Riser Modulus and the Feeding Volume Check

The first is modulus -- volume over cooling surface area, a length that stands in for solidification time. A riser must solidify AFTER the section it feeds, so its modulus must exceed the casting's by a ratio commonly around 1.2, and a cylindrical riser of height equal to its diameter reaches a modulus of about a sixth of that diameter. The second is VOLUME: the riser must actually contain enough liquid metal to make up the solidification shrinkage, which for many alloys is a few percent of the casting volume, and a riser only delivers a fraction of its own contents before its feeding path closes. A riser that satisfies the modulus condition and fails the volume one stays liquid and still runs out of metal, and the porosity appears directly under the riser. That defect looks like a feeding failure and is a volume failure, and the two are corrected differently -- which is why both are reported here and why sizing on one condition alone means sizing on whichever happened to be the easier. Modulus is a shape argument rather than a size argument, and that is what makes it useful. A thin plate and a thick bar of the same volume have quite different moduli, so the section that needs feeding is not always the heaviest one, and a riser placed on the heaviest section can leave a thinner one unfed. The insulating or exothermic sleeve is the lever worth knowing. It raises the riser's effective modulus without raising its size, so the same feeding is achieved from a smaller riser -- which lifts the casting yield without giving up soundness, and is the move that resolves the yield-versus-quality tension rather than trading one side against the other. This computes a modulus for a rectangular section and a cylindrical riser at an entered ratio. It does not identify which sections need feeding or how many risers a casting takes, compute feeding DISTANCE (how far along a section a riser reaches, which is a separate limit and a common cause of porosity midway between risers), model directional solidification, chills, or padding, select a sleeve or supply its factor, size the gating, or account for the riser neck, which is where feeding is most often lost. A solidification simulation, the alloy's own shrinkage data, and the methods engineer govern.

casting modulus = volume / cooling surface area; the riser modulus must exceed it by an entered ratio (commonly about 1.2), and a cylindrical riser of height equal to its diameter has a modulus of about d/6. The VOLUME condition runs alongside: riser volume >= casting volume x solidification shrinkage / feeding efficiency.

Riser sizing on Chvorinov's modulus rule with the volume check that accompanies it. The modulus ratio, the alloy shrinkage, the feeding efficiency and any sleeve factor are all ENTERED.

Two published rules and one geometric relation.

Estimate. AHJ and licensed professional govern.

Field names used by the API: section_length_in, section_width_in, section_thickness_in, modulus_ratio, shrinkage_pct, riser_efficiency_pct, sleeve_factor, section_volume_in3, section_surface_in2, casting_modulus_in, riser_modulus_in, riser_diameter_in, riser_volume_in3, volume_needed_in3

• Rectangular section, cylindrical riser real geometry needs a solidification simulationa casting simulation
• Feeding DISTANCE is not computed how far a riser reaches along a section is a separate limitthe methods engineer
• The riser neck is not sized and is where feeding is most often lostthe methoding drawing