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.
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Mold fill time
The fill time — how long the molten metal takes to completely fill the mold cavity — is one of the most critical parameters in casting, and its basic calculation is simple: t = V ÷ Q, the volume of the cavity divided by the flow rate that the gating system delivers. What makes this time so important is that it has a narrow optimum window, with severe defects at both extremes. If filling runs too slow: the metal loses heat along the way and may start to solidify before everything is filled, causing a misrun (the casting comes out incomplete) or a cold shut (two partially solidified metal fronts meet but fail to fuse, leaving a line of weakness). Thin sections are the most vulnerable. If filling runs too fast: the metal enters at high velocity and with turbulence, drawing in air and gases (trapped as bubbles), eroding the walls of the sand mold (whose grains end up as inclusions in the casting), and oxidizing the metal surface (forming 'dross' that contaminates the part). The optimum time depends on the weight and thickness of the casting (thin parts demand fast filling before they solidify; large parts tolerate and require more time) and on the metal (its fluidity and freezing range). Empirical formulas (such as Caine's or weight-based ones) estimate the ideal time, and from it engineers size the required flow rate and, consequently, the areas of the gating system. Computational mold filling simulation now makes it possible to visualize the process and optimize the system before pouring. Enter the cavity volume and the flow rate.
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.
Solidification Time (Chvorinov)
Calculate the solidification time of a casting by Chvorinov's rule, t = B × (V ÷ A)², from the mold constant B (min/cm², depending on the mold material and metal) and the ratio of the part's volume V to its surface area A. The result, in minutes, is the time for the metal to fully solidify. The rule shows that parts with a higher volume/area ratio (more 'massive') solidify more slowly — a fundamental casting design principle: risers (metal reservoirs) must have a larger modulus than the part to solidify last and feed the shrinkage. Enter the mold constant, the volume and the part area.
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.
Metallostatic Pressure
Calculate the metallostatic pressure exerted by molten metal at the bottom of a mold, P = ρ × g × h, from the molten metal density ρ (kg/m³), gravity g and the metal column height h (m). The result, in pascals, is the pressure the molten metal exerts on the mold walls and bottom due to its own weight — analogous to hydrostatic pressure, but with the high density of metals. It is essential to size the mold strength (which can 'burst' or deform under pressure), predict core flotation and metal penetration into gaps. Dense metals (iron, ~7000 kg/m³) generate high pressures. Enter the metal density and the column height.
Plastic Injection Flow Rate
Compute the injection flow rate by dividing the injected volume by the fill time, in cm³/s. It is the speed at which the molten plastic enters the mold — a parameter that controls the shear rate, molecular orientation, surface finish and defects such as jetting or flow marks. High flow fills fast but may degrade; low flow may solidify before filling. Enter the injected volume and the fill time.
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.