Product Development Journey

I’m Dr. Feng, the designer of Muro Box, the world’s first app-controlled music box. Let me share my maker’s story, how a firmware engineer, without any prior mechanical background knowledge, invented Muro Box from scratch.


Before telling you my story, I would like to clarify that I did not mean to challenge anyone. The pros and cons of tools and methods may differ from person to person. My following comments only present my experiences in searching for the solution to create the first workable Muro Box prototype.


Okay, here is the story.

If you google “electric music box”, you will find many results. Most of the results are toy-like music boxes with piezoelectric speakers (buzzer) or loud speakers. Its operating principle is simple: one main MCU (Micro Controller Unit) with Flash Memory (internal or external, depending on its degree of integration) to record melodies. The sound from a speaker is driven by a PWM signal. Most of the specialized MCU for toys have dedicated PWM hardware with internal amplifier to drive the speaker. The following image shows an example of a typical electric music box.

Electric Music Box (Picture Source: Screenshot from Taobao.com)

However, this kind of electric music box is not what I am looking for. This type of music box neglects that the charm of a music box is its mechanical movement. In other words, what makes a music box attractive is its rolling cylinder plucking the comb to produce the crystal-clear sounds of notes.

A Traditional Music Box (Picture Source: Sweet Garden music box shop in Taiwan)

If you continue searching for mechanical music boxes online, then you will find many makers’ projects. I categorized these projects into two types as follows.

1. Makers with more knowledge in woodworks:

Their music boxes usually include a large wooden cylinder with many holes on it. There are wooden pins inserted into the cylinder at different locations on the cylinder to create melodies when plucking the comb made with iron or something looks like a xylophone. The following image is an example of how their projects may look like.

(Picture Source: http://www.instructables.com/id/Build-a-Programmable-Mechanical-Music-Box/)

2. Makers with more knowledge in electrics

Their music boxes often combine many solenoids or many step motors for each of the notes. They use a set of arms or wheels to transfer the mechanical force to its musical comb for producing music. The following image is an example of how their projects may look like.


However, this type of music box is still not what I want to do. This type of music box is more like public artwork for exhibit, which higher budget for its materials and parts is allowed. However, this type of music box cannot be mass produced. Another limitation is its size. It is often too large for the users in their daily life situations.

I want Muro Box to become a real product, so people can hold it with hands and feel its vibration when playing the melodies.
Our first proof of concept prototype is shown in the following video. This prototype includes 11 solenoids to knock an 11-note xylophone. The testing the MCU is Nordic 51822, a common BLE module. BJT are used to amplify the signals from MCU to drive the solenoids. The whole prototype cost me one week to complete. I googled a midi file of Mary Has a Little Sheep online for free download. Fortunately, the midi file’s size is small enough for me to program it directly into the MCU to test playing.


Now, let’s turn the prototype into product!

Although the concept is simple, when I tried to carry out this plan, I ran into endless challenges and frustrations. My previous training as a firmware engineer only covers the technical knowledge of the electric parts, not including the mechanical design. Therefore, at the beginning of the Muro Box project, I had no idea of how to design any workable mechanical structure.

I was dreaming like many engineering guys who tried to invent something great. I thought once I finished the software coding, someone will magically show up later to help me fix the rest of mechanical problems and then the final product can be made soon. This kind of illusion stayed for several months, until my brother came to my home to wake me up with harsh comments and suggestions.

After realizing the fact, I must put aside my coding work and search for professionals to help me solve the mechanical design problem. My first step was to ask for help from a factory of music box movement in Taiwan. This factory (Kyooh Precision Industry Co., Ltd.) is the only music box factory in Taiwan, and it already has 40 years of experience in making music box movements.

(A group picture of Muro Box and Kyooh Precision Industry Co. Ltd. shows our collaboration relationship. I spent almost 1 year building their trust.)

The fact is: Factory managers were too busy to listen to a crazy maker’s idea because they already knew that most makers’ ideas could never be mass producible and will never become a real product. After realizing the fact again, I knew that I had to solve the mechanical design problem on my own.

My solution was to find design studios specialized in prototyping to help me. I learned this solution from visiting the exhibit of inventors’ works in the world trade center in Taipei, Taiwan. I asked the experienced inventors how they made their prototypes. Then, I realized that there are design studios to help clients make their product prototypes.


The above image shows a quote that the design studio asking 680,000 NTD (about 22,000 USD) for a mechanical design based on my requirement. This quote did not include the actual cost of prototyping, nor including industrial design. This contract shows that I had to confirm the design and complete the payment within 7 days, no matter the prototype works or not. After 7 days, the contract would expire and no more revision could be made. However, a real workable product can never be fully tested in 7 days. There always be validation/development cycles. The service fee is too high with the unexpected risks. Even though they said that they could provide feedback after the end to the contract, this service was not written in the contract, and I doubted about how much time they could spend on my case.

When looking back of how much time I have spent in designing Muro Box, if a design studio can really make a good Muro Box prototype, it is fair for them to ask even 1 million NTDs, and I will pay for it. But the real problem is that Muro Box will never be a good product by relying on a design studio’s service.


An inventor, or a concept initiator, may naively think that the degree of involvement in product design of a design studio is as high as his. In fact, a design studio is just an agent trying to take as many cases as possible and get those cases done quickly to earn money. If I don’t know how the product should look like, how can an agent design the product for me?

At the beginning I tried to save money by finding a freelancer of industrial design online to take my case. I spent 20,000 NTDs to get the following illustration in four months. It turned out to be a trash.

(The above image is the first version of the cylinder structure of Muro Box. It looks like a feasible design, but the truth is not, and it is the worst example of designed for manufacturability (DFM).)

I still remembered the day. I got this 3D model and looking for factories to produce a prototype based on it. I am thankful to run into a nice lady working in a factory. She told me that why this was a problematic design. She told me an example that CNC machines cannot cut a 90-degree angle from inside, and the 3D model was full of this kind of faults. I suddenly realized that I hired a wrong guy. How could he even don’t know this basic limitation of CNC production method? After this frustration, I realized that it was also my fault because I should have known that this person was not the right one from Day one.

Drawing a lesson from such a bad experience, I tried to go back to find a reliable product design studio. I hoped that I could meet a more experienced mechanical engineer to become my partner. This time, I finally met a right person who saved me from repeating the same mistake. Mr. Liao is how I called him; he is the very key person that saved me from spending more money and time on the wrong directions. He told me the truth:

“Experienced mechanical engineers will not take you case of electronic music box (at that time was not called as Muro Box) because they knew how difficult it will be. An inexperienced guy may take your case, but he will never make the right design for you. Now, you are caught in the dilemma.”
I would thank him forever because he became my technical consultant for free even though he did not take my case. I started to learn everything in mechanical design on my own with the advice from Mr. Liao.


With Mr. Liao’s advice, the above video shows my first workable electromagnet sample. The next step was to test its ability to pluck the comb of a music box. At that time, I already accepted the fact that to bring Muro Box into life, I had to rely on myself. By following Mr. Liao’s suggestions, I started to learn Fusion 360 to draw a 3-D model of Muro Box piece by piece.

(Starting from zero background knowledge and training, I draw the first 3D model illustration of the heart of Muro Box.)

After discussing with several factories and design studios, I already learned that the cost of prototyping is too high. I had to find a cheaper alternative. Then, I decided to buy a 3D printer with best customer reviews. Although my 3D printer, LulzBot Mini, is not the best deal with lowest price, its quality is stable. I started to test various designs more efficiently with my 3D printer.

(My 3D printing prototype of the vibration plate of Muro Box)

When looking back my product development journey, it is worthwhile to buy a 3D printer to do tests at home. Although there are many maker spaces to use 3D printer for free in Taipei, my experiences in 3D printing taught me that a 3D printer is like a buddy with his own temper. You need to spend time getting to know him well before working with him. Each 3D printer has its own limitations and requires different adjustments to increase its precision. Only when you have tested it, you can finally get its best performance. Muro Box requires the dimension error to be lower than 0.1mm, so understanding the limitations of a 3D printer is very important.


When the design of the mechanical part was about to settle down, I started to wonder how to design the look of Muro Box. Since Muro Box is a kind of music box, its appearance plays an important role in marketing. I already knew that an engineer guy’s design is not attractive enough for customers to be interested in it, so I decided to find someone to help me design its look. At the beginning, I hired newly graduated students with design degrees to help me design the look of Muro Box, but I found that their designs could never be produced by factories because they lacked real experience in designing a manufactured product . At that time, my startup company did not show any promising future yet, so I could understand that they lacked the passion and persistence as I did when designing the look of Muro Box. They treated Muro Box as a job to make some money, not his own invention that deserved more time and effort.

After asking them to leave, I started to find experienced design studios. An old friend recommended me a design studio whose team members were industrial designers from big companies, and this collaboration gave me some hope.

In fact, the experienced design studio still could not solve all of the problems in design because Muro Box needs to show its mechanical movement from the transparent lid as the key attraction and the design studio was afraid to handle the mechanical part. In fact, our communication problem in designing Muro Box is a typical problem faced by many product inventors. The product inventors often had the wrong expectations about the degree of involvement of a design studio and even expecting a design studio to solve all the technical problems. However, when I heard that the designer of the design studio told me that he is just an agent taking my case, I knew that I had to rely on myself to complete the design of my ideal smart music box, Muro Box.

(3 design proposals of a smart music box provided by the design studio)

The product’s look was determined: Proposal C was my first choice. When it’s time to assemble parts to test playing music, I made a wrong decision again. I tried to save money by using 3D printer for making the parts, but plastic material cannot replace the real metal parts in a music box. In fact, the material matters to produce the crystal-clear sound in a music box. The reality is that replacing the 3D printed plastic parts with the real metal parts created new problems. Until this stage, I finally realized that saving money should not be the only thing in prototyping.


Until now, I still often think that I already made enough mistakes and learned from them, and the next lesson from a new mistake came to me quickly. As an example, I once had an unfortunate experience with the electromagnet. When I needed the coil to arrive soon to complete the assembling tests, I did not realize that its factory in on full capacity a month before the Chinese New Year holidays. Their lead time was delayed for two months. In order to catch up my test schedule, I decided to order the raw material of magnet wire to DIY electromagnet. That’s why I made a video as shown above to record how I DIY my own electromagnet for Muro Box.


Now, when I looked at the classical music box movement, I realized that every tiny part of it was designed and crafted carefully after endless experiments. Although I was too naive to believe that innovating a music box was not that hard when deciding to jump into this trade, this music box innovation journey let me witness the efforts in manufacturing. At least I could still share my experiences with other makers like me.


Muro Box, the world’s first smart music box, will be the biggest innovation in the 200 years of music box industry. We hope the mechanical music box lovers can program their music, set up their own playlists with our app and cloud library service, and even share their favorite songs with other music box lovers around the world. We hope that each music box lover will stay tuned for our latest news and support us. Please join us to initiate a new chapter of the music box history, and have your dream come true.





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