How I Engineered a Beloved Vibrator: an Introduction to Prototyping

By Janet Lieberman 

Originally published on Kickstarter.com

We count the day that I met my co-founder, Alexandra Fine, as the start of Dame Products. We had both already begun working on our own sex toy companies, and got business-engaged on the first breakfast date. When we met in June 2014, Alex was already working on what would become our first product, a hands-free couples’ vibrator called Eva. By the end of that year, our launch had become the most successful crowdfunding campaign for any sex toy, ever.

Eva (right) with its successor, Eva II (left)—which took even more prototyping and testing  


Part of the impetus for starting my own company came from graduating college right before the recession. I hadn’t been able to find a lot of job stability and decided if I wanted something stable, I’d need to build it myself. But I also had a lot of confidence that I would be able to take on a category I’d never worked in before, because my tumultuous work history meant I’d designed everything from dustpans to 3D printers. While constantly getting thrown into new fires isn’t a super pleasant experience or one I’d recommend, it is highly educational. I got to see how a lot of different companies work, and learned to adapt fast and build my own structure. Here’s the approach to prototyping that I’ve developed over years working on all these different products.


BASICS OF PROTOTYPING


When you’re designing, you need different types of prototypes at different points in the process.

It’s an optimization game to balance the value you put into each prototype (time, resources, planning) against the value you get out of it (what you learn, how close it brings you to the final design).


I was taught to think of prototypes in four main categories: sketch, works-like, looks-like, and alpha/beta. Although sketch models really shine in the beginning and betas don’t come up until the end, the types of prototypes are intermixed throughout the development process, and I encourage makers to think about the purpose for employing each one. Here’s how and why we used each variety of prototype as we created Eva.


SKETCH PROTOTYPES


Sketch prototypes are the 3D equivalent of paper sketches, and can help answer simple questions quickly. Sometimes they’re made from foam core, or by scavenging parts from other relevant products.


The goal behind Eva’s design was to create a vibrator that could tuck into the folds of the labia and provide clitoral stimulation during penetration without getting in the way. My co-founder Alex made the very first sketch model for Eva—out of a half dollar and Saran Wrap—to test if something could even be held there. In the dozens of models that followed, she learned more about the product requirements, like a flexible wing.


When I took over Eva’s product development, I started with the wings, because they were the highest-risk part of the product. If I couldn’t get them to work, we would have chosen something else to be our first product.


I made small, controlled changes to test variations on the wing shape. I 3D printed them in PLA because it was fast, reliable, and cheap. I knew it was the wrong material properties for the final wings, but it worked for comparing geometries between models.

Just some of the Eva wing prototypes. In these we learned that certain geometries have unwanted effects such as pushing the product away from the body or pinching the user.


I printed at least 75 wing prototypes, mostly for less than $1 each of material. Flat profiles have the shortest design and print times—I could design, print, and test several per hour—so I learned what I could from them, then moved on to the third dimension. With a desktop FDM printer, about $100, and a couple of weeks, I was able to prove to myself the product was probably viable. I had approximated the final dimensions of the product, found the wing shape with the most consistent spring force over the widest range of motion, and stumbled across many other insights I wasn’t specifically looking for—that’s the power of sketch prototyping.

WORKS-LIKE PROTOTYPES

Works-like prototypes should function like the finished product, so you can start to better understand what’s going to be required of it in use. Aesthetics are not part of that, so most works-like prototypes look awful. Depending on the product, they might give you ideas like “Man, friction’s gonna be high in this part of the system - better be careful or the gantry will never move!” or “Man, I’m always making contact with this same spot - better be careful there’s nothing pokey there!”.

Sad, warped 3D-printed part


The wings needed specific material properties, which influenced how I tried making works-like prototypes. At first we ordered parts in a polypropylene-like 3D-printing material. We were considering polypropylene for production, so if those had worked out, we would have bought that style of 3D printer to make parts in house—it would have been the fastest and cheapest option for functional prototyping. Unfortunately, the material couldn’t hold its shape in this thin geometry. Ordering these parts cost us $150, which might seem expensive for parts we couldn’t use. But as an investment to investigate a process that could’ve had high rewards, it was fairly low-cost.

Two rounds of works-like prototypes


Since the new 3D printing process was a risk, I ordered our optimal flat wing design machined in nylon at the same time. Flat shapes aren’t just the quickest thing to print, they’re also the cheapest thing to make on a milling machine or laser cutter. As the rest of the parts didn’t have functional material requirements, I designed them for 3D printing and added hooks to hold the wings. I started with a motor and a coin cell battery soldered to a switch, then moved to using electronics from Adafruit. The first version didn’t have silicone; the second version I (only somewhat successfully) painted on silicone.


The works-like models each took less than two weeks to design and test, and they each cost under $100. We took them home and did our first “field testing,” where we saw, for example, that partners’ bodies coming together increased the pressure on the device and created varying intensities of vibration. So we decided that pattern settings probably weren’t very important, or could even be distracting. With the works-like prototypes, we began to learn about how the product would be used and what would matter the most to the user, well before I’d designed much beyond the wings.


LOOKS-LIKE PROTOTYPES


While making the ugly-but-functional works-like prototypes, I also made non-functioning looks-like prototypes to explore aesthetics and ergonomics.


FDM prints were key to our industrial design explorations. Holding a full-scale model in your hand gives you a completely different sense of a product than a render on a screen. Each prototype took about a day to design, three hours to print, and used about $10 in materials. They allowed us to guide the appearance of the product before knowing exactly how all the parts would go together. Because we didn’t need to use them to communicate with investors or buyers, we never had to go beyond FDM prints for appearance models, but they can get very intricate and expensive.

Earlier aesthetic models for Eva

 

More refined aesthetic models for Eva

Dummy ergonomics model for Eva


I also made dummy human-factor models for Eva, which is another category of (primarily) looks-like prototype. We gave these prototypes to testers to wear while having sex, even though they didn’t vibrate. The bottom was machined nylon, so the wings would have the right flexibility, and the top was 3D printed in PLA. The silicone is cast around the prototype using a 3D printed mold. Even though we didn’t have a final industrial design direction or PCBA layout, we knew the approximate size of the product. I put a motor in as a non-functioning placeholder, and added a quarter inside to match my estimate of what the final product would weigh.  


These prototypes cost about $350 a piece, took about two weeks to design and make, and told us a lot about how the product would function during sex. As a result of this testing, I adjusted the design to make it harder for a partner to knock out. And we got some hints about how feedback could vary as we broadened our tester pool: we only ever expected to hear “make it smaller and lighter” (and that was pretty common feedback), however one of the testers said she enjoyed the weight of it, and might even want Eva to be heavier.


ALPHA AND BETA PROTOTYPES


Alpha and beta prototypes combine the functionality and form into a single design. They’re as close as possible to the final devices, going past appearance and performance to include design for manufacturing.  


At this stage, any details that don’t match the plan for production should be conscious decisions and monitored carefully for potential effects on performance. Also, this is when you start making multiple identical prototypes to catch potential variation problems. Your final product will need to work regardless of part variance, every time you assemble it, for any person who uses it, in any way they want to use it.


I call a round “alpha” if it still has some big unanswered questions and “beta” when I’m testing exactly what I expect to do for production. You plan the number of rounds based on how well-defined things are going into the process, but you continue the testing rounds until you get it all right. We wound up doing two rounds of alpha testing and three rounds of beta testing, in part because we needed feedback from our users and our manufacturer along the way.


I ordered the plastic parts machined in production materials. We used production silicone cast in SLA molds for most of the silicone parts. By beta, I knew I’d need a silicone button cap for production, and since that was going to be integral to the user experience, I got that part injection molded so it would have precise geometry and the correct durometer.


We had two PCBA revisions. For the first revision, I ordered PCBAs from quick-turn prototype vendors and our intended production vendor at the same time. We started assembling units with the former, and switched to the latter as soon as they came in. That allowed us to verify the design and start our user testing as quickly as possible, but also field-test the quality of the samples from the manufacturer.  For the second revision, we were too close to production, so we only tested with the quick-turn version.

Naked beta 1 prototype, beta 1 prototype with silicone, and beta 1 SLA mold for silicone

Alpha or beta prototypes cost us about $600 each, with two weeks of design time and two weeks for shipping and assembling parts. We made 55 total alpha and beta prototypes for Eva—fewer than any other product we’ve released to date. Someone who isn’t me might have trouble distinguishing alpha 1 from beta 3. But they revealed critical insights, like when a change we’d made for aesthetics had a huge effect on how well the product stayed in or that ABS wings will break off after a few uses. We also used alpha prototypes and testimonials from early testers for our crowdfunding video, which then helped fund production and the last rounds of betas. That $33,000 accounted for the majority of our development costs, but we couldn’t have had a successful product without it.


CLOSING THOUGHTS


Prototyping is about learning the boundaries of the problem you’re trying to solve. To be efficient, you want to start by trying a lot of different things and failing often, which helps you map out those edges quickly. At the beginning, you’re finding the broad requirements that will ensure you make a good product. At the end, you’re spending the time and money to find the nuances to ensure you make a great product.


To see how the type of prototypes fit into a bigger picture, here are few key takeaways:


  • Split the product into different sections to test them quickly and separately before tackling the whole product. If you can’t get them to work separately, they’re not going to work together.
  • Narrow down as much as you can before investing time or money into any given prototype. That way, you won’t be learning anything from a $500 prototype that you could have learned for $5.  Blowing your entire budget on one initial prototype is one of the biggest mistakes people make when they’re new to hardware.
  • Integration tells you a lot. To minimize how many surprises you get at the end, find ways to test different aspects of integration throughout the process.
  • You’re not going to going to be able to find all the interdependencies of aesthetic design, ergonomics, functionality, and manufacturability until you have prototypes that have attempted to account for all four, so scale-up testing is expensive, necessary, and might require several rounds. Skipping straight to manufacturing because the design is already “done” trips up even people who’ve been through the process a few times before.