I accepted a challenge to try and make a CNC machine out of cheap readily available components from the local hardware store. My first thoughts were use plywood. Its cheap, and easy to work with and I had seen others use drawer slides for the linear rails but these where at least $20 a pair. As I wandered the aisles of said hardware store looking for my answer I came across the plumbing aisle. The miles of PVC pipe sparked an idea in my head. I said to myself aha! Challenge accepted!
So for a while I pieced together this little machine on the hardware store floor while the clerks passing by watched, and asked me what the hell I was building and how could they help me. I had drawn out the idea for the frame, but how would the linear movement work? I grabbed up all the parts I had laid out on the ground and went searching for an answer. This time I had found myself on the electrical conduit aisle , I knew that I was getting close. Then, laying there in all their plastic glory, Wall mounts for 1/2 conduit! These where easily modified to slide rather than grip the pipe. All I had left to do was visit the hardware aisle to figure out how to fix everything together. I wanted to make the machine semi-modular and expandable (although being PVC it could only expand out so far before losing rigidity. maybe switch to metal pipe ?) I settled with a box of 1/4″x 20-TPI “Philips” head screws because I could force them into the holes of the wall mounts thus threading them in the process. I also used 1/4″x20-TPI threaded rod with accompanying long nuts that would mount to the linear slides and move them. To attach the stepper motors (which I acquired from a broken scanner)to the threaded rods I used 1 inch long pieces of 10mm diameter steel rod drilled out for 1/4″ on one end and 5mm on the other end with 5mm set screws to hold them together. I used the 1/4×20 Philips screws as anti-rotation pins later in the build because the friction fit of the PVC did not hold up to the vibration and back-and-forth movement of the liner slides. All was good until the Z axis came into play. How would I build this ? I ended up using a linear actuator and frame from a broken CD-ROM drive as my z-axis. This was the most cheap and easy solution at the time. For the cutting tool I got lucky and found a $25.00 rotary tool with a cable drive at SAMS CLUB that was perfect for the job. Hot glue zip-ties and patience were my friends while assembling these random pieces and parts. and my poor coffee maker…. The Chinese TB6560 based cnc driver board I chose to use with this project came from eBay and it has not been a bad experience I read a lot of forum junk about these boards and they have their quirks but they can be ironed out. One simple mod is to strategically replacing a series of optoisolators with jumper wire because the isolaters really do not serve their intended purpose of isolating the computer from the circuit because they all shared a common ground, and thus cause missed steps and noise. I chose LinuxCNC as my software/OS of choice to run this pile of shenanigans. It fit the bill perfectly because they have a version that runs like a dream on my old HP/Compaq NC6000 laptop. yeah, I could have used the Mach3 cd that came with the TB6560, but linuxCNC was easier to use in my opinion! plus its FREE, and has a live option if you do not want to install Linux on your rig. (but where’s the fun in that.)
Parts Needed for the frame: 1.) 25 feet of 1/2 inch PVC. ( Lowes sells 5 foot sections for less than 2 dollars ) 2.) x8 1/2 side outlet ( corner) end fittings. 3.) x2 elbows. 4.) x10 “T” joints. 5.) x2 4-way cross endfittings. Parts Needed for the slides: 1.) x10 1/2 inch conduit wall mounts. Please note the modifications necessary for the slides:
2.) 1/4-20 screws, nuts, ans washers.
4.) x3 Stepper motors acquired from broken scanners or printers .
5.) And last you will need some kind of control board with at least 3 axis.
( This is the “TB6560″ chinese cheapo from ebay which I used )
For control you need a computer with a free LPT printer port and software to send the signals to the driver board. The “TB6560″ driver board comes with a full version of mach3 machine control software , but I chose to go the Linux route because I find it easier. I downloaded the LinxCNC live cd here and installed it on an old laptop I had laying around.
(Email me for my config file if your interested maybe my config could help you firstname.lastname@example.org)
Be careful here! certain laptops have bad latency issues with their respective LPT printer ports it has to do with the power control and the fans coming on and interrupting the signals. If your using a laptop turn off “speed stepping” or the like and make sure your printer port is set to EPP mode in the system bios to get the best compatibility.