How to use this calculator
- Enter the mold contents. Enter the net casting mass, castings per mold, runner/gate mass and riser mass.
- Set the batch target. Enter the target accepted casting count plus expected reject rate.
- Add melt-shop allowance. Enter the melt or handling loss percent and the user-entered metal price per kilogram.
- Review charge and returns. Use mold count, charge mass, return metal and cost per accepted casting as a first-pass accounting screen.
How it works
The gross yield starts with one mold:
Y_gross = n_c * m_c / (n_c * m_c + m_gate + m_riser)
where m_c is one finished casting mass and n_c
is the number of castings in the mold. This separates useful casting
metal from the gate, runner and riser metal poured with it.
Batch count is rounded up from the target accepted castings: N_molds = ceil(N_good / ((1 - R_j) * n_c)) Batch poured mass is then the mold count times poured mass per mold, and melt charge is increased for melt and handling loss: m_charge = m_p,batch / (1 - L_m)
Return metal is reported as gate, runner and riser metal plus expected rejected casting mass: m_return = N_molds * m_feed + N_reject * m_c It is shown separately because alloy chemistry, dross, remelt percentage, inspection history and melt-shop practice control how much return metal can actually be reused.
Worked example
Verified against the live calculator
Suppose a foundry wants 20 accepted castings. Each casting is 2 kg, the mold has 2 cavities, runner/gate mass is 1.2 kg, riser mass is 1.6 kg, expected rejects are 5%, melt loss is 3% and metal is entered at $6/kg.
Feed-system metal is 1.2 + 1.6 = 2.8 kg, so each mold takes
2*2 + 2.8 = 6.8 kg of poured metal. Gross yield is
4 / 6.8 = 58.82%. The batch needs
ceil(20 / (0.95*2)) = 11 molds, which pours 22 castings and
expects 20.9 accepted castings.
Batch poured metal is 11*6.8 = 74.8 kg. With 3% melt loss,
melt charge is 74.8 / 0.97 = 77.11 kg. The batch generates
about 11*2.8 + 1.1*2 = 33.0 kg of return metal, with an
estimated raw metal charge cost of about $463, or about
$22.14 per expected accepted casting.
Frequently asked questions
What is casting yield?
Casting yield is the finished casting mass divided by the total metal poured into the mold. Gates, runners and risers lower gross yield because they are poured metal that does not become finished casting mass.
What is the difference between gross yield and net batch yield?
Gross yield looks at one mold before reject and melt-loss allowance. Net batch yield compares the expected accepted casting mass with the melt charge required before melt and handling losses.
Does return metal reduce the charge automatically?
No. The calculator reports gates, risers and expected rejected casting mass as return metal, but it does not credit that metal back against the batch charge because remelt limits, alloy control and shop practice vary.
Can this replace foundry methoding?
No. It is a transparent metal-accounting worksheet for early estimates. Riser feeding, gating, freezing pattern, alloy chemistry, dross practice, inspection acceptance and production approval still need foundry-specific review.
Method & assumptions
- Net casting mass is the finished casting mass before gates, runners and risers.
- Castings per mold and target accepted castings are rounded to whole-count values.
- The metal price input is user-entered dollars per kilogram; it is not a live commodity, alloy surcharge or supplier-price lookup.
- Return metal is reported separately and is not automatically credited against the batch charge.
- No alloy chemistry, melt recovery table, remelt limit, riser feeding, gating turbulence, shrinkage rule, chills, inspection acceptance, scrap cause, heat treatment or production-trial approval is modeled.
- Pair this with the casting gating system calculator, Chvorinov solidification time calculator, metal weight calculator and material density chart before detailed foundry methoding.