CATI-SolidWorks Tool-Room Series
Part 3: SplitWorks & ElectrodeWorks

by Robert Konczal, CTO, CATI

Preface:

Plastic part designers seldom take into account the manufacturability of the design. The mold designer on the other hand is presented with a plastic part for which a mold has to be created, which means that usually he has to start an iterative process with the part designer adding shrinkage, draft angles, extracting undercuts and in general transforming the original part into one that can be molded (as cheaply as possible) while still maintaining its original purpose and shape.

The SplitWorks environment addresses this problem on two levels. First it allows the part designer to assess the consequences for every feature he adds by a continuous (either automatically or on demand) update of the color scheme (i.e. core/cavity, no draft and both sides faces) at every stage of the design. Secondly the mold designer will use this tool to modify the plastic part to make it manufacturable as well other new tools to actually create the core/cavity inserts and side cores.

ElectrodeWorks allows the quick and easy creation of Electrodes. The technological information relating to spark gap, rough and finish cuts, type of cutting pattern etc.

Split and Rebuild

The Split dialogue gives a dynamic response to changes in the split direction or draft angle and on creation of a silhouette.  Once a preferred direction has been chosen, we create the SplitWorks property page under its own tab. This property page is made up of folders containing the part faces according to their pull direction (Core/Cavity/Both Directions and No Draft) as well as a folder containing the open and closed parting lines.  The SplitWorks property page contains a wealth of functionality accessible through a context sensitive pop up menu on the RMB button.

These menus consist of Options (i.e. Automatic Rebuild On/Off), Actions (Create Surface), and Action/Option  (i.e. Show Open Parting Line(s), which shows the open parting lines and activates the option for their continuous display and Hide Open Parting Line(s) which performs the opposite)

Part Designer

In the previous screen shot you can see 2 bosses on the cavity side, which belong to the core. The part designer would then select the specific boss feature from the FeatureManager design tree and modify the draft angle (i.e. check the Draft outward parameter).

As the part is updated so is the SplitWorks property page.

Each new feature added to the model will be automatically classified showing the part designer the moldability of the part.  You can switch off the Automatic Rebuild option to work without checking the result and reactivate it at any stage, which will then update all the modified faces after the next rebuild. Faces, which have been moved through the MOVE to menus, will not be affected by the update, so that the designer can put aside faces of the model, which might need special attention (i.e. side cores or lifters etc.)

Mold Designer

The mold designer would use these menus to check where to modify the part and the result of these modifications.  The automatic Parting Line information and menus show the mold designer what has to be done in order to finish the cavity (or core) definition. Below we look at a part read in from an IGES file. Here the Open Parting Line(s) have been displayed, indicating that there are still modifications to do.

First some work has to be done to correct draft angles.  This is done using a combination of the SolidWorks Split Line and Draft Faces menus. Here is an example from the front side.

The result (after moving no draft faces to the core) includes automatic update of the core and cavity colors as well as the open parting line.

Splitting faces/changing draft angles and modifying the part with the Cut-Extrude and other standard functionality (using the Automatic Rebuild option to get dynamic updates) enables us to complete the parting line as displayed in the following screen.

It is always enough to create either the core or the cavity and use the SolidWorks Cavity menu (automatically through the API’s) to create the complementary insert. Although care must be taken to check that the complementary insert does not include undercuts. We have chosen to ignore the obvious undercuts on the core side at this stage, however we will use the standard SolidWorks menus to create them at a later stage.

Once reaching this point, the cavity is now well identified and we create the cavity surface through the Create Surface command and then using SplitWorks Plug Holes menu to create the shut-offs on the cavity surface in one action.

Next the cavity surface must be “extended” in order to create the solid inserts around the part. This is done through a mixture of the special SplitWorks menu Loft (based on SolidWorks API’s) and standard SolidWorks Surface functionality i.e. Sweep, Loft, Planar and Extend etc.

Using standard SolidWorks functionality is important to make sure that the final solid inserts will be coherent within SolidWorks so that any changes to the original part (i.e. scaling) will be correctly reflected in the inserts.
Next we create the core and cavity inserts through the Create Solid Insert menu.
Here again we integrate SolidWorks API’s to remain coherent within SolidWorks. As we can see the core has to be modified to include the side cores.

Finally we use pure SolidWorks functionality to create the side cores on the core insert. Adding core insert as a base part to each side core, creating the relevant sketch, using the Cut-Extrude (flipping the material direction to leave the inner part of the side core). Here we show an example of one of the steps to create one of the side cores.

Sketch for Cut-Extrude	Side core

Similarly we create the new core insert by subtracting the side cores from the original side core (added as a base part). Here we show an exploded view of the core, cavity, side cores and the original part.

Summary

We have shown here that SplitWorks and SolidWorks create a completely integrated environment to cover all the phases needed by the mold designer to create cores and cavities. Furthermore the integration of SplitWorks into SolidWorks adds a “design for plastics” environment to the standard SolidWorks base functionality bridging an important gap between the design and the manufacturing of plastic parts, by allowing part designers a dynamic preview of the moldability of the part during the design process.