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How the bending process can make the difference when manufacturing high-end metal eyewear
Bending metal is an essential process when manufacturing high-end eyewear. High-quality bending not only determines the aesthetic appeal of the glasses, but their durability and accuracy too.
Michelangelo Pisan, a toolmaker with many years’ experience in the eyewear industry and a long-standing member of the D.F. team, is specialised in this key stage of the production process. His responsibility begins with building the tools (such as the moulds) the company needs to ensure first-class bending.
But how do you get the perfect bend for metal glasses? What technical challenges do you have to overcome? In this interview, we reveal the secrets behind bending metal glasses, an art where tradition and innovation meet to create products of the highest quality.
Hi Michelangelo, you’re responsible for bending the metal parts of the glasses. Could you explain what it is you do exactly?
Sure. My main job is to prepare and install the tools we need on the machinery we have at D.F. to bend the various parts. I deal mainly with moulds, which we use to bend specific parts of the glasses, such as the temples, endpieces, bridges and nosepieces. I work with a team to come up with the best way to get the bend we want and make the most suitable mould. Once the mould is ready, I install it on the machine and explain to the operator what to do to get the correct bend.
How important is the bending process when manufacturing eyewear?
Bending is crucial. It’s one of the final stages in the production process and impacts the overall quality of the product. If the metal isn’t bent correctly, both the performance and appearance of the glasses can be affected. Every part must be bent with the utmost precision and sometimes it takes more than one go. Sometimes you need to bend the part several times and make corrections to achieve the curve you want, especially when working with materials like steel or titanium which are subject to springback, where they tend to “return” to their original shape.
Tell us a bit about the tools you use in the bending process. What kind of machinery and moulds do you use?
Moulds are at the heart of the whole process. We make them out of different materials according to the part we have to bend. We use steel, polymers or plastic, depending on how gentle we have to be. For instance, when bending a nosepiece, which is a very visible and key part of the glasses, we sometimes design highly sophisticated moulds so we won’t ruin the material.
The first thing we do is study the part that needs bending in detail. If we haven’t already got a suitable mould, we make one from scratch using either CNC machines or manually with milling machines or traditional lathes. Once the mould has been made, we install it on the press and do some test bends. It calls for the utmost precision, you have to be very patient and gentle when handling the material.
How automated is the bending process?
The bending process is not very automated. Actually, it’s hardly automated at all. The machine can make simple bends, but when a bend is more complex or it’s a custom project, we need to intervene manually. Because every material behaves differently under pressure. For example, if we have a complex radius or a difficult curve, we tend to test it manually before setting up the machine.
We often have to intervene manually during bending as well to correct minor defects or adjust the curves. The control and precision you achieve when working manually are crucial in certain projects.
It sounds like the artisan approach is important in your work. How do you remember all the stages you go through to obtain a certain result?
When I bend a part, I make detailed notes in my notebooks: the pressure we use, how we position the piece, the number of times it is bent and any corrections we need to make.
Every step is recorded in my notebooks and they become a kind of manual, with all the instructions for the projects we’ve worked on over the years. If I need to bend a part again or if one of my colleagues takes over a job because I’m not there, they can look at my notes and know exactly what to do. I write everything down, from the exact position the piece should be placed in to the spacers we use and the pressure we need to get the right bend. I also add drawings and photos which show where to put your hands and the components to obtain the right bend.
Do you think the process could be more automated to make it easier for toolmakers and operators?
That would be very hard. It’s almost impossible to automate the bending process, especially when processing complex parts like bridges or nosepieces. Every material has a certain degree of elasticity and you can never be 100% sure what will happen. Despite all my experience, I still have to do multiple tests to find the ideal bend.
You can’t expect the machine to do everything. Each material is different. Even something like how the pieces are cut from the metal sheets, with respect to the direction of the metal fibres, can affect how the parts react during bending. You are constantly having to make alterations to compensate. Automating this process would mean losing control over the quality of the end result.
What is the secret to manufacturing high-end eyewear?
I think it’s all about achieving a balance between technology and manual skill. Even though numerical control machines are technologically advanced, you still need experience and good manual skills to get certain results. The bending process is an art and every pair of high-end glasses we produce reflects this combination of technical and artisan expertise.
