Appendix I
ZCast Design Guide - 11
5.3.1 Direct
Pour
Before addressing the mold design specifics, we will consider the basic steps of designing a mold
using a standard CAD package.
Most middle to high-end CAD packages such as Pro/E, SolidWorks, Catia, Unigraphics, and
Autodesk Inventor, etc. as well as some tooling packages such as Magics Tooling will contain the
tools you need to create a mold. These are the steps required to design a mold:
1. Import part data. It is advantageous to use native files. If it is not possible, next best
would be an IGES or STEP file. If neither choice is available an .STL (sterolithography
slice file) would be suitable with a package like Magics Rapid Prototyping. Processing
tends to be much slower when working with .STL files.
2. Add finish stock to machined surfaces, typically .080” (2mm).
3. Apply shrinkage factors based on material to be cast and part geometry.
4. Define and divide out cores, using surfaces generated within the model.
5. Add core prints to the cores.
6. Design the gating system as a positive component around the part to be cast.
7. Encapsulate the part and gating within a larger form (typically a rectangular block).
Subtract the casting and gating and core prints away from the larger block, leaving the
mold cavity.
8. Generate a parting surface and split the mold block.
9. Add mating features to help align the mold components. These can be simple holes
pegged with dowel pins, or mating positive and negative features built into the model.
10. Add venting to the mold cavity and to the cores.
11. Add flanges or seats for prefabricated pouring cups (if utilized – direct pour only).
12. (optional) Lighten mold pieces by cutting out material from heavy mold sections (direct
pour only), or shell the entire mold to approximately 0.5” to 0.75” (13 to 19mm) (shell
method only).
13. Add mating surface offsets to facilitate assembly of components.
14. Divide the mold components into sections suitable enough to print in your Z Corp. 3D
Printer (typically shell method only).
5.3.2 Shell
Method
If you plan to use the shell method you’ll need to:
1. Begin with steps one through five from previous.
2. Divide out the core geometry (if a core or cores exist in your design) and add core prints
3. Isolate the casting surfaces of your part to be cast and divide it into desired number of
sections.
4. Shell each of the resulting open surface sections.
5. Design gating system on a separate conventional pattern.
6. Incorporate alignment features into shell and patterns.
7. Incorporate locking features so that shells are firmly held into place by foundry sand.
