A Learning Adventure in the Workshop

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.

Vector Photo Engraving on the CNC - test #1

Over the weekend I successfully used the "7th" to engrave a photo of my daughter onto a piece of wood.  Turned out very well.  This was just a test cut, so I just used some scrap hardwood plywood.  I'll do it again on real wood later.

I used a carbide v-bit as the cutter and attached the plywood to the y-axis table with double-sided tape (after cutting through a clamp with the cutter on an earlier attempt!).

This engraving used the raster-to-vector method.   Essentially converting certain highlights and edges on the photo to vectors using various freeware and shareware software routines.   I took a digital photo of my daughter and loaded it into WinTopo (the freeware addition).  In Wintopo I converted the raster photo to vector and then eliminated a lot of the "noise" vectors that were created to get a fairly clean drawing.   I then saved the vectors out of WinTopo as a DXF file.   I then used Acer (freeware DXF to g-code converter) to convert the DXF file to g-code.  I set the maximum z-axis cut to 0.1 inches in depth. The g-code was then loaded into the my CNC machine's PC and I used TurboCNC (shareware CNC controller software) to run the machine.

The CNC machine took about 1 hour and 45 minutes to cut the picture (engraving is about 13" x 9").  I ran the machine slowly about about 6 ipm for this test run.  Everything worked beautifully.

I rubbed a cherry stain over the finished piece to darken the engraving marks.

For my next photo-engraving experiment I want to try the depth-of-cut shading type (I don't know what to call this method) engraving.  This method leaves the photo as raster and engraves deeper for darker pixels and more shallow for lighter ones.  I am using shareware called IMGTOGCODE for this attempt.  These engravings take much longer for the machine to carve, so I will do I much smaller image.

Diamond bit in the CNC machine

Tried a cheap diamond burr bit in the "7th" last night and quickly broke it when the machine moved laterally in a cut.  These bits apparently do not have enough lateral cutting ability for CNC.  Back to regular carbide or HSS bits tonight.

Let's call this one complete!

Last night I disassembled the x-axis and z-axis on the "7th" and tightened all of the connections and reassembled the machine.  Now that I am running the machine I realize just how tight the machine needs to be for accuracy.  I also readjusted the y-axis by setting a bit in the spindle at a fixed Z-axis depth (maximum) and then moving the spindle horizontally to each corner of the y-axis.  At each corner I did a fine adjustment of the rails until the bit just touches the table.  It is now adjusted perfectly.

Now, I consider the 7th to be "complete."  I'm sure it will continue to evolve from here, but it is time to use it for awhile before I do any more work to it.

First CNC Engraving

My g-code problems are fixed and below is a photo of the first piece made with my newly completed CNC milling machine!  Was supposed to say "Mason's Room" (my son). but I misjudged the length and size.

Overall, I am very pleased with the machine's performance.  I want to do a couple more fine adjustments to improve the accuracy a tiny bit though.   I can't say enough about John Kleinbauer's machine design, it is a really impressive piece of work.

I needed to run the machine fairly slowly at this point (<7inches per minute [ipm]) for good results in oak, but I'm in no hurry.  I'm told it has to do with the quality and strength of the used stepper motors that I am using.  Someday, I'll upgrade them, but for now, slow is fine.

7th Powers Up!

Here it is!  Above is a photo of the finished machine (click here for more photos). Last night,  I mounted it on an old kitchen cabinet that I put on small wheels.  The PC that drives the machine resides inside of the cabinet. Makes a nice portable setup.

I powered the machine up and configured the software.  Everything runs great under "jog" control from the PC. 

I began to test a g-code file and got mixed results.  I am clearly making some kind of error in my g-code files, so I need to do a little more research on that issue before the machine real cranks up.

"7th" is ready for testing

Lots of progress on the "7th" this weekend.  It is now essentially finished except for the wiring of the final home-switch.  The table is fully installed, 2 of the 3 home-switches are installed, all of the wiring is complete.    The machine is mostly calibrated.  I am basically happy with the calibration, although the table may need a final bit of adjustment once the machine is run.  Very little wiggle in the spindle axis...very good. 

Testing begins next!  I generated a test g-code file, and am now ready to connect the machine to the PC and crank-it-up....hopefully in a couple of days.

I'm looking forward to getting back to woodworking.  My "experiments" with CNC have taken me away from woodworking for much longer than I intended.

Skates and a scratch awl

I made aluminum "skates" for the moving-table for the "7th" last night and installed them.  I also made the drive bearing for the lead-screw out of PVC and aluminum and installed it also.   Next I need to make the threaded-rod axles for the roller-bearings and install them into the table.  After that, the table will be ready for mounting into the machine.

I also received my second tool from Blue Spruce Tool Works yesterday (first one was a marking knife).  It is a hand-turned scratch awl made out of cocobolo wood.  It is beautiful.  Perfect balance and shape and great workmanship. 

I wanted to make one of these for myself, but the project list was too long already and I already knew that Dave Jeske's work was excellent and well-priced.  Hightly recommended.

There is nothing like working with finely handmade tools.  They make me strive to improve my own work to match.

I also want to try a bird-cage awl soon for piercing rather than marking.  I may make that one (if I get time), or I may order another one from Dave and sharpen it into the bird-cage shape.

More "7th" Progress

Last night I calibrated the rails, installed the power strip for the spindle, ran some of the wiring,  and drilled and counter-sunk the moving table.  Tonight I hope to make the aluminum "skates" and install them onto the table.