Let's Make Robots!

CNC Machine -- Valkyrie-Clone CNC

Cut, engrave and drill using GCODE scripts
AttachmentSize
serial_script.pl_.txt1.66 KB
cnc_surfacing.gcode_.txt4.32 KB
clone_CNC_first_trace.JPG435.85 KB
clone_cnc_terminal_board_sm.JPG58.87 KB
clone_cnc_terminal_board_lg.JPG131.77 KB
clone_cnc_PM42S_wires.JPG72.74 KB
clone_cnc_halfdead_L298.JPG66.01 KB
tiny2313_stepper.sch259.26 KB
tiny2313_stepper.brd16.3 KB
tiny2313_multiplexer_sch.png23.64 KB
tiny2313_multiplexer_brd.png35.59 KB
tiny2313_multiplexer.JPG55.24 KB
clone_cnc_august2.JPG1.51 MB

Old pic: http://letsmakerobots.com/files/clone_cnc_closeup_1500px.jpg

TinHead's Original: http://letsmakerobots.com/node/9006

Vector Drawings: http://letsmakerobots.com/files/clone_cnc_vector.pdf (draft)
Measurements will be available for these drawings sometime over Christmas Break 2009 or if somebody asks me for it.

Specs:

  • ~175mm x ~115mm cutting area
  • Cuts 4" x 6" copper-clad boards
    (http://www.oselectronics.com/ose_p56.htm)
  • Resolution: On a copper-clad board on a surfaced table, a fresh sharp 60° bit, and a carefully set cutting depth, I can get down to 0.4mm traces in the X-direction.  To minimize errors I try to keep to 1mm traces or larger (1.4mm typical, with 1.6mm pads on vias).  Traces can be made at 0.4mm between pads of a DIP IC if "0.12mm" isolation is selected from the pcb_gcode/pcb_gcode_setup plugin in EagleCAD.
  • ~35mm Z-axis travel (allows boards to be stacked on the base)
  • Cutting speed: I added some pauses to the RepRap feedrate code, so I know it isn't going as fast as the feedrate says it's going.  However, I did surface a 110mmx160mm area with 1.2mm passes in about an hour with a ~2mm bit (cutting off about a millimeter depth of particle board off the surface) -- so about 256mm/minute for surfacing, corresponding to reported feedrate of 1000.  On copper-clad board, with a 60° engraving bit, I have used a feedrate of 1400, but it could go faster.  The feedrate of 1400 means ~360mm/min.  
  • Machine Dimensions: about 20"x17"x22" clearance (X,Y,Z) (0.50 x 0.43 x 0.56 meters) -- the base stage is 18" long by 12" wide with extra room on the sides for the motors/lead screws/X-stage which brings the Y-dimension out to 17" (from 12").  The motors on blocks extends the X-dimension to 22" (from 18").  (1" = 25.4mm)
  • Measurements shall be added to vector drawings soon!
  • Computer runs Inkscape with GCODE plugin for design, EagleCAD with GCODE plugin for PCB.  Code executes on Chris Meighan's "GCODE for RepRap", running on Windows XP. 

Documentation:

Tools for construction:

  • Workmate Bench, Drill, Circular Saw, 500 pc (est.) drill set, coping saw for aluminum rails, tape measure, ruler
  • Proxxon 12VDC Rotary tool for spindle, 36pc Dremel set including metal-cutting bits for cutting lead screws
  • Soldering station
  • Adafruit USBtinyISP AVR Programmer (plus WinAVR software)
  • ISP target board with 16MHz Crystal Oscillator (pictures to follow)
  • Wire cutters, pliers, linesman pliers, C-clamps, socket wrench, adjustable wrench
  • (Circuit board etching setup or PCB trace routing machine or PCB vendor)
  • EagleCAD with SparkFun Design Rules plugin (keeps traces from getting too close to each other)

Components:

  • Adafruit DC Boarduino for control (requires FTDI cable) or Arduino Duemilanove
  • Stepper-Driver components described in Bill of Materials http://letsmakerobots.com/files/cnc_partlist.pdf
  • 24VDC Stepper motors
  • ATX Power Supply Unit, 300W or (http://www.rackmount-devices.com/045-6854.html, http://www.interinar.com/fs-15024-1m.html)
  • 20' CAT-3 cable -- for signal wires (20' = 160' of 24AWG wire)
  • 25' wire -- 20AWG for power wires
  • 1/4" interior diameter clear tubing
  • heat shrink (various sizes)
  • 5/16"-18 fully-threaded bolts x 2" or longer (M8-1.25 equivalent, 60mm or longer) to fit the interior diameter of the skate bearings
  • 40 inline skate bearings (e.g. "China Bones" and "ABEC-1" used for this machine)
  • An IKEA nightstand worth of particle board/MDF -- or 1/3 sheet of particle board or MDF from the lumber yard

Cost: I built up my workshop while building this project, so it is hard to estimate the true cost.  For folks who have access to a wood shop, an electronics lab, an AVR programmer, a circuit-board etching setup, creative part sourcing and a rotary tool, you can probably build this for $150 in about a week.

Code: Based on the Valkyrie CNC stepper driver/Arduino source code: http://github.com/TinHead/Valkyrie-CNC-source-code/tree/master.  Perl Script loaded http://letsmakerobots.com/files/serial_script.pl_txt, attachment to this page.

Prior Art:

Tricky Parts:

  • Setting the ATTINY2313 "lfuse" to a 16MHz oscillator: "lfuse" to "0xFF"
  • Aligning the lead screws: I used floating blocks that were aligned at each end and screwed down. (http://letsmakerobots.com/files/clone_cnc_floating_block.PNG)
  • General alignment problems: Of the four rails used for X-stage travel, the two rails on the top and bottom of the base-stage should be parallel to <1mm, and the rails on each side of the base should be parallel to ~1mm.
  • Aligning the X and Y axis: the X and Y stages should be perpendicular to each other to 1mm over the runout of the stage: "Clone CNC" has 3mm of Y travel over the 165mm X runout :(  I'm not sure whether it'll be a problem while drilling holes in PCBs
  • Alignment of the Z-axis -- the floating block may not be possible, or may have to be positioned on top of the stage near the motor.  Good alignment will make it easy to lift the stage.  Bad alignment will make it difficult for the little motors to lift the stage.  Rails and screws should be parallel.
  • Switching to 24V -- the ATX PSU is not meant to put out a whole lot of power from the -12V (blue) wire -- only about an amp from -12 to GND.  You may only get one quarter amp to work with when you run the steppers on the -12V/+12V wires.  The Clone CNC is running fine, but I have a spare PSU in case the current one dies from too much load on the -12V line.
  • The Boarduino must be hooked up to the same ground as the stepper drivers -- run it from -12 to GND (GND is positive/high, and -12V is ground: confusing?) if you use 24V from the ATX PSU.

Kudos:

Credit where credit is due: My CNC is deeply indebted to TinHead's work on the motor driver (node/6967), driver software, Arduino controller software, and hardware design, along with the discussions on the "Valkyrie" robot page (node/9006).  Driver software is http://github.com/TinHead/Valkyrie-CNC-source-code/tree/master .  Somewhere in the driver and Arduino source code, the RepRap project gets kudos as well.  Debt is also owed to http://buildyourcnc.com for some of the construction tips.  I wouldn't be able to join the wood so well without learning good drilling technique (last time I joined more than 2 pieces of wood was in Middle School shop class in '93).  Also, ladyada's AVR tutorial ( http://www.ladyada.net/learn/avr/ ) was essential to programming the ATTINY2313 used in the stepper drivers.  The controllers were programmed on a minimalist target board from evilmadscientist.com ( http://www.evilmadscientist.com/article.php/avrtargetboards ).

Rear View:  The picture above shows the Z and Y axis drivers, plus the homemade power and I2C terminal block. The +12V bolt is heat-shrinked in yellow, the -12V bolt is heat-shrinked in blue, and the I2C is bare (because it is >100x less likely to kill me or burn me).  I chose a telephone-style terminal system -- wrap the wires around a bolt, between washers, and tighten.  Fasten the bolt on an insulating surface (wood in this case) and mount the terminal in a convenient place (screwed onto the X-stage).  The pairs of wires are not twisted together for neither power nor I2C pairs -- Instead I run the wires parallel and keep them seperated at a fixed distance with tape.  I got the idea from outdoor "Ladder Line" antenna wires used in ham radio, for which you also don't want crosstalk between wires.

Update 19/11/2009: Trace routing on copper-clad board -- There were some lockups due to bad table surfacing and wrong choice of routing bit.  Also, the machine was losing steps on the Z-lifting steps, so I added rubber bands and zip-ties until it stopped.

Update 21/12/2009: I loaded "serial_script.pl" as an attachment, which is a perl script to control the CNC.   I improved my clamping system and re-surfaced the table.  I still needed 60° trace-routing/engraving bits.  Up-cut router bits are the wrong tool for trace-routing.  In "serial_script.pl", the Perl script receives either no arguments, in which case it runs a script, or a GCODE command string, which it sends to the microcontroller.  So >>./serial_script.pl "G01X10Y10" would step the CNC 10mm in the positive X and Y directions (along a diagonal).  The 5-second delay is needed for the controller to initialize when the script starts.  Also, there needs to be a "Serial.println("zomfg");" inserted in "arduino_gcode.pde" after initialization is complete or the script will never continue.

Update 24/12/2009: http://letsmakerobots.com/files/clone_CNC_first_trace.JPG -- I got my new 60° trace-etching bits, a new Java application by Chris Meighan (http://www.chrismeighan.com/projects/g-code-for-reprap), courtesy of avantgps and with help from brickbatbae, and a vacation day to play with it all.  I attached the second X-axis lead screw.  I used the back of a used copper-clad board to test my new bits.  The only problem was that there were empty lines in my GCODE file, so the GCODE for RepRap would send the line, but the arduino would not reply, so the script would not continue.  There were no problems with the I2C failing.  From start to finish, the board was routed and drilled without having to home the machine.  As long as I make my EagleCAD boards with wide traces and big pads for the components, I should be able to use the pcb-gcode plugin to make circuits.

Update 29/12/2009: Guitar Effects Pedal Power Supply Project, for which I used EagleCAD and this beautiful little CNC.  http://letsmakerobots.com/node/13983

Update 09/Jan/2010: 83MB of photos of the Valkyrie-clone CNC at http://www.freakivy.com/clone_cnc_complete.zip

Update 25/Jan/2010: The CNC is hard at work etching and drilling new drivers for some bigger motors for a motor upgrade.  It has been up and working for about a month now (since I got the 60° bits a little before Christmas).  I am a little nervous about changing my machine since it works (it's fabricating its own drivers), and the little printer motors are kind of charming.  I think I'll work on the control system and hold off on building (buying?) a new machine until the old one breaks or starts to fail.

Update 30/Jan/2010: The machine seemed to be failing.  It became extra-sensitive to changes in current, for example, when the machine is cutting.  I blamed changing my power supply from multiple supply wires to a single supply wire (I had my supply wired bundled at first, but then just used a single wire), and also blamed changing the drivers to be inside the box.  I noticed TinHead made a change that seemed to help -- while moving the drivers inside the metal case, he upgraded to a 24V power supply.  I was wondering if my seeming I2C problem was a power supply problem.  Later, I remembered that I also moved the Arduino inside the box from on top.  The final fix was to move the transformer brick for my Proxxon drill from the top of the machine to the other side of the machine, and to plug it into a different outlet.  As of February I'm fabricating boards as good as or better than ever.

Update 11/Feb/2010: I made an 8-channel full-bridge rectified and regulated DC 9.0V power supply for my brother's many guitar pedals.  Another brother will be making a pedal board, and the power supply will allow for no more 9V batteries.  Also, I'm working on the machine upgrade -- I'm planning to change the control system from a smart 4x ATTINY2313 board to a RepRap v1.2 style stepper driver system with a single ATTINY2313 working as a multiplexer via I2C.  I'm cutting the ATTINY2313 multiplexer board now.  The multiplexer will take an I2C command from the Arduino and move one of the stepper drivers.  Since there are 9x digital channels controlling the steppers, I wanted to move these wires to a dedicated board off the Arduino.  The three-wire drivers (x3 unique channels) will be clipped into the ATTINY board.  Schematic attached. GCODE files need to be relabeled from ".nc" before I can attach them.
http://letsmakerobots.com/files/tiny2313_multiplexer_brd.png
http://letsmakerobots.com/files/tiny2313_multiplexer_sch.png
http://letsmakerobots.com/files/tiny2313_stepper_0.sch
http://letsmakerobots.com/files/tiny2313_stepper_1.brd

 

Update: 17 August 2010 -- New Drivers!

The short of it is that I got the Valkyrie-clone CNC working with new drivers (http://letsmakerobots.com/node/15686).

In the picture from top-left, clockwise to bottom-left: the terminal block (24V power up to 13A), the 2 X-axis drivers, the Y-axis driver (blue heat sink), and the Z-axis driver (blue heat sink), the Arduino controller (direction x3/enable x3/step x3), and just below the terminal block there is a small 9V regulator board to shift 24V down to 9V for the Arduino.  Everything is mounted on an MDF board, and the board is mounted with baling wire.

More to follow, but it seems to work fine.

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>> Also, You said you were using perl? Tinhead with python, you and perl, and avent with java. I wonder which one I should use.

Yup.  I have the code attached to my robot page (I think it's under the robot pic).  I would use the java app!  It's cross-platform (unlike the Visual Basic 6 GUI I was considering building) and it lets you pause your script.  The pause button is amazingly useful, let me tell you.  I found that Tinhead made almost the same script that I did, so we have about the same features.

>> I'm building a cnc to devlop build-plans for a simple, cheap and reliable cnc and hopefully a team and I can supply community high schools with these machines to feed the brains of tomorrow's engineers.

That's a great idea -- I'm sure you'll keep safety considerations in mind, and do some research to find out whether high school administrators most value one of the following: "cheap"/"reliable"/"safe"/"low-maintenance". 

If you check out some of the "prior art" links, there are some good CNC frames available for cheap.  Bluumax CNC described his machine on a forum post I had read as a "Playschool" type version (Playschool is a US toy company), made of plastic, that is good enough for light duty and learning, and costs about $230.  It would be difficult to beat that price -- I've spent twice as much as that to build up my workshop so I could make this machine.  I heard good things about using a Proxxon Professional Rotary Tool instead of a Dremel -- it is reportedly quieter and better-made for the same price.   Shopbot is a professional low-cost CNC that may be durable enough for long-term use in a high school classroom, but it costs $20k.  The Fireball CNC is a widely used hobbyist frame for about $1200 that should be durable enough.  Bosch Colt spindle is recommended as a router for the Fireball CNC. 

If I were building a project like yours for a High School classroom, I would be inclined to either use a higher-end machine, or to market a "Build a CNC Machine" class for high school students.  Providing a cheap CNC might not be enough.  Just my 2¢, so don't take it too harshly. Great idea, definitely -- we do need to train more machinists and more techies in the USA.   I'd love to see it take off, so think it through, know your customer, and know how to market your product.  I want a shop class in every school and a CNC in every shop.  :)

 >> I2C

Regarding the I2C, I'd say forget about it.  I don't regret building it -- I learned a lot about AVR programming, EagleCAD, and parts procurement -- but it is a little too smart for what is needed.  Get yourself an EZ Driver and Mach 3, and run it on a computer with a DB25 parallel port.  http://www.hobbycnc.com/

It seems like every day a new CNC comes out.  I just recently saw the "Sable" CNC for $500, now I see a new USA DIY CNC kit at http://www.mikebeck.org for $500 (edit: oops, it's $500 for frame and router, plus $500 for the high-torque controllers and a sturdy power supply).

Also, this dual-drive system looks familiar: http://www.pdjinc.com/

Woah, I've been looking all last night for people who've built cnc's with an arduino controller, I wake up today and find two more (los angeles). Great, great. I've posted on aventgps and tinheads build page to help myself with issues sending g-code through the serial link. I see various people used different things--tinhead using python and you using java. I found your source code for the java program and opened the .jar and .bat files, and nothing. I know I have a JVM on my computer, as I was remember fiddling with java a few weeks ago (maybe I deleted it >.< )

 

Well, the big question do you recommend a certain JVM?

and I can't seem to find the rxtx libraries on the net for the life of me. 

EDIT:

I think I just found them *facepalm*

Are these it?

http://reprap.org/bin/view/Main/RepRapMicrosoftSoftware#Java_Development_Kit_JDK_Java_Ru

http://reprap.org/bin/view/Main/RepRapMicrosoftSoftware#RXTX_Serial_Library_serial_port

Which version of the rxtx should be used?

That was a great link!  I installed

  1. JDK -- development kit, which also installed JRE v1.6
  2. J3D -- 3D Java
  3. RXTX -- into each of my JRE folders (bin and lib/ext) according to instructions, and also into my JDK/jre/bin and JDK/jre/lib/ext folders
  4. The GCODE for RepRap into an arbitrary folder.
After it was installed, and I restarted my Windows PC, I launched the .bin file in the reprap_gcode folder and it launched the program.  Thanks!  I'm looking forward to testing it out with the CNC.

I have no idea!  I just found the site http://www.chrismeighan.com/projects/g-code-for-reprap after aventgps mentioned the fellow Chris Meighan, and was planning on testing it out over the Christmas break.  It is certainly a more refined program than my Perl script.

Thank you for doing the research!  I will also be looking to get the "Gcode for Reprap" program and the JVM to work over the holidays.  Avantgps may be able to help with the install, and if you do work it out, I'd be interested in how you got it to work.  I am definitely looking for an upgrade from my Perl script.

Thanks! -John

ps -- I owe comments on my script and a new version that works with Tinhead's latest revision.  For example, one of the "feedback" lines that the script looks for contains "zomfg".   That is not an original TinHead/RepRap message, it is part of a colorful debug line I inserted while discovering that if I did not power up the driver boards, the Arduino would not completely initialize.  The "zomfg" line occurs once the drivers are loaded and ready to go.  So anyway, I owe some comments and source code.  If you are modifying Tinhead's code and want to use my perl script with minimal changes, I'd insert a line in "arduino_gcode.pde" at the end of the "setup()" sequence after "init_steppers();" that says

void setup()
{
  Serial.begin(19200);
Serial.println("start");
//other initialization.
init_process_string();
init_steppers();
Serial.println("finished loading! zomfg!");
}
If you were a linux geek, I think hooking up a Beagleboard and a monitor to one of these would be cool. You could even make the designs on the actual device, and have it run the motor drivers itself. I dunno...

That would be a great way to control it!  It could run Mach3 from the side of the X-stage.  If I wanted to down-spec my controller instead, there would be some cool possibilities too.  My control computer (a 2003 Dell Inspiron 1100) is more than is needed to do the job of sending GCODE scripts -- all it needs is the FTDI serial drivers and a perl script to time the execution.  Pause/interrupt/abort could be implemented on the microcontroller.  If I weren't short on memory on the Arduino, a WizNet ethernet shield could be added, and the controller could run over LAN, or I could add an SD card reader and it would run the script from the SD card.  Right now I'm working on getting it to be an adequate CNC, but some neat things could be done once it runs well. 

What's up ?

Not so much :)  Thanksgiving in the States was at the end of November, so I set the robot aside and went to visit my family.  Since then I've had a midterm, a final exam coming up, and a lot of push from work to get things done (probably because it's the end of the year and I'd taken time off to study).  I can get a new picture up though -- the CNC has some helper rubber bands to assist the Z-axis in lifting the stage. 

From December 24th to January 1st my company shuts down, and without classes or work, I'll have some time to test out some new stuff.  I'd like to see whether something like Mach3 is suitable for interfacing with the Arduino controller -- all I need it to do is feed GCODE over serial port, but I don't know anything at all about Mach3 yet.  Also, my experiments with an EagleCAD drill file led to a broken drill bit, so I'd like to figure out how to use the drill files.  And for all my experiments with copper-clad board, I did not pick up any 60° PCB trace etch bits, so I was experimenting with up-cut router bits.  I broke the smallest (which led to me resurfacing the table), and the larger one worked fine but was too coarse.  In a few days I'll have a pack of new PCB bits to test, which will be fun.

For the hardware, I've been thinking of upgrading to NEMA-17 after Christmas, especially since all the cool kids are doing it :)   I heard the wires can get hot using CAT-5 (24AWG), but I have some thicker 20AWG wire that I used to power the boards.  I was perhaps unduly worried about voltage drop and running too much current through the wires, and I tried to spec to a 2 amp motor, hence I have a spool of 20AWG wire for the power transmission.

You have several different options:

 

  • Putting them in a metal case and earth grounding the case
  • Faraday Cage around the board or the EMF transmitting device
  • Seeing if Ferrite bead, cores, rings will cut down on the EMF
  • Use a squirrel as a mechanical power source for the cutter

 

Other than that, I don't know

 

Mech  

Got no squirrels here either, will go for lots of space between the EMF producing Dremel and the sensitive drivers :P