Project Bubble Machine

The brief "I need a head-mount for my bubble machine" Anaesthetist by day, and glorious costume designer by night, our client came to us with a particularly unique request. They wanted a mount for a bubble machine that they could wear on their head, with costumes built up around it: a starfish, hats, whatever the march called for.

• Secure, because it would be worn in a crowd for hours
• Light, because it sits on someone's neck all day
• Red, to match the machine

How it was made

1. Step 1 the plan. Two pieces, for two reasons. The mount is two parts, printed separately: a base plate that carries the machine, and a helmet section that fits the wearer, which we call the head shell. This is for 2 main reasons: 1. If the head dimensions proved wrong, only the shell would need reprinting, and the shell is the long print. 2. The plate prints flat with no support material at all, while the shell carries its supports on the outer surface, leaving the inner face that rests against the head smooth. A support scar there is felt for hours. And of course the final reason is, that if the bubble machine needed to be mounted elsewhere (like on the shoulder or arm) in the future, the base plate could stay the same!
2. Step 2 the scan. The underside, captured as a point cloud. The head could be measured with a tape. The machine's underside cannot. It is a moulded enclosure with a raised turntable boss, and the base plate has to register flat against it. Traditionally, manual measurement would take place with a set of vernier calipers, however because of the non-flat and bevelled geometry, it would be quite time-consuming. To speed-up the process we decided to use another method. So the machine went onto a turntable, inverted, in front of a Revopoint structured-light 3D scanner. Below are the two meshes that came out: the raw reconstruction exactly as the scanner returned it, and the same mesh after a shrinkwrap remesh in Blender, which closes the holes and reduces sensor noise to a single smooth surface that dimensions can be taken from.
3. Step 3 the base. The plate, drawn over the scan. With the shrinkwrapped scan as a reference body, the base plate was drawn over it in Onshape: a flat spoked cross with a central window for the machine's spindle and a second opening over its battery cover, every dimension taken directly off the scanned surface. The battery opening is why the mount never has to come off. The cover stays reachable through the plate, so a battery change happens with the machine still mounted. And a spoked cross rather than a solid disc, because the plate only has to span the four posts and frame those two openings. Everything between the spokes would be printed weight on the wearer's neck. The recording runs from the imported scan to the finished plate; the model below is the part that printed.
4. Step 4 printing. One version, and no supports at all. The plate is flat, so it prints face down with no support material anywhere, which is half of the reason the mount is two pieces. It ran overnight and was dimensionally right the first time, so only one version of it exists.

   Printer

   Snapmaker

   Material

   PLA

   Colour

   Red

   Supports

   None

5. Step 5 measure. First, we took their measurements. Everything begins with the head the mount has to fit. Three measurements, taken with a tape: the circumference at the brow, and the front-to-back and side-to-side breadths across the crown. Three numbers are enough to define the idealised head form the shell is designed around. And because of the split, an error here would have cost one reprint, not two.
6. Step 6 modelling. From head form to printable shell. An oval, cut into slices. In Onshape, the head was modelled as an idealised oval form. Lofting the whole surface in a single operation proved unreliable, so the form is built from elliptical slices cut at intervals up the head and swept between in steps. That construction is why the surface is faceted rather than smooth: straight segments stepping along what should be a continuous curve. At the shell's printed wall thickness, the facets are below anything a wearer can feel. Only the crown gets printed. The shell is a cap, not a helmet. It is cut about a third of the way up from the brow, so the printed part sits on the crown and stops well above the eyes. The brow is on the drawing because it is the datum the cut is measured from, not because the shell reaches it. The cut height is the one parameter that moves everything else. Cutting lower covers more of the head and sits more stably; it also adds hours of print time and puts more mass on a neck that carries the mount through a march. Cutting high keeps just enough shell to hold the machine. The triangle is a schematic of that trade-off, not a measurement of it. From hemisphere to finished shell. This is the whole Onshape modelling session, filmed. It starts with a plain hemisphere and ends with the printable part: the sketch planes go in, the loft runs between them, the solid is hollowed to a constant wall, the form is cut above the brow, and the posts and strap slots are added last.
7. Step 7 printing. Version one, supported in its own PLA. The four posts stand on a doubly curved surface, so they cannot print unsupported. Version one used the shell's own red PLA as the support material. Same-material support needs no second spool, and it holds the posts true while they print. It also fuses to the part along every contact face, which is what the rest of this card is about. Printed in red. The supports were the hard part. Both parts printed on a Snapmaker in red PLA, matched to the machine. The shell ran overnight and came off the bed the next morning. Then the supports had to come off. PLA separates from PLA only where the bond happens to be weak, so removal took four to five hours with pliers and a hot-air gun. The photographs are that afternoon: the part still on the bed with its support band on, the support part-way off, and the surface it finally left behind.

   Printer

   Snapmaker

   Material

   PLA

   Colour

   Red

   Supports

   Same red PLA, under the posts

8. Step 8 assembly. Stand-offs, hex nuts and screws. Version one is held together with M2.5 hardware: plastic stand-offs and hex nuts fasten the base plate to the machine's underside, and machine screws through the plate seat into the four posts on the shell. Plastic where possible, because the whole stack rides on someone's head and every fastener is carried weight.
9. Step 9 fitting one. Version one on the client. Surprisingly, the fit was very comfortable and worked first time with the stability of the headpiece being very secure with side-to-side motion. However, back-and-forth motion caused some slippage, as there was a gap between the shell and forehead. This was fixed with a foam piece cut and stuck in place. There was more speculation as to how to secure the headpiece. Perhaps a swim cap could be worn over the shell. Perhaps an additional slot could be added to pass a fastening strap inspired by the bike helmet. Regardless, it was apparent that a small redesign was required.
10. Step 10 redesign. Why we went for magnets. To fasten V1, a screwdriver and two people were needed. The machine had to go on last, in one motion, by one person. Especially if wonderful hats and other cardboard costumes needed to be built around it. Using magnets seemed like the obvious solution. The addition in weight being the trade-off for easier assembly. Back in Onshape, the four posts, were filleted and therefore created gentler gradients for a cleaner print and less support material. Countersunk pockets for 16 mm neodymium pot magnets were added. The additional slot holes at the front and back were added to help secure the head piece with chin straps.
11. Step 11 printing. Version two, on breakaway support. Same shell, same red PLA, one process change: the supports printed in a dedicated breakaway filament instead of the shell's own material. The interface between the two materials does not fuse, so the support snaps away by hand, in minutes, and comes away white. Every white fleck in the clip is support, not shell. The post faces also come out flat, which now matters: they are the seats the magnets register against. The trade-off however is the rough and visible layers at the interface of the two materials. In the end, the client did not mind as this was not an outer-facing piece of the costume.

    Printer

    Snapmaker

    Material

    PLA

    Colour

    Red

    Supports

    Breakaway filament, under the posts

12. Step 12 assembly. Assembly v2. Version two assembles itself. Pot magnets sit countersunk in the four posts, each held by a screw through its centre, and the matching set sits under the plate, which was still the v1 base plate, but the plastic standoffs and screws were removed and replaced by magnets with the opposite polarity. Bring the plate close and it pulls into register: nothing to drive, nothing to hold still, nothing to find by feel overhead. To ensure that the magnets were held in place, they were not just screwed in, but were first heated and pushed into the shell, giving the chance for the surrounding plastic to melt/and conform in-place. To test the strength of the magnetic interface the full assembly was held by the head shell and turned upside down, to ensure the bubble machine would not fall off. This was done with and without fluid in the bubble machine's chamber, to ensure the holding force of the magnets was sufficient. Not only did it turn out to be sufficient, but disassembly proved tough when pulling the magnets straight apart. Instead, the recommended way to remove the two parts is in a rotational/levered motion.
13. Step 13 the model. Take it apart yourself. A bubble machine, worn on the head: measured with three tape numbers, modelled in Onshape, printed twice in red PLA, and clicked together with neodymium magnets after the screws failed the overhead test. The model here is the real thing. The shell and plate are the Onshape exports that went to the printer, the machine is a textured scan of the client's own unit, and the blue wireframe is the approximate head the shell was cut from. Choose a version, hide the parts you are not looking at, pull the assembly apart, and turn it with your hand.
14. Step 14 fitting two. Click, strap, go. Second fitting, same office. Shell on, strap under the chin, machine lowered until the magnets engage: a few seconds, one person. The client spun it up, tilted their head, and walked the room with it running. Signed off on the spot, and taken home the same day. Strap trials. The chin strap is the client's own line of iteration. They are designing and testing different head straps with the finished mount, and their videos of those trials land here as they arrive.
15. Step 15 the march. Bubbles on the march. The march came, and the machine went as a starfish. The client built the costume up around the mount exactly as the brief promised: the headpiece is the machine, fringed and googly-eyed, pouring bubbles over the crowd from the top of their head. The design and engineering for the past few weeks all lead up to this moment.