Author: Maker Block

Overengineered Stepper Motor Mounts, Filament Guides

Simple - see?
Simple – see?

If you’re just tuning in, I’m working towards overengineering a drawing robot.1 Here’s my progress to date:

  • PolagraphSD case – discussed here – done!
  • Mounts for a paper roll – discussed here – waiting to upload…
  • Filament spools – discussed here – waiting to upload…
  • Stepper motor mounts – discussed in this post – waiting to upload…
  • Filament guides – discussed in this post – waiting to upload…
  • Pen holder/gondola – TBD

The most difficult part is definitely going to be the pen holder.  I’ve seen some good ones, but… well, that’s another blog post.  :)

  • Motor Mounts.
    • I’ve designed these motor mounts using the same exact groove system that I used to mount the paper roll holder.  This means I’ll be able to adjust, mount, and dismount the motors by just adjusting a single bolt.  I’m a little concerned about whether the plate the motors are attached to is thick enough to prevent it from wobbling.2
    • I’ve also left space around the motor so that I can add some kind of insulating material.  I’ll try a few different materials, starting with the cheapest and most readily available – cardboard.  After that, I’ll try polar fleece, foam packing material, a sheet of rubber or silicone.
    • With some minor modifications to the design, I could use some zip ties hold down the motor.
    • Since I don’t have any really really short M3 bolts, the length which would be ideal for holding the motor to the mounting plate through a thin layer of material, I’ll use an M3x16 with several M3 nuts on it.
  • Filament Guides.
    • In my earliest version of my drawing robot I tried to use a plastic filament guide which was incorporated into a motor mount.  While a cool idea, the original just didn’t work.  The filament squeaked and tended to bind on the filament guide.  This may have been due to the filament rubbing against the wood of the project box.  This new one is basically a plastic cylinder that will be insert into a hole in the wooden project box.
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  1. Photo courtesy of Casey Hussein Bisson [↩]
  2. Wibbly wobbly, timey wimey [↩]

Best Super BoWl Day Ever

Capslock is NOT persuasive
Capslock is NOT persuasive

ToDAY i’ve tinkerED with my DigiSpark From dIGIsTUMP and run it throUGH A few little programs.1 My experienCE with arDuinos is acTUALLY quite limited.  SincE i’M faMILIar with c-style proGRAMMIng languages, I can teLl what an ARDUINO sketch is Doing if i spend enough time staring at the COde.  I staRted off with “Blink,” then cHAnged it tO blink fASTEr, then FOUnd some COde for FLIppING CapsloCK on and off.2

WhAT i like about the dIGIspARK IS that IT IS so small I can keep IT IN THE coffee Table drawer nearesT MY Laptop to tiNKER with WHenever I THINK OF something to TRY.  TherE ARE SOMe interesting littLE FEATURes to the DiGISpark from the arduino i’LL cover IN another posT THAT doesn’t look liKE it was typeD BY A chimp.

The MOST FUnctional pARTS of TODAY have BEEN devoted to PLAYing, MAKING tangram dESIGNS, bloggiNG ABOUt robot pART design, fiddling with a tiny miCROcontROLLER, and, of course, A NAP.  HOW Did you spenD Your super bowl sunday?

  1. Photo courtesy of Adam Fagen [↩]
  2. SEE! [↩]

Overengineered Spools

Overengineered soda-fountain valves, in Hamburg, Germany
Overengineered soda-fountain valves, in Hamburg, Germany

This post is a sub-series concerning the redesign of the various parts of my DrawBot.  In short, I am looking to design/redesign

  • PolagraphSD case – discussed here – done!
  • Mounts for a paper roll – discussed here – waiting to upload…
  • Filament spools – discussed in this post – waiting to upload…
  • Stepper motor mounts – TBD1
  • Pen holder/gondola – TBD
  • Filament guides – TBD

After several iterations, I printed the parts2 for spools for the newest version of my DrawBot.  ((Photo courtesy of Cory Doctorow))

The original spools I designed were simultaneously over-and-under engineered.  They were over-engineered since, for spools, they required two separate parts that would be friction-fit together around the monofilament line.  They were under-engineered since, ultimately they once came apart while still attached to the robot – resulting in a lot of monofilament line unspooling everywhere.  While not tragic, it was a small hassle.

The second iteration of the spool for my DrawBot was far simpler.  You feed the monofilament line through a tiny hole in the spool and slide it onto the stepper motor shaft.  It was a single print where one end of the spool was flat and the other end was beveled to comply with the “45 degree” rule.  This spool design worked wonderfully – once I forced them onto the stepper motor shaft.  They were also bubble gum pink, according to my daughter’s specifications.  However, once I decided to upgrade my DrawBot into a PolargraphSD, I needed to remove the motors from their mounts – which meant I needed to take the spools off.  Unfortunately, taking the spools off proved to be a problem.  I had to literally hack them off using some heavy wire cutters, pliers, and a no-foolin’ hacksaw blade.  It did not help that I printed them at 100% infill.  I cannot imagine for the life of me WHY I wanted to print spools, that are basically non-weight-bearing, in solid plastic.  The big problem with this design was that the tolerances on the spools were not right – and it is entirely possible they never would be.  Slightly too tight and they would have to be destroyed to be removed or adjusted and slightly too loose and they might not stay on the shaft or have too much play as the robot operates.  In the end, I’m just not sure I could really “trust” a single-print press-fit spool to be removable and reliable.

Which now brings me to the spools I have designed over a few days and printed yesterday.  After several revisions I now have two spools3 which are themselves compromised of two parts.  I would have to say that although this spool is more complex than the first version I used, it is probably going to be the most reliable overall.  Each spool requires 2x M3x16 bolts, 1x M3x12 bolt, and three M3 nuts.  The two M3x16 bolts hold the top and bottom parts of the spool together tightly and the single M3x12 bolt is used to tighten the spool to the motor shaft.  The result final result are two spools that are symmetrical, do not have a beveled end where monofilament can be gathered over an increasing diameter, and can be tightened on the motor shaft or removed with ease.  They’re also somewhat heavy which gives them a good respectable “this-is-definitely-a-robot-part” feeling.

I will be sharing these designs on Thingiverse and they will be able to be found under my Designs or tagged with DrawBot, but I’m going to wait until after I’ve assembled the entire robot and have actually drawn something.  For all I know these could be abysmal failures.

Stay tuned – next, I’ll overdesign motor mounts!4

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  1. To be designed! [↩]
  2. Plural?!?! [↩]
  3. Printed at only 10% infill! [↩]
  4. Then, it’s ten somersets I’ll undertake on SOLID GROUND! [↩]

This project is not going to overengineer itself

Seriously, why would anyone with hands buy this?
Seriously, why would anyone with hands buy this?

This weekend I worked on my DrawBot.  ((Photo courtesy of Relly Annett-Baker))  I stripped my current DrawBot for parts so that I may build it back together with a PolagraphSD brain/heart.  ((Bart?  Hain?))  Given that there aren’t a ton of parts involved, the process went quickly.  I disconnected the two steppers, pulled all the screws1 and all the nuts and bolts2 from the project.  Right now all that is left of my once mighty3 drawing robot is an Arduino and shield duct taped to a chunk of plywood.

To assemble the new robot into the desired configuration ((Sketch D for those of you playing along at home)) I needed to design:

  • A new PolargraphSD case
    • This new case is about 2/3 the volume of Sandy’s design and has vents along the sides and top to help with heat dissipation.  It can also be assembled without any tools or hardware – with the LCD actually keeping the entire thing together.  At this point I now have three perfectly serviceable cases.  My goal, once the entire robot is put together, is that it look and feel like a finished and polished project – a DONE project.  But, really, I’d like to have it semi-permanently installed somewhere in my house as a drawing appliance.  My prior ‘bot while cool with tons of nifty little hacker cred to it was little more than a chunk of plywood with bits hanging off.  I’d draw something with it, put the board away, then bring it out later.
    • My ideas for building out the robot have changed slightly since designing this case, so I might need to adjust the code and print another one.  The issue now is that the case is designed to be mounted by being bolted into the base of the project box.  However, if I do that a nut or bolt will have to stick through the back of the project which will prevent the paper roll from being able to travel behind the project box.  I figure I could print a new case and bolt it to the side of the project box – but that might interfere with the location of the motors/motor mounts.  I might be able to just ziptie the case to the top of the project box – which might not be good as the bot is expect to shake a little in operation and I don’t want the board shaken unnecessarily.  Frankly, at this point, I think I’ll get everything else situated completely within the project box and come back to figuring out how to mount the case.
    • Although, an idea which just occurred to me is that I could glue some plastic mounts, with captive nuts, into the inside of the project box and bolt the case into that.  Again, this would best be done once all the other issues are resolved.
  • New monofilament spools
    • I had to completely destroy my existing spools to get them off the motor shafts.  For some god-awful reason I printed the two spools at 100% infill creating the sturdiest monofilament spools in existence.  I cannot imagine what possessed me to do this.  They were heavy and impossible to remove cleanly from the motor shafts.  I didn’t get the tolerances right with the prior spools, so I had to force them onto the shafts – but then they were stuck.  I had to use a big pair of wirecutters to chop chunks of plastic off until I could pull the last bits free from the motor.  When I finish designing and printing a new set of spools, I’m going to make sure the tolerances are right before I assemble.  I want the spools to fit snugly becuase I don’t want the motor to slip when it reverses directions – as it will do frequently across a large drawing.
    • I’m still kicking around ideas on how to improve the spools.  My first spools were way too complex and the friction fit wasn’t enough to keep them together.  My second set was too tight and too short.  While I wouldn’t mind a friction fit spool, I need a spool that can’t come apart during operation4 , can be tightened on the motor shaft, and can be removed easily if necessary.  Additionally, I’d like the final spool to be taller – so that there is more of the spool center and less of the flared end of the spool for the filament to wind onto.  The flared end was flared so that the spool could be printed as a single piece.  While this was nice for simplicity’s sake, I found that sometimes the filament line would “ride up” the flared end – which introduces unnecessary error into the process.
    • Looking at the AS220 Labs website page for their drawing robot kit through Archive.org, you will notice that they use a tall spool with a low-friction monofilament line guide.  The benefit of the tall spool is that it can keep a more consistent diameter for more of the filament versus a narrow spool that will accumulate layers of filament more quickly.  The benefit of the line guide is that it forces the robot to maintain the proper distance between the two motors even when the spools are mounted horizontally.  I also happen to like the horizontal spool mount system since it means the motors won’t stick out from the wall quite so much.5
  • A new gondola
  • A way to mount a roll of paper to my project box
    • Besides tearing my drawing robot apart, this is the one thing I did manage to design, print, and put together over the weekend.  Since the paper roll I’m using did not come with a center of cardboard or wood or on any kind of spindle, it is not an immediately mountable thing.  My roll of paper is just that – a really long roll of paper.
    • What I wanted was a modular way to mount a roll of paper to the top of my project box so that it could be adjusted to fit different diameters and widths of paper rolls.  My solution was to print two “caps” to go at either end of the paper roll, with a hole through them to run a long wooden dowel.  The nifty part is where I then bolted two printed plastic tracks to the top of my project box, onto which I can slide a plastic arm which the wooden dowel fits into.  Once the two plastic arms are in place, they can be tightened down onto the plastic track.  The result is a rock solid paper roll mount that lets the paper roll freely turn.  I was so happy with the way this turned out I almost couldn’t see straight.  Yes, it is just a mount for a roll of paper – but it is the most solid and polished way one might hope to mount a core-less roll of paper on top of a wooden box.
  • A new way to mount the stepper motors to the project box
    • Given the amount of time I’ve spent just mounting a roll of paper and obsessing about spools, is it any wonder I haven’t finished thinking about how to mount the steppers?  With the first incarnation of my drawing robot I had designed and printed no less than three completely different motor mounts.
    • I would like the final version of the motor mounts to be easily adjustable, probably using a similar track/mount system that I used to mount the paper roll.  While this kind of solution takes more time to design, the result is a robot that can be quickly and easily improved and adjusted.  As suggested above in the spool section, I am leaning towards mounting the motors so that the shafts are horizontal on the plate of the wall.  This will let the motors keep a slim profile in the project box and allow the use of a tall spool which will enable more even and uniform reeling and unreeling of monofilament.
    • I’m tempted to incorporate a monofilament line guide directly into the motor mount.  In the interests of modularity, it makes sense to keep these things separate, but it might just make sense to do this given the limited space I’ve got within the depth of this shallow project box.6

I’m undecided whether I want to put a cover on the front of my project box.  On the one hand leaving the front of the project box open allows the viewer to peer into the robot and marvel at its simplicity.  On the other hand, without viewing the internals all you would see is a box mounted on the wall, a paper roll on top of that, a power cord coming out of the side, and a drawing pen moving by two almost imperceptible monofilament lines.  Perhaps I should explore this idea in another long winded post?

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  1. Four total [↩]
  2. 12 nuts and four bolts [↩]
  3. Mighty UGLY, that is! [↩]
  4. When one of the friction fit spools failed mid-drawing, it was like watching my robot puke monofilament line.  Frankly, a monofilament puking robot is pretty awesome – just not when it is made from a drawing robot [↩]
  5. If you were betting on me not being able to type an ENTIRE Page of text just on the considerations of the spools in my robot, you would have lost. [↩]
  6. For reference, the box I’m using is less than 2 inches deep. [↩]

A watched DigiSpark never boils

Itty bitty microcontroller
Itty bitty microcontroller

I’ve been refreshing my DigiSpark Kickstarter backer/order page for days now watching my spot in the queue go from #3800 to just now under #200. ((Photo courtesy of Clarence Risher))

Since I have such limited experience with Arduinos, I am hoping that this project is a good place to start.  To date my experience with Arduinos had to do with the minor modifications/updates with the Arduino powered motherboard and extruder board for the Cupcake CNC and my DrawBot.

One of the benefits of the DigiSpark that interested me the most was it’s extremely small form factor.  It’s so tiny that I can pop it into a USB port and try out a small Arduino sketch1 without tangling with a USB cable.  And, when not in use I can drop the whole thing into the coffee table drawer.  An Arduino plus USB cable, while still small, are just a little too bulky to toss into the same drawer.  ((Mostly because of all of the other little projects I already have tossed in the same drawer!))

  1. Blink, you say? [↩]

Every Body Needs a Skull

Delicious brains
Delicious brains

Is there anyone out there who built their own Polargraph, but does not have a plastic case for it?1

In designing my own I’ve got two perfectly serviceable cases that I’m not going to use.

Each case fits Sandy Noble’s PolargraphSD which consists of an Arduino Mega 256 clone plus an LCD touch screen and his custom shield for running the drawing robot.  I’m also going to be taking my current Arduino Uno plus Adafruit Motor Shield powered drawing robot apart.  When I do I will have another plastic case.

If interested, please drop me a line.

Oh, what’s with the skull and brains?  Well, if you have a robotic brain, wouldn’t a nifty plastic skull go nicely with it?

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  1. Photo courtesy of chotda [↩]

Oh the places you’ll go!

Something like six months ago I checked in on the Piccolo by Diatom and watched the cute little video that goes along with it.  That video led me to the video for their Antler lasercut chair featured above which, in turn, lead me to the album for Wet Wings and their song Keep It Together.

I mention this only because a new tiny CNC on Thingiverse reminded me of the Piccolo, which lead me back to the video for their Antler lasercut chair and to the song all over again, and it is a song I happen to like a lot.

DrawBot Aesthetic Re-Design Ideas

Ideas for DrawBot Designs
Ideas for DrawBot Designs

I’ve been kicking around some design ideas for how my new DrawBot will look.  I’d like it to be aesthetically pleasing and reasonably compact so that when not in use it will be reasonably unobtrusive.  For the most part none of these designs would require the DrawBot to operate in a mechanically different way.  However, most of them would probably look best with a fishing line spool rather than beaded cord and sprocket system.

  • Design and create a nifty DrawBot mounting system
    • Above you can see some of my ideas for mounting a DrawBot to a wall. It is probably most ideal for a DrawBot to operate at a slight slope – so that a little bit of gravity is keeping the drawing gondola pressed against the drawing surface. That said, here’s my thought behind some of those designs.
    • Designs, Generally.  Several of the designs above contemplate the drawing robot brain being housed inside a long thin box.  I had tried housing my current DrawBot inside a box, but it just didn’t work very well.  Since wiring would be easier if the motors are mounted near the robot brain and running the power cord to the robot would be easier if the brain were situated to one side, it might be most pleasing to use a wooden box that has a lid which can be flipped down over the front, rather than leaving the robot brain and motors exposed.  One other interesting item is that while I’ve typically mounted the motors so that the motor shaft is pointed towards the wall with the spool on the outside, there’s no reason to design a clever mount which would orient the motor shaft perpendicular to the printing surface with the spool on the inside.  This could result in keeping the fishing line a lot closer to the wall than would otherwise be possible.
    • Design A. This design features the motors, DrawBot brain, and roll of paper mounted directly to a piece of plywood essentially as my current set up exists. I figure I could pick up some cheap hardware store rulers and nail them to the board on the left and right side to keep the paper pressed against the DrawBot surface. While this is probably the easiest design to implement, it lacks the symmetry of the other designs.
    • Design B. This design features a similar motor and brain mount to Design A, except that the paper roll is mounted behind the board. This design also features a wide horizontal slot cut into the board near the top through which the paper roll could be fed. This would require the plywood board to be set off from the wall, which is not really that big a deal. One additional problem is that the best roll of paper I could find is actually a fair bit wider than the board itself. Of course, I could have someone chop down the roll of paper, but this seems like it would be a huge hassle.
    • Design C. This is wall-mounted system similar to something I first tried when I set up my DrawBot. I mounted the brain and the motors inside a long thin pine box I had lying around. I had tried a number of variations on this without much success.
      • Fishing line. I tried running the fishing line through holes in the bottom of the pine box, but the fishing line kept getting caught on the wood. I tried routing the fishing line through screw-in eyelets, but the fishing line would get caught on that too. In both instances the fishing line just wouldn’t run smoothly back and forth. If I tried this again, I would need to basically cut out the entire bottom of the box so that the fishing line would run off the motor and directly down onto the drawing surface. I think that unless I use bearings and pulleys, there’s no good way to route fishing line in a way that won’t be bothersome.
      • Robot Mounting. What I particularly like about this set up is that all the important bits are completely enclosed inside a box that could be mounted nearly anywhere. If the paper roll was not mounted to the wall and just a sheet of paper was used instead, the entire robot would become very portable.
      • Motor Mounting. Assuming the fishing line routing issue was just solved with bearings and pulleys, both motors could be set right very near to the robot brain in the center with a pulley on either end of the box. I’m not sure if it is is better to have all the weight in the center or somewhat distributed across the length of the box. That said, it would be a lot easier to deal with wiring if the parts were all close together.
      • Drawing Surface. This is the big problem with this design. Since the drawing surface is the wall and most walls have some sort of texture, it would cause a degree of randomness and unevenness to creep into the drawing itself. In some cases this might be desirable, interesting, or part of the effect – but I think I just prefer a drawing to be smooth unless I specifically cause it to be otherwise.
      • Paper Mounting. Assuming the robot was really installed on a wall, which does contradict somewhat with the desire to this design make the robot portable/modular, a paper roll could be mounted directly onto the wall, held in place by two hardware store rulers on either side. I suppose I could always put a big sheet of flat plastic behind the paper.
    • Design D. This wall-mounted system is very similar to Design C, except that the paper roll is mounted to the box housing the robot and the paper runs behind the box.
      • Aesthetics. I really like this design overall because it would be very compact, more “portable/modular” than Design C while still providing all of the functionality of Design C. Interestingly, it might actually be a lot better to mount the robot brain far to one side or the other. By doing so the AC adapter cord would not have to travel nearly as far to get to the brain.
      • Mounting Considerations. One big difference is that while Design C could be mounted with all of the mounting hardware hidden by the box itself, Design D might require all of the mounting hardware to be very far to either side of the box or outside the box entirely. This design would also only require one hardware store ruler to be placed on the wall, below the robot, since the top part of the paper would be kept flush against the wall by the robot box itself. This, of course, assumes that the robot would be mounted to the wall – but not so close that it would keep the paper from unrolling behind the box.

        One more DrawBot design
        One more DrawBot design
    • Design E.  As I was typing this up another idea occurred to me.
      • One of the problems I had with a box-mounted system was that getting power or a USB cable into the box was difficult.  For any interesting sized drawing the box would have to be mounted several feet off the ground.  The benefit of this design is that the paper roll could be mounted below the wooden box1 and the wooden box could be mounted near the floor – with easy access to an electrical outlet.  The downside is that the brain is basically on the floor where it can get kicked and that you’re going to have route the fishing line up over the drawing and around pulleys on either side.
      • One thing about this particular design is that I’ve drawn the DrawBot brain and both motors off to one side of the box as suggested in the “Designs, Generally” section above.

Having gone through the trouble of sketching and articulating the various benefits to each system, I think my favorite so far is Design D, with a lid over the front of the box, and the brain and motors mounted off to one side to make routing power to the project a lot easier.

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  1. Or, like some of the designs above, it could be mounted to the wall off to the side. [↩]