SDM v2a

I implemented "Option B" as described in SDM v2 concept. The issues that I wanted to address with this iteration were:

• Embedding of optical components (1 mm diameter glass fiber, in this case) into the urethane;
• Comparison of different urethanes, specifically Task 4, 14 and 18.

As it turns out, Task 4 (white) cured well, while the Task 14 (black) and Task 18 (gray) parts did not cure well. I believe that the latter two had problems curing because I did not mix the A/B parts very well. Here are the poured molds:

Some thoughts:

• Task 4 (white) is nice in that the material is slightly translucent, which makes it possible to visually observe the filling of the mold.
• Task 18 (gray) is considerably more viscous than the other two urethanes, which makes pouring into small molds difficult. It may be necessary to utilize a syringe with this material.

Here is the extraction of the Task 4 part:

Note: the fiber placement in the base mold was misaligned. I had some issues with the zero master of the CNC that I am using, which grossly misaligned the fiber in the pocket.

Here's the extraction of the Task 18 part:

Note: the Task 18 part was not properly mixed, and the consequence was that the resulting part was somewhat wet and "soggy." When applying a nontrivial amount of force to remove the part from the mold, I ended up breaking the part into two:

I plan on repeating the pour, taking into account the proper mixing of parts A and B, and fixing the zero master of the CNC so that the fiber can be accurately placed in the mold.

SDM v2 concepts

In my second SDM run, the idea is to embed 1 mm diameter optical fiber into the hard urethane. Some brainstorming sketches:

Fleshing out Option 2:

Note: "v2" will be a single material part. I will make at least four pieces: Task 4, 14, 18 and Vytaflex 20. The first three are hard urethanes, and the last is the soft urethane.

SDM processing v1 (part 2)

Roughly 24 hours after pouring soft urethane (Vytaflex 20):

After a lot of rubbing:

Chiseling it out:

Final parts (the Vytaflex 20 is extremely soft!):

I think I dinged some parts when chiseling them out of the block. Next, time I will machine them out of the mold, rather than chiseling it (especially when glass fiber is embedded).

Here is the flexibility of the medium-thick wrist:

SDM processing v1

With help of Eric from BDML, poured in hard urethane (Task 3) today:

Then, in the evening, I faced the hard urethane. I had some delamination issues (see below) and the "chips" seemed very sticky. I wonder if this has to do with the fact that the Task 3 part B was not properly shaken in the bottle prior to use:

Trajectory for the second pass machining, for the soft urethane:

Close up of result. I did not use a finishing pass and I did depth cuts of 1 mm. The Task 3 is not as nice to cut as the machinable wax, will use a more conservative trajectory next time:

Machinable urethane

A quick compilation of hard urethane from Smooth-On: Google spreadsheet. The materials of particular interest to me are highlighted in red:

Here's the plan for getting my feet wet with SDM. The width of the bar is 12.7 mm:

Parts (fat, mid, and skinny):

Try out 3D milling

I like the look of silicone parts made from sandblasted aluminum molds. Up to this point, I have been performing mostly 2.5D CNC work; it is now time to try out 3D milling ("surfacing" operations), in order to create more interesting shapes without relying on 3D printed molds.

A part to start with 3D milling (also trying out the Creo renderer...):

First time using "surfacing" on MasterCam:

Result (shown with some dowel pins):

The result. The finish is quite good -- looks almost like something that one might buy at a store (cheaply):

Tool holder presentation

Style was inspired by the students from "product design" (I usually use a much more plain presentation style...): Tool holder presentation

Some images from the talk: