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Free lost-PLA sprue builder

Add a sprue, pour cup, and vents to a 3D-printed pattern for lost-PLA casting. The page joins them into one closed solid, picks the smallest standard flask, and works out the investment and the metal.

Runs in your browser. Your file is never uploaded.

Your model

Drop an STL, OBJ, or 3MF here.

Up to 250 MB. All processing stays on your device.

Files stay on your device.

Options

Model and placement
Orientation
Points
Sprue and pour cup
The sprue grows wider by this angle as it rises.
Vents
Up to four vents, from the points you click up to the cup rim.
Metal and casting
Extra metal to feed the casting.
Investment mix
Calibrated to the Ransom & Randolph flask chart at a 40/100 ratio. Use your investment maker’s value.

Result

Choose a file or try the example.

How it works

  1. 1

    Open and turn the model

    Drop an STL, OBJ, or 3MF, then turn it so the part you want to feed sits on top.

  2. 2

    Place the sprue

    The sprue starts at the highest point near the middle. Click the model to move it, or switch to vent points and click up to four vents. Set the sprue, cup, and vent sizes.

  3. 3

    Download and plan

    Save the joined STL or 3MF. Read off the flask, the investment powder and water, and the metal to melt.

Sprue, cup, and vents
The sprue widens toward the cup so metal enters smoothly. The cup is a cone on top of it. Vents rise from the points you click to the rim level of the cup, so air and gas can leave as the metal arrives.
Joining
A closed model is united with the sprue into one solid. Large models take longer to join. An open model, or a model that the solid engine cannot join, is combined without a union, and the page says so. The STL then has overlapping shells, and the metal volume is an estimate.
Flask and burnout
The smallest standard flask leaves 6 mm of investment around the pattern and 13 mm under it. Casting numbers are estimates. PLA needs a PLA- or resin-specific burnout schedule from the maker of your investment, and this page does not give one.

Questions

Where should the sprue go?

Usually on the heaviest part of the model, so metal flows from thick sections toward thin ones. Turn the model so that spot is on top, then click it.

How is the flask chosen?

It is the smallest standard round flask, from 2 × 2.5 in to 6 × 9 in, that holds the pattern with 6 mm of clearance at the sides and 13 mm at the bottom. If none fits, the page says what size you need.

Does it give a burnout schedule?

No. PLA and resin patterns need a schedule from the maker of your investment. The results link an example of a maker’s manual, and the maker’s instructions are the ones to follow.

What is the button allowance?

Extra metal poured so the sprue and cup stay full as the casting cools. It is added to the metal in the pattern. The default is 10%, and you can change it.

Is my file uploaded anywhere?

No. The conversion runs in your browser with the JavaScript on this page. Your data never leaves your computer, and nothing is kept after you close the tab.

Quoting castings or patterns every week?

I build quoting tools that read a customer's CAD file, work out weight and metal cost, and price the job automatically.

Ask about automating itSee custom software work

Source code and license

You can inspect the code and the licenses here. Models are parsed and measured on your device.