A modern racing bike helmet such as the "FP1" from Uvex consists of around 30 parts. The main components are a 350 x 415 mm thick polycarbonate plate, which is screen-printed with different layers of colour depending on the colour design. The main protective function is performed by "expanded polystyrene", known as "EPS" or polystyrene for short. This is initially available as granulate in the form of rods and is pre-foamed using steam at 90 degrees, whereby it increases its volume sixfold and is now available as beads. The quantity required for one helmet is 120 grams, as in our example. You can also see a so-called insert in the form of a plastic grid, which is foamed into the helmet shell and is intended to guarantee that the polystyrene shell holds together on impact. You can also see the strap system including chin lock, cut-out and already embossed helmet pads, the twist lock in individual parts for size adjustment, as well as a number of stickers. Step by step, we show how a helmet is made at the manufacturer of Uvex and Alpina helmets, B-S-A in Obernzell near Passau.
Step by step
1. the polycarbonate sheet is heated in the drying cabinet at 80 degrees Celsius for one hour until there is no residual moisture left
You can recognise the helmet from the very first step
2 The preheated sheet is clamped in a frame in the thermoforming machine and then heated for 37 seconds at around 450 degrees Celsius. The heating process is interrupted, the sheet, which is still around 200 degrees Celsius, is preformed at a pressure of one bar, an aluminium mould is raised and gives the outer shell its final shape. This reduces the shell thickness by 30 per cent
Now the shape is right too
3 An automatic milling machine mills the air holes and the final shape of the shell at 40,000 revolutions with a milling cutter. The remaining material is processed into new raw material by external recyclers
The ventilation slots are milled out
4. a CNC-controlled cutting and sewing machine cuts endless straps to the model and size-dependent dimensions, welds the ends ultrasonically and sews the loops to the ends of the straps
A sewing machine processes the belts
5 The helmet pads are produced on a combined punching and embossing machine.
Well padded: the helmet pads are manufactured
6. headbands and chin straps are prefabricated at home and fitted with loops, padding, chin locks, etc. The size adjustment system, including the twist lock, is assembled on the production line. One worker assembles around 2,000 systems per shift
Manual labour: the fastening and belt system is assembled
7 The actual helmet production takes place using the in-mould process. Depending on the helmet model, up to ten individual parts, such as the outer shell, inserts, fly screen or belt holders, are inserted into the split injection mould. The mould, which is divided into different segments, then moves together pneumatically, fixes the parts and closes the mould. Residual water and air are evacuated by negative pressure and the injection mould is preheated. The filling process then begins with the pre-expanded EPS, the filling valves are closed and steam at a temperature of 120 degrees Celsius flows in. Now the polystyrene beads begin to fuse at their edges. After a further four minutes, the process is completed and the mould is cooled to 60 degrees. The upper and lower moulds move apart again, the helmet core and outer shell are firmly bonded together and the helmet can be removed from the mould.
In-Mould: The individual parts are connected
8 In the final production step, the helmet is completed with all the individual parts. Micro Velcro pads are glued in, the strap and adjustment system are integrated and stickers such as size information or the manufacturer's logo are affixed. The final step is packaging. Overall, the net production time for a helmet is a good 30 minutes.
Ready! Now the helmet can go on sale
Photos: Matthias Borchers
