CNC Cameo

The last two weeks have been rather crazy getting ready for the Shopbot Contest. Several months ago Mike and I wanted to perfect a photo-to-product idea using a bust or head as a starting point. It has been challenging, to say the least. Having very limited CNC experience just 3 months ago, I have jumped on the learning curve in a big way and been endlessly distracted by all the cool stuff there is to know.
This project is not complete as we had visioned it. But the submission must go in before midnight. It is, however, mostly finished except for the photo to mesh part. Therefore, this is the ongoing quest.

Step 1: Your STUFF

Things you need / Materials and equipment list:
Computer
Vector Drawing Program
CAM generator
Mach3, EMC, or similar   (http://www.machsupport.com/) (http://www.linuxcnc.org/)
CNC Router or a contract fabricator – (www.100Kgarages.com)
Tooling Bits
Portable Drill
Staple Gun or screws
X-Acto, utility knife, something sharp
Blue insulation foam, 1"
3/4" Corian Plastic (counter top stuff)
Sandpaper, foam blocks, dremel tools

Step 2: My STUFF

(Things I need)
Lots More Patience
Dust collection system
Writing skills
Photography Skills
More tools
Bigger tools
Faster tools

Step 3: Drawing Programs

(CAD – Computer Aided Design)
There are so many design programs out there (http://www.freecad.com/) (http://crunkish.com/top-ten-cad-software/). Some are free, some are not. Try the free ones, or the trial downloads, and spend some time assessing their capabilities. Make sure you look at what they can import and export. This will be important in moving your drawing files to the CAM generator (more about that later). The higher end ones, have a steep learning curve and take a while to be comfortable with.  The lower end and free are getting better all the time.  Check out Sketchup (free) with the ruby script that allows output in .stl and .dxf formats. Sweet!  (http://www.guitar-list.com/download-software/convert-sketchup-skp-files-dxf-or-stl)

Step 4: Output to CAM

(Computer Aided Manufacturing)
Some drawing (CAD) programs have no way to get g-code from them. G-code is a language defining where the router must go to perform the task you have in mind and is generated by the CAM. Some CADs have CAM with them but they tend to be the pay for types.  For those of you who are using a CAD program that does not have this function, you’re going to have to find a separate one to do this. Here is some links. (http://www.rhino3d.com/resources/display.asp?language=en&listing=545)
(http://www.freecad.com/CAM_Programs/)

For those of you who want to learn about g-code there are sites that will show you what it all means. (http://www.cncezpro.com/gcodes.cfm)
(http://www.cnccookbook.com/CCCNCGCodeCourse.htm)

Step 5: Head Hunting

The search for a usable 3D mesh finally settled in on one from Tgi3d (http://www.tgi3d.com/index.php?Page=Gallery) made originally in Sketchup. She was a simple girl, no hair, and a small size file. Somehow, I'm reminded of the woman from the first Star Trek Movie, you know, the one that is an officer that everyone on board is stumbling over and eventually becomes V'ger.

Step 6: Selecting the Bit

On our homemade CNC machine, is a Porter Cable Trim Router. It will accept ¼” shank bits, and with collets, will size down to 5/32” and 1/8” shank tooling. For the foam tests, the rough cut choice was a 1/4" shank 1/4" end mill, and a  ¼”shank 1/8” ball mill for the finsh cut. The Corian was denser, so I chose a  ¼”shank 1/8” end mill for the rough cut, and a 1/4" shank 1/16" ball mill for the finish. Lots of thought went into these selections because this was the first time I had cut Corian plastic. Pass depth, tolerances and speed through the material were experimented with. Also, I only have ONE 1/16" end mill. Cant break it before the contest.

Our router only goes one speed in rotation and maxes out at 25 linear inches per minute, so the only control we have is how deep it cuts per pass, and the inches per minute speed it travels thru the material.  Before any machinery is turned on, install the bit into the router you have. Be VERY careful, they are quite sharp. I wouldn’t know that, but there are a wide range of band aids and compresses readily available in our shop, just in case.

Step 7: Load the Material

Most of the time for a test run, I will select blue or grey insulation board. This allows me to see how many things I screwed up in the CAM and CAD. It also creates a prototype that can be looked at to see if it really is what I am expecting. 

Make sure that the piece you load on the machine is bigger than the project.  Seems obvious, doesn’t it?  Also, that the material is oriented correctly in the X and Y plane. I never made that mistake before.

Many treacherous opportunities lie here. Cut the foam larger than the project. You want extra room for clamping down the outer edges with screws, cam locking devices, or even double-sided tape.  In this case I used sticks and screws it clamp it down. Regardless of the method, one wouldn’t want the highly rotating router bit or the router itself crashing into something hard and unyielding. Some very interesting results WILL occur and you really don’t want that experience. The least is you may lose some steps in the g-code and get the remainder of the cut all cockety-wampuss, and the worst is flying bits of high speed steel flying around. Which brings us to the all-time favorite subject of OSHA,   da-da… SAFETY.

Step 8: SAFETY

Here we go, ignore this at your own peril. Ok, the condensed version:
---Ears - CNC machines are loud. I like to put on noise cancelling earphones with my favorite music playing in the background. Not       too loud as you want to lightly hear the machine as it runs, giving you a heads-up to any problems.
---Eyes and face – Flying objects do sometimes come from the machine, best to protect them. I use a face shield.
---Breathing – All materials have some dust created during the cut. Use at least a filter mask for non-toxic woods and cardboard. Use a much better mask for foam and plastics.
---(If at all possible make or buy a dust collection system to keep the fumes and dust to a minimum. That’s the next project for us after this contest. Wish I had done it earlier.) (http://solsylva.com/cnc/vacuum.shtml)

Step 9: Power the Machine and Computer

At last the fun begins. Power the machine and computer and open up Mach3 or EMC. These are the interfaces that actually translate the g-code into movement by the router. EMC is the open-source Linux version, Mach3 works with windows. Next load the g-code using a flash drive, wireless or whatever you move files with from your cozy office to the cold and manly shop. Click the Reset button. Now you can move the non-running router around to position the 3D coordinates (X,Y and Z) of the bit by using the number pad on the keyboard.

Step 10: Zero, Zero, Zero

You really want to fire that thing up. You have been at it for a while. You are impatient (well that, at least, describes me at times). But we have to get off on the right foot, or inch, or thousandths of an inch. X, Y and Z must be zeroed. Most of the time, this point will be the top-lower-left corner of the drawing.  Be slow and careful to NOT run the bit into the material or hold-down clamps. The tooling bits, I’ve found, do break, and are pricey. Once over the zero, lower the bit ever so gently down to just above the top of the piece. Then I place a feeler gauge below the bit and, extremely slowly, move it down to just touch the gauge. Using .002 gets the bit located in space just half-a-hair above the material. You do remember NOT to have the router on during this step. Right?

Step 11: The Magic

It’s finally time to turn the router on and start the sequence of cutting from Mach3.  Just like your mother used to say “don’t forget your mittens”, remember the safety stuff.  Turn the router on first.  Then click the green button on the screen labeled Cycle Start. You’re off and cutting. Yeah!  If it takes off in some bizarre direction, be ready to shut it down by clicking the STOP button. Remember the adage that computers, (along with dangerous machines attached to them) only do what you tell them to do, not what you want them to do. If all is going well, just watch and enjoy the moment. To me, this is amazing stuff, I used to hand cut all of these projects. It’s a wonderful world!
When the cycle ends, and the router comes back to zero, turn it off. Then remove all the clamps, screws, staples, or what-have-you that is holding the material firmly. Pick up the piece and be amazed.  Remove the waste sections, and vacuum or blow off the dust so the machine is ready for the next fabulous experiment.

Step 12: Examine

Now is the time to really look at the test.  Look it over closely. See how the choice of tooling bits has affected the surface
If you think it needs improving, return to Step 3, and go for Plan-B, or Plan-C.  In my case, it always takes several iterations and tests to get the effect you want.

Step 13: Finishing

The first Corian test had some major grooves where the bit had dug too deeply. I started sanding the first piece while another test was running. I ran the program again and added another finish cut at right angles to the first finish cut. This didn't work as well as I had hoped.
It seems that the stability of our homemade machine may not be as good as a commercial unit. That may be what left the grooves in the first Corian piece. The second try looks as if a line or two of g-code may have been jumped.The beginning of the second finish pass did start well as it began the forehead, but didn't appear to have touched the material throughout the remainder of the run.

After some sanding, she looked pretty good anyway, but I want the machine to do a finer job.I will need to also reduce the size of the polygons around her cranium, the're big and visable.
Well, time has gone wherever it goes and this must get submitted.

Future tests will, I'm sure, resolve the machine problems and I can get to the most perplexing part of this project. How do I make 3D meshes from photographs?
There are several sites I have found that will allow you to upload a series of pics and will return to you a 3D mesh to spatially define the subject in the three axis, X, Y, and Z. Although I have done a number of uploads using a small statue of Ben Franklin and my Wife (patient as she is), the results back were not good enough to work with, considering my lack of experience with 3D drawing. Working out this set of challenges will be at the heart of the next few weeks, and I will post the results here. When I can manage meshes of my kids and Wife, I will mount them on a nice piece of walnut.(http://www.123dapp.com/catch) (http://www.hypr3d.com/)(http://www.tgi3d.com/index.php?Page=PhotoScan)

Please post any help, ideas, or suggestions for this work. I doubt that this is the first time in history a head has been cut by a router.
Thanks for reading this far. The game is still afoot.

Step 14: Why We Want to Win

Last summer Mike and I began getting together at least once a week or more, for what we called guy time. We would work on some idea, hack, project, or repair of some item with what we had in the shop. This resulted in some clever solutions using rather odd materials. The interplay between us was so fun we began to invite others to our “club”.  Thus a Maker Space has taken over my shop. I love it. About this time Mike introduced me to Instructables.com and I was hooked. He also brought over his homemade CNC Router.  We got it up and running and have been creating a number of interesting projects that are being submitted for this contest.
Our club of makers will continue to explore the vast world of CNC routing. We have in mind a large backlog of ideas that would be furthered by winning the PRS Standard 96-48-6 ShopBot .  Our homemade CNC can cut 31” x 21” and cuts at a maximum of 25”/ min.  The 4’ x 8’ table and 300”/min will vastly improve our ability to produce prototypes, develop and improve designs, create larger projects and test out 2.5D, then move to full 3D sculpting.
Here is a small selection of my personal list of projects:
2D
                Giant Spirographs using chalk for outside
                Wing Ribs for Experimental Aircraft
                Mazes for more than one player
                Multi-level mazes
                Giant mazes on a half sphere to be played by young children
                Interchangeable mazes of increasing difficulty
                Picture frame mazes
                Patterns for Cabinet doors
                Wood Blocks for printing from ancient lithographs
2.5D
                Bas-relief
                Negatives for molds
                Negative busts
3D
                Sculpture
                Full Busts
               Art prototypes

Thank you for considering this submission
Rick Shore