Step 01

Model Size and Orientation

The first thing I did was import the STL file into SRP Player and check that the dimensions looked right: 82.73 x 60.00 x 13.06 mm. I kept the XYZ ratio locked so nothing would get stretched. I also made sure the top surface was selected as the face to cut, which sounds obvious but if you get it wrong the machine goes after the wrong side entirely.

Step 02

Type of Milling

Here I chose Better surface finish instead of faster cutting time, because for a mold surface quality is everything, any mark left by the tool will show up in every single cast. I also selected Model with many curved surfaces since the figure has no flat planes at all, and set it to Cut top only since this is a single-sided open mold.

Step 03

Workpiece Setup

Before generating the toolpath, I entered the actual dimensions of the polycarbonate block: 149 x 88 x 37 mm. A dialog popped up asking me to install a 3mm tool so the machine could physically measure the workpiece height. It touches down on the surface to get an exact Z reference. I placed the model at Center so it sits evenly in the middle of the block.

Step 04

Roughing Pass

The roughing pass is all about removing material fast. I set the feed rate to 1000 mm/min at 9000 rpm, cutting 0.27 mm per layer with 1.5 mm between passes. I left a 0.20 mm finish margin on purpose, that thin layer protects the final shape and lets the finishing tool do a clean, precise last cut. At this stage the surface looks rough and steppy, which is completely normal.

Step 05

Finishing Pass: Area Setup

For the finishing pass I added a 5 mm margin on all sides so the tool wouldn't miss the edges of the model. The cutting strategy was set to Contour + Scanline, which first traces the outline of the shape and then fills in the surface with very tight parallel lines. You can also see the Make sloped option is still off here, that comes next.

Step 06

Finishing Pass: Without Draft Angle

This is what the model looks like with the slope option still at 0°, walls perfectly vertical. I wanted to capture this view before enabling the draft angle, because without it, pulling the silicone out of those deep narrow walls would be a nightmare. Vertical walls grip the cast material tightly and can tear it on the way out.

Step 07

Finishing Pass: Draft Angle Enabled (10°)

I enabled Make sloped and set it to 10 degrees. The change in the viewport is subtle, but physically it means every wall now tapers slightly outward, enough for the silicone to release cleanly without a fight. I settled on 10° as a balance: too steep and you start losing the sharpness of the design, too shallow and it's still hard to demold.

Step 08

Finishing Pass: Tool Selection (R2 Ball)

I switched to a ball end mill (R2 Ball) for the finishing pass, a 4mm cemented carbide ball nose tool. Unlike the flat square end mill used for roughing, the rounded tip can hug curved surfaces without leaving flat steps. For a mold that's going to get filled with silicone, this makes all the difference in surface smoothness.

Step 09

Finishing Pass: Cutting Parameters

The finishing parameters are much slower and tighter than roughing: 800 mm/min, 8000 rpm, and a path interval of just 0.10 mm. That tiny spacing between passes is what gives the surface its smooth feel, 15x denser than the roughing scan. The finish margin is set to 0.00 mm, meaning this is the final cut, right down to the intended surface.