Chris Collins

Tools · casting

Foundry: metal casting calculator

Metal casting for a hobby foundry — an alloys table with pouring temperatures, shrink and hazards; metal needed from a volume, an STL or a pattern's weight (the wax-to-metal rule) with crucible size and number of melts; sand-casting allowances, Bernoulli choke area, pouring time, gating ratios and Chvorinov risers, flask and sand mix; investment powder and water and wax or PLA burnout schedules on a graph; lost foam; the energy, fuel and time to melt; a crucible-furnace build; and a printable safety checklist.

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How to use it

The numbers I want at the furnace, in one place: how much metal to melt and whether it fits the crucible, how big to make the sprue and riser, how much investment to mix and how long the burnout takes, and how much propane it will cost. Pick the alloy at the top; every tab uses it. Work in °C, mm and kg or °F, inches and pounds — the choice is remembered, and so is everything you type.

How to use it

  1. Alloys. Choose the metal. Each one shows its density, melting range, a conservative pouring range, the flask temperature for investment casting, the patternmaker’s shrink, what helps it cast (flux, degassing, deoxidising) and what can hurt you. Tap a row of the table to switch. The Never melt list is there for a reason: beryllium copper and cadmium-bearing scrap are not a matter of ventilation.

  2. Metal needed. Enter the casting’s volume, or load an STL (the volume is computed in your browser; it needs a closed mesh), or weigh the pattern and choose its material — metal = pattern weight × (metal SG ÷ pattern SG), which for wax is the jeweller’s rule (sterling ≈ wax × 10.4). Add the gating as a percentage, the risers (the Sand casting tab can fill this in) and a spare. You get the melt, the smallest A-size crucible that holds it, and how many melts your crucible needs. The crucible sizes use the usual rule of thumb — the number is about the pounds of aluminium it holds, roughly three times that in bronze — so check your crucible maker’s table.

  3. Sand casting.

    • Pattern allowances: the shrink scale (pattern = casting × (1 + shrink)), machining stock, and how much a draft angle widens a pocket.

    • Gating: the sprue height, basin depth and where the gate enters give the effective head; with the poured weight and a pour time (from t = K√W, or your own) Bernoulli gives the choke area. The gating ratio sizes the sprue base, runner and ingates, and the tool checks the ingate velocity — aluminium wants it under about 0.5 m/s so the oxide skin isn’t folded in.

    • Riser: Chvorinov’s rule — the riser’s modulus V/A at 1.2 × the casting’s — and a check that it holds enough liquid to feed the shrinkage. Use the casting’s shape, or the loaded STL. Use this riser weight puts it into the metal total.

    • Flask and sand: flask size from the pattern and the clearances, sand to fill it, and a greensand or oil-bonded mix by weight.

  4. Investment. Tree size → the smallest standard flask; powder and water for it at the product’s water : powder ratio (editable; 38–40 : 100 for most gypsum investments); working time. The burnout schedule starts from a typical wax, PLA or castable-resin schedule ending at the flask temperature for your alloy; edit any segment and the graph, the total time and the gypsum limit (732 °C) follow. Open in the kiln tool sends the same schedule to the kiln and firing calculator.

  5. Lost foam. Metal from the foam pattern’s volume, what the foam weighs, and notes on foam density, coatings, gating and pouring temperature.

  6. Furnace. Heat to melt the charge (sensible heat to the liquidus, latent heat, superheat to the pour, plus the crucible), then propane, charcoal or electricity at an efficiency you set, and the time at your burner’s power. The build calculator sizes a cylindrical crucible furnace round your crucible: chamber, steel shell, castable and blanket quantities, and a rule-of-thumb burner size.

  7. Safety. A checklist to tick through before a pour, and Print the checklist for the wall by the furnace.

The numbers are starting points from published data and common practice, chosen to be on the safe side. Jewellery alloys and investments vary by maker: when the supplier’s sheet disagrees, the sheet wins, and you can type over any default.

Related tools: designing the mould pieces themselves (parting, sprue, risers and vents for a printable mould) is the mold maker; the lathe and metal calculator has a shrink-rule table; metal weight for bar stock; plating for finishing. For silicone moulds and resin, plaster, concrete, candles and soap see mould making, resin casting, concrete casting and candles and soap.

Browser support

Any current browser. STL loading uses the site’s own mesh reader; nothing else is fetched.

Sharing a set-up

Every field can go in a link (Share link), so a set-up — an alloy, a pattern weight and a burnout, say — opens the same for someone else. The short names are the ones in the page’s state, for example 4 g of wax in sterling or a lost-PLA burnout for aluminium.

Privacy

Everything is calculated in your browser. An STL you load is read locally and never uploaded; what you type is kept in this browser’s local storage.

Runs entirely in your browser; nothing you type leaves this page.