Dramatic improvements in efficiency have been achieved in the manufacture of car interiors by a design innovation which is based on a simple concept but which required specialist know how.Mannings Thermal & Environmental Engineers of Southport have been able to speed up production and reduce energy consumption by modifications to the Thermoforming Tool Presses which are used to produce car trims, such as door panels, roof liners, parcel shelves and other moulded parts.
The presses operate by bringing together two preheated metal tools which compress the raw material between them to create contoured shapes. The improvements were achieved by embedding electric heating elements inside the moulding tools so that the heat could be directed at the point where it is required. As a result, power savings of over 75 per cent have been recorded and heating time has been reduced to half. The Thermoform Tool Heating System was developed in conjunction with the Lear Corporation of Colne in Lancashire who manufacture interiors for many major car companies such as Jaguar, Rover, Toyota and Honda, using environmentally friendly materials.
A prototype unit was produced on which flexible mat ceramic heaters were installed to heat the front working faces of the top and bottom tools. Each 'pocket' in the rear of the tool castings was then fitted with individual heating elements. Measuring thermocouples were fixed to various points on the tool and temperatures as well as power consumptions were carefully monitored and recorded. On production units, the heaters are arranged vertically and horizontally in the moulds to create separately controlled temperature zones. This enables different amounts of heat to be applied at different parts to cater for the complex shapes being formed by the press.
Mannings had to work closely with the specialist tool designers so that the heating system for each new tool could be individually assessed and then custom built to suit the component to be manufactured. Les Oliver who is the Manager of Industrial Heating at Mannings said "This is one of the most interesting projects we have worked on and it shows how the application of the latest heating technology, in a simple way, can have major benefits".So that tools can be changed after each production batch has been completed the electrical supply can be disconnected from the control system by means of flexible, quick release power and control cables. These cables connect the tool to a control panel which contains the necessary controllers, contactors, chart recorders and power unit. Digital readouts on the panel show the temperature allocated to each zone and this can be checked against the actual measured temperature.Since each press is used to produce many different shapes, the control panel is pre-programmed with individual heating cycles for every tool. By selecting the tool number on the panel, the correct cycle is automatically initiated. Numerous programmes can be retained in a single programmer.
Graeme McFarlane, who who is the Technical Engineering Manager for the Lear Corporation at Colne said, " before installing The Thermoform Tool Heating System we had to wait eight hours for the tool to reach the correct moulding temperature and this new development has made significant improvements to our production process as well as reducing running costs". As an added bonus it has been found that downtime between mould changes can be almost eliminated. This is made possible by the use of a standby heating system which is used to preheat moulds so that they can be made ready to be transferred to the moulding press when required. They are then simply plugged in and production of the next moulded shape can begin immediately.
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