Our Secret Story of Development
Who can resist a challenge?
The trigger for the project was something I had heard from a dentist about making fillings and false teeth. For fillings and false teeth, the accuracy of the initially-formed tooth shape is extraordinarily critical and the success of the outcome is determined by that accuracy. Up to the present a material called alginate has been used as an impression agent to take on the shape of the tooth. Alginate starts out as a powder, is dissolved in water to form a paste, and then the paste is pressed against the tooth. It hardens in just 2 or 3 minutes. Whether used to make fillings or false teeth, it has an extraordinarily short pot life (usable time); therefore, it must be mixed as quickly as possible with no air bubbles. Twenty years ago, when we began developing our mixer for dental offices, it was said by dental office personnel, "You are only fully qualified when you can mix alginate." This was such difficult work that it became a standard criterion for judging the technical level of dental hygienists. Even then, there were devices that mixed alginate; however, there was no big difference from manual mixing and eventually, they would not to be used very often. Future customers of our mixer told me, "If you could make such a machine, it would sell at any price." If you hear that sort of thing, I think you will agree that as a manufacturer you want to take on the challenge. For that reason, we launched a development project.
Breakthrough from zero
We didn't have any knowledge about mixing and deaeration, and started from zero. First we decided to apply conventional methods and tried propeller type stirrers. However, the end result was even worse than kneading by hand; full of bubbles. It was also difficult to clean the machine after use. For deaeration we thought of using the vacuum deaeration method, but we found that in practice the mechanism was not easy, so we gave up the idea. In those days, to be honest, we often became pretty disillusioned and we felt we were banging our heads against a brick wall.
However, through repeated experimentation, we noticed that if we could knead without a propeller or spatula, this would be better, and if we could deaerate at the same time as mixing, this would be more efficient. The target was to knead alginate within 30 seconds, so we thought mixing and deaeration at the same time would lead to time reductions as well. At such a time, our R&D eyes came to rest on the possibility of the centrifugal deaerator. When we took alginate that had been mixed into a paste using a spatula and tried to just deaerate it with a centrifugal deaerator, it did take too long and the alginate may have hardened, but the bubbles were successfully removed. I thought that if there was some way to accomplish mixing within the centrifugal deaerator container, it might be possible to mix and deaerate both simultaneously and quickly. That thought became the root of the image I formed in my mind of the THINKY MIXER. What I imagined for providing the mixing force was a mechanism like a "planetary gear." Just like planets rotating while revolving around the sun, I thought that imparting rotation forces to the section of the mixer where the container is mounted on the centrifugal deaerator might make mixing possible. At first, we were anxious about how it would turn out, but we decided to utilize this design structure.
Flying apart - the struggle against G-force has just started
The most serious problem was the incredible G-force generated by the centrifugal force. Deaeration required an acceleration of at least 200 Gs, and this is almost 30 times the load for a space shuttle launch. With a regular centrifugal separator, the container is fastened securely, so it withstands high G-forces, but if the container were to be rotated, a drive section would also be required. When we tried incorporating drive mechanisms in the prototype, as soon as rotation began, the drive mechanism broke down and parts came flying out; many times we were nearly injured. I frequently asked major companies to help us with our designs, but they'd hear our idea and just say no. In the end, we realized we would have to do it ourselves. It took about a year from the project start until we reached the rough outline of the design mechanism, and it took another two years to get the angles of the container side and the joint section for transmitting the rotation just right, and to complete a prototype ready for evaluation that could mix and deaerate simultaneously.
A tough struggle before finally releasing the product onto the market
When we thought our mixer was complete, and we tested the prototype for 5 to 10 minutes, there were no problems; but when we ran it for 2 to 3 hours, smoke came pouring out from the rotation section, and finally it broke down. The cause was friction on the joint section. The oil film applied to the bearing completely dispersed due to the powerful centrifugal force. When we disassembled the joint section, we found that it was completely dry as though the section had been washed clean. As a result of this discovery, we created a structure that located the bearing in a sealed container full of oil and similar to a soup bowl; we continued carrying out test operations and learning through trial and error. Finally, we abandoned the joint section and adopted V belts for the first generation of the THINKY MIXER.
We managed to make a prototype and mixed epoxy resin and hardener; the moment we opened the container the contents at the bottom were so transparent, and free of air bubbles that for an instant we had the illusion that it had all leaked out somewhere. After we introduced our machine to the market, we diligently worked on addressing any teething problems and suggestions from customers and made repeated improvements, which are now incorporated in the present THINKY MIXERs. If 200 Gs of acceleration acts on 100 grams of material, a load of about 20 kilograms is applied to the drive section. We worked quite hard to reach the point where the drive section could withstand that sort of weight and generate a usable centrifugal force; I'll be honest we are more than a little proud of our achievement.