Introduction: Animatronic Plush Heart With 3D Printing

About: The name "Ikkalebob" was invented by my cat when she ran across the keyboard. I attempt all manner of projects, from home engineering to prop replicas. Follow me on Instructables and my YouTube chann…

I wanted to make a realistic animatronic heart, and as I was developing the 3D printed mechanism I used a sock to try and get a vague idea of how the silicone skin would move once the design was finished. Since the silicone casting turned out to be quite challenging and very expensive, the sock test gave me the idea to instead use a slightly elastic fabric to make a plush heart design, which could be fitted over the 3D printed mechanism.

This means that the plush version of my animatronic heart design cost me under £20, whereas the materials for my silicone jacket cost upwards of £100 on its own! I also have an option to have a battery pack inside or a wired connection.

This project is very simple on the 3D printing/assembly/electronics side, but I'd recommend you have a little sewing experience because, as a sewing amateur, I'm not 100% confident in my patterns. A sewing machine is not necessarily required and a lot of the sewing is by hand anyway, but it would certainly be useful!

Downloads are throughout this instructable or alternatively use my download pack:


Hardware and Tools

Fabric Jacket

  • Some stretchy fabric
    • The stretchier it is the less strain it will put on the motor
  • Filling
    • I stole some from a pillow
  • Thread
  • Fabric Scissors
  • Needle
  • Sewing Machine [optional]

Step 1: 3D Printing

There's no particular requirements for the printing, all of my components were printed at around 0.25mm layer height in PLA, and supports were only necessary for the side panels.

I didn't really post-process any of the prints because they all worked fine straight from the printer, the only thing that may be necessary however is to drill out some of the holes on the linkage components to be the same diameter as the screws which form their pivot points.

Step 2: Assembly

The assembly may be quite fiddly, so check with the video and reference images as you go to make sure it goes together correctly.

  1. Prepare ball-linkages. Cut away a small amount from each of the 8 M2 servo ball-links, roughly half of the hexagonal section. Save these offcuts, they make good alternatives to M2 Nyloc nuts (which normally are pretty expensive). Get an M2 screw or threaded rod and cut off four short lengths of up to 10mm with a saw or some old pliers (if you're careful). Screw pairs of ball-links into each other using the offcuts, and tighten them such that the holes are at right-angles to each other.
  2. Attach linkages to the base. Check the images to see exactly how the linkages go together. The innermost pivot point should have only two "uneven linkages" on the outside of the base, secured with an M3 x 8/10mm screw. The outermost pivot points should have four "even linkages" secured with an M3 x 20mm screw and a Nyloc bolt. Ensure that the linkages on the bottom side of the base (the side with the raised sections with holes) are on the inside (i.e., closest to the base with the top side linkages on top of them). With all pivots, take care to ensure the screws are loose enough to allow the components to move smoothly.
  3. Prepare the motor. There are a few different variations I've seen of the dual-shaft motor I'm using in this design, so you may need to make minor adjustments. The wheel should be very close to the base of the motor so you may need to use a file to extend the flat face on the output shaft so that the wheel can slide down further. The wheels should fit very tightly and securely (if not use some glue), and the end of the shaft needs to be trimmed off carefully.
  4. Solder motor. If you're building the battery version, you just need two short lengths of wire to power the motor which can be soldered to the terminals. This length can be adjusted later so leave around 120cm on each wire. If using the wired design, remove the outer sheath from the cable to leave two exposed wires around 80cm long and strip the ends, then feed them through the holes in the base of the design. You must solder the wires to the motor with them running through the base. It's a good idea to wrap some electrical tape around the terminals to protect them too.
  5. Fix motor in position. Carefully put the motor in position in between the two sets of linkages, and secure it with an M3 screw in the top tab. Some of these DC motors have a hole in the top that can be screwed into with an M3 bolt, others' holes are a bit bigger so you'd need to screw from the opposite side into the base. You could always secure the bolt with a nut if you need to. Also secure the motor with a "motor support" component on each side of the base with an M2 x roughly 8mm screw, taking care to ensure the wire is comfortable running through the holes in the base.
  6. Attach the "teeth" components. Take note that there is a narrower and thicker version of the tooth - the narrow version is for the bottom side of the base which has the linkages closer together, and vice versa. Also note that the teeth components have the pointed end pointing outwards, and the protruding triangular section should face inwards to the centre of the design. The narrow teeth are secured on the even linkages with an M3 x 16mm screw and Nyloc nut (with the head on the outside), whereas the thicker linkages use M3 x 20mm screws (also with the head facing outwards). The ball-linkages screw into the other pivot hole using M2 x (around) 15mm screws.You can use the offcuts from the ball-links you made earlier instead of M2 Nyloc nuts!
  7. Affix the ball links to the wheels on either side. Using an M2 x 12mm screw, screw the ball links one on-top of the other to the wheel, and ensure the two sides are even. The wheel has multiple holes to account for the fact that sometimes the two output shafts are misaligned on some motors.
  8. [BATTERY VERSION] Attach battery pack. Build the battery pack by screwing in the four brackets into the battery base using 4 M2 x 4mm screws, and screwing the assembley on to the main base using M2 x 20mm screws and M2 bolts. This will be very fiddly! Using short lengths of wire, connect the two pairs of battery slots using some wire and twist the stripped ends so that the battery will be able to make good contact with the bare wire. One the other side, use one long length of wire to connect the two furthest holes, the two near holes will be the positive and negative inputs for the power supply. The battery pack has a build in space for the speed controller, so simply clamp the positive and negative wires into the DC input terminal and do the same for the motor (polarity won't matter for the motor). The controller can then be slotted into place and secured with the nut that it comes with.
  9. [WIRED VERSION] Attach top panel. The wired version features a top panel which provides strain relief to the wire, so start by pushing the wire through the panel and sliding it along until it meets the heart, at which point you can secure it with 4 M3 x 5mm/6mm screws.
  10. Attach the side panels. Using M2 x 6mm screws, attach the side panels to the model.

Step 3: Creating the Jacket

For the plush jacket, I'd recommend a stretchy jersey, the stretchier the better since it will make the movement look more natural, but it also makes it harder to sew!

Using the pattern provided, print out the shapes and cut them so you can trace them on to your fabric. Cut each part out leaving a space outside the lines to allow you to sew. If using a zip, start by sewing this into the back panel, but note that you'll need to leave the top open because the zip itself is not long enough to allow the entire mechanism to fit through, so the fabric at the top of the zip needs to be able to flex to account for this.

The front piece has a little section that needs to be folded over to make it rounder, so fold along the line and sew shut, trimming off any excess fabric. The the zip side and the front side can be sewn together to form the main pouch - if using the battery pack you'll also need to sew in a third panel along the top to make room for the larger mechanism, this is labelled in the pattern. Its best if you test the fit frequently and make adjustments if the jacket is baggy in some places.

You can now make all the other giblets by sewing the two halves together, turning them inside out and stuffing them. I have some markings on the main jacket pattern for where these should be attached, but feel free to use your own intuition about how to arrange the top bits, after all no two hearts are identical! It was simpler for me to just sew these on by hand, but if you're skilled with the sewing machine then you may be able to use that instead.

You should find that the heart now fits into the jacket and works as intended!