Finished Star Clock

Here is the finished Star Clock.  We did a little modification of the code as the 1hz pulsing of the points proved a bit distracting.  It's kind of hard to see in the pictures here, but the points begin as purple and fade over to blue, 1 per minute.  When all five points are blue, the minute hand kicks over another 5 minutes.
A couple of further tweaks are planned, a shift of the clock face itself in color from a.m. to p.m.  With the RTC chosen it's even possible to make the clock change colors on a particular date.  Also completely un-used (except to say Happy Christmas at the moment) is the 16x2 LCD display and navigation buttons mounted on the the back.

Making Kirstin's Christmas Gift

One more project to close out the year, a gift for my wife.  She likes things that light up, and I have a "star" theme going this year.  Perusing my favorite electronic supply sites I came upon these Adafruit addressable LED string.  Very similar to a product I'd used in the past (Sparkfun BlinkM) but cheaper, and you don't need to set each unit's address.
It took me a couple of days to work out a concept to take advantage of the lights.  What I would do is to make a clock with the LEDs changing color to indicate the position of the hands.  12 of the LEDs will make up the face, and then 5 additional ones will occupy the points of the star, pulsing to indicate seconds, similar to the way the light on my Macbook Pro pulses while sleeping.

To make the major portion of the clock I used a piece of white delrin plastic.  This part is just slightly smaller than the table travel of the mill.  Additionally both sides of the part need to be machined, which further complicates the setup and fixturing.  To begin, I cut the holes in the back side of the clock to hold the LEDs.  The 12 central holes are for the "hand" display, and the 5 peripheral holes for the pulsing star points.  The large central cavity provides a convenient place to stash the RTC (real time clock) chip which keeps track of date and time with a battery backup.   It will also come in handy for one of the next steps.

In order to cut the front portion I need to hold the part down, as well as know where it is in space, so that the two sides register correctly.  This piece of delrin is cut to engage the central pocket and the "12 o'clock" LED hole.  The large flat areas provide space for the double stick tape.  I machine a lot of things with double sided tape to hold them down, it works very well, even more so when you have boss features like this fixture does to prevent any sideways movement.  

Here is the part placed on the fixture and roughed out.  I wanted the star to have rounded "puffy" look similar to the stars in more modern Mario games.  I almost left the piece the way it looks here, I thought the topographic map effect was rather interesting, but the smoother look won out.  

Here is the finished part.  You can see the outline of the double stick tape used on the fixture block in the background.  The 5 smaller holes in the back will let me mount the control electronics.  

I still need to take a few pictures of the finished product.  The software and colors need a bit of tweaking as well.  More to update soon.

Here is some video of the bands being cut.  The video has been been sped up, with the spindle speeds in use, titanium cannot be cut as fast as the videos show.  

Wedding Bands

Here is the project I have been working on for a while.  It's the reason I needed 4th axis support in the first place.  These are the wedding bands for Kirstin and I.  They are made from Titanium.  The profile of the band itself was cut on the mill, and then the knot work and constellation art was engraved into the surface.  The final step is to polish out the surfaces, first using sandpaper, and then progressing to various grades of lapping paste (silicon carbide grain mixed with oil) applied with a hard felt buff.
These pictures show the knot work common to both rings, and we put the constellation for each others birth months on the part closest to the hand.  These still need one final level of polish, and they will be complete.

Finished Amulet

Kirstin mixed a little paint to add an older weathered and worn look, and a piece of oven bake modeling clay was used to form the "gem" in the center.  Clear drying craft glue adds a bit of shine.

Amulet Construction

To make the amulet shown below in CAD drawings I first start with a piece of 360 brass stock.  It is held to the plate below with a layer of paper and wax based adhesive.  This can be applied or removed with just over 200 degrees fahrenheit, easily supplied by a hot plate.  This has the advantage of not having to be pried off like double stick tape.  It allows you to cut all sides of the part free without additional clamping.

The first program cuts the outside of the amulet profile and the center pocket for the gem.  This cut is made with a square end mill.

The second program roughs out the 3 dimensional contours of the part.  I use a 1/8" diameter ball end mill.  It leaves a minimum of .007" of an inch everywhere on the part to allow for a finish cut.  This cut took approximately 20 minutes to make, and removed the bulk of the material.  Although the cut is shiny, the detail does not match the model very closely.

The finish cut is made with a 3/64" ball end mill.  The tool moves in a spiral from center to outside. Each  arm of the spiral is .0015" apart.  It moves up and down at the same time to form the contours of the part.  This cut takes much longer to make (~2hrs) but produces the fine finish seen here.  The part and plate it was resting on were returned to the hot plate and separated.  

Setup And Testing

In order to make sure that everything lines up, the first thing that has to be done is to make the axis of rotation of the rotary table parallel to the table travel.  Once that is done, I chucked a piece of machinable wax in the 4 jaw.  

By cutting 4 faces at 90 degrees I can measure to the center of rotation, and set the center of the system to the center of the rotary table.  In this picture I am starting to "turn" down some of the excess wax to make a cylinder.  The wax is entirely recyclable, it can be remelted and re-poured at a little over 200F.  It doesn't wear tools either making it perfect for testing out unproven complicated programs.  

In this video I have "turned" the cylinder down further and I am engraving a pattern on the outside.  It's a very simple knot work pattern.  The final project may evolve this style a bit.  Again Alibre is a bit different than other software I am used to.  I need to work with the rotary axis post/setup to get the output that I want.  Currently I don't have things working so rotary feed is output correctly.  Everything is correct, but I had to trick the system into moving this fast.

Here is a close up of the result.