to be about 1.2 times that of the part, so it solidifies later and feeds the shrinkage, avoiding shrinkage cavities. Enter the part volume and area.
Mold Fill Time
Calculate the fill time of a casting mold, t = V ÷ Q, dividing the cavity volume V by the metal flow rate Q of the gating system. The result, in seconds, is the time to completely fill the mold with molten metal. It is a critical parameter: filling too slowly lets the metal cool and solidify before filling everything (cold shut, misrun defects), while too fast causes turbulence, gas entrapment, mold erosion and inclusions. The optimal time depends on the part's weight and thickness and the metal. Sizing the gating system for the right time is central to casting design. Enter the cavity volume and the flow rate.
Shrinkage Allowance
Calculate the pattern (mold) dimension accounting for solidification shrinkage, dimension = part dimension × (1 + shrinkage ÷ 100), from the desired final part dimension and the metal's linear shrinkage coefficient (%). The result is the larger dimension the pattern must have so that, upon solidifying and cooling, the part shrinks to the correct size. Each metal has its linear solidification shrinkage: steel ~2%, gray cast iron ~1%, aluminum ~1.3%, bronze ~1.5%. Patternmakers use shrink rules ('contraction rules') already scaled up. Ignoring shrinkage results in undersized parts. Enter the part dimension and the shrinkage coefficient.
Riser Modulus
Calculate the minimum modulus of a riser (feeder) by the modulus rule, M_riser = 1.2 × M_part, from the part's cooling modulus. The result, in cm, is the modulus the riser must have to solidify after the part (about 20% slower) and feed it with molten metal during solidification shrinkage, avoiding shrinkage cavities. The riser is a metal reservoir placed over the thickest region of the part; if it solidifies first, it fails its purpose. From the modulus, the riser geometry is sized. It is a fundamental rule of casting design. Enter the part's cooling modulus.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.