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Facial deconstruction

There comes a time in everyone's life when they realise that their hobby is getting out of control.  And if there was ever a bright red, extra-large, "go-and-join-your-local-roboticists-anonymous" warning flag about when your little robotics project is being taken too seriously (and it's actually not so little any more), it’s when a 3D printer arrives in your home.

Yes, that's right.  DIY robotics is about to be dialled up to 11.  We'll grow to love the (slightly sweet) smell of PLA in the morning.

We’re pleased to announce that Rosie Patrol is about to receive a long overdue makeover, and be given a random digit with a meaningless decimal point just because.  Get ready.  Rosie Patrol is about to be painstakingly updated to become Rosie 2.0 (pronounced two-point-ohhhhhhhh).  Thanks to the wonders of 3D printing.

All superheroes need:

  • Can you guess what you need if you want to do some 3D printing?  Anyone?  Yes?  Clearly, you'll need some sort of 3D printer.  We're using a FlashForge Finder, but many other makes and models are available.
  • ...And you'll need some colourful filaments to feed your 3D printer.  We're using perhaps the most popular type of material used in 3D printing today - a bioplastic called polylactic acid, or PLA for short.
  • There are several bits and bobs you should have on hand when it comes to 3D printing.  Some masking tape, glue and isopropanol cleaning liquid are useful for making sure that there's no warping (don't worry, more on this later).  Also, a caliper is essential for making precise, real-life measurements.  Pliers and a palette knife are also recommended if you have additional plastic that you need to remove from your creation, like supports, or brims and rafts.  Nope, we're not making these terms up.
  • You may need to invest in a new set of servo motors... all this fancy plastic being added to your robot anatomy will need some heavy lifting.  Your cheap, micro servos are unlikely to be up to it.

Already completed these missions?

You'll need to have (ideally) completed the Rosie series... because we are trying to build a robot (clue is in the title of the site).  In which case, quite possibly, you'd also like to look at:
  1. Lights in shining armour 
  2. I'm just angling around 
  3. Eye would like to have some I's
  4. Eh, P.I?  
  5. Lights, camera, satisfaction
  6. Beam me up, Rosie!
  7. a, b, see, d 
  8. Code: read
  9. Farcical fartificial intelligence

Your mission, should you accept it, is to:

  • Google* all that there is to know about 3D printers, and printing.  *Other search engines are (apparently) available.
  • Print a few random objects when you think you have your 3D printer up and running.  It's true.  Practise really does make perfect, here.  Thingiverse is a great source of objects that you can simply download and print.  Take this opportunity to populate your workshop with random orcs and unicorns.
  • Begin your very own designs of primitive robot parts.  We used SketchUp for this step.
  • And once your designs have been exported into STL (stereolithography) format, you can print these non-award winning works of art on your 3D printer.  We used FlashPrint (software that happened to come with our 3D printer) to do the printing.
  • Go and do something else.  Somewhere else.  3D printing is not fast, especially for bigger parts.
  • Attempt to assemble the components.  And when you realise that they are a tad rubbish, repeat all steps (except the one about orcs and unicorns).

The brief:

Like Bitcoin or sliced bread, you've probably heard of 3D printing by now - although you may have quite literally been living under a rock.  But you've probably not had the urgent need to experiment with it... orcs and unicorns aside.  Well, as it turns out, building your very own robot is a pretty good excuse to have a go.  After all, even NASA is in on the act.  So we can legitimately claim that we're employing technology of space travel.

3D Printing pretty much does what it says on the tin (except we're not using tin, but plastic... and it comes with nothing written on it).  You design - occasionally useful - stuff that is not one, not two, but... wait for it... three dimensional.  And you watch the 3D printer painstakingly create them, from the bottom up, one minute layer at a time, until - yes - they magically materialise on the platform in front of you.  We're using PLA (Polyactic Acid) which is a biodegradable bioplastic.  You purchase them in filaments, and they get fed into the extruder of the 3D printer that ominously hovers above your platform.  And once the entire contraption is used to build whatever object you've designed, the results can be pretty impressive.  Almost indistinguishable from real plastic, in fact.

So let's get going.  Let's design Rosie Patrol's new head.  And watch it materialise before our very own eyes.

The devil is in the detail:

If you want to do some 3D printing, you need a 3D printer.  There.  We stated the obvious (again).  Just in case you weren't sure.

There are many different types of 3D printers available; some expensive, others cheap.  Some you self-assemble yourself.  Others come all ready for you to use (except making sure that the bed is even and flat).  They come in many different shapes and sizes.  Different colours.  And often allow you to "print" different materials, other than PLA (although beware of the properties of alternative materials... others such as ABS can be toxic).  Therefore, like when buying a new family pet, it's best to do some careful research before choosing the one that best meets your needs.  As Confucius probably once said, do not buy an ostrich, if what you need is an emu.

We're using a FlashForge Finder, and it seems to work well for us.  It can print stuff using PLA filaments to a build volume of up to 14×14×14cm.  Which is good enough as we're not (yet) planning to build a life-size replica of the Titanic.  And most importantly, it comes in red.  Like Rosie. Or Rosie Patrol.  Or whatever it is that we've now decided to call her.

Let's get our mandatory health and safety announcement out of the way nice and early this episode.  As there's an abundance of opportunities for serious oops I do not want to do that again moments when it comes to 3D printing.  Which means... adult supervision is a must.  Did we just hear you boo?  Seriously.

Filaments are heated to well over 200 degrees in the extruder so there's always the potential for some burns.  If you're using a blade to remove unneeded bits from your model, there could be blood.  And some chemicals you may be using (like cleaning products) are probably not so good in your eyes, or stomach.  And no - none of these hazards are actually as cool as they appear in Arnie films.

Having said all this, 3D printing is pretty safe and is regularly ran in well-ventilated schools, offices and make-shift robot workshops all around the world, by people of all different backgrounds and skill levels.  But you get the point.  Always read instructions and labels, and when at all in doubt, take advice from someone more experienced than you (who isn't Arnie).


Here's the obligatory photo of our printer doing something


It just so happens that it is printing an early version of the back of Rosie Two-Point-Ohhhh's head.  And look at it go. What you don't see here is the build platform gradually (and extremely slowly) moving down over the course of half a century, to allow the extruder to lay down layer after layer of fresh PLA goodness.  This is how the third dimension (z), or height, of the object is realised.  Horizontal x and y dimensions, on the other hand, are achieved by the extruder moving back and forwards, and sideways.  But you probably guessed that bit.

It's worth reminding ourselves; that it's important to Google all the basics and more.  From how best to operate the printer.   To which materials to use.  And once you've done some serious online reading, you'll need to follow the instructions that come with your machine, and load the end of the PLA filament into the extruder.  Only then, is it possible to start your print.  But not so fast (which it is not).

We quickly discovered that enemy #1 of 3D printing is warping.  And it's not a Star Trek-type of warp.  Warping is when the first layers of plastic begin to cool rapidly and contract, making the bottom portion of your objects (most often the corners) lift up away from the build platform.  It appears to be compounded if you are printing in a cold room with a draft (which is quite likely the case if you're in a well ventilated room, which you should be, in the Arctic, during winter).  Adhesion is the name of the game, and without it, you'll be in for some serious disappointment after hours of waiting for something to finish printing.

Here is a badly warped version of the rear of Rosie 2.0's head.  As you can see, the corners have significantly lifted up, and as a result, this one is pretty useless.  Yes, warping does cost you time and money.  It's best to address it before it happens.


The Wonderful World Wide Web (WWWW) tells us that people use all sorts of different techniques to prevent objects from warping.  We use a combination of masking tape (3M ScotchBlue Painter's Masking Tape) and glue (Pritt Stick) - which turns out to be a very popular combination.  The theory is that if you first lay down some very sticky tape onto the platform, and dab some glue on it, the first layers of PLA should remain stuck to the plate and not lift off.

Make sure, however, to clean the plate with some serious cleaning liquid (like isopropanol) before laying down new tape onto the platform so that any previous gunk is properly removed.  Otherwise, you might find the tape itself lifting off away from the plate, along with your model.  Which kinda defeats the point.


There are other more structural, and arguably drastic, ways to address warping, which involves adding additional bits to your model to achieve better adhesion to the platform, such as brims and rafts.  Pliers and a palette knife will come in handy if you go down this route, to remove the extra plastic that is added to the bottom of your object.  Some build plates are actually even heated.

Here's an equally exciting photo of some pliers, and a palette knife.


Right.  You're ready to print stuff.  And that's when the real fun begins.

Let's work backwards.  In order to instruct the 3D printer to print a three-dimensional object, the design of what needs printing needs to be in STL file format.  You can just download a design straight from the Internet.  Thingiverse is a very popular website from which you can download designs that others have kindly created for us.

Search for "robot" in Thingiverse and you'll see what others believe robots should look like.


There.  You can print out a few random mementos to make sure you can get this 3D printing business to work.  Printers work differently, but the FlashForge comes with software called FlashPrint that allows you to load the STL file, and send it to the printer for printing.  You can actually do a little bit more here, like slice the object, view it from different angles, and add supports to it (more on this later).

But these robots don't look very much like Rosie 2.0, do they?  They look far too professional.  And designed by people who clearly know what they are doing.  No. What we actually want to do is generate these STL files ourselves.  Design original robot parts using something.  Then print them off.  Rosie 2.0 robot parts, to be exact.

And that something can be one of many design software out there.  We decided to use SketchUp, as it's very popular in the 3D printing world, and it's free.  Plus it's known to be beginner friendly.

There are many excellent tutorials on how SketchUp works, so it's best to go and look at them first, and take it all in.  Evidently, this is where you will spend a majority of your time doing something.  Design some basic objects first, like a circle, and print them off.  Invest in a big monitor, and use a mouse.  You'll be less frustrated this way.

Note that in order to export your designs into STL file format, however, you'll need an "extension" in SketchUp.  Go to Extension Manager and search for it, and download / enable it.


This is important, as it allows you to export the model you create into STL file format.


Right.  We got distracted by technicalities.  Back to Rosie 2.0.

So what we really need to do now is design ourselves a few robot parts in SketchUp.  Without going into too much detail here, this process basically involves drawing shapes in the workspace, and giving them all 1, 2, 3 dimensions.  It takes a lot of practise, patience and test prints to become familiar with the end to end process.

But here are a few things we learnt along the way.  Cue the boring bullet points.
  • 3D printers can't magically print over thin air (called overhanging).  After all, they print layer by layer, from the base upwards.  Some less steep angles might be printable.  You can always use supports (that snap-off) if you really need to print something that overhangs.
  • Use a digital caliper to measure what you've actually printed so that you can make your designs in SketchUp even more precise.  This is really important if you want pieces to slot together, or fit snugly around real-life objects, like servo motors.  We're dealing with distances in millimetres (and often less).  It's best to get some accurate measurements, and don't rely on that plastic ruler that you've kept on your desk since school.

  • PLA will expand slightly around the edges, relative to what your design states in SketchUp.  We found this to be around 0.2-0.3mm along all edges.  Design the edges of your objects with tolerance in mind, so that if parts need to snap-in together you allow for some compensation.
  • Think about how parts join together.  Will they be glued?  Screwed?  Snapped-in?  Bashed together by a thousand elves?  You'll need to make sure that these considerations are "designed in" (other than the option that relies on the goodwill of elves).  Where you're planning to screw or bolt pieces together, it's more preferable to design and print the holes in your objects, rather than drill through them with your Turbo Electro Mega-Driver 9000 once they are printed.  This is particularly relevant when infills are fairly low (see next point below).
  • Solid objects don't necessary need to be pumped full of plastic.  Most printers can be told to be creative, such as subtly use a "honeycomb" structure inside solid parts to conserve material, speed up printing time, and lighten the weight.  In most cases this is preferable.  However, for some parts, you may want to change the "infill" percentage, or type.
OK.  That was boring.  Let's take a peek at the parts we (badly) designed in SketchUp instead.


What you might (or might not) see is Rosie 2.0's head.  There's 2 major parts; the front and rear.  The front has slots for her eyes, camera and purely cosmetic mouth.  The back has a slot for a Pi, and its USB and network ports.  There are other bits too, to allow things to be mounted with mixed results.  There are holes for where bolts are meant to be inserted.  And some clumsy attempts have been made to allow the "snapping-in" of some parts (although likely to resort to good old superglue in reality).

Convert these parts into STL, and we're ready to print.


Some larger parts can take hours to print.  For example, back of Rosie 2.0's head can take up to 8 hours to print, while some other smaller components only take around 10 minutes.  Let's see what these parts actually look like when they have been printed.

For a bonus point, you can play a round of spot the difference.  Can you see which part we printed but doesn't form part of our final design above?


We're on a roll.  Let's proceed to manufacture the neck as well.

This bit is slightly more intricate... as we need to design and build something that resembles a pan and tilt mechanism, incorporating our servo motors.  In short, we need to have brackets that both hold the servos in place, but combined, allow both vertical and horizontal movement.  You'll also notice that we've graduated from the tetchy SG90 micro servos we set up before, to some beefy HiTEC servos.  Why?  Because all this plastic is adding weight to Rosie 2.0's head, and we need something with a lot more torque.  Servos are available for cheap on eBay, of course, if you don't mind them having a few bruises.

A table with geeky specs:

UseMakeModelTorque
Servo for horizontal movementHiTECHS-525BB4.1 kg-cm (at 6V)
Servo for vertical movementHiTECHS-5485HB6.4 kg-cm (at 6V)

Here's our design of the neck mechanism in SketchUp.


And here are the STLs that we will be printing, as seen in FlashPrint.


Note that the overhanging bit of the far left bracket will be printed with a support, which FlashPrint can add for us using the auto support function.

Once this is all assembled using screws, glue, nuts and bolts, Nutella, and elves, it's ready to be moved around.  Note that we continue to use the Pi's GPIO pins, and PWM, to control the two servos via the Monk Makes ServoSix board.  It has to be said, however, that the Pi is not very good at supplying reliable PWM signals.  And coupled with the fact that we're about to embark on a *new* project using lots more servos, we're likely to move onto a dedicated controller that can supply reliable PWM signals in the near future.  More on this soon!

Now, using the four slots for the bolts, we can attach the head and the neck pieces together.  As you can see, we don't yet have a body.  And that's why all her internals, like battery packs, are ingloriously spilling out onto the desk like a scene from a Tarantino flick.


And finally the moment of truth.  Let's get the whole thing to do stuff.  Start the Python applications from our previous excursions that randomly control her eyes and neck servos, and it all comes to life.


Of course, the great thing about 3D printing is - if you don't like something, or it doesn't quite work - you can always re-design and re-print pretty painlessly.  If you are working on some complex parts that work together, it might also be worth just printing the relevant subsection first so that you don't waste PLA filaments just printing the whole component over and over again.  This is especially important when trying to make designs align with real-life objects.

So there it is.

It might not look too sophisticated.  And she's still missing a body.  But what we've proven is that 3D printing can work.  And, what's more, hopefully you have ended up with a few orcs and unicorns along the way.

Bye bye old bits of pink plastic.  You have served us well.

The (further) face lifts:

The most noticeable advantage of 3D printing- of course - is that you can make changes to your designs pretty easily, and re-print them; whether they are for minor improvements, or a complete overhaul.

Further into Rosie 2.0, we decided to revisit Rosie's head for many different reasons.  First of all, we didn't want it to be so bulky... or square.  But more importantly, while we are still officially "mucking about", it remains convenient to be able to - quite literally - access the bits insider her head.  And add more to it, whenever, and however, we wanted to.

Which led us to a design which is arguably slicker, and versatile - although pretty exposed.

We won't guarantee that this won't change any further.  In fact, it most probably will.

Information overload:

We're using a FlashForge Finder 3D printer:
Incidentally, if your FlashForge Finder gets "jammed", here's a great video on how to "un-jam" it.
...And SketchUp for the design:
Thingiverse is a great resource for 3D printing, and designs:
We've graduated to using HiTEC servo motors which are very popular for more serious usage:

    Comments

    1. Wow - Rosie really graduated. Graduated to the "big league", and so quickly. Very impressive. Congratulations on pulling so many technologies, skills, and time together. It has been very neat to read the well documented project notes that are filled with levity and energy.

      As an undergrad at "R3 Elementary School", (I've been modding my 17 year old bot to run "Don't reinvent the eel"), it is somewhat sad to see the senior classmate graduate to embark on a unique journey.

      Also sad is to hear that Rosie is shedding hardware as "she" graduates. I was hoping Rosie's mind would find its limits, before "her" hardware did. It is true that Rosie's new form will open a wider range of synthetic emotions to investigate.

      The mind and "maker" behind Rosie is impressive. Rosie is fulling the: "continuing mission: to explore strange new worlds, to seek out new life ..."

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      1. Thanks for the feedback, and good luck with your robot project!

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