By Christian Decker and Bjoern Dormann, DESMA, Desmastrasse 3/5, D-28832 Achim, Germany
Producers of polyurethane goods, including footwear, are increasingly being forced to consider methods that reduce the carbon footprint of their production and to look for approaches to “greener” manufacturing.
Such trends are forcing the industry to think of new processes and technologies. While some new solutions are obvious, existing technologies also have to be improved.
Current trends affecting particularly the athletic footwear sector are:
- green aspects;
- lower carbon footprint;
- lighter weight;
- increasing domestic production;
- brand trust; and
- shipping costs-shipping time, energy use, globalisation generates a range of effects.
These trends have generated new production philosophies, leading to new challenges, some of them contradictory.
The challenges include reduction of environmental effects, lowering the VOC (volatile organic compounds) levels, and cutting material and energy consumption. Other desirable aspects include minimising production and logistics costs, the ability to make individual products, a high level of production flexibility and mass-customisation.
At the same time, manufacturers must look for innovative design possibilities, and ways to improve product performance.
New technologies for assembly process
At Desma, now strategy in recent years has been to develop new technologies, so as to be prepared for major change in large-scale production of all kinds of footwear.
One central target was an easy machine-user interface, which is a key point in any automation solution.
Developments are focused on reducing the complexity of use of technical equipment. Software has been optimised, and from generation to generation, customers have confirmed that the stability of control solutions has improved a lot.
But one point has remained a barrier for users to invest in high-technology robotic automation solutions. Either the customers did not want to pay highly skilled operators or could not fit them to drive the equipment.
This made Desma reassess what it was doing and change the target. This became the development of a totally self-programming system, which needs no operator for programming or to set parameters.
One hardware solution has been a robotic cell for the treatment of shoe soles or parts with primers and adhesives. Intelligent control of the cell, combined with the right senses, generates the required software information for the robot.
At Desma, this rapidly earned the nickname “black box,” because it works like a box. A product will be fed into the box on one side, and its geometry is automatically recognised. A treated product comes out the other side. Meanwhile line operators have not had to concern themselves about the internal process.
The programs are generated automatically and will be used just once. A great feature is that the cell compensates for sheep deviations, and so maintains final product quality.
An application for the first type of black box is the contactless spraying of the shoe sole.
In the prototype, Desma used hot-melt adhesive spray equipment to treat the surface with a boundary spline of a temperature-activated polyurethane-based reactive hot-melt.
Different filling strategies were tested at the time the material saved using a boundary spray delivered a more than convincing result in bonding forces.
In less than eight seconds, a UK size 9 soul can be treated with 1.5 g of hot-melt adhesive. The sole adhesive is activated and the soul then manually set on a just cleaned textile upper, and compressed for about two minutes in a press.
Using this relatively easy process, a manufacturer can eliminate all the workers who roughen the upper, and treat the soul and upper with primers and cements. For athletic footwear made on various production lines, this amounts to about 15 to 20 people.
Additionally, the process saves a lot of primer and cement material. These are currently applied by toothbrush, in most production plants, at a level of around 10 g to 15 g per shoe.
The cell can be fed with different products with changing sizes, colours, shapes and orientation.
In order to supply systems which marry with the production philosophies of the footwear producer, Desma has designed to logistics styles for the Black Box solution.
One can be integrated into existing production lines, the other can operate independently as a stand-alone solution.
It is also possible to combine the process for conventional primer-cement systems and integrate piece flow in production through the following steps: “feeding-spraying of primer-drying-spraying of cements-drying.”
Such Black Box technology can be integrated into existing production lines by the design of a totally new production scenario, with far fewer people and less equipment. It also gives lower output, but with much higher efficiency and investment utilisation.
In some scenarios the black box is just one part of the total equipment. Such a scenario may contain another robot system, which is responsible for the preparation of the upper. Robots can be used in various ways to guide and operate tools or to guide objects into place.
Shoe manufacturers can set up various automated processing cells within their production lines, for example the upper processing cell. This integrates several processes which are conventionally carried out manually.
For each process step, the robot needs maybe 10 seconds, adding up to a total of around one minute. At first this seems slow, but a second check shows that the total productivity is much higher than the traditional production.
Such integration of multiple scenarios in a total production setup can give an output of about 1200 pairs per eight hour shift with just nine people in production, the seven people in the finishing and packing department.
All ideas at Desma focus on the mainstream of “lean” manufacturing principles, which are more and more being realised within the footwear industry and which allow huge increases in utilisation of the invested capital.
About this feature crosshead
Desma is continuously improving its technologies for industrial footwear production. One target is for economically viable technologies to replace labour-intensive processes.
Use of robotics in combination with highly developed materials is one route to future footwear production concepts.
Desma is the only supplier in the shoe industry to offer complete automation. The necessity of integrating automation aspects is becoming more and more important because production costs of to be ministered with no loss of quality.
Here we give an overview of the latest developments in automating traditionally assembly processes, where up is an soles have to be “married.” Much mass production of shoes is through manually support process change, in low labour cost countries. New solutions and automation of the possibility of quality improvements while at the same time reducing labour costs.
The main targets are:
- Reduction of production costs;
- Reduction of material use
- Improvement of article quality; and
- A possible move into high labour cost countries.
Improvement of working conditions, by eliminating problematic work environments, such as rough just, solvents, noise and uncomfortable temperatures and conditions ( bad environments are useful for robots)
Optimisation of material useful primers, adhesives and release agents.
Reduction of VOC in the final product from using less material and solvents, or use of water-based adhesives and hot melt types.
Possible step into high labour costs countries, giving a realistic chance to cup distance between production and important customer market; short logistics chains; fast and effective shipping; and reduction of the total product carbon footprint.
Improvement in quality, since robots always work the same way every cycle.
Reduction of costs through cutting labour costs, and higher production flexibility. Robots need no holidays, no breaks, and work three shifts without increased fixed costs.
Risk reduction, since robots are not in a union.
About the authors
Christian Decker joined Desma in 1997 to reorganise its enterprise resource planning and tall design. In 1999 he took responsibility for mechanical design of Desma products, and in 2001 became manager of all design disciplines and integration of the latest technologies in production.
In 2004, Decker took responsibility for polyurethane, thermoplastics and rubber processing developments.
Now, as managing director of Desma, Decker has great interviews as for handling the challenges of customers and global markets, within the company structure and product portfolio.
Bjoern Dormann is manager of the technology department of Klockner Desma Schuhmaschinen. He has experience in developing, use and servicing of machines and systems for footwear.
He joined Desma in 1990, and has installed Desma machines worldwide, and also helps to develop robotic systems for footwear.
his work gave him experience in soling materials; thermoplastics, all urethane and rubber. Since 2003, he has been manager of the technology department.