Techniques for Machining Simple Pendant Jewelry

In this article we explore two possible ways of creating a single piece of pendant jewelry. In the first method the pendant can be machined directly on a metal stock using a combination of 2½ and 3 Axis toolpath methods.  For higher volume production, single or multi-cavity injection mold plates can be machined.  The resulting mold cavities can be used to produce what is called a “positive master wax model”.  The positive master wax model is then used to produce the final pendant using an investment casting process.

Watch the video at: https://youtu.be/EB3G5TsOjwo

Direct 2½ Axis Machining

Shown below are the 2½ Axis toolpaths used to produce a single piece of pendant jewelry consisting of a prismatic shape.  Prismatic simply means that the side walls are vertical and the floors of the pockets are horizontal.  Note that side walls with a positive draft can also be machined with these methods by using tapered end mills like in the example detailed below.  On the left, the pendant and each toolpath is shown with the Control Geometry for the operation highlighted.  The resulting cut material simulation for each toolpath is shown on the right.  Let’s have a look:

About the Techniques Used:

1. The first 2½ Axis Profiling operation uses a 0.3 mm x 5 Deg Taper Mill.  This allows it to serve as both a re-roughing operation (getting to areas that were not machined) and a finishing operation for the side walls.
2. The last 2½ Axis Profiling operation creates four (4) tabs automatically placed.  These serve to anchor the part to the stock during machining.  

Prismatic 2½ Axis Pendant, 3D Part, Stock: 60 x 60 x 3
2½ Axis Facing, Tool: 3.175 Flat Mill, Stock: 0, Stepover: 25%, Cut Levels: 1
2½ Axis Pocketing, Tool: 1.0 Flat Mill, Stock: 0, Stepover: 25%, Cut Levels: 3
2½ Axis Profiling, Tool: 0.3 x 5 deg Taper Mill, Stock: 0, Cut Levels: 1)
2½ Axis Profiling, Tool: 3.175 Flat Mill, Stock: 0, Cut Levels: 2, Bridges/Tabs: 4 (H:1 x L:4)

Injection Mold Cavity Plate Machining

Shown below are the 3 Axis toolpaths used to machine a multi-cavity mold insert block.  In this example, the cavities are NOT prismatic.  This means that they have contoured pockets that cannot be machined using 2½ Axis toolpaths.   Again, on the left, the cavity block and each toolpath is shown with the Control Geometry for the operation highlighted.  The resulting cut material simulation for each toolpath is shown on the right.

About the Techniques Used:

1. In the 3 Axis Horizontal Roughing operation, no geometry needs to be selected.   
2. Notice that the 3 Axis 3D Offset Pocketing operation uses a 0.25” x 2 Degree Taper Mill to machine the contour of each cavity.

Contoured 3 Axis Pendant Multi-Cavity Block, Stock: 4” x 2.5” x 0.875”
3 Axis Horizontal Roughing, Tool: 1/16” Flat Mill, Stock: 0.005”, Pattern: Offset, Stepover: 25%, Cut Levels: 20%
3 Axis Clear Flats, Tool: 1/16” Flat Mill, Stock: 0”, Pattern: Stock Offset, Stepover: 25%
3 Axis Horizontal Re-Roughing, Tool: 1/16” Ball Mill, Stock: 0.002”, Pattern: Offset, Stepover: 25%, Cut Levels: 20%
3 Axis 3D Offset Pocketing, Tool: 0.025” x 2 Deg Taper Mill, Stock: 0”, Stepover: 0.005

3 Axis Pendant Mold Examples (courtesy of sicadcam.com)

Don LaCourse

Don LaCourse is an Application Engineer with MecSoft Corporation. Don brings over 20 years of experience in CAD/CAM operations in both automotive and mold design applications. Don also has extensive experience in documenting CAD/CAM products and is actively involved with writing the on-line help as well as creating training tutorials for MecSoft's products.