The C-Turtle makes progress, then snags

Now that my first CNC machine is completed and working, over the holiday weekend I continued to try and refine the design of my other experimental machine, the "CNC Lathe Attachment" based on John Klienbauer’s Wood Turtle design.  That machine is now also complete, as John designed it, and it works successfully as a CNC-lathe duplicating machine, but that was not my purpose in building it.  I wanted to make a machine that could be used to cut creative spiral patterns in wood spindles…that was the original goal of my whole Rube Goldberg venture into CNC!

In the meantime, I’ve learned a lot about CNC, and I really expect that my "7th Sojourn" milling machine is the one that I will use the most.  That’s good, because I’ve hit a snag on the "Wood Turtle" spiraling machine design (I’m calling this modification of John K’s design the C-Turtle).

Over the weekend, I completed a more solid mount for the C-Turtle to the lathe.  It is now rock-solid and has no wiggle at all in its mounting to my Nova lathe.  This will allow it to work better even in its original duplicating-machine functions…but I’m shooting for spirals.

Next, I designed and built a mount for a stepper-motor which attaches to the "outrigger" on my Nova lathe.  This outrigger in its folded position allows me to line-up the stepper-motor with the outboard hand-wheel on the lathe headstock.   I then mounted essentially a jamb-chuck into the cup of the hand-wheel.  I installed an 1/4" axis on the jamb chuck and linked it to the stepper-motor with a 1/4" coupler.  Now I had a stepper-motor that could turn the lathe’s main axis under control of the computer.  So, basically, I could carefully coordinate motion of the C-Turtle’s cutter head with the very slow rotation of the lathe’s axis (much slower than the lathe’s motor could turn).

Everything works great.  The problem is that my 60-oz stepper-motor can just barely turn the lathe’s axis and if any pressure at all is applied to the wood, the motion stops…the stepper-motor is just not strong enough to work like this.

So, I’ve proved two things:

1.  My design for the C-Turtle works in concept, but
2.  I will need a strong stepper-motor to make it work.   The stepper-motor on this axis does not have the mechanical advantage that the 1/4" threaded rod drive screw provides on the other axis.

Since my FET-3 board will require a bigger power-supply and a resistor to drive a bigger-stepper, a cascade of upgrades occurs in order to take this experiment to the next level. 

I may put this experiment aside for a while before I invest more money and time into it.  I am happy to  have completed one of the CNC machines and may move to another project for a while before returning to CNC design school.   I am now confident that this contraption would work if I spend some money on parts…but that may wait for a while.