Article published in the July/August issue of European Rubber Journal magazine:
Automation opens door to high-speed manufacture of large rubber components, writes Koen Spaanderman of Dutch company Taniq BV
Mandrel-built products are a niche part of the rubber industry, typically including large-diameter rubber hoses, high-end expansion joints, bended hoses and pipe plugs.
The industry is characterised by specialist companies, manufacturing products to unique customer specifications in small orders.
Conventional products rely on manually applied rubberised reinforcement sheets. At the end of the product the sheets are slit and in some way connected to a coupling or other connection mechanism. For straight products this process can be reasonably fast, but especially for products with a double curvature, such as bellows, it is particularly difficult and time-consuming to place the sheets.
By replacing the reinforcement sheet by single cords/yarn/fibres, it is possible to apply the reinforcement material in a continuous manner from end to end, without the need to slit the cords. This enables a high-speed continuous process, suitable for automation.
While, the idea of individual-cord winding systems for rubber composite structures is not new, this technology has not been successfully adapted to the large product variations within the mandrel-built product niche market.
However, using a robotic arm in combination with a digital design environment, can overcome these shortcomings: automatically applying the cords and different material layers and providing the required agility and flexibility to handle the variations in size, material and design between different products.
Industrial robot arms have six degrees of freedom which enable manipulation of the material for accurate placement on the rotating mandrel. To apply different types of materials the robot can be fitted with different end-effectors dedicated for a specific job.
For instance, placement of the fibres is achieved with a guiding tool at the end of the robot arm. The robot can switch the tools automatically, and thereby also automate rubber and tape application, so that materials are continuously wound over the product, following the contours of the mandrel back and forth at high speed.
As part of digital manufacturing, special software has been developed that incorporates and automates the reinforcement structure calculation, as well as rubber and tape layer design.
Robotic arms normally require reprogramming for each change made to the production process. However, by using software incorporating a robot controller-program output function, manufacturers can automatically generate a production file for the robotic system based on the product design – eliminating the need for reprogramming.
As a result, setting up the robot is very fast, providing the required flexibility for various products. In addition, designing the product in software makes it possible to perform finite element analysis/modelling for different load cases with the exact geometry of the design. This means that the designed product, analysed product and manufactured product are identical.