It’s been a tough, but a good seven weeks.
We’ve been making steady (although slower than we’d like) progress on manufacturing. We’ve been overcoming the various challenges around molding plastics, especially around the three most difficult parts: the speaker box and string assembly (done), the guitar body front (done), and the guitar body back (almost done). We’re about to cast all the remaining plastic and rubber parts of the guitar.
We’re working to start manufacturing the metal parts in the guitar (strings, speaker grille, guitar strap button supports, neck button hinge, and input ports support).
We have a plan for finishing the electronics and firmware.
We’ve also starting to resume fundraising – working on our new investor deck, and getting introductions to angel investors.
On to the details.
In our last update, we were making progress casting the guitar body front. When we started on this part, we were most concerned about whether the detailed features on the inside of the guitar body – the ribs that provide structural integrity, hold the circuit boards, and the screw bosses that hold the speaker box and strings assembly in place – would form properly. However, these features formed well, almost from the beginning.
What was more difficult than expected was having persistent voids on cosmetic surfaces, particularly around guitar bridge, which is curved.
In between each attempt, we made modifications to the mold, cutting additional channels for the resin to flow:
We were also bedeviled by the mold leaking polyurethane resin out of the sides of the mold during the injection process, resulting in a number of attempts with insufficient resin to fully form the part:
To fix this, we modified the end plates by sawing out notches so we could wrap additional elastic bands around the end plates to keep sufficient pressure evenly across the two mold halves to prevent leaking:
Something else we discovered, to our surprise, was that using vacuum to evacuate air bubbles out of the resin was causing issues. Vacuum is supposed to pull bubbles out, but in a large mold with a large volume of resin, and in a large pressure pot with a lot of air, the vacuum pumps we were using weren’t strong enough to quickly evacuate all the air. As a result, they were just agitating/boiling the resin while it was hardening, causing more air bubbles to be captured in the part – the exact opposite result to we wanted:
Once we stopped using vacuum and cast using just gravity, by tipping the mold to enable the air bubbles trapped within the fine cavities to roll out, the quality of the parts increased significantly to the point.
Finally, on attempts 7 and 8, we were able to obtain repeatable, high-quality parts that were acceptable for manufacturing. Here is shot #8:
While there are still a few tiny surface imperfections, the part is fully formed, and smooth to the touch. (And once we paint the part, we shouldn’t have any issues with the finish.)
We’re happy to be able to cast this part without using vacuum, and even happier that we didn’t have to procure and use a large pressure chamber. This means that our ability to scale up manufacturing of the largest, most complex part will be far easier and less capital intensive. (The pressure pot would have been the bottleneck, and our ability to scale up would be constrained by how many expensive, massive, 25-gallon pressure chambers we could procure and operate simultaneously.)
Now that we made the guitar body front, we needed to test that the speaker box and string assembly would fit. Fortunately, it nested in perfectly:
The guitar body front being successfully manufactured, we next turned our attention to molding to the final large, complex part: the guitar body back. We successfully created the first half of the mold:
We went to buy more silicone to make the second half of the mold… and UH OH, our preferred silicone was out of stock - and unavailable from any of our usual distributors! Apparently, the silicone manufacturer had been purchased by another company and the silicone was likely discontinued! This forced us to scramble around to find an alternate supplier with a silicone with similar properties as our preferred silicone. It took us a couple of weeks to source, procure and test different types of new silicone to ensure they had similar properties to our previous silicone. Fortunately, we were able to find a good replacement silicone, and then we were then able to complete the mold for the guitar body back.
Note that the bottom half of the mold and the top half of the mold are different colors – the result of having to switch suppliers and silicones:
And once we demold the master part... the mold looks good!
As a result of all the time and effort we put into making the guitar body front, we learned some lessons that we were able applied to the guitar body back. We didn’t try casting under vacuum, we went just used gravity. We used the same pressure plates that we had made for the guitar body front.
Fortunately, the leakage of resin from the mold was trivial:
And now the moment of truth…
Checking out the detailed internal features of the guitar body back:
OK, that looks really good for a first shot! Here are some other photos of the part, compared to the master part (in black):
And yes, the speaker box and string assembly fits nicely on the guitar body back:
And YES, the guitar body back and the guitar body front fit together nicely, with the speaker box / string assembly sandwiched perfectly in between! SWEET!
(Note the parts haven't been screwed together, as they would with a finished product, so there is a slight gap where the back and front come together in these photos.)
However, we still have some work to do on the guitar body back. Specifically, the battery bay has thin “fins” into which the battery spring terminals slide.
These fins didn’t form fully, and two of the silicone fins ripped when we demolded the guitar back. As a result, we have some re-engineering required on the battery bay and the mold to solve this issue.
In the meantime, we’ve made the molds for all the remaining plastic parts of the guitar by claying up the master parts and building the silicone-pouring mold boxes.
The guitar neck front and back:
The 90 buttons on the fretboard:
The knobs, and various other internal parts:
Light pipes for the LEDs in the guitar neck:
Rubber parts that secure and dampen the guitar strings:
The battery bay door:
And then we poured silicone to make the molds:
We’re demolding early next week, and should be able to start casting the remaining plastic and rubber parts of the guitar over the next few weeks.
The other mechanical parts of the guitar the metal parts: guitar strings, speaker grille, guitar strap button reinforcements, neck button reinforcement, input port reinforcement and battery spring terminals.
Here is a photo of the guitar strings, over the metal speaker grille (mounted on an earlier design of the speaker box/string assembly):
The guitar strap button reinforcement:
The guitar strap button reinforcement and the neck button reinforcement:
The input ports reinforcement:
We tried sourcing the metal parts from local metal fabrication shops in Southern California, but the quotes we received were exorbitant for small runs. We’re now exploring sourcing them offshore, and we’re awaiting quotes from several different metal fabricators, and are hoping they’ll be a lot more reasonable. More on this in future updates.
Now that we have a clear path forward on the mechanical parts – especially on the large plastic parts – the electronics and firmware now represent the biggest hurdle for us to overcome to start shipping guitars. While we’re pretty close on both electronics and firmware, we still have a ways to go to cross the finish line.
We need to do a circuit board revision for the strings board (the PCB that processes and filters signals from the piezoelectric transducers that record the string actuations when you pluck or strum one or more strings). The challenge we’ve been facing is that the piezoelectric transducers are hyper-sensitive, so when you pluck a single string, all 6 strings fire. We’ve determined that by adding a simple resistor-capacitor circuit (also known as a “low-pass filter”) to each string, we should be able to filter out a bunch of the false-positive string actuations. We need to rev the firmware for this.
The second major task on the firmware is to finish porting the existing firmware from the current Arduino microprocessor over to the STM32 ARM microprocessor (MCU) on the main PCB. We’ve done most of the work to “bring up” the new MCU, but still have a bit of work to finish before we start porting the firmware.
Finally, we need to add a couple of minor new features to the firmware: adding support for the LEDs on the neck, and adding a third encoder (that switches the guitar’s mode between “Magic” and “Traditional”). More on this also in future updates.
Once we have all the parts – mechanical and electronic – we’ll have to figure out how to assemble the guitars in an efficient manner. We’ll also have to test and configure each guitar, flash the firmware on, and calibrate the piezos in the strings.
We’ve been relentlessly focused on approaching manufacturing in a capital-efficient manner. We know that some of you would rather we go to a high-volume factory and have them do most of the heavy lifting and move faster. Of course, if we had the capital to afford that right now, that would certainly make our lives easier, and make the process go faster. The silver lining for us is that we’ve found less capital-intensive ways of manufacturing, which makes our business more sustainable. And when we’re ready to scale up, we can always move our production over to a contract manufacturer (onshore or offshore) with a higher throughput, particularly with injection molding the plastics.
Regarding schedule, it looks like we should be able to start manufacturing all the plastic and rubber parts starting in June. We’re hoping to receive some samples of the metal parts in June as well. The firmware work will be ongoing over the next few months, as will ordering and receiving the circuit boards. So, if all continues to go well, it currently looks like we should be able to start shipping initial units either towards the end of Summer or early Fall.
Lastly, we’ve finally started to fundraise again. We had taken a hiatus from fundraising to focus on manufacturing. Now that we’ve validated urethane casting as a viable manufacturing technique to produce high-quality plastic parts, and have more visibility into unit economics and our ability to scale up production, we’re now going back on the road to raise capital from angel investors. We’ve revised our investor deck and are getting introductions to angel investors. If you are, or know of any angel investors who might be interested in investing, please have them email us at firstname.lastname@example.org.
(Disclaimer: This is not an offer to sell or a solicitation of any offer to buy any securities. Offers are made only by prospectus or other offering materials. To obtain further information, you must complete our investor questionnaire and meet the suitability standards required by law.)
As always, thanks for your continued support!