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Up to 15 tons load - polymer plain bearings in root ball transplanters


Root ball transplanters are indispensable tools for tree nurseries and for garden and landscaping businesses. They gently transplant trees of any size. Hydraulic cylinders are used to slowly, but with immense force, push the spades into the soil, cleanly severing the roots. Maintenance-free polymer plain bearings demonstrate their strengths in all areas that involve rotating and swiveling movements. They are maintenance-free, have a dry operation and are resistant to dust and dirt.
 
"If up to 1000 trees have to be planted in a nursery in a day, a root ball transplanter is always in play. The machines must be robust and reliable," says Roland Schlesag, CEO of Optimal-Vertrieb Opitz GmbH, a family run enterprise with 15 employees. "Our compact root ball transplanters are in use worldwide. " They have been produced at the site in Thalmässing for nearly 40 years. In the A to Z of applications in the transplantation of trees, they eliminate the tedious and time consuming manual work, and let the machine do the work. "Our machines are extremely robust," says the CEO. "Maintenance-free polymer bearings have been assuring this for many years. These are used in the hydraulic spade guides, various hinges, locks as well as in the connection between the primary arm and pivot arm. This allows us to ensure our customers low maintenance costs and longer service intervals. “

The spades are pushed slowly into the soil. Root ball transplanters with iglidur plain bearings: High loads are no problem.

Problem

The previous solution was elaborately manufactured from gunmetal. In addition to the high amount of time, this also had other disadvantages Firstly, the bearings had to be lubricated, which was a burden on the environment. And secondly, the gunmetal bearings required a relatively large installation space, since wall thicknesses of 2 mm are quite common.  

Solution

Due to polymer plain bearings made of the material iglidur G, complex manufacturing and additional lubricants can be avoided.  This eliminates the environmental impact of additional lubricants when the root ball transplanters penetrates up to 2.5 m deep into the ground.  iglidur G impresses in this application with a high pressure and wear resistance.  Thus the service life of the bearing points could be increased.  


"Since the plain bearings are lubrication-free, no damage can occur in storage due to the good dry running properties at the critical points. We rely on hard-chromed parts for the bolt material. It is the ideal pairing that ensures a robust machine technology for us. “
 
Roland Schlesag, Managing Director of Optimal-Vertrieb Opitz GmbH

 

Technology and mobility

For almost ten years the agricultural technology company has been relying on the standard iglidur G material of the igus GmbH, Cologne. The all-rounder bearing is very resistant to external influences. There are more than 650 dimensions available from stock. "And we use this range," says mechanical engineer, Reiner Irsigler. "There is almost no dimension that is not used in our extensive range of models. Moreover, the price-performance ratio is right, which of course pays off economically. “
 
With the development and production of modern systems for transplanting, the company's founder, Dieter Opitz, set a milestone in gardening and landscaping. Developed in the sixties, the machines enabled an enormous ease of work and have become indispensable today in the nursery and landscape sector. Clean cut roots, tree-friendly ball shapes, gentle working in rows and safe transport: the tree transplanting machines allow for a smooth and time-saving use with a very good cost-benefit ratio.
 
The crucial factors that were considered in the technical design included not only functionality and durability, but also flexibility. It is a very compact device that can be mounted as needed on various carrier vehicles and maintained with little effort. Even fully customised special constructions are possible.
 
Today there is the appropriate solution for every tree. The product range consists of twelve tree transplanting machines. They dig up root balls with diameters ranging from 36 cm to 2.50 m at a ball depth of over 30 cm to 1.50 m. Transplantations usually take place in spring and autumn. "When the season ends, the machine is usually sprayed with a steam cleaner and is best stored indoors in winter," said Roland Schlesag. "Since the plain bearings are lubrication-free, no damage can occur in storage due to the good dry running properties at the critical points. We rely on hard-chromed parts for the bolt material. It is the ideal pairing that ensures a robust machine technology for us. “


 

The hole for tree planting is also dug up by the root ball transplanter. The hole for tree planting is also dug up by the root ball transplanter.

Plain bearings for rotating and swivelling movements

The ideal root ball transplanter handles the trees with extreme care. Its low working height allows the injury-free removal of woody plants. The ball corresponds in shape to the natural rooting. Thanks to the effective spade geometry and clean cut, it is neatly dug up. Firmly enclosed by the spade, the root ball remains intact. The low weight of the farming machine protects the soil and roots.
 
In agricultural engineering, the lubricant-free property and long service life are at the focal point of the requirement profile. In the root ball transplanters the iglidur G plain bearings are stressed mainly during the pivoting movement. This is in particular in the gimbal suspension of the hydraulic spade cylinder as well as in the hinges and the lock of the opening and closing frame parts. Furthermore, in the large machines that are built upon lorries, plain bearings at the hinge points provide a secure connection of the primary arm with the pivot arm.
 
The maximum stress on the machine elements takes place in the area of the gimbal mounted spade cylinder, when the four spades are pressed continuously into the soil with enormous force. A spade of a large machine can theoretically press down 15 t. This means that when about 150,000 N hydraulic force is applied, the material is not protected.

Left: Bearing point with iglidur plain bearing surrounded by damp soil; right: iglidur plain bearing visible in the bearing point Functional bearing points despite moisture and dirt

"We have had the best experience in this field with the plain bearings," says Reiner Irsigler. "They withstand the enormous surface pressure continuously. And what's more, its lubrication-free property has proven itself in harsh everyday conditions. The soil gets stuck continuously on the lubricated machine elements. It penetrates gradually into the bushings and cause friction and can eventually lead to failure. “
 
In the area where the spade plunges into the earth, every conceivable abrasive loads also occur. The topics humidity and wide temperature range are also a factor to consider "As part of the new construction of the train station in the Stuttgarter Schlosspark in the winter of 2011/2012 there was a very tight time frame for the translplantation of the trees. Furthermore, temperatures lay in the lowest minus range," relates Roland Schlesag from experience. "The used large machines had no failures whatsoever. " The tribologically optimised plain bearings coped with every edge load easily, when the spade, for example, encountered stones in the way.

asdf iglidur plain bearings in the hinges, locks and hydraulic cylinders of the root ball transplanters

No more in-house production

"In the past we produced the necessary bearing laboriously even in red bronze, which naturally had an impact on the installation space," recalls Reiner Irsigler. "Wall thicknesses from 2 mm were on the one hand simply not possible. On the other hand, we always had to pre-produce, which did not pay off in the long run. Today one phone call is enough and the necessary components are on site within a working day. " This allows us not only to dispense with grease nipples at the critical points of the machine but also with the expensive storage of parts produced in our own factory. "The iglidur bushings go to the shipping from stock. They are technically mature, tested and meet our high requirements," says the CEO.
 
Tribo-optimised cylindrical standard plain bearings made of the iglidur G material are used in many available dimensions in the root ball transplanters. They are simply ordered from the catalogue. The range of applications is always the same for all machines, which enables the company active in the agricultural technology sector to resort to standard solutions. "It simply works," comments Dirk Lanuschni, the igus sales consultant in charge. "The iglidur G material is known as the all-rounder. It covers a wide range of applications and is characterised by high wear resistance and low friction. “

From left: Uwe Sund (igus GmbH), Roland Schlesag (CEO of Optimal-Vertrieb Opitz GmbH), Dirk Lanuschni (igus GmbH), Reiner Irsigler (mechanical engineer at Optimal-Vertrieb Opitz GmbH). From left: Uwe Sund (igus GmbH), Roland Schlesag (CEO of Optimal-Vertrieb Opitz GmbH), Dirk Lanuschni (igus GmbH), Reiner Irsigler (mechanical engineer at Optimal-Vertrieb Opitz GmbH).

Heavy duty applications for iglidur G plain bearings

There is a further technical detail plays a decisive role in this application and emphasises the versatility of the polymer bearing: "In the event of a unilateral load a red bronze bushing will deflect at some point, which goes at the expense of the tolerances. The clearance continues to grow, until a bolt gets broken. Even though we previously used, for example, hardened bolts in the hinges, they still broke," recalls the mechanical engineer. "Broken bolts now belong to the past. The soft plastic material yields elastically, which completely eliminates a notching damage that comes at the beginning of a break point. “
 

In this application the tribo-optimised iglidur plain bearings display their versatility in the most severe conditions. They prove their durability, especially in the hydraulic cylinders of the spades when they slowly press into the earth, resisting all external adversities. "We supply technology for professionals. Our aim is to produce the 'made in Germany' quality for our customers worldwide at any time," concludes Roland Schlesag. "And the maintenance-free and dry-operating plain bearings thereby play a vital role. “

3D illustration of the guide box: a variety of applications for polymer plain bearings. 3D illustration of the guide box: a variety of applications for polymer plain bearings.

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