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New dimensions of wear protection

Understanding, developing, producing and advising – these four elements are brought together by Stahlwerke Bochum (SWB) to combat wear in the field of shredder technology. The focus is also on a shared conservation of resources with customers.

This tech story appeared in the last edition of Recycling International >>

SWB is constantly researching pioneering solutions against wear. Among the company’s latest developments is an internationally patented shredder hammer with a structured inner circumferential surface at the bearing opening. The idea behind this invention is, by relatively simple means, to reduce the risk of wear in the bearing opening even under high stress.

Inside the shredder, a new hammer is mounted on a used or new axis on the rotor. There, a centrifugal force of about 40 tonnes pulls on the hammer that weighs only 140 kg. Initially, these forces are at work as extremely high point loads on the hammer’s bearing opening and the axis.


The new inner surface quickly creates a large contact area between axis and hammer bearing opening, leading to a fast reduction in localised strains. This makes the hammer more resistant against overloads during the first operating hours.

Patented shredder hammer with a structured inner circumferential surface of the bearing opening

Furthermore, depressions in the bearing opening absorb metallic material that is displaced due to strain during use and prevent it from being pressed out of the bearing opening and creating a thickening in the moving gap between hammer and rotor protection cap.

At the same time, compression stress in the inner circumferential surface of the bearing opening is reduced, decreasing material displacement and lowering the risk of crack formation or other damages such as chipping.


Another new SWB hammer comes with an enhanced bearing opening that increases stress resistance and facilitates hammer exchange/turning. Studies to determine the dynamic strain on shredder hammers show zones with relatively low strain and those with extremely high strain.

Enhancing the opening increases the ability to absorb dynamic strains impacting on the bearing area during use as they are absorbed through an enlarged surface which reduces friction and therefore lowers the risk of cracking/breakage in the areas adjacent to the bearing opening. A patent is pending on this invention.


SWB has also invented a reinforced rotor protection cap that extends the lifetime the caps. Practice indicates that the caps mounted next to a shredder hammer show a strong wear on their long side. Such wear requires these caps to be exchanged earlier than others.

Replacement requires a temporary deactivation of the shredder leading to a loss of production. SWB has reinforced the cap on the rim side next to the hammer to match the lifetime of all protection caps on the rotor, making a premature exchange of the hammer adjacent caps obsolete. This invention is awaiting a patent.


All three product innovations have in common that they ease the daily work of SWB’s customers, save costs and reduce set-up times. They complement recent product optimisations:

  • wear optimised shredder hammers
  • boast improved stress resistance and
  • reduced risk of chipping while the
  • trusted ‘winter hammer’ has the highest possible operational reliability
  • under harsh winter conditions.

Currently, 37 different types of alloy steel ensure an optimal fit of the wear parts for their respective uses. Observation of the entire production process and extensive quality controls guarantee consistently high quality from SWB products.


SWB teams advise customers on site in more than 50 countries worldwide and offer individual support for customer specific challenges. Wear parts are specifically produced for their dedicated application area to improve plant efficiency.

SWB opts for a sustainably CO2 reduced production, operates a DIN EN ISO 50001: 2018 certified energy management system, and has always offered its customers the chance to return worn impact tools and linings at reasonable cost. With its products made from steel scrap, SWB is fundamentally involved in the steel recycling process of its customers.

Together, they deliver sustainable environmental protection and save resources since, by recycling of one tonne of steel scrap at least 1.67 tonnes of CO2 emissions are prevented compared to primary raw materials.

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