How plastic profiles enable exact positioning in conveyor systems
A joint project was launched at the beginning of the year by Technoform and Paul Vahle GmbH & Co. KG, one of the world’s leading system providers for mobile industrial applications, to develop a plastic support profile intended for use in a new positioning system.
In industry, especially where automated conveyor systems are used, precise positioning in the single-digit millimetre range can be of crucial importance. VAHLE’s positioning solutions, available with magnetic or optical position detection, provide the basis for this precision. For one particular customer application, a magnetic positioning system in a new performance class was going to be needed. VAHLE worked with the customer to determine what criteria the new system with higher performance levels would need to meet. The solution that was developed involved a conductor rail being used in conjunction with a support profile.
Many requirements for engineering plastics in electrical engineering result from regulations and standards. How must the material behave in the event of fire? How safe must the plastic be against electric shock? Are there special requirements for leakage current? What about substances that are hazardous to health?
Standards ensure that the materials and substances we use to make plastic profiles have clearly defined properties. This makes it possible to find the right material for every requirement in a project. You don't have to decide which material to use on a case-by-case basis. As your implementation partner, we will do that for you. However, it is worth having a rough idea of which standards are relevant and what they cover.
Some of the standards described below refer explicitly to the materials, in our case plastics, while others refer to the finished product, which is made from engineering plastics. The flammability and insulation properties of plastics are particularly important for use in electrical engineering.
A single profile design for many applications
The absolute positioning unit is part of a system solution that uses a conductor rail to supply the required energy. The product bundle is suitable for use worldwide in a large range of industries, and in any application requiring reliable and robust positioning: in production lines in the automotive industry, in amusement park rides, in crane applications or in conventional intralogistics applications.
The market has already signalled a demand for higher load capacities in container ports where large gantry cranes are used. This would also be of interest for sawmills, which use these systems to transport tree trunks.
VAHLE wanted the positioning system’s plastic profile to be as robust and as flexible as possible.
Maximum reliability
The positioning system uses a magnetic code strip that is clipped into the groove of the support profile. The absolute position value is encoded magnetically, with the use of north and south poles, similar to the basic function of a conventional bar code. Detection, however, is performed optically, by means of a camera system.
In this system, a read head with integrated electronics moves across the magnetic code strip. The read head is guided along a set path by the plastic profile and it determines the absolute position by decoding the code strip in real time. Using a magnetic solution ensures that position detection remains reliable even in highly demanding environments, as its measurements cannot be distorted by environmental influences such as light reflections, dirt, dust or oil.
The system retains its position in the installation even in the event of a power failure and subsequent restart. The customer’s control system is therefore able to localize the read head carriage precisely at all times.
As a result, the plastic profile needs to have maximum dimensional stability, as the read head is continuously pressed against the plastic profile and its integrated code strip.
“We have a narrow tolerance limit of 10 mm, so a reinforced material was required. We were able to identify the right material in discussion with Technoform. Initial calculations and tolerance ranges have revealed potential"
says a VAHLE development engineer.
Plastic profile with high rigidity and flexibility
The plastic support profile needed to permit fitting in all orientations within the curve of the insulating rail. At the same time, it had to be highly rigid over two metres so that its suspension intervals could be the same as those of the system with the conductor rail. This simplifies assembly of the system as a whole at the customer’s premises, where the supports are generally positioned up to two metres apart. The aim here was to keep deflection as low as possible whilst also permitting a radius, so that the customer can produce radii on site during construction without having to use tools.
Requirements for the plastic profile:
- High rigidity: deflection below 10 mm in use
- Suitability for harsh environments
- Resistance to acids
- High wear resistance
The development project at VAHLE includes testing of the plastic profiles in an overhead conveyor in VAHLE’s in-house test laboratory. This involves testing the limit tolerances of approximately five samples. A radius is created with the profile and its performance and properties are checked in the test suspension.
“The challenge with this project was to achieve rigidity in the profile that was neither too little, nor too great”
says Holger Hofmeister, project developer at Technoform.
Conclusion
Eight to twelve months after the launch of the project for development of the plastic profile, VAHLE will be able to launch the new system on the market that can support higher load ranges and permit greater intervals between suspension points.
The new development provides a robust solution for a wide range of harsh environments. At the same time, a high level of compatibility with other VAHLE conductor rail system products is achieved.
The project conducted jointly by Technoform and VAHLE permitted swift design of the optimum plastic profile geometry and selection of the best possible material.