Maker Faire Bay Area 2015!!!

Join me at Maker Faire 2015!!!

Join me at Maker Faire 2015!!!

Maker Faire Bay Area 2015 is just a few days away!  I hope you’re as excited as I am!

I’ve made some minor improvements to my large drawing robot and am going to bring a tiny drawing robot as well.  The changes to the big drawing robot are:

  1. “Feet” for Underside of Project Box
    1. My robot is built into a shallow wooden box.  On the top of that wooden box there is a “holder” for a roll of paper.  By adding little “feet,” as short as 1/8 inch or so, to the underside of the project box, the box no longer pushes against the roll of paper – which makes it easier to pull paper down when drawing.
  2. Revisions to Paper Roll Holder
    1. As it is, the paper roll holder is a little close to the project box, so the paper sometimes bumps against it.  This isn’t much of a problem, but one that can be eliminated easily.
    2. A notch in the top of the paper roll holder.  This way, rather than having to dismantle the robot, I can just lift the old paper roll out and drop in a new one.
  3. Batteries for Pen Holder
    1. The pen holder uses AA batteries, not for power, but for dead weight.  Right now the batteries are held in place by hot glue.  I would rather there was a slot on the holder for actually holding the batteries.

And, for those of you interested in seeing more of my TinyCNC, I’ll be bringing that too!  I’ve been working on a little something there as well.  Here’s what I’ve done:

  1. Mounted TinyCNC
    1. On a cigar box!  The TinyCNC is bolted to the top of a cigar box kindly donated by a local smoke shop.  A small solderless breadboard and Arduino now live inside the cigar box as well.
  2. Trying out New Interface
    1. I tried using the TinyCNC at first with an Arduino, feeding it Gcode-like commands over the serial interface.  Then I tried saving designs as coordinates and flashing an Adafruit Trinket with the coordinates and drawing that.  Since the Trinket doesn’t have a serial connection, this meant I lost a lot of the functionality of the tiny robot.
    2. This time I’m using a membrane 3×4 matrixed keypad to control the robot.  The keypad is also mounted to the cigar box.
  3. Trying out New Code
    1. I can get the Arduino to recognize keypresses reliably, but I can’t get the ‘bot to move in response… yet.  🙂  Heck, I still have almost 36 hours until showtime, which is plenty of time.  So far, it does absolutely nothing at all – except shudder.  I’m not that worried about it though, I can always go back to an older version of the Arduino sketch.

As far as actually showing a working demonstration of the TinyCNC, I have a few ideas.  Here’s what I’d like to show off, in descending order:

  1. Tiny robot, controlled by a numeric keypad, letting people draw on pieces of paper and take them home.
  2. Tiny robot, with several pre-programmed designs, letting people hit a number on a keypad, having it draw a pre-programmed design, and taking the piece of paper home.
  3. Tiny robot with a single push button mounted on box, which draws a single pre-programmed design when pressed, people take the piece of paper home.
  4. Tiny robot, connected to my laptop, drawing things sent from the laptop, and let people take a piece of paper with the drawing home.

What will be ready by Friday afternoon?  I have no idea!!!  You can either stop by and see for yourself or tune in on Monday night when I post a recap of the weekend.

Setting up at Maker Faire Bay Area 2014

PlotterBot - packed up and ready to go

PlotterBot – packed up and ready to go

One of the things I appreciate most about the design of my PlotterBot is that it is extremely modular and portable.  All of the parts have been designed so that the entire robot can be assembled and disassembled with a single 3mm hex wrench.  Pictured above is everything I need to setup the robot and spend all weekend drawing – the tools, hardware, replacement parts, extra tape, paper, and pens.1  Best of all, all this stuff fits neatly into my car’s trunk.  The robot underneath in the “well” of the truck, with the large pieces of plywood on top.

I took pictures from the same standpoint as I set up the booth.

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Or, if you prefer, here’s an animated GIF of the setup.  🙂

Maker Faire Bay Area 2014 Setup

Maker Faire Bay Area 2014 Setup

  1. If only I had remembered the metric ruler! []

Doctor Who “To Victory” Dalek Poster

Doctor Who "To Victory" Dalek poster, red Sharpie on banner paper, 28" tall x 23" wide

Doctor Who “To Victory” Dalek poster, red Sharpie on banner paper, 28″ tall x 23″ wide

Another robot drawing from exhibiting at Maker Faire Bay Area 2013.  This is the result of my PlotterBot drawing a cropped version of the “To Victory” Dalek poster on the BBC website which was released with the “Victory of the Daleks” episode from 2010.  ((Those faithful readers of my blog posts may recall my other attempt to memorialize this same drawing))  This drawing is red Sharpie on banner paper, 28″ tall x 23″ wide.  The dimensions refer to the drawing, not the sheet of paper.  This drawing took about eight hours.

Unfortunately, this drawing was longer than the sheet of paper I had allocated for it.  You can see at the bottom of the drawing a white uncolored patch where the blue tape was covering the edge of the paper.  However, if you can get over that defect, this is still a cool poster – and the biggest drawing I had ever done up to that point.

Since this drawing was posted on the fence at Maker Faire 2013, rolled up, archived, unrolled, transported to Maker Faire 2014 where it was displayed again, you can see a little wrinkling of the paper at the edges.  As you can also see, the drawing went off the edge of the paper.

Tiny Drawing Robot Updates, Incremental Progress, and More!

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It’s been about a week since my last blog post and I’ve really been enjoying working on all aspects of the Tiny CNC.  With the year winding to a close, I wanted to squeeze in one last update.

The really cool thing about working on a robotics project from the ground up is that you can work totally different aspects of the project, whatever happens to interest you at that moment.  Sometimes 3D design appeals to me, other times working on Arduino or Processing code.  And then sometimes working on making the project really real by contacting suppliers to source parts for kits.  Here’s what’s going on now:

  • Adventures with Online Ordering.  I pulled the trigger and bought 100 micro servo motors.  I’m hoping that once I get this tiny drawing robot’s designs a little more finalized some people will be interested in having me create kits for them.  I simply cannot tell you how much fun it was to open up a box fresh from China stuffed with 100 motors.1 I spent several days shopping around on Alibaba and trying to reach out directly to motor manufacturers and in the end I finally placed an order with a “distributor/middleman” because it was a decent deal and he could ship immediately.  I know I overpaid a little, but this is kind of a test run anyhow.  With 100 micro servo motors, and each robot taking 3 motors, I’ll be able to create at most about 30 bare-bones kits for sale.
  • Micro Servo Motors.  These are the really common, and reasonably cheap, TowerPro SG90 motors that you see for sale everywhere.  People who have printed the Tiny CNC on Thingiverse to date have had to try to get their more standard micro servos to work in my designs that were made for the more badass Batan 2122 analog feedback micro servos that I received courtesy of Adafruit and Make.2
  • Arduino Code.  With the gentle prodding of TechNinja42, I created a Github account where I’ve uploaded some of the Arduino code I’ve been experimenting with so far.  While I have uploaded my prior sketches to Thingiverse, Github does seem like a better place to share these files which are changing quickly.  If you grab this code and load it up, you’ll be able to control your Tiny CNC drawing robot just by using the Arduino’s serial monitor and the WASD for directional control and OL to raise and lower the Z axis.
  • Teaching Programming to a 6 Year Old.  Christmas day was the first time I wrote some Arduino code that actually made my robot do something interesting.  Long story short, I actually got my daughter on the first step to programming.  I had her draw a simple shape on some graph paper, we took down the coordinates, plugged the coordinates into the Arduino code, and then the little robot got to work.  We had a great time creating the program and an even better time watching the robot repeat her drawing, pause for five seconds, and do it again.  The reason for the five-second pause was so that we could slip a sheet of paper into the robot, have it draw something, then pull the paper out.  I can’t wait to get this robot drawing more complex pictures.  🙂
  • Tiny 3-Axis CNC Redesign, Again.  I’ve already started revising my designs to work with the Tower Pro SG90 motor form factors, so it will be easier for everyone to print and build their own drawing robots.  I’ve added lots of improvements based on feedback from those who have printed their own, and I’m very nearly done with this latest version.  So far it is shorter, probably uses less plastic, should be offer more stable and accurate drawing, and uses one more plastic piece than prior versions – all while slightly increasing the drawing area.  Since I offered a sneak peak at this design in progress in an earlier post, I’ll leave off with a glimpse of this design-in-progress.
Tiny 3-Axis CNC version 0.34

Tiny 3-Axis CNC version 0.34

  1. And one Arduino Uno of dubious authenticity []
  2. I call these motors badass because they’ve got metal gears inside rather than plastic, analog feedback so they can sense and report their position back to the microcontroller, and cost $15 each []

Tiny 3-Axis CNC Drawing Robot – Software Update and Design version 0.29 postmortem

Above is a very short video showing the Tiny 3-Axis CNC, powered by an Adafruit Trinket, using all three axes.

In order to push the Tiny CNC robot design further, I had to actually wire it up and test it.  Only by actually trying to put it through its paces am I able to detect design defects for correction/improvement in the next version.  What follows are basically my notes working with the Trinket and thoughts on the design of the robot thus far.  It helps me to document such notes for future reference – so you may or may not find this stuff interesting.  🙂

  1. Adafruit Trinket
    1. While I’ve wired the Tiny CNC to an Arduino Uno and a Mintduino before, I really wanted to get it to work with my Adafruit Trinket (courtesy of Adafruit and Hackaday!).  I figured this was as goo a time as any, so I soldered the headers onto the Trinket and got started on the process of augmenting my Arduino IDE to work with it.
    2. The Adafruit Learning System website has an entire section introducing the Trinket. The process is well documented, but still a bit fiddly.  It’s not nearly as “plug and play” as working with an Arduino Uno.  However, this is a perfectly acceptable tradeoff for the size and price of the device.  If you want a “quick start” guide to getting the Trinket to work with your Windows system, this a rough outline of my process:
      1. Download the Trinket drivers.  The notes for different operating systems is helpful here.
      2. Add ATtiny85 support to your Arduino IDE.  This is for the “slow” way of augmenting your existing Arduino IDE.  I prefer doing this to having multiple versions of the Arduino IDE on my system.
      3. Rename and replace the avrdude.conf file in the “hardware\tools\avr\etc” folder.
      4. Rename and replace the avr-Id.exe file in the “hardware\tools\avr\bin” folder.
    3. In an ideal world, I’ll be able to use the Trinket to both control three servo motors and speak to the fake serial port so it I can send instructions from the computer.  However, due to the limitations1 of the Trinket, the way it handles servos and serial communications are a bit hacky.
      1. Trinket servo motor control.  Servo motor control apparently requires the microcontroller utilize an internal timer/clock.  However, since the Trinket sacrifices this for size/space reasons, a work around using an internal clock/timer has to be implemented.  The result is that you have to use a different servo motor controller library that implements the software clock/timer.  The trick is that the timer has to be refreshed every 20 ms or so to operate the servo.  Using a simplified version of the Adafruit Trinket servo motor control sketch, I was able to get the Trinket to move all three axes.
      2. Trinket serial port communication.  Again, the Trinket sacrifices serial port communications in favor of size/space requirements.2 Fortunately, there appears to be a work-around for this limitation using a “fake USB serial” connection.  I haven’t finished this process and don’t have much to say about it at the moment.
  2. Tiny CNC Arduino (not Trinket) Sketch
    1. Using Oliv4945’s Arduino Gcode interpreter for Mini-CNC as a starting point, I wrote a sketch for making the Tiny CNC respond over the USB serial connection to WSAD (forward, back, left, right) and OL (up, down) commands.  The good thing about this sketch is that you can give the ‘bot a series of commands, hit Enter, and have it carry the instructions out.
  3. Tiny CNC Trinket Sketch
    1. This sketch is a simplified version of the Adafruit Trinket servo control sketch.  The XY servos move over about 30-40 degrees while the Z axis pumps up and down.  This is what you see happening in the video above.
  4. MORE Tiny CNC Design Thoughts
    1. Overall, I’m very happy with version 0.29.  The bottom line is that it works.  As Michael Curry recently pointed out, “at this point you have something that works, so the rest is just corrections.”  If you build this version on your own, you’ll get a little robot that is a bit finicky – but will actually be a no foolin’ tiny 3-axis CNC.  It won’t be super precise or able to handle a router or mill attachment, but it also won’t cost $400 for a kit.  🙂
    2. Here’s What Worked
      1. Z axis.  My first attempt at printing a Z axis works.  The Z rack isn’t much more than a thin plank of plastic with a rack of teeth and some holes to help mount a pen or whatever to it – but, again, it works.
      2. Y rack and Y stage/motor mount.  The parts in this little robot are designed to fit/slot/snap together and lock themselves and each other into place.  I’m really really happy with how this designed worked out.  I basically entirely changed the entire method of securing the Y rack from version 0.18 to version 0.29.  In version 0.18 the Y rack slid along each side of the X motor mount.  In this version, it rides between the X and Y mounts, held in place by the Y pinion (gear), riding over the Y stage motor mount, and constrained by the X and Y motor mounts.  While not actually simple to accomplish, I feel like this was an elegant solution.  While I have some improvements planned for the next version, I don’t anticipate this changing at all.
      3. Rubber band gaskets.  The problem with using printed pinions (gears) instead of the servo horns that come with the servos is that they don’t have the itty itty splines to mesh closely with the grooves on the servo motor gear.  As a result, no matter how hard you tighten down the servo motor set screw, the gear can twist away.  My method of dealing with this was to cut a small piece out of wide rubber band to use as a “gasket” between the set screw and the gear.  As you tighten down the set screw, it puts pressure on the rubber band and gear.  When the gear moves, the rubber band gasket prevents the set screw from rotating/sliding and loosening with use.
      4. Zip tie.  The zip tie on the Z motor seems to work very well.  I used a similar system for holding the servo in my PlotterBot pen holder.  The motor is held in place securely without much room for wiggling.  Although it is definitely possible to create a printable Z motor holder that doesn’t require any zip tie, the version I designed doesn’t require any overhangs.  I’m trying to avoid overhangs and support requirements in parts (which rules out all kinds of nifty groove/slide systems) so make everything easier to print and possibly easier for injection molding.
      5. Twist tie.  While not part of the directions or other documentation so far, I found a twist tie very helpful in controlling the sevo motor wires by bundling them together.
      6. Thinning and hollowing the XY pinions.  Since the most recent published version I made these big pinions slightly thinner and hollowed them out a little.  This theoretically reduces plastic a little.  Indeed, the 3-axis version of the robot actually uses less plastic than the 2-axis version I had uploaded a few weeks earlier.
    3. Here’s What Didn’t Work/Could Be Improved
      1. Rubber band gaskets.  These gaskets provide a drastic improvement for the gear’s ability to stay properly tightened on the servo shafts.  However, they’re not ideal since the rubber band gaskets just serve to create a little extra friction/traction between the set screw and the pinion (gear).  Now I’m trying something new that seems to work even better.  My daughter has these adhesive foam stickers in the shape of letters and animals.  For shapes with cutouts (like the letter “O”) the inside of the cutout is useless to her and is either found floating around the bottom of the bag or still slightly attached.3 I’ve place one of these between each of the set screws and pinions (gears).  The benefit of these is that they actually adhere to the surface of the pinion and actively resist being turned against the pinion. Another benefit of these is that they are thicker than a rubber band, so the set screw has to sink into them – creating more surface area contact between the “gasket” and the set screw.
      2. Y rack/Z motor mount.  I found that the zip tie for the Z mount interferes slightly with the Y rack slide.  I’ll need to raise the Z motor mount slightly to compensate.  Plus, I only just now realized there’s a slight overhang in this part I would like to eliminate.
      3. Z pinion.  The Z pinion includes a little flange to keep the Z rack in place.  The flange is a little too large and needs to be reduced slightly for easier operation.
      4. Z rack.  The Z rack isn’t much of anything, as mentioned above.  It’s just a rack with a plank with holes in it. It could be better refined to work as a pen holder without a lot of design work.  I just banged this one out so that I could have an actual no foolin’ 3 axis CNC to work with.  I have some ideas on how to make a simple pen holder.  Ideally, I would have two separate Z racks for this robot – one for holding a pen and another for use as an actual 3 axis CNC.
      5. Carriage tipping.  When the XYZ carriage has the Y rack extended as far out a possible, the weight of the extended Y rack with the Z motor and pen are more than enough to cause the entire XYZ carriage to tip out of the X rack.  This could be fixed by just creating a little guide, applying a piece of wire, or any number of minor hacks.  However, I’d like to have this issue resolved as part of the design of the robot.  Thus, I’m thinking of inverting the entire X rack to cause the X pinion to lock the X gear in place against the X motor mount.  The problem with this method is that it will basically require redesigning the X and Y pinions again.
    4. Anticipated Hardware Changes.  If I implement the improvements and changes I’m contemplating, this would mean redesigning the X rack (to invert it), X and Y pinions (to work with newly inverted X rack), Z pinion (to reduce the flange size), Z rack (to include a better pen holder). Y rack/Z motor mount (so the Z motor zip tie doesn’t hit the X motor mount), possibly Y motor mounts (to thicken the base slightly), and possibly the X motor mount to reduce plastic usage (since it wouldn’t have to be as big any more).  And… that’s a change to all 8 pieces.  :/
    5. Anticipated Software Changes.  Trinket space permitting, I would like to incorporate a small Gcode interpreter and fake USB serial connection.  I don’t know if this is possible, but I’d like to do this.  Also, my daughter specifically requested a 6-button interface to operate the robot.  I don’t know how to do this yet – but I’m willing to learn.  🙂  With three pins on the Trinket used for the three motors, there are only two pins left for buttons.  I’m pretty sure there’s no way to hook up a set of 5+ buttons to a Trinket and still have it operate all three motors.
    6. Fanciful Potential Changes.
      1. Keypad.  If this robot were to be powered by an Arduino Uno, you could probably incorporate this awesome 10-digit keypad from Adafruit to control the robot.  I think that would be a fun and accessible way for a kid to interact with this robot.
      2. Robotic Gripper.  With a fourth servo, a small robotic gripper hand could be attached to the Z axis – allowing this robot to do all kinds of interesting things.  It could be used to play chess, sort marbles, flip switches, or pick peas out of your dinner.
  1. And, again, these are perfectly acceptable tradeoffs given the size and price! []
  2. And, again, this is totally worth it []
  3. Much like a hanging chad []

How to Build a Tiny 3-Axis CNC Drawing Robot

Assembled Tiny 3-Axis CNC Drawing Robot

Assembled Tiny 3-Axis CNC Drawing Robot

FYI, if you like drawing robots and want to stay updated, please consider joining my newsletter.  Just stuff about drawing robots, no spam.

The Tiny 3-Axis CNC robot is a cheap, easy to build, extremely minimalistic but very capable little robot.1 This is the assembly guide for the version 0.29 robot available for download from Thingiverse.  The above picture shows the fully assembled robot.  If you have ever put together a lego set or built anything from Ikea, you should be able to build the entire robot in less than 5 minutes.  I’ve uploaded step-by-step photographs with each “step” organized into a short slide show of pictures.

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Here’s everything you need to build your robot.

Stuff You Need

Tools

  • One small precision screwdriver
  • Scissors and/or wire cutters

Parts

There are eight plastic parts, one rubber band, one zip tie, and three micro servo motors.  Once the robot is assembled, you’ll need to wire it up to the microcontroller of your choice.  I’ll link to the wiring tutorial at the end of this post.

Assembly

Step 0:  Print the plastic parts

All 8 plastic parts

All 8 plastic parts

Although you can fit all 8 parts onto the build platform for a MakerBot Replicator 1, you’re probably better off only about half the files at a time.  I would suggest printing the five short pieces at once and the three tall pieces together.  All the parts together are about 30 grams of plastic and took my printer about 2.5 hours total.  I should point out that I incorporated thin little discs onto the corners of the larger STL files.  These are only to help the parts adhere to the build platform and fight warping.  You should be able to easily peel them off the pieces without any tools.

Step 1:  Build the Z axis

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  • Gather the parts for the Z axis.  You will need three plastic parts (the printed Z pinion (gear), Z rack, and Z motor mount/Y axis), the zip tie, and a rubber band.
  • Use the scissors (or wire cutters) to cut a 5-10mm long piece out of the wide rubber band.  This piece of rubber band will work as a “gasket” to keep the Z pinion tightly secured to the Z motor shaft.
  • Push the screw through the rubber band gasket.  Place the Z motor into the motor mount.
  • Insert the screw (with gasket) into larger side of the Z pinion.  Insert the zip tie into the hole in the Z motor mount and secure the motor in place as show.  Try to zip tie your motor in a similar way – if you do it differently the zip tie can hit other moving parts.2
  • Cut off the excess zip tie with your wire cutters3
  • Place the Z rack as shown and secure the Z pinion in place using the precision screwdriver.  Rotate the pinion back and forth to make sure the Z pinion is placed well on the Z rack.
  • All done!

Step 2:  Build the Y axis

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  • Gather the parts for the Y axis.  You will need two plastic parts (the printed Y pinion and Y motor mount) and another rubber band gasket.
  • Insert motor into motor mount and set screw into the gasket
  • Secure the Y pinion onto the Y motor using the set screw and you’re done!

Step 3:  Build the X axis

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  • Gather the parts for the X axis.  You will need three plastic parts (the printed X pinion, the X motor mount, and the big X rack) and another rubber band gasket.
  • Insert motor into motor mount and create another screw-gasket-pinion combo
  • Secure X pinion to the X motor using the set screw
  • Looking at parts from top, rotate the X pinion counterclockwise until it stops and place it on the X rack as shown.  Roll it back and forth to make sure it stops at either end.  If it stops in the middle, just pluck it out and move it to where it needs to be.

Step 4:  Put it all together!

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  • Gather the Y and Z axes.  The Z axis is basically the same part as the Y rack.4
  • Looking at parts from top, rotate the Y pinion clockwise until it stops. Insert the long flat “fin” on the Y axis through the thin slot in the Z axis.  The Y pinion teeth should mesh well with the Y rack.5 Make sure the Z axis is as close to the Y axis as possible.  Roll Z axis back and forth to make sure it stops at either end.  If it stops in the middle, just reposition the Z axis to where it needs to be.
  • Gather the X axis.
  • Route the X motor wires through the hole in the Y axis “fin.”6
  • Pressure fit the YZ axis assembly onto the X axis.  Make sure the Y axis isn’t too tight on the X pinion.

Step 5:  Add something to the Z axis

Pen secured to Z axis with rubber band

Pen secured to Z axis with rubber band

This Tiny 3-Axis CNC is designed to be a platform for you to turn into anything you want.  Personally, I think it would be most fun as a tiny drawing robot.  If that’s your interest too, you could use a rubber band or zip ties to secure a pen to the Z rack.  However, there’s no reason you couldn’t use it to perform any number of tasks.  A fully functional Z axis allows the little robot to actually apply pressure to the drawing surface – making crayon drawings feasible, painting with brushes, some kind of automatic pin-pricking machine, or a gentle tickling robot.  By adding a fourth servo motor you could add a robotic gripper, automated syringe/plunger/eyedropper, or something else so entirely amazing that no one has thought of it yet.

Step 6:  Wire the robot to a brain

If you want to use an Arduino, I’ve already written a guide on how to run your DIY drawing robot to a variety of Arduino boards.  However, there’s no reason you couldn’t run this robot from any other kind of microcontroller or computer provided you figure out a way to operate servos with those devices.

Step 7:  Program your Tiny CNC drawing robot

Okay, confession time.  I don’t have any software to offer you … yet.  As I write this post, my first Tiny CNC design isn’t even 30 days old and is being improved upon and changed quickly.  Fortunately, at least two other fine persons have already contributed to this area.

Stephen Laporte has written some software to run an XY version of this robot.  Additionally, Thingiverse citizen Oliv4945 has created a Gcode interpreter just for the XY version of the Tiny CNC.

Room for Improvement

Even though this design is only a day old as I write this post, I’ve already got lots of ideas on improving it:

  • Pen Holder.  I want a better Z rack that is specifically designed to work as a pen holder.  I will always offer a non-pen-holder version so people can use this robot as a 3-axis CNC to do their7 bidding.
  • More Secure Drawing.  A redesign of the X pinion and X rack.  Right now the entire XYZ carriage can pop out of the X rack if the robot meets too much resistance.8  I have an idea to fix this problem completely.  If it works, the robot could be bolted mounted vertically or upside down and still work just fine.
  • Reducing plastic.  Interestingly, I reduced the amount of plastic in the design from version 0.18 to version 0.29 even though I added an entire additional axis.  The plastic could be reduced by thinning some parts and adding holes to other parts as The NewHobbyist did.  The interesting thing about “holes to reduce plastic” is that the actual “savings” may be illusory.  With 3D printed plastic parts adding holes to a design can significantly increase the amount of plastic used – when you’re printing at less than 100% infill. As a thought experiment, think of two plastic cubes with a 1mm thick wall around all surfaces.  One plastic cube has no holes and is printed at 10% infill.  The second plastic cube is also printed at 10% infill – but because it is riddled with holes that require a 1mm wall around every hole, there  is basically no space for the 10% infill.  The “holes to reduce plastic” trick only works on 3D printed parts that are thin pieces.  When it comes to parts that are injection molded, it’s my understanding that additional “holes” all the way through a part adds to the design complexity and can increase tooling costs.  That said, it would actually result in a reduction of plastic in a design.
  • Electronics.  For a variety of reasons, there isn’t one particular electronics/microcontroller solution that strikes me as the “best.”  ((That said, the Adafruit Trinket is ALMOST perfect for this job!))  For this reason I’ve considered possibly designing a tiny Arduino board with three or four servo pin-outs specifically for this robot.
  • Software.  I have some ideas on this and a heck of a headstart from Stephen and Oliv4945.  🙂
  • AFRON UAER Challenge.  If you haven’t heard about it, African Robotics Network (AFRON) has a new Ultra Affordable Educational Robot (UAER) design challenge this year.  They’ve also extended the submission time for the 2013 challenge to January 15, 2014.  With some creative sourcing and scrounging, I think I could bring the “cost” of this robot down to $10-$20.  This is a somewhat artificial goal since the “cost” as far as the UAER does not include shipping, taxes, tools, packaging, computing, and is based on the proportional cost of bulk-pricing.  I think I could enter this robot into the hardware, software, and community challenges.  I don’t have enough experience designing educational curriculum to outline the 20+ hours worth of material necessary to enter the curriculum category of the challenge.

If you’ve enjoyed this post, perhaps you’d consider donating a +1 to my WyoLum Innovation Grant challenge entry.  🙂

  1. Smaller than a paperback novel!!! []
  2. It won’t damage anything, but it will be a nuisance! []
  3. This is where they really come in handy []
  4. I know, the teeth are a dead giveaway []
  5. AKA Z axis []
  6. I really need to think up a better name for that design feature []
  7. Very tiny []
  8. RESISTANCE!!! IS!!! USELESS! []

Better video of Tiny CNC Drawing Robot actually drawing

I wanted to share a video of the ‘bot in action that was slightly less terrible.  In this one I’ve elevated the robot on two stacks of index cards, taped it down to keep it from wandering off, and given it a pen to draw with on another 3″x5″ index card.

I elevated the robot for two reasons.  First, it allowed the ‘bot to have a better “grip” on the pen (rather than just holding it near the tip) and resulted in a much better drawing.  Secondly, I’m using an old version of one of the gears which extends slightly below the larger rail due to the set screw.  By elevating the ‘bot, the screw doesn’t hit the surface and cause a wobbly walking motion.

The other day I discovered that I could use the Adafruit FTDI Friend to provide power to the Mintduino as well as reprogram it.  All I had to do was run a little red wire from the VCC pin to the positive rail and a black wire from the GND pin to the ground.  Easy!  Since then I’ve abandoned powering the Mintduino by 9V battery.  🙂  The next time I find an old USB mouse or keyboard, I’m going to definitely clip it’s leads so I can turn it into a USB source of 5V power for projects.  It’s convenient to use the FTDI friend to reprogram and power the board, but it’s a little awkward and not a great permanent solution.

How to Build a Tiny CNC Drawing Robot

Tiny CNC - all the parts needed

Tiny CNC – all the parts needed

UPDATE: Here’s everything you need to to build a Tiny 3-Axis CNC robot using just 8 plastic pieces.

The above are nearly all the tools and parts you’ll need to build your own itty bitty CNC drawing robot.1 If you have a 3D printer and a spare Arduino, the rest of the parts should cost you around $20.  Right now this robot only has two axes, but in the very near future I hope to add either a Z axis or a pen lift.  Without further ado the tools needed are:

Tools

  • One small precision screwdriver

Parts

You’ll also need an Arduino, some wire to connect your servos to the Arduino, and a USB cable to communicate with the Arduino.

Assembly

Step 1:  Print parts

All printed parts

All printed parts

There are only six printed parts necessary for this mini-CNC.  If you’re careful, you’ll be able to fit all six on your MakerBot Replicator into a single build plate.

Step 2:  Assemble the X axis stage

step04

Grab your Micro Servo, the little screw that came with it, the flat gear (really, pinion), and the X axis stage.  Just insert the Micro Servo into the X axis stage (it only fits one way), push the gear onto the Micro Servo’s motor shaft, and use the screw to secure the gear.  It should look like this when done:

Assembled X axis stage

Assembled X axis stage

Step 3:  Place the X axis stage on the large X axis rack

X axis stage and X axis rack

X axis stage and X axis rack

With the X axis stage gear-side down, rotate the gear clockwise until it stops.

X axis stage and X axis rack

X axis stage and X axis rack

Then place the gear into the X axis rack as show.

Step 4:  Place the Y axis rack

Y axis rack

Y axis rack

Locate the Y axis rack and place it over the X axis Servo Motor.

Y axis rack in place

Y axis rack in place

Like so.

Step 5:  Assemble the Y axis stage

Building the Y axis stage

Building the Y axis stage

Just as with the X axis, gather the parts and assemble.  This time, the servo motor goes into the stage (it only fits one way), the thick gear is then pushed onto the motor shaft with the gears toward the Y axis stage.

Assembled Y axis stage

Assembled Y axis stage

Like so.

Step 6:  Add the Y axis stage

With the Y axis stage gear-side down, rotate the gear clockwise until it stops.

Getting the Y axis stage ready

Getting the Y axis stage ready

Route the X axis servo motor wires through the rectangular hole in the Y axis stage.

Routing X axis servo motor wires through the Y axis stage

Routing X axis servo motor wires through the Y axis stage

Place the Y axis stage down, with the large rectangular hole around the X axis motor.

Almost done building a robot!

Almost done building a robot!

Almost done!

Step 7:  Ready the pen holder

Place the rubber band around the pen holder as shown.  You will probably have to wrap it around a few times.

Rubber band wrapped pen holder

Rubber band wrapped pen holder

Insert a pencil, pointy-bit down, into the pen holder.

Full assembled drawing robot

Full assembled drawing robot

Step 8:  Admire your work

A baby robot is born!

A baby robot is born!

Your robot is done!

Step 9:  Wire Robot to Arduino

To save you a little bit of trouble reading the Arduino sketch and figuring it out, here’s how you would connect your robot to the Arduino:

  • Use a piece of wire to connect the orange wire from the bottom X axis servo to pin 13 on the Arduino
  • Use a piece of wire to connect the orange wire from the top Y axis servo to pin 12 on the Arduino
  • Connect the brown wires from the servos to the ground pins on the Arduino
  • Connect the red wires from the servos to the 5v pin on the Arduino

Step 10:  Draw!

Download my Arduino sketch to operate this robot.  The movements of the robot are hardcoded at the moment, so please check back for updates.  Also, if you don’t tape or glue or somehow affix the little bot to a heavy surface, it will literally jerk itself all around the table.  (Although, in retrospect, I could have made it draw slower…)

It’s a little difficult to see the lines as the robot is drawing, but it really is drawing a grid in this short video:

Room for Improvement

I hacked this little project together just in time for the MAKE and GE Robot Hacks presentation on 11/20/2013, so I know there’s lots of room for improvement.  Here are some things I’m working on:

  • An entire Z axis or pen lift mechanism using a third servo
  • A better pen/pencil holder
  • Actual code to use XY coordinates instead of directly specifying the degrees for each servo
  • Actual motion control software from Processing or Python
  • A few adjustments to the Y axis stage for a better fit
  • Possibly thicker gears so that I can use set screws
  • A variation on the gears to use less plastic
  • Getting the robot to work with my Adafruit Trinket!

I hope you enjoyed this quick to print and easy to use desktop drawing CNC!

  1. You’ll also need an Arduino and some bits of wire []

Building a PlotterBot Arduino Drawing Robot – An Overview

Completed PlotterBot

Completed PlotterBot

A PlotterBot Arduino-based drawing robot is an easy to build robot you can make from off-the-shelf electronics and easily repurposed parts.  At it’s heart, this robot uses a microcontroller to drive motors to reel in and out two spools of wire to move a pen across a vertical surface.  One of the best thing about this particular robot is that it is extremely forgiving.  Your robot will still be capable of drawing huge amazing pictures even if you don’t mount the motors perfectly level, your spools aren’t quite symmetrical, or if your measurements are a little bit off.1

Here’s an overview of what you’ll need to do to build your own PlotterBot:

  1. Parts
    1. 2x Stepper motors
    2. 1x Servo motors (if you want to do pen lifts)
    3. 1x Arduino Uno or greater
    4. 1x Adafruit Motor Shield
    5. USB cable
    6. Power adapter
  2. Hardware and Supplies
    1.  Assorted wire, nuts, bolts, screws
    2. Monofilament fishing line
    3. Solder
    4. A project box or the stuff to build one with
  3. Tools
    1. Soldering iron
    2. Power drill
    3. Screwdrivers, hex wrenches
    4. A 3D printer is very helpful – but not necessary
  4. Assembling the Electronics
    1. Build the Adafruit Motor Shield
    2. Connect the Shield to the Arduino
    3. Load the Polargraph firmware
    4. Connect motors to the shield
    5. Test the assembled electronics
  5. Build the Robot
    1. Connect spools to the stepper motor shafts
    2. Mount the motors in your project box
    3. Wind monofilament fishing line on the spools
    4. Tie the fishing line to your pen holder
  6. Calibrate the Robot
    1. Measure the diameter of the spools and distance between motors
    2. Save your settings and upload your measurements to the robot
  7. Draw
    1. Load pictures into the software and start drawing

Keep in mind that once you have the basics (an Arduino, the shield, and two steppers) you can change the setup to suit your needs.  I’ll discuss more about each of these points, and turning each one into a separate blog post (or more!) soon.

Finally, join the PlotterBot newsletter now so you don’t miss out on the latest information!

  1. Of course, it will do a better job if you get everything right… []