Enjoy coffee with a high-tech coffee cup! Our initial ideas for KRUG didn't immediately lead us to this conclusion. Instead, our cup first emerged as an innovative concept born from everyday annoyances encountered while enjoying a cup of Americano, cappuccino, or latte macchiato! The exact circumstances under which KRUG was born are described in an entertaining narrative, "The Idea for KRUG." Fortunately, we had no idea at the time that the subsequent development would lead us from flow simulations and bearing technology to the creation of a special, thermally active material! But let's start at the beginning:
Anything that rotates needs an axis.
Now that the basic idea has immediately won everyone over and the design is already showing initial progress, it's time for hard facts: "back to engineering." After all, our spoonless cup still needs to be manufactured! The central issue first: storage.
How do we create a precise and, above all, smooth-running bearing for our high-tech cup that survives both dishwashers and microwaves without immediately exceeding our budget?
The initial approaches were rather unconventional: a seawater-resistant ball bearing between the base and the cup, for example. Unfortunately, the prototype showed that the orientation wasn't precise enough – our cup wobbled, and the contents spilled onto the table…
So we mounted tiny wheels in a radial arrangement on the bottom of the cup. The prototype rotates reasonably well – but quickly collects dust and particles on the "tires," significantly impairing its smooth operation. And it only works on smooth surfaces – a definite no-go.
"Anything that rotates needs an axis." This simple comment from our model maker's wealth of experience prompted a change of thinking and, consequently, a breakthrough in the design: Instead of extending our wing only a short way from the inner wall, as in the initial drafts, we now extend it to the center of the cup, where it provides space for a central axis of rotation. This simultaneously solves another problem: Initial mixing tests with the prototypes revealed that some sugar always remained unmixed at the bottom of the cup, precisely in the center. The reason is simple: even in the center of a tornado, there is, due to the laws of physics, no wind. Our new wing simply claims this position for itself, thus preventing the invertebrate zone.
Magical Magnetism
There's something magical about magnets. The way two repelling metal bodies float above each other is simply astonishing. Since this creates absolutely no friction, it makes sense to try incorporating this principle into our bearings!
Planned, built! Now our mug sits on a pin in its center, which determines the axis of rotation. Two magnets face each other at the pin's tip and the mug, repelling the mug and making it float. Everything spins beautifully for dozens of revolutions after the slightest push. Ingenious! Or so you'd think…
In reality, things are usually much more complicated than initially assumed.
Due to the different weight of a nearly empty and a full cup, it sometimes hovers half a centimeter higher or lower above the base, bounces uncontrollably up and down, and often spills its contents onto the table after being pushed. Furthermore, the base simply falls out when the cup is lifted to drink. A mechanical locking mechanism is needed – but this isn't entirely straightforward – it must not cause friction, must allow the base to be removed for cleaning, and must also compensate for the different heights depending on the fill level.
It is slowly becoming clear how much the realization of a "main idea" depends on finding several "secondary ideas"!
An important side idea arose from a short commercial in which a basketball player skillfully rotated his ball on his fingertip. Minimal friction.
Interesting.
The magnetic bearing was simply reversed, and instead of two repelling magnets, we equipped the next prototype with one magnet and a small metal ball as a "fingertip".
It was immediately clear that this would be our solution. Once again, several problems are solved at once: The cup glides smoothly on the top of the ball, while for cleaning, the base can simply be pulled to overcome the magnetic resistance, allowing both parts to be easily separated and reattached as needed.
The devil is in the details / Frozen Design
The next phase of product development is often very frustrating. The basic design is in place, the technical solutions have been developed in principle, and the prototypes function as intended.
We can get started!
Or should the rim be 0.5 mm thicker? Is the shape of the wing perfect, or does something spill out when it's twisted too much? Can we further refine the wing's contour to create even more swirls, or have we already achieved the optimum? Does our cup fit ideally in the hand for both women and men, or should the height of the center rim be raised slightly? Or lowered? Or made thinner, thicker, flatter, steeper, smoother, rougher, more uneven, straighter, softer, harder, and so on and so forth…
Only one thing helps: patience and diligence. Even from what seems like a "finished" cup, dozens of different prototypes are created, hours of flow calculations of the wing are compared, testers and guinea pigs are consulted, and all the data is objectively evaluated – until finally it is decided: the legendary "Frozen Design"
How is it done?
Now we know what it should look like. But how is it made? And, most importantly, what is it made of?
Familiar image: initially wild attempts.
Ceramics and porcelain were ruled out from the start – the necessary precision for our storage requirements is hardly achievable in series production… After creating several prototypes using 3D-printed plastic and milled metal parts, we initially chose investment casting concrete as our starting material. This came closest to our existing concept of "tableware" and, at least visually, looked appealing. Complex, multi-part molds were created with silicone inlays and pin sliders that formed the central axis.
The results are rather disappointing – bubbles and inclusions, some even cracks. Enormous effort is required for each cup, not only in terms of materials, but also preparation and finishing. While the final product looks great, it feels cold to the touch and mouth and is very difficult to clean because the surface isn't properly sealed.
And: Fine concrete is not food-safe. We are trying to find a glaze, but in the end we have to admit – it won't work like this.
With the stunning appearance and substantial weight of the cast concrete in mind, our next step is to find a suitable replacement binder for the mineral components. Food-grade epoxy resin initially appears to be a promising candidate. New molds and work processes are developed. Two-component resin is mixed with food-grade marble sand and pigments, purged of trapped air bubbles in a vacuum chamber, and then poured into a complex casting apparatus.
The results are fantastic! The feel, weight, appearance and precision are excellent - the finished cup is also almost "indestructible", even if it falls onto a hard surface.
We've come a long way.
Deus ex machina
However, there are two major problems: Producing a single cup requires almost an hour of preparation time, and the curing process even takes overnight. Secondly, although the resin used is food-safe, this solution is truly "hard on our stomachs," because the resulting resin composite material is never recyclable and is anything but environmentally friendly.
A difficult discussion ensues within the team – because everyone secretly knows that such a complex geometry, the required precision, and the design of the bearing axis actually only allow for one sensible solution: a sophisticated injection molding tool made of steel.
With the impressive results of the prototypes, nobody shies away from the effort required for such a tool anymore; quite the contrary – what has been achieved is far too convincing to give up so close to the goal!
But here too, we have to overcome several problems that stand in the way of the ideal product and that ultimately forced us to delve even deeper into research and development than we could ever have imagined!
Materialize!
The challenge was to find a suitable casting material that would reflect the desired properties of our cup and could be processed as hoped. Ordinary plastic was obviously out of the question… It couldn't adequately replicate the weight, feel, precision, or perceived quality. Its thermal properties also left much to be desired.
We need to develop our own product! Therefore, we are examining base materials and additives, composites and fillers in detail.
Once again, a single idea brings about a breakthrough for several aspects:
We simply lack the "mineral" component that both porcelain, as well as the previous concrete and marble mixture, contained. It provides the necessary weight to maintain the rotation and, of course, also ensures the high-quality surface.
"Micro glass spheres" are the ingenious alternative and solution. With advanced technology and even more expertise, it's possible to fill the inside of our cup with highly concentrated, tiny glass spheres during the casting process. The result is a virtually ideal cup mass, which, thanks to the thermal properties of the new material, cools the coffee to drinking temperature in a very short time and then slowly releases the absorbed heat, keeping the coffee at the ideal temperature for significantly longer.
This is KRUG
"The kinetically rotating stirring vessel ." In stark contrast to the long development history of KRUG, the naming process was completed after the first suggestion.
The entire Urmacher team wishes you the ultimate coffee experience with our beloved KRUG product and its numerous hidden refinements!
