6 steps to sole satisfaction
Light, supportive, cushioning… may be the first things that literally spring to mind when you step out in a pair of Hotter shoes. But to create each comfortable step there’s a precision engineering process that has to be correct to one tenth of a millimetre. Hotter’s technical team draws on the international expertise of world respected Italian mould makers and highly technical German last makers for such exacting accuracy. But let’s take this story one step at a time…
"The whole process starts with inspiration," explained Andy Whittle Product Engineering Manager, "our design team visit the world’s shoe fashion capitals to find the latest trends; taking inspiration from upper design, materials and trims to heel heights, toe shapes, toe heights, sole textures and colours."
Creation of the last
A last, which creates a shape similar to the human foot, is ‘anatomically sound’ and needs to encompass elements such as heel pitch (height of the heel), toe spring (height of the toe from the floor) fit and fashion. All our lasts are based on unique Hotter fit criteria which, combined with established British manufacturing standards, allows us to maintain the ‘Hotter’ fitting experience.
"It can take our last maker up to a week to make the first wooden prototype from our detailed technical instructions," explained Andy, who has worked in the footwear industry for 37 years, starting his career as a pattern cutter. "There can be several versions before designers are happy with the aesthetics, but when they are we create a model of the sole and upper development can commence – leather thickness, for example, is critical for mould development."
Following an initial fitting assessment on our Hotter standard feet (size 4 ladies and size 8 mens), we create the prototype sole. This can be achieved manually by a bespoke model maker or by using our mould maker’s digital rapid prototype machine. The initial sole model may not contain all the finished textures but will allow designers to see their exciting new concept for the first time.
Preparation for the sample mould
One of the most costly areas of development is the creation of the aluminium sample mould and accompanying last, which are engineered to fit our state-of-the-art direct injection moulding machines. Using computer data provided by the last maker our mould makers will create a highly detailed technical mould drawing. Before any metal is milled, designers and technical staff working closely with our founder Stewart Houlgrave will assess the drawing to ensure that the finished sole will not only be manufacturing friendly but also aesthetically pleasing and engineered correctly.
The sample mould
The arrival of the new sample last and mould can trigger a great deal of excitement. Once Stuart Leath our Senior Hi Tech Technician, who joined Hotter in 2013 and now heads our technical team, has checked the mould and last on our ‘dummy’ mould station the sample will be introduced to one of our four moulding machines and the first sample soles created. After a little tweaking and adjustment our first direct moulded shoe is passed to our design team for appraisal and fit.
A sole will not only be appraised aesthetically by our design team, but also for its extended wear properties by our factory technical team. Stuart Leath explained: "The tread design of our soles may be influenced by fashion, grip properties and even water dispersion – similar to how a car tyre tread is designed."
The soles will be fixed to a "rolling belt machine" to replicate the flex of the shoe in wear, only after 50,000 cycles have revealed no weakness will it pass our Hotter standards. Following this a sole may still be sent to an outside laboratory for independent testing.
Once technical and fit testing is completed the production moulds and lasts are ordered – it can take one month to order four sets of lasts and six weeks for one set of moulds. Designers create moulds that can last for several seasons and each mould can make 3 or 4 styles. Each season there are several moulds in development.