Aid to Calculate Sprues, Ingates and Runners for Castings in the Foundry

    Calculator Outputs
    This site contains a sprue calculator to help calculate the dimensions of sprues, runners and ingates for bottom gated castings made in the foundry. This calculation is often carried out by foundry methods engineers, computer modellers and designers to work out the dimensions of the hole through which molten metal enters the mould if they wish to control the flow in any way.

    Who is the Calculator for?

    The sprue calculator is primarily for bottom gated systems in which the metal falls under gravity to a point below the casting and enters the casting at its lowest point as shown in the sketch. It will be of interest therefore to foundrymen and foundrywomen in sand casting, gravity die casting (or permanent mould) and investment casting.
  • Explanatory Notes on Calculator

  • Explanatory notes on the terminology used and the limitations of the method are here.
  • Calculator

  • The calculator as a web page is here.. Explanatory notes can be called up in the left frame of the calculator by clicking on the sketch or text.

    Download: You can also download the original excel spreadsheet from which the calculator was made. Note that there are no help files or explanations on how to use it in the spreadsheet. If you are confident you know the meaning of all the terms feel free to use it: you are a better man than me in that case. It can be downloaded by clicking here; if that does not work right-click and choose 'Save file' or 'Save link' in the usual way.
  • Densities

  • Figures for densities of common alloys (used in the calculation) are available for Aluminium, Copper, Cast Iron, Magnesium, Lead, in the explanatory notes
    These can also be called up directly from the left frame of the calculator page. 

    Animations of Mould Filling

    Animations of flow in top and bottom gated castings obtained by computer simulation with different designs of running system and with filters and real-time radiography. 

    These can also be called up directly from the left frame of the calculator page. 

    Experience with Aluminium Bronze Feeding and Running Systems

    Notes I made for a steel foundryperson starting as method engineer in a new job with aluminium bronze sand castings (shows photos of radiographs of defects).

    Derivation of Calculator

    The calculator uses the formula:

    Sprue Area = M.T/t.d(2.g.H)0.5.Cd
    The terms are described in more detail in the explanatory notes

    M = cast weight, casting and feeders, kg;
    T = bottom pour correction factor: average filling rate/initial filling rate at start of pour;
    t = measured or required filling time of casting including feeders, seconds;
    d = liquid metal density, kg/m3;
    g = gravity constant; 9.81ms2
    H = metal head: in the case of the sprue exit this will be the total head above it including the pouring basin; for the sprue entrance this will be the head in the pouring basin. mm;
    Cd = discharge coefficient to allow for variations in mass distribution in the mould and friction losses; when T is based on experimental measurement this is equal to 1;

    The calculator was developed from a Quattro Pro spreadsheet using SmartTable, a program which converts spreadsheeets to Java applets, unfortunately no longer available. It should be noted that a similar conversion can be carried out with the Excel 2000 spreadsheet program. However the resultant calculators will only run on Microsoft browsers and therefore are of limited value for use on the internet. Java is a program language which instructs your browser how to perform the calculations. It works best with Netscape browsers.

    Last updated: May 2007

Who is the



 Densities of

of formulae 
used to 

of Mould

Experience with Aluminium Bronze Feeding and Running Systems



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