JÄGER Business Blog

Rubber spring elements in the agricultural industry:
a cautionary example from practice

Material expertise and product design that meets requirements are basic prerequisites for the successful use of rubber and plastic components. In many engineering development departments, steel is the predominant material and there is a lack of experience in working with polymer materials. The lack of materials expertise repeatedly leads to problems with products. What these difficulties are based on and how companies avoid them is illustrated by the example of rubber spring elements in the agricultural industry.

The initial situation

Rubber spring elements are used in agricultural engineering, especially on machines for soil cultivation. In disc harrows, they form the pivot joint between the rigid machine frame and the movable disc arm on which the metal discs are pulled through the soil. Rubber spring elements ensure that the hard shocks generated by inhomogeneous soils (e.g. stones present in the field) are decoupled from the machine frame. They also increase the soil contour tracking capability of the individual discs. They are therefore of high value for the reliability and lifetime of an agricultural machine.

Case Study: Spring elements for agricultural technology

In our case study, you will learn how rubber spring elements can be used to dampen vibrations in agricultural machinery.

Rubber spring elements for disc harrows are produced all over the world by specialized suppliers. Jäger Gummi und Kunststoff, for example, has developed special rubber spring elements based on a high-performance elastomer compound together with several European OEMs of soil cultivation technology. These elements have proven themselves in the field for years and are permanently being further developed.

Some time ago, a mechanical engineering company approached the Jäger team in this regard. It was initially a loose inquiry in which the company provided relatively little information on the functional requirements as well as the material specifications relevant for its rubber spring elements. In addition, it specified a low target price, which – according to the first impression – could not be realized without restrictions regarding material quality.

The customer provided a sample of its previous component for testing. Jäger examined the component both in the in-house test rig for rubber spring elements and in the physical-chemical laboratory. The focus was on functionally relevant physical properties such as rebound, compression set and tear resistance. In a second step, Jäger tested the fully assembled components on a test rig that simulated real-life field use over several weeks.

What trap did the mechanical engineering company fall into?

The laboratory and test rig results were unsatisfactory. The actual function of the rubber spring elements, which are arranged around a square tube to form the swivel joint and are supposed to return the deflected disc arm after the application of force (e.g. by a stone in the field), was not given. The identified malfunction of the rubber spring element was due to the poor physical properties of the elastomer material. The permanent deformations of the disassembled rubber spring element suggested poor compression set. Laboratory testing substantiated this hypothesis. Among other things, the component contained a high proportion of fillers, which had a negative effect on the mechanical properties of the elastomer compound.

Despite these test results, the mechanical engineering company continued to work with the supplier of the sample component. This decision, which subsequently caused major problems, was initially quite obvious from the company’s point of view. It was caused by the interplay of various factors that occur again and again in the rubber and plastics sector:

Strong price fixation
Particularly in the case of B and C components, machine manufacturers act in a very price-driven manner. This strategy often also affects functionally relevant components made of rubber and plastic. In this area, however, price alone can very quickly take its toll, because unfortunately there are always components circulating on the world market that are unsuitable for their intended industrial application.
Poor matching and imprecise material specifications
In the case of low-cost suppliers from abroad, coordination with the supplier can also be difficult. If their components do not meet the customer's expectations, this is sometimes due to the fact that the material and functionality requirements have been insufficiently defined. This was also the case in our project example, where the mechanical engineer had little experience with rubber spring elements. His supplier, in turn, did not address the customer's specific needs sufficiently for cost reasons. The monetary advantage resulting from the low purchase price was accordingly quickly negated.
Lack of infrastructure for testing and validation measures
Not every company can afford to install its own testing facilities for rubber or plastic products. The extent to which a component meets the requirements therefore often only becomes apparent in field tests with the fully assembled machine. In this case, the results from the test bench trials at Jäger reached the machine builder at a late stage in its development process, so that the release date of the machine might have been jeopardized if the component had been replaced.
High time pressure
In agricultural technology in particular, manufacturers are always keen to avoid delays in development projects. Field tests of agricultural machinery are limited to certain periods of the year due to harvesting times and legal regulations, so even small shifts in the project schedule can delay the deployment of a machine and thus cause high costs.

What were the consequences?

Six months after the initial inquiry, the agricultural machinery manufacturer contacted Jäger Gummi und Kunststoff again. As feared, the rubber spring elements installed in the agricultural machinery failed after a short time. This resulted in numerous returns from the market worldwide, which not only caused the company immense costs, but also damaged its reputation.

Due to the existing damage case, the agricultural machinery manufacturer decided to resume the development of the rubber spring elements. In close coordination with the material experts from Jäger, the requirements for the material were precisely defined and a high-quality elastomer compound was adapted to the functional needs of the component. By means of an intelligent tooling concept, prototypes could be produced and extensively tested at short notice.

This care paid off for the agricultural machinery manufacturer in the end. Together with Jäger, the manufacturer designed a spring element that is suitable for the demanding work in the field and is still being installed in numerous other agricultural machines today. The feedback the company receives from the market is now positive again.

Conclusion

Examples like this are not uncommon in mechanical engineering. Due to the high time and cost pressures to which many companies are subject, they repeatedly make the wrong decisions when dealing with rubber and plastic components. Especially since experience and know-how in this area are not available in every development team. The scenario we have presented in this article can be effectively avoided if customers involve their suppliers in a development at an early stage and discuss the specifications of the component in detail. Experience has shown that if this happens at the beginning of development projects, the best conditions are created for making the best decision with regard to the required functionality of the component and the targeted price.

Whitepaper:
Secure the Start of Production

Learn which factors influence your SOP!

Author: Lukas Grünig

Lukas Grünig supports OEMs from the agricultural machinery technology sector in the development of components made of rubber and plastic. Since 2020, the graduated mechanical engineer has been working for Jäger as a cross-location industry manager in the field of agricultural technology.

L.Gruenig@jaeger-gk.de | +49 511 5358 118

Share this post!