Aloysius Krenzer KG produces Europool pallets and customer-specific wooden pallets using a high level of automation. When the company’s technical experts order new systems, they use their practical knowledge and influence the system manufacturers so that they employ igus® drylin® linear guides for certain uses. After all, these bearings have been successfully used in linear drives that operate highly dynamically under great strain.
Abtsroda in the Rhön area is famous for two groups of specialists. The first are model airplane pilots: On the Abstrodaer Kuppe, 20 km to the north-east of Fulda and right by the Wasserkuppe, the highest mountain in Hesse with a height of 950 meters, is a popular airfield for model airplanes where competitions are even held.
The second group are experts in logistics, goods handling, and material flow technology. The reason for this is that Abtsroda, which has been part of Poppenhausen since 1972, is home to the head office of Aloysius Krenzer KG. Established in 1924, this is one of the few pallet manufacturers that covers every element in the pallet production process chain, from log transportation through sawing, preparing, and processing, to logistics with its own fleet.
Three company-owned saw mills provide the base products for the largely automated production lines. As the main Krenzer product, several lines produce Europallets in accordance with EN 13689-1 and EPAL quality criteria. However, the company also manufactures chemical, glass, and customer-specific disposable and reusable pallets.
Through continual expansion, the three second-generation managing partners, Werner, Rudolf, and Gregor Krenzer succeeded in developing the company into one of Europe’s leading pallet manufacturers. Consequently, the production facilities are continually expanded. The newest system is characterized by exceptional flexibility as it produces customer-specific pallets of different sizes with a high level of automation.
The system was developed and built by a pallet production systems’ specialist. However, the client had a great deal of influence over the design - even down to the finest of details. Gregor Krenzer, the managing partner responsible for technology: "As a machine user, we have gained a great deal of experience, especially in relation to the service life of the movable drive and handling components." Here, the designer has to consider the special environmental conditions, which include not only wood chips and dust but also humidity and resin.
In addition to the above, the dynamics of many drives are extremely high. For example, this applies to the handling units of the nailing station where the pallet cover boards are nailed on. The machine automatically takes all the necessary wooden parts from the magazines and nails them together. The servo drives position the cover boards.
The axes, which have diameters of 30 to 50 mm, are precisely guided by dry running drylin® linear guides with iglidur® liners that best withstand the specified conditions. That means 50,000 strokes à 30 cm per day in a dusty environment and under varying loads as the moving ends on the axes move up and down when removing a board from the magazine. The continual vibrations from the nailing process must also be withstood.
This type of bearing was selected as a result of a recommendation from Krenzer as well as experiences with the drylin® linear guides. Gregor Krenzer: "We also use the drylin® housing and pillow block bearing in combination with reinforced steel shafts on other systems. Although this isn’t the optimal friction pair recommended by igus®, it offers a far longer service life for our usage." “
4.5 million operation cycles under unfavorable conditions In Krenzer’s experience, these linear guides have a service life of approximately three months. At first glance, that does not appear very long. However, if we multiply 50,000 strokes by 90 days, that results in 4.5 million operation cycles - while withstanding dirt, high dynamics and varying loads. The most important thing is that the service lives of the other types of bearing, such as ball bearings and recirculating ball bearing guides, which Krenzer has tested in other systems under similar conditions, are even shorter. Furthermore, the guides operate maintenance-free under the unfavorable conditions and Krenzer is extremely satisfied with the precision achieved by the drylin® axes.
Krenzer does not only use drylin® systems for removing cover boards from the magazine, but also for feeding and precisely positioning the boards. In this regard, two linear guides, each with two drylin® bearings, are used per station. These dry running bearings are also used in the other pallet production systems. Gregor Krenzer: "We also have our own mechanical engineering department whose tasks include retrofitting existing systems and designing and building individual components such as feeders. Our experience shows that you have to precisely consider the environmental conditions when selecting a bearing. If, for example, a rack steering should be driven or the travel distances are extremely large, we use different solutions. In our experience however, the drylin® linear guides achieve the longest service lives in relation to the regular, dynamic movements in our handling and feed units." “
Snowplough effect: drylin® linear guide at a feed station.
Krenzer specializes in the production of Europallets and customer-specific pallets.
Gregor Krenzer, managing partner of Aloysius Krenzer KG, (right) speaks to igus® sales consultant Dirk Merlin (left).
Linear drives with moving ends that move upward remove the cover boards from the magazines.
The dry-running drylin® housing bearings are successfully used in many applications in which other linear technology drive and guide systems are unable to offer impressive service lives.
Dust, chips, dynamic movements, and varying loads: These are the conditions which drylin® linear guides have to withstand in the pallet production systems at Krenzer.
drylin® bearings are also used for the feed and precise positioning of the cover boards.
The dry-running plain bearings are also suitable for vertical movements on converters and stacking units.