Star Wars Droid - Chopper - Aluminium & 3D Printed WIP

edited May 2020 in Props
I’ve been working on some 3D modelling for my Industrial Design portfolio and thought Chopper (the Astromech droid from Star Wars Rebels) would be a great excuse to do some CAD with detailed internals. I completed some initial 3D modelling near the end of 2019 but due to Covid 19 I've found myself with plenty of free time in isolation, so I've started the physical build too!

With that said I figured I may as well start documenting it. These first couple posts will be to get up to speed with where the progress is at currently.

For context, here's a reference photo from Lucasfilm of what Chopper looks like next to R2-D2:

July 23, 2019
After two evenings of modelling he’s starting to take shape. There's also plenty of accuracy tweaks I need to make, so don't mind any of the geometry that's inaccurate. Next up is the body, feet and dome arms. I've been doing a screen recoding time-lapse of the entire 3D modelling process so I can create a video detailing the modelling process.







Post edited by Jonah Pope on


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    August 9, 2019

    I'm excited to say the exterior of the 3D model is pretty much finished. It still needs a couple extra greebles and accuracy tweaks, but it’s finished enough to start on the internals. I modelled him from scratch in Autodesk Inventor using screenshots and other production reference images. Then I rendered it all in Keyshot today.

    The next step is to design an Aluminium frame for the internal structure






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    August 12, 2019
    Usually folks see finished 3D models or WIP renders, so I thought it could be cool to document the entire modelling process. I took 12 hours of design/modelling footage and cut it into a 12 minute time-lapse screen recording showing what happened behind the scenes. I know most will find it boring since it’s 12 minutes, so if anything it’s cool to have a personal record the project.
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    January 22, 2020

    After completing some other projects I was able to circle back around to working on Chopper and I’m now in the process of designing an aluminium frame for him.

    The idea then is the skins will be 3D printed to sleeve around the frame and have the ability to be removed. The frame design is still very much a WIP, but it’s slowly taking shape.

    The features I’ve included thus far include:

    - Removable 3D printed skins

    - Removable skirt

    - Adjustable legs (can position in 2 leg or 3 leg mode)

    - And I’ve designed it to be modular so I can do maintenance and modifications more easily down the line

    I’ve designed this to be built from 3mm Aluminium as I have a bunch spare of that and this way I’m using the material I have on hand. That’s why in the model I have two pieces of 3mm layered together to create 6mm thick parts. The plan then its to cut the frame cut on a water jet and assemble it from there.







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    edited May 2020

    May 14, 2020

    All this spare time in isolation is dangerous because I've start to build and produce parts for my life-size Chopper.

    I’ve been making the most of my spare time by detailing the structural components like the internal frame which will be aluminium. The other thing I'm really pleased with is I’ve also designed it so the 3D printed skins can be removable.

    3D printing has begun on the body and the aluminium frame is almost ready to be prepared for the water jet cutter.





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    May 20, 2020 

    Well it's full steam ahead now! Printing has well and truly begun.

    First up was the skirt which I printed in 3 sections and then glued together with the aid of some clamps.

    For context this is the same spot that his centre leg and rocket are housed.



    I also started printing the utility arm around this time which you can see the initial parts for next to the skirt below:


    And then this is the giant Radar dish that sits on top of the dome getting printed.


    After the radar dish components had been printed, I moved onto starting the biggest part of the build with printing the skins.

    I've been printing in ABS and have dialled the settings to a 0.19mm thick layers. I could go lower, but it would take forever to print. At this layer height I was able to get really nice crisp details on the skins while reducing the number hours needed in sanding down the line. Only catch is it was 1.5 to 2 days to print each of the 8 section that make up the main body. A small price to pay for saving my sanity down the line!


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    May 21, 2020 

    The other aspect that I'm enjoyed with this build is spending a bunch of time detailing the actual assembly and structural integrity of the parts. For instance, I designed the front greeble below to in 2 sections to make sanding easier and I also designed it to incorporate threaded nuts. This way I can simply mount it to the skins with a bolt and it will be in precisely the correct spot. It also means I can disassemble it easily if need be.


    And then with the Utility arm I had a similar approach. I have a female cabinetry bolts that act as an axle of sorts for the main pivot in the centre. These can be loosened or tightened depending on if I want to tweak the angle. I also have designed these longer thinner parts to accommodate metal tubing/pins that allow me to make sure that it won't be as fragile as your typical 3D print would be.


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    May 22, 2020 

    Some huge progress on printing the skins for the main body section. With my printer having a build volume of 300x300x300mm I was able to split the entire thing up into just 8 parts.

    With that in mind I decided to design the parts to all be connected with some dowel joins. I purchased some aluminium rod from Bunnings which I chopped to the right length for the dowel join. These new dowels were around 80mm-90mm in length depending on where they were being used.

    The holes on the prints for dowels were designed so it would be a really nice friction fit, which meant I've been able to do all my temporary assembly without any glue! Naturally glue will be needed, but I can hold off until I have everything ready to go which is handy. The ends of the dowels were also chamfered so they didn't catch when being inserted into the mounting holes.


    In addition to the dowel joins, I also designed the parts to accommodate countersunk rare earth magnets that I could mount with a screw. I've designed my Chopper so that the skins can be removable, so these magnets are mounted on the faces where the front and back skins join, and they will help that bit more in pulling them together when installed on the frame.





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    May 23, 2020 

    While waiting for the printer I've been working on Chopper's eyes. I was going to go with an acrylic disc for the lens, but decided I wanted to go for something with some cool glowing effects and details to add some extra character.

    After some digging around for items that would suit the eyes diameter, I found some arcade style buttons at the local electronics shop (Jaycar). I ended up gutting two of these blue ‘arcade’ buttons from Jaycar so I could mount my own LEDs inside. After that I cut a circle out of some baking paper that I could insert between the led and inside of the top of the switch to diffuse the light emitted from the LED. With the centre being diffused it helped light up edges of the edges of the plastic switch to give some cool extra depth.




    And then his third eye is a recessed one that just looks like a camera lens. I know it doesn't really light up, but I wanted to be able to build it so I have the option.

    However it to still needed to have the darker/black centre like in the show. From some research though this third eye has a silver ring around its outer diameter, which was the perfect spot for my light source! From that I got the clear version of the arcade button, took it totally apart and then cut up some Smokey translucent visor material and popped that in! That way you get a mostly black/grey centre with a silver/lit up rim.



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    edited May 2020
    And that's currently where the build is up to as of right now :) 
    I'll be sure to update this thread as I progress through the build.
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    Awesome progress!   Are you a member of the R2 Builders Group?  Great group of people and a really fun community. A few of my friends from that group have made chopper.

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    edited June 2020
    Thanks so much Chris :) 
    And indeed I am, I've been building MY R2 over the last 3 years. He's slowly but surely he's getting there, I just keep adding extra things I want to building hence the delay haha
    Here's what R2 looks like currently:

    I also rigged up and installed a projector in the dome so he can project 'holograms' onto nearby walls. That was a fun addition :smiley:
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    Awesome, I've been "building" my aluminum R2 for about 10 years.  I have pretty much all the parts (still need aluminum booster covers)  I really need to get back to that! haha

    Nice work on the hologram.   Did you have to remove the dome lens on the holoprojector for it to work?  I was trying to find a solution that allowed the holoprojector to still move around and also project a good-sized image.  One thing I looked into was laser projectors, as they keep focus no matter what distance the projection surface is.


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    edited June 2020
    That's awesome! R2 certainly is one of those long-term projects haha And thanks for the kind words mate.

    With the projector I ended up removing the spherical/fisheye type lens that was in there and instead cut a disc of clear polycarbonate that would sit in there as a simple friction fit. That way it had a lens and stopped the prying fingers of any kids poking the projector.

    Unfortunately my projector on the front can't move because of the way that I designed my mounting system. With mine I already had a mounting ring that the help the holo in place on the dome, so I swapped out the bolts for longer ones so I could design my housing to mount directly to it. I've included some photos below for you in case you were curious :)

    I'd not thought of that with the laser projectors! Fantastic idea there, I'll have to have a look into that. For this I just used a cheap and nasty projector that I can run off a USB power bank until I can the slip ring installed. It's not the greatest projection clarity, but I figured that Star Wars holograms never looked clean anyway so it kind of adds to the vibe of it all haha


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    edited June 2020
    I've been making a lot of good progress on Chopper these past couple weeks. The biggest leap is the body is now totally printed along with the first quarter of the dome! I've also got the LED's inserted into his dome for his eyes. Very pleased with the look of those.

    While I'm at it... No one asked for it, but here it is any way, part of Choppers partially printed dome on top of R2
    “Your designers were so preoccupied with whether or not they could, they didn’t stop to think if they should.”
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    Coming along nicely!

    Nice work on the projector mount.  I figured it would be a challenge to project through the typical half-hemisphere lenses we use in the holoprojectors.   Nice looking mount design for the projector too!

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    While I was printing the first part of the dome, I decided it'd be cool if I could give Chopper functional dome arms. They're a great part of his personality so figured I may as well have a go

    My main goal was for them to be sturdy enough to withstand any prying hands of kids coming to have photos with him. I explored a few ways of doing it but ultimately settled on using a linear actuator/servo. The Chopper used by Lucasfilm uses Actuators to great effect, so I drew inspiration from that and modified that concept to suit my needs.

    Best part was I was able to find 3D IGES files for the linear/servo actuators I was going to purchase. Which meant I was able to modify their IGES files to make functional actuators to test in Autodesk Inventor! (You can see a video of that below, sorry for the dodgy video)


    After testing that it worked in Inventor, I printed out the parts for the arm mech to do a prototype test. The actuators I ordered were Arduino compatible so I was able to hook up my Servo Tester and do a proper test! When it comes to the final version the rail at the top will be aluminium extrusions, and arms that connect to the actuary will be 3mm aluminium and the arm itself will be 3D printed.


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    Finally found a solution I’m happy with for the Centre foot/wheel.

    I wanted it to be a functional rubber castor wheel while also getting as close as I could to the specs of the actual wheel design. After a bunch of digging online I found that certain styles of Jockey wheels (typically used for trailers) were surprisingly close in their diameter and tread design to Choppers!

    (The jockey wheel is the black wheel on right side of the images below)

    With the wheel sourced I needed to find a solid castor mount that I could mount my new wheel to. After some digging on eBay I found a winner (which is the gold rimmed castor wheel you can see on the left of the images below). The specific thing I was after was a fork that was wide enough that I could fit my wheel on. It also was perfectly flat on the sides meaning I can design up some parts to glue on the sides to make it look even more like choppers Centre wheel mount (that’s a job for another day though).



    And finally, I wanted to cover up the writing on the sides of the jockey wheel. I could have 3D printed something, but I had some castor wheels on hand that had curved covers (picture six). I was then able to remove them and fit them within the wheel assembly. The covers help round out the wheels shape to reflect the show and also have the grey included for the ‘rim’ seen on choppers Centre wheel.




    Obviously, it’s not 100% screen accurate, but with this specific part there’s no way to get it 100% accurate without 3D printing it, and that wasn’t a route I wanted to take for something that’s going have to deal with wear and tear while rolling around.




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    After much designing, printing and prototyping I'm excited to say that Choppers dome door mechanism works!

    There were a number of design challenges with this, specifically with the dome is somewhat conical in shape. This meant I wasn't able to just insert a simple flat sliding door. For those not super familiar with these doors, they're the doors that Choppers dome arms come out of and then need to retract/slide back into the dome to allow access for the arms.




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    edited July 2020

    Ultimately my solution was to add a slight curve to the door that matched the inner profile of the dome. With this curve I was able to have it slide in and out without the issues I would have faced with a flat door.

    The next challenge was adding movement to the door. I went through a number of different solutions but ultimately decided to make my own DIY version of Linear Servos as typical linear servos wouldn't cut it (in the same way the flat doors wouldn't work too well). I designed up my own custom 'linear servos' but had it operate with a curved rail. This curved section matched the profile of the dome and would allow me to retract and extend the door easily within the confines of the dome’s geometry.

    Next I needed to motorise the door mech. To do this I sourced some continuous rotation servos and then designed up a prototype that consisted of the gear (which I mounted to the servo), a curved rail with corresponding gears/teeth and a housing that that rail could slide through. After I set it up and hooked it up to my servo tester and test my prototype you can see in the video below.


    While I'm at it, here's some tech drawing showing some details of the dome that I've designed which also includes the door and dome arms mechanism. You can also see in the back where the grooves are for the custom curved servo rails I designed along with embedded mounting spots for the servos.







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    Nice, you're making a lot of great progress!

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    Thanks Chris! Very pleased with how he's coming along :) 
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    I've been making some good progress on the dome arm mechanism this week. The mech was designed so that I can create a cross beam from aluminium extrusions I have from the local hardware store. After measuring the up extrusions, I modelled them in Inventor so that I could design the beam.

    I have to all this with hand saws as I don't have a lot of room for tools in my home workshop for stuff like this. First, I chopped a flat bar and right angle to length, so they'd fit nicely within the dome:


    I then keyed up the surfaces of the flat bar and angles with sandpaper so I could glue them together:


    After which I needed a bracket that would allow me to connect the beam to the 3D print. Essentially once I have the top plate cut and glued to the dome I can simply slot in the cross beam on the inside and then this bracket will hold the beam up against the underside of the top plate.

    This way the entire dome arm mechanism can modular and removable if needed. I also designed my 3D printed dome to include embed M6 nuts so that I could simply use a bolt to connect the bracket. So that the bracket could fit in between the sides of the cross beam I had to trim back the overall width of the bracket. I just used my hacksaw for this, you can see the difference below:


    And then this is that bracket installed in the dome:


    With the bracket installed you can see how the aluminium cross beam I've made slots nicely into the opening of the print and around the bracket:



    Next I needed to cut some openings in the cop of the cross beam to allow some extra head room for the linear actuators to retract. I simply drilled some holes and around the perimeter of my marked out area and then used a mini hacksaw to cut the remaining connecting material. After which the beam was placed in my vice and the inner edges filed down smooth.




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    With the dome progressing nicely I couldn't help but do a mock up with the dome and body.

    This was super satisfying to see Chopper progressing like this!




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    With the bracket installed properly for the first time ever I was able test it out! And I've very pleased to say it worked great :) 

    The 3D print of the arm is still the rough prototype print I did, so that will get replaced with a far nicer and sturdier print. The arms connecting the 3D printed Arms to the cross beam will also be water jet cut Aluminium rather than the roughly printed parts you see in the video.

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    Linear actuators sure are awesome!  Droid is coming along great!

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    It's my first time using actuators in a project and I must say I'm blown away at how handy they are! I'll be using them in other projects that's for sure!

    And thanks man. really appreciate it :) 
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    edited August 2020

    This is where the fun begins! Very excited to say that I picked up all the parts for Choppers Aluminium frame and the parts that form the internal frame of the legs.

    I designed these from scratch myself, so It's incredibly satisfying and exciting to have the tangible result of all my hours of 3D modelling and design

    Many more photos to come soon... assembly has already begun!


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    edited August 2020

    Very pleased to say I made a huge amount of progress yesterday! I was able to nearly get the frame totally assembled!

    I used 3mm thick Aluminium in my build as that was material I had on hand already and by designing around using that it saved me money on materials. I designed my frame to double up layers of each part to increase the structural integrity.

    In this first photo you can see the first test fit I did. At this point I only had a few bolts inserted just so I could test the tolerances of the slot and holes.


    And then this is where it gets exciting!

    You can see the main sections of the frame total assembled! The only items missing is the chamfered bottom ring which I'm currently 3D printing. Since I'm using doubled up layers of 3mm aluminium I figured it would more trouble than it was worth to tap threads into the parts. My solution then was to use 90 degree angle metal brackets from Bunnings and use them with M5 Nylock bolts to help connect everything together. And I'm pleased to say this frame is rock solid! No way anything is going to move now I'm done installing the bolts and it was very easy to implement.




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    The next stage was to start the assembly of the internal framework for the outer legs. I wanted the legs to be robust but simple to assemble, so the legs consist of two plates that were cut on the water jet and then 2 pieces of square aluminium extrusions. I also designed the aluminium parts so I could then sleeve 3D printed parts around them.


    Since the assembly with the 3D printed parts relies on the printed part sliding down around the aluminium parts I needed to be able to have the two plates bolted together and still be flush on both sides. This meant I couldn't just run a bolt through on side and have a nut poking out the other side.

    To result in a flush fit I needed to run a bunch of Nyloc Nuts along the inside of the square aluminium extrusion and I needed to work out how to thread a nut onto a bolt that's 300mm down inside a narrow aluminium square extrusion.

    My solution was I designed up this little 3D printed block that allows me to friction fit nylock nuts into the 3D print which slides down inside the square extrusion. This way when I thread the bolt into nyloc the 3D printed cube prevents the nyloc from spinning, essentially acting as a spanner.



    And then here's all the aluminium parts assembled.

    Very pleased with the result and it's extremely strong as well!



    And then here's the leg connection hubs that I'm also 3D printing at the moment icon_smile1gif


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    Awesome progress!  Love those water jet parts.

    One thing you may want to try (which was a massive game-changer for me) is threaded brass heat-sink inserts for your 3D printed parts.  You print the parts with slightly under-sized holes and use a soldering iron with a special tip to set the inserts.  They let you work with 3D printed parts much like you would with machined metal.  Bolting everything together rather than needing glue or solvent welding, so it's super easy to take parts off for upgrades, maintenance, or modular design.

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