Multi-Fuel Pizza Oven

Designing the Door

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Technical Challenge 1: Provide Clear Visibility When Cooking- ClearView™​

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The previous generation of this oven has a removable door with no viewing port. Not only does this mean the user cannot see their pizza being cooked but it is harder to manage the fire, harder to safely cook a pizza if a door is held in one hand whilst cooking with nowhere to put it.

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The simple solution was to create a glass door not unlike the Karu 16, an existing Ooni product. The problem with the existing design was that it was a complicated, expensive, under-performing design which took a long time to assemble with adhered gaskets and multiple fixings. The technology developed to reduce soot depositing on the glass was temperamental and short-working. 

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To reduce the sooting on the Karu 2, I helped to develop a new technology that leveraged part geometry and assembly to produce a much improved local pressure differential and significantly improve the cleanliness of the glass in high-soot scenarios: ClearView™.

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To do this, I had to balance the manufacturability of pressed sheet metal with performance. Another example where real world products always have to compromise. The end result was nevertheless one of the biggest winners on the Karu 2 project. It was one of those unicorn moments in design where you increase performance whilst also reducing cost. Not only can you clearly see beautiful rolling flames and your cheese bubbling away on your pizza while you cook, you pay a significant amount less for the pleasure. 

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Compared with the previous glass door, ClearView offers:

• Far better performance in soot reduction

• Significantly lower BOM cost (double digits lower)

• Significantly reduced part count and complexity (double digits)

• Significantly fewer fixings and assembly complexity

• Over 24 hours in door assembly time saved ​

• Larger viewing area achieved (less obstruction than previous technology)

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In fact, the architecture proved robust enough that it was later adopted in the redesign of the Karu 16 platform (Karu 2 Pro), the improvements only compounded the results mentioned above in a larger product.

 

It's rare to get these moments in design where the time, cost and spec triangle are all pulled in the right direction with one design decision. Usually you're compromising between the three. By thinking architecturally from the start instead of adding components to manage soot. The solution became much simplified the geometry itself performed the task. 

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It is easy zoom in and add complexity to solve issues and then add complexity on top of that to solve further issues caused by the initial design decision. Zooming out and rethinking at a conceptual level is such an important practice.

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Technical Challenge 2: Magnetic Latching

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Magnet selection and placement were non-trivial due to extreme temperatures within the oven. As with any engineering, adding extreme environments makes everything much more complicated. One door latch on an existing oven was considered mechanically clunky, due primarily to behaviour under the extreme heat. To remedy this on the Karu 2, a magnet was proposed to latch the door. One glaring issue which presented another technical challenge is that permanent magnets are de-magnetised by high temperatures. 

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Not only do they lose their magnetism at high temperatures but magnets lose efficiency when thermally cycled and Samarium Cobalt (high-temp) magnets are also extremely brittle; not a desirable feature of a material being repeatedly hit by an opening and closing door.

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To protect the brittle magnet, it needed to be encapsulated. An early assumption suggested encapsulating the magnet in a magnetic cover would maintain the size of the magnetic module. After a quick feasibility check of the latching proposal, however, analysis of flux return paths showed that a magnetic enclosure would create an easier return path and reduce holding force at the latch interface.

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From this basic engineering analysis, a non-magnetic threaded cover was instead used, significantly increasing effective holding force while protecting the magnet. This meant that the magnet strength could be decreased reducing cost and size. The threaded design also allows the user to service their product with a replacement if degradation ever occurs.

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This another example of early assumptions without the correct engineering theory can be harmful to cost and performance. Feasibility studies on proposed technologies is incredibly important for long-term project benefits. 

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Technical Challenge 3: Removable Mechanism 

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The original concept included a removable door mechanism combined with hinging beyond 90 degrees to reduce knuckle-burn risk when launching pizzas.

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User testing revealed a behavioural issue since the removal motion unintentionally mirrored the unlatching motion of a previous oven generation, increasing the risk of unintended detachment.

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I advocated for removing the detachable function due to feeling discomfort about the safety of the product. Although initially kept, the feature was ultimately removed late in development which resulted in a post-tooling redesign. Using steel-off solutions only became a challenge but was important to preserve the tooling investment when adapting the parts to get rid of the removability feature.

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The final hinge architecture retained structural robustness while removing unintended detachment modes.

This episode reinforced the importance of designing for real user behaviour and user testing has become a critical part of my design process where appropriate.