The first attempt at 3D printing the part produced this:
All I can say is – awesome! It is really neat to see something that was only a sparkle in your eye be turned into a hard touchable object! Apparently, there is a problem with the machine printing objects over 8″ and the printing head bumped the part, strewing the printing material everywhere. The work around for the moment is to split the cone in-half, which is what will run this weekend, and glue the results together.
Besides a buildup of TOF work, I spent the last few days looking at electroplating solutions and I am convinced they will not work. There are three problems:
- Cost – upwards of $500, which is expensive considering I can buy a thick 4′ by 8′ (yes foot) sheet of pure copper for $360
- Electroplated Thickness – typically only a couple microns, where a thousand microns is 1 mm. Unfortunately, because we are using high power microwave, it isn’t so much penetration of the microwave energy as, it is momentary heating. I can just see a bit of heat bubbling the plastic and electroplated surface, which will then arc doing something like this.
- Adhesion – getting the copper layer to stick, or plate evenly sounds very difficult. Part of the problem is that for electroplating, it needs about an amp per square inch, which in our case is a lot of amps given the inside volume of the part. Too many amps leads to unpredictable results.
I spent many hours reading through forums dedicated to electroplating to get a sense of the difficulties involved and it sounds cumbersome, for example, here. Other people have been thinking of plating 3D printed products too but haven’t reported back any successes. I also looked at using copper leaf which is actually pretty inexpensive, but probably too thin and the surface can be tricky to get flat.
Once the plastic part shows up, I am going insert a copper lining into it, which means I am back to square one with seams. However, the external plastic will act like a mold, and as long as I can cut the copper closely enough, I should be able to glue it in place, the braze the seams
I built a plastic model to get an idea of what the seams will be like:
The great news is that
- I figured out how to calculate the angles and heights I need to draw out a pattern for the “frustum” cone. Creating a frustum cone pattern is pretty easy actually.
- I learned Rhino 3D has an “unroll” function where I can take the cone and roll it out in preparation for water jet cutting.
My plan is to cut two cavities at the same time by putting two sheets of copper together and waterjet cut them at the same time.
The plastic model makes something apparent – the angle at which the frustum cone joins with the long tube section is pretty extreme and is going to be difficult to join properly.