BIZOMAT MAKEOS · Fabrication
Casting Pour Plan (Riser, Feed Volume, Gating and Ladle)
Will this riser feed the casting, how much metal must I pour including riser and gating, what choke area gives my pour time, and is the ladle big enough?
Plan of a gravity sand casting: casting and riser moduli, solidification times by Chvorinov’s rule and the modulus ratio (as the casting solidification tool), riser volume against the feed volume the casting shrinkage needs at your riser efficiency, metal poured including riser and gating, casting yield, choke area and sprue diameter for the pour time (as the gating choke area tool), pattern dimension with shrinkage, and the ladle capacity check.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Casting | ||
| Casting volume | cm³ | Volume of the casting. |
| Casting cooling surface area | cm² | Surface area through which the casting loses heat. |
| Metal density | g/cm³ | Density of the poured metal (about 7.0 cast iron, 7.8 steel, 2.4–2.7 aluminium alloys). |
| Mould constant | min/cm² | Mould constant in Chvorinov’s rule for the metal and mould (from trials; your value). |
| Volumetric shrinkage to feed | % | Liquid and solidification shrinkage the riser must make up (about 1–2% grey iron, 3–7% steel and aluminium; your value). |
| Riser | ||
| Riser diameter | mm | Diameter of a cylindrical riser. |
| Riser height | mm | Height of the riser. |
| Least riser ÷ casting modulus | Least ratio of riser to casting modulus (often 1.2). | |
| Riser feeding efficiency | % | Share of the riser volume that can actually feed (about 14% open cylindrical, more with insulating sleeves). |
| Gating and pouring | ||
| Sprue, runner and gates as share of casting mass | % | Mass of the gating system as a share of the casting. |
| Pour time | s | Time to pour the mould. |
| Effective sprue height | mm | Effective metal head above the choke. |
| Flow efficiency | Efficiency of flow through the gating. | |
| Runner ÷ choke area | Runner area as a multiple of the choke. | |
| Total gate ÷ choke area | Total gate area as a multiple of the choke. | |
| Ladle capacity | kg | Metal the ladle holds. |
| Pattern | ||
| Part dimension | mm | A part dimension to scale for the pattern. |
| Pattern shrinkage allowance | % | Linear shrinkage allowance for the pattern. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
Casting
What this means: Casting volume
- What it is
- The volume of metal in the cast shape itself, without riser or gating, from the 3D model or casting mass ÷ density. It sets the casting modulus and the feed metal the riser must supply.
- Units and format
- Enter a number in cm³: cubic centimetres. The form accepts 0.000001 cm³ to 100000000 cm³. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2000 cm³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger volume raises the casting modulus and the feed volume needed, so the riser must grow to pass both checks.
- Get it right
- Use the as-cast shape including machining stock, not the finished machined part.
What this means: Casting cooling surface area
- What it is
- The outside surface of the casting that touches the mould and loses heat while it solidifies. The casting modulus is volume divided by this area.
- Units and format
- Enter a number in cm²: square centimetres. The form accepts 0.000001 cm² to 10000000 cm². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 900 cm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More cooling area lowers the casting modulus and solidification time, making the riser modulus check easier to pass.
- Get it right
- Leave out the face where the riser joins the casting, since heat does not leave through it.
What this means: Metal density
- What it is
- The density of the alloy being poured. It turns casting, riser and gating volumes into the mass of metal poured and enters the choke area flow equation.
- Units and format
- Enter a number in g/cm³: grams per cubic centimetre (1 g/cm³ = 1000 kg/m³). The form accepts 0.000001 g/cm³ to 20 g/cm³. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 7 g/cm³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Take it from the alloy data sheet; g/cm³ is numerically the same as tonnes per cubic metre.
What this means: Mould constant
- What it is
- The constant in Chvorinov’s rule, t = B M², linking modulus to solidification time for this alloy, pouring temperature and mould material. It is best found from your own foundry trials.
- Units and format
- Enter a number in min/cm²: min/cm². The form accepts 0.000001 min/cm² to 20 min/cm². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 min/cm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Casting and riser share the same constant, so it scales the times shown but does not change the modulus ratio check.
What this means: Volumetric shrinkage to feed
- What it is
- The loss of volume as the metal cools from pouring temperature to solid, which the riser must make up, as a percentage of the casting volume.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 15%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The feed volume needed rises in direct proportion.
- Get it right
- Use the shrinkage figure for your alloy from foundry data; it varies widely between alloys.
Riser
What this means: Riser diameter
- What it is
- The diameter of the cylindrical riser (feeder) placed on the casting. The tool counts heat loss through the riser’s side and top, not its base where it joins the casting.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 130 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A wider riser raises its modulus, volume and mass: better feeding, but lower casting yield.
What this means: Riser height
- What it is
- The height of the cylindrical riser, from where it joins the casting to its top surface.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 3000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 160 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A taller riser adds feed volume and some modulus, and adds to the metal poured.
What this means: Least riser ÷ casting modulus
- What it is
- The smallest riser modulus divided by casting modulus you accept, so the riser stays liquid longer than the casting and can keep feeding it.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 2. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- This is a ratio of moduli, not of solidification times; the time ratio is its square.
What this means: Riser feeding efficiency
- What it is
- The share of the riser’s volume that can actually flow into the casting before the riser freezes; the rest stays in the riser as solid metal around the shrinkage pipe.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 5% to 60%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 15% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Feed volume needed is casting shrinkage divided by this efficiency, so a lower efficiency calls for a much larger riser.
- Get it right
- Insulating or exothermic sleeves raise it; use the figure from your sleeve supplier or foundry trials.
Gating and pouring
What this means: Sprue, runner and gates as share of casting mass
- What it is
- The mass of the sprue, runners and ingates poured with each mould, as a percentage of the casting mass. It is added to the metal poured and lowers casting yield.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 15% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Pour time
- What it is
- The target time to fill the mould, from the start of pouring until the mould is full. The tool sizes the choke area to deliver all the metal poured in this time.
- Units and format
- Enter a number in s: seconds. The form accepts 0.000001 s to 600 s. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 12 s as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A shorter pour time needs a larger choke area, in inverse proportion.
What this means: Effective sprue height
- What it is
- The effective head of metal driving flow through the choke: the height from the pouring level down to the choke, adjusted for how the mould fills.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The choke area falls with the square root of the head.
- Get it right
- With bottom gating the head falls as the mould fills, so the effective value is lower than the full sprue height.
What this means: Flow efficiency
- What it is
- A factor for friction, turns and contractions that reduces the actual flow through the gating below the ideal free-fall velocity.
- Units and format
- Enter a plain number with no unit. The form accepts 0.3 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.8 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A lower efficiency gives a larger choke area and sprue diameter.
- Get it right
- Use a value from your gating practice or trials; it is a fraction of 1, not a percentage.
What this means: Runner ÷ choke area
- What it is
- Part of the gating ratio: the runner cross-section area divided by the choke (sprue base) area.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 10. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- The current calculation does not use this value in any result; size the runner from the choke area shown.
What this means: Total gate ÷ choke area
- What it is
- Part of the gating ratio: the combined cross-section of all ingates divided by the choke area.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 10. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- The current calculation does not use this value in any result; size the ingates from the choke area shown.
What this means: Ladle capacity
- What it is
- The mass of molten metal the ladle can carry and pour in one go, compared with the total metal poured per mould.
- Units and format
- Enter a number in kg: kilograms. The form accepts 0.000001 kg to 100000 kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 80 kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the safe working fill, allowing for freeboard and slag, rather than the brim capacity.
Pattern
What this means: Part dimension
- What it is
- A casting dimension you want scaled up for the pattern, such as an overall length or a hole centre distance.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The pattern dimension is this value × (1 + shrinkage allowance).
- Get it right
- Add any machining allowance before scaling if the casting will be machined.
What this means: Pattern shrinkage allowance
- What it is
- The pattern maker’s linear shrinkage allowance: how much larger the pattern must be than the casting to allow for the solid metal contracting as it cools.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 5%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- This is linear shrinkage of the solid, not the volumetric feed shrinkage entered above.
Method and formulas
- Modulus M = V ÷ A; solidification time t = B M² (Chvorinov) for casting and riser (as the casting solidification tool).
- Feed volume needed = casting volume × shrinkage ÷ riser efficiency, against the riser volume.
- Metal poured = casting + riser + gating; yield = casting ÷ poured.
- Choke area A = W ÷ (ρ t C_d √(2gh)) with W the metal poured (as the gating choke area tool); pattern dimension = part × (1 + shrinkage).
- Example: the riser modulus ratio is 1.2156; 30.966 kg is poured (45.211% yield) through a 232.66 mm² choke.
Limitations
- Chvorinov approximation with a simple cylindrical riser; feeding distance is not checked.
- Gating ratios and mould constant must come from foundry practice.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Plan the riser and gating for a new casting
- Check a ladle for a heavier casting
- Estimate metal poured per mould
Who it is for
- Foundry engineers
- Pattern makers
- Casting buyers
What you get
- Moduli, solidification times and riser feed volume
- Metal poured, yield and ladle check
- Choke area, sprue and pattern dimension
Interpreting the result
- A sleeve on the riser raises its efficiency and modulus, often halving the metal poured into risers.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1404–1420. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Risers and feeding
In Metal Casting by the Numbers
What it covers: Sizing risers that hold enough metal as well as freezing last: feed volume from shrinkage and efficiency, feeding distance, metal poured, yield, and a riser that piped into the casting.
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Open the Casting Pour Plan (Riser, Feed Volume, Gating and Ladle) calculator