Shopping trolleys, as most of us know, have a mind of their own. To try and break that mould, a group of international companies has come together to develop a new concept in supermarket trolleys. The idea is to produce a range of trolleys from 60l to 138l that will break the design boundaries established by existing metal and plastic technology.
The motivation for Mike Woodhall’s design was not to produce a plastic version of the traditional metal trolley, but rather to design a product exploiting the many benefits provided by engineering polymers and to fulfil changing retail and consumer requirements.
The trolley concept was developed in Australia as a leaseable, user-friendly and re-cyclable product. In addition it would hold advertising, and allow scanning of products within the trolley, thereby reducing customer time at the check-out.
Industrial Design Consultancy (IDC), run by Mike Woodhall, worked closely on the concept, design and manufacture with DuPont in both the selection of the appropriate material, in this case Zytel nylon, and the most appropriate and effective method of the moulding the trolley.
Simply interpreting the plastic metal trolley format into a plastic product does not use the material advantages of plastic, ie fluidity of form and the ability to integrate functions. The problem with existing plastic products is that they are mainly moulded in commodity plastics, such as PP and HDPE, to reduce the cost of materials.
The decision was taken to use Zytel (R) 73G15 (nylon) 15% glass filled, which, although more expensive kilo for kilo than commodity materials, provided tremendous design and product advantages – especially when combined with gas injection.
Gas injection provided the ability to create internal cavities, allowing the design to get away from consistent sections, and also to design and handle three dimensional masses of material, in a new sculptural format.
Other design criteria included stacking, construction methodology, ergonomics of use, appearance and advertising options.
With regard to stacking it was found that by bending the bottom tube in a three dimensional manner, the legs stack in a very compact format – the castors’ diameter being the limiting factor. This enabled the stacking distance to be reduced on average from over 240mm to 110mm, saving in a 50 trolley stack around 7m of floor space.
Eventually it was decided to design the trolley with two large mouldings, with the handle integrated with the basket. This brought together the practicality of assembly, which reduced tolerance problems, and press capacity into a workable and manageable product, using ultrasonic welding to join the components.
Tooling trials were completed in March this year and the first trolley is due to be used by the public in Marks & Spencer’s later in the summer.
In parallel to this programme a carrying basket was designed, embodying the same principles of design and manufacture. It will go into production at the same time as the trolley.
Du Pont (UK) Tel: 01442 218547
Industrial Design Consultancy Tel: 01753 547610