Mold Design CAD Tutorial

This tutorial contains step-by-step instructions for making a solid model of a PneuNets bending actuator mold in SolidWorks 2013. The SolidWorks part files can be downloaded here. If you prefer to use a different software package, you should be able to apply the general tutorial steps to most solid modeling environments or you can refer to the dimensioned drawing below to guide you.

As discussed in the previous pages, this actuator consists of two parts: the main body, which expands when inflated, and an inextensible base layer composed of a piece of paper embedded in elastomer.

The two parts will be cast separately and then glued together, so we will need separate molds for the main body and the base layer.

The mold for the base layer is simply a flat rectangular plate with a lip around the edges.

The main body is more complex, and is cast in a two-part mold. The mold contains overhangs, and if we were to use a one-part mold, we would have to destroy it in order to remove the actuator once it was cast. By using a two-part mold we can reuse the same mold again and again.

Before making our mold we must decide its morphology (See this page for a discussion of PneuNets morphology). There are several dimensions that affect the actuator’s behavior: chamber height, sidewall thickness, spacing, and overall number of chambers.

In addition, there are other dimensions to be determined: chamber width, thickness of the other chamber walls (which must be thicker than the sidewalls so that they don’t expand much in comparison), and size of the central channel.

In this tutorial we will make an actuator with 11 chambers. Each chamber is 8mm long, 15mm wide, 15mm high, has 1mm sidewall thickness, with other walls being 2mm thick, and is spaced 2mm from the next chamber. The central channel will have a 2mmx2mm cross-section. Of course, you can alter these numbers to change the morphology of your actuator and the general steps covered in the tutorial should still apply.

We will first create a solid model of the actuator, and then use this to derive the solid models for the mold pieces by following these steps:

  • Encasing the actuator in a solid block
  • Subtracting the actuator from the block
  • Separating the resulting shape into top and bottom mold pieces

This image contains dimensioned drawings of the main body of the PneuNet actuator

PneuNet Molds SolidWorks Files (.zip)729 KB