Author: Les Charneca
The ZAPP-Group is one of the leading companies in the fields of cold forming and material applications technology. They produce a comprehensive range of precision made semi-finished products and high performance materials.ZAPP-Group products are made of stainless steel, alloyed tool steels, titanium and special materials and come in the form of wire, bars, profile and precision strip in semi-finished condition. The Group also trades in special materials consisting of nickel and nickel alloys, cobalt alloys, reactive metals, high performance alloys and powder-metallurgical steels.
Zapp’s origins date back to 1701, since then they have become an international group with four steel processing mills in both Europe and the USA. I was kindly shown round their mill and in Ergste just before the New Year.
Now, unless you are biomechanical engineer you have probably never seen a working steel mill, let alone even have visited one. I remember studying them at school, so I knew the basics, but there is no substitute for a hands-on approach in my opinion. So here is my guided tour, which I will leave deliberately light on the technical details, so if you are an engineer, I apologise in advance.
The factory is approached by a historic frontage that really deceives you to what lies behind it. The plant is massive and modern, and this is just a small mill. Despite the size of the site, the distances between production facilities, laboratories and the sales and administration offices are extremely short. Communications between the various departments are central to the Company's success and they have obviously spent time planning the site over several years.
Zapp is a steel-processing mill. That is to say they do not do the hot melting of steel and rolling it out. They simply process the raw product into something that the orthopaedic manufacturers can work with easily. From a chat to their marketing people, it is obvious that their selling point is producing a high quality product consistently, so that there is less further processing required further down the line. For medical metals, quality seems to be bar or sheet straightness, tight tolerances and surface finish.
The management at Zapp talk about wire pins, bars (for hip implants and screws), profiles (for fixation plates), strips (saw blades), sheets (bone plates) and tubes (cannulated screws) – admittedly, I find it difficult to differentiate between the products. When does a square bar become a profile, for example. Basically, though, the same processes are applied to all the raw material, it is just that the sheet products (sheets and strips) require different machinery.
Lets look at the sheets first. Outside in the yard there are massive rolls of sheet steel for clients. These come in a few fairly standard sizes. Zapp take these and roll them to the required thickness and sizes. This is done on huge rolling machines. Now, although this mill only does cold work, do not be fooled. Compressing metal produces a fair amount of heat.
The interesting thing is that there are limits to how much you can flatten a sheet in one pass. So it is usually required to have several passes to achieve the required specification. To make life more complicated, as you flatten the sheet the tensile strength changes, making it stiffer and less pliable. To make the metal soft and pliable it requires heating. This is done in line in furnaces on the move. After that, more flattening can be performed. It is all very clever, and at the end you get a sheet or strip to the correct sizes within required tolerances with the specified tensile strength. The products are then put through a straightening machine that looks like it would do the exact opposite. Rows of rollers above and below the sheet bend the sheet back and forth and amazingly after the last roller a bent sheet becomes a straight product.
The bars, wires and profiles work along similar lines. In the yard huge coil of raw material are processed. These coils are fed through machines with a die and drawn out. The dies require water-cooling as so much heat is generated, and a lubricant is applied to before drawing to make it easier. Again, as with the sheets, there are limits to how much you can draw in a single pass, so several passes are usually required. Obviously, huge annealing furnaces heat up the product when required, and bars are then straightened in a similar way to sheets with the wire normally coiled at the end. Some of the wire produced was so fine it was barely visible.
Profiles are really machined bars, and the round bars are subjected to pressure to give them a required shape - like a curved shape for fixation plates, for example. This reduces further processing.
During my tour of the laboratories, it became clear that the quality assurance and Research & Development Departments are not simply working on today's surface treatments and quality, but also on the materials of the future.
One of the interesting things about the building was the lack of people. Obviously, hundreds are employed, but considering the size and amount of machinery it was amazing to see it looking so empty. Another interesting point was the speed - this is not a fast process. To give you an idea, you can work along a wire drawing machine at the same sort of speed that it draws the material out.
Back in the smart office building I was told about lead times! Typically, the orthopaedic manufactures are thinking a year ahead. Zapp can actually process the steel very quickly – the long lead time is understandably due to the time required to actually process the raw project. If anyone can supply an actual time frame from ordering the steel to supplying a hospital with a product I would love to know.
Another point of interest is that medical grade steels are very low in contaminants. This is good for implants, but bad for machining. The lack of sulphurs make machining the products slow and difficult. We will look at how medical steels are produced in a later issue.
One obvious thing that stood out from my visit is that titanium is rare stuff. There was, I would guess, hundreds of rolls of steel - granted not all medical - and I would say only a couple of titanium. The lead times, I am told, are even longer for titanium and the price has doubled in the last year. So you basically order blind without knowing how much you will pay by the time it turns up! The steel market itself makes an interesting topic which we will also cover in a separate issue.
Finally, it is important to me to mention that ZAPP makes a great deal more than products for medical technology. In addition to these, ZAPP manufactures products for the automotive, chemical, electrical and consumer goods industries, food manufacturers, aerospace systems, the textile industry and the watch and jewellery industries. In their showrooms, I also spotted very intricate and delicate components for Rolex watches, so they obviously have the skills and technology to go well beyond what is required in the orthopaedic market place.
Many thanks to all the staff at Zapp for their hospitality. I was very impressed by not just the steel mill but by the knowledge and the skills of the people there. If you want to learn more about them, then you can visit the Company's website at www.zapp.com.
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