Shoe Construction Insights
By Pete Roy, Senior Technical Officer
There are many factors to consider when constructing a pair of shoes. Here, I offer my comments on the shoe industry, fabric in footwear, the manufacturing processes, and wear.
Firstly, it is always interesting to think about what our shoes and feet have to go through. The “average” person, with a normal, not too active, job will walk a distance similar to travelling to the moon and part way back in a lifetime. In just three to six months, for example, that person can make up to half a million steps. Each time they step, the foot pulls the upper of the shoe away from the sole with about 2.5kg force per cm at the flexing point on the front of the shoe. A runner on a flat surface can strike with a force 2.5 times their body weight as their heel hits the ground in running. This force can be even greater on rougher ground.
Even in walking, estimates of up to 1.2G (force of gravity) have been quoted for harsh walking. While in normal, everyday activity it is typically between 0.5 and 0.75. Meanwhile, your feet have more nerve endings than most other areas of the body and have a mix of tender and hardened areas of skin. Plus each person’s foot is unique and shaped differently. To complicate matters, the feet of any one person are a slightly different size and shape from each other.
Thus, a great deal of thought needs to go into the making of shoe fabrics, including the lining, interlining,reinforcing materials, and outers. Woven, coated, micro-fibre, knitted, and braided fabrics of both natural and synthetic substrate are used, and can be entirely and fully functional, or reinforced by another material. Clearly, the utility of these materials is important. But even the most utility-based applications have to look good and perform well.
For example, linings must not abrade the skin, must not pill, hole, bleed colour, or irritate the wearer. In some shoes, the linings are a decorative selling point too, and may be metalized, pearlized, or have a coloured finish. They may also be treated to be functionally anti-bacterial or anti-fungal .
There is any number of braids, scrims, interlinings, paddings, or tapes used for general reinforcing, or such things as a softer feel, seam or spot reinforcing, and for padding purposes. The outer, upper is often the part the shopper sees first. Fabrics in this application can be of every construction imaginable, and every colour and texture. Scuff resistance, as well as scratch, rubbing, and even light resistance are important qualities. Occasionally, shoes need to be resistant to machine washing and tumble drying.
There can be trims or flashes, which, as the name suggests, can be more about shoe design. However, in some uses they form an integral part of the strength or wear resistance of a shoe or boot, behaving almost like an exoskeleton.
For the complete article, please follow this link to AATC News May 6 2014