SolidWorks 2010 Bible

Chapter 32: Using Plastic Features and Mold Tools

Again, you can save out these core pins as individual part files. You can use similar techniques to

create side cores or lifters or other types of side actions.

Intervening Manually with Mold Tools

You have already seen that any sort of mold modeling resembling even a moderately complex part

requires some level of manual intervention to get the Mold Tools to deliver usable results. You can

do the entire mold modeling process manually, without using any of the semiautomated tools from

Mold Tools. You may even come across situations where you do not need to use surface modeling

at all. These situations will tend to be parts with a planar parting line, with no shut offs or cores.

I know several experienced mold designers, and they all tend to use different techniques, from cut-

ting away chunks with solids, to using all manual surfacing methods, to using about 80 percent

Mold Tools techniques and the rest manual surfacing. To me, it makes most sense to use the Mold

Tools for the things they are good at, because they do speed up some tasks, such as planar shut-

offs and separating out the cavity and core faces.

I want to run through two examples of manually intervening in the Mold Tools process. In the

first, I will show you how to create a passing shut-off (shut-off with a stepped parting line), and in

the second, I will show you how I created the Parting Surface shown in Figure 32.24.

Passing shut-offs

Snap features are often achieved in molds by using passing shut-offs rather than some sort of a

lifter or horn pin slide. Eliminating actions from a mold can be economical, as long as the passing

shut-off does not introduce wear or alignment problems. When creating parts that require this sort

of feature in the mold, it is a good idea to consult your mold builder.

Passing shut-offs can be difficult to visualize, even for seasoned professionals. It might be a good

idea to open up the part on its own and see the geometry for yourself. The filename on the

CD-ROM is Chapter 32 – passing shut off start.sldprt. This is a clip that holds a CD

in place in a plastic case. The draft analysis colors have been left on it to help you see which faces

belong to which side of the mold. There are no undercuts on this part, as shown in Figure 32.27.

In this part I have actually modeled two pair of passing shut-offs.

Using the rollback bar is probably the best way to see what is going on with this part. The surfac-

ing involved here may be confusing to you if you are not well versed with surfacing, but looking at

the part and understanding the steps will help you learn. The basic steps to create the surface body

called Shut-off 1 are as follows:

1. Create Ruled surface for the planar edges.


2. Loft surfaces between the parting line edges and the Ruled surface.


3. Extrude a flat shut-off face at the parting line of the snap feature.