An American manufacturer contacted us after the backrest of one of their armchairs failed. The product was already in production and the mould had already been made, yet every chair coming off the production line had the same structural flaw. A simple adjustment was not enough, because the problem lay in the geometry of the structure itself. The only solution was to remake the mould from scratch, writing off an investment that had already been made. Yet the issue could have been avoided with a structural analysis carried out during the design stage.
A few millimetres in the wrong place can mean remaking the mould
When designing a chair, every part of the structure performs a different function. Some areas are constantly under stress, while others carry very little load. The difference between an armchair that passes load tests and one that fails after only a few cycles often comes down to just a few millimetres of material placed in the right location.
The problem is that you cannot see where those critical points are. Experience helps, but it is no longer enough when geometries become more complex and stresses are distributed in ways that technical drawings alone cannot predict. And once the mould has been manufactured, mistakes become extremely costly.
FEM analysis shows where the structure will fail before it is built
Finite Element Method (FEM) allows us to simulate the structural behaviour of a chair before the mould even exists. It identifies where stresses are concentrated, where reinforcing ribs are required, and where material thickness can be reduced without compromising strength.
At Sititaly, this is the starting point of every project. We begin with a preliminary structural study, using the actual material properties of the polymer that will be moulded and simulating the loads the product must withstand to pass CATAS certification tests. We also simulate failure behaviour, because understanding where and how a structure will fail under load is the most effective way to prevent it. By the end of the process, we have a detailed structural map showing exactly how the product should be engineered before a single euro is invested in tooling. Rib geometry and wall thicknesses are defined using real engineering data, and that changes everything.
With Dalia, we reduced material usage by 20%
When we designed the structure of Dalia armchair, FEM analysis enabled us to reduce material usage by 20% compared with a conventional design based purely on experience. The chair maintained the same strength and passed all tests while using significantly less polyurethane. For manufacturers, that 20% translates directly into either higher margins or a more competitive market price.
Every rib in the shell was designed according to the actual stress distribution. Each reinforcement and every variation in thickness was based on data verified through simulation. As a result, the product passed CATAS testing at the first attempt because the structure had already been validated virtually before any physical prototype existed. When you know the design will perform as intended, the first mould is the final mould.
What happened to that American manufacturer doesn’t have to happen to you
The American manufacturer who contacted us had already invested in the mould and was producing defective components. We carried out a new FEM analysis, identified the critical areas and redesigned the structure. The required modifications were too extensive for a simple correction, so the mould had to be completely remade.
In the end, the problem was solved, but the cost of that initial mistake — together with the production downtime — could have been avoided entirely. Had the analysis been carried out at the beginning of the project, the first mould would have been the right one.
From simulation to tooling, Sititaly supports you every step of the way
Every chair we design undergoes FEM analysis before moving to the tooling stage. It is our way of protecting your investment and ensuring the product passes CATAS certification tests without unexpected issues.
If you are developing a new chair, or if you already have a product with structural problems that seem impossible to resolve, let’s talk. We can help you identify the cause of the issue and solve it before it turns into an unnecessary cost.
