Findling Wälzlager offers damage analysis as an independent partner
Damage analysis for roller bearings: added value for operational safety
Roller bearings are standard components, yet, when installed, they are functionally critical machine elements. When bearing technology fails, it usually causes entire production systems to come to a standstill. To prevent this from happening at all, it is especially important to choose the right application-specific, highly reliable roller bearings. However, if ball bearing defects have already arisen, the causes need to be investigated and permanently eliminated as soon as possible. With over 100 years of experience in thousands of applications, Findling Wälzlager GmbH has the necessary experience and expertise to optimally support those who have suffered damage.
Damage analysis – how does it work?
A damage diagnosis in the field of roller bearings essentially means performing a root cause analysis based on the damage characteristics of the affected products. For this purpose, Findling Wälzlager GmbH has defined concrete processes that are carried out step-by-step using checklists. It always starts with a visual assessment of the ball bearing defect and the precise documentation, sometimes involving photographs, of the design, in particular the connecting parts, up to the theoretical, structural design. An FMEA (failure mode and effects analysis) is used to determine initial indications based on this. If necessary, the experts then take a grease sample and carefully dismantle the affected roller bearings. For each damaged roller bearing, the damage characteristics are then documented using another checklist. These damage characteristics include peeling, scoring, fractures, cracks, cage damage or fretting corrosion.
![[Translate to Englisch:] Schadensanalyse – wie geht das überhaupt](/fileadmin/Inhalt/Bilder/Technik/Findling_Prozessdiagramm.png "[Translate to Englisch:] Schadensanalyse – wie geht das überhaupt")
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Root cause analysis
Rolling bearing damage can have a wide variety of causes and is not necessarily caused by a faulty original product. However, most companies are unable to carry out a detailed damage analysis – good thing Findling Wälzlager’s experts can provide further assistance here: Damage analysis is part of the service portfolio. Findling Wälzlager acts as an independent partner that looks into the causes of the ball bearing defects and helps solve problems. The Application Technology department is responsible for damage analyses. In this way, the experts ensure a holistic approach to the root cause analysis. A modern and well-equipped in-house quality assurance lab makes professional measurement methods and highly accurate tests possible.
- Peeling: When small parts of the roller bearing material peel off due to material fatigue on the surface of the raceway or the rolling element.
- Roughening: Matte/cloudy patches form on the surface from which cracks form.
- Scoring: This occurs due to sliding friction caused by improper lubrication or rough operating conditions. It appears as small score marks on the surface.
- Smearing: Characterized by numerous score marks on the surface and usually occurs due to sliding or a cracked lubricating film.
- Cracks: Excessive loads or severe impacts may lead to fractures:
- Risse: The progression of fine fissures may lead to the formation of cracks. Excessive loads, very tight fits, local heating and progressive peeling are all considered causes for this.
- Cage damage: Typical cage damage includes the deformation and fracturing of the cage as well as wear to the cage pockets.
- Impressions: Impressions form when foreign objects get into the area of the contact points. Impressions also form due to impacts and static loads, but in the spacing of rolling element.
- Pitting: Pits are small dimples that make the surface look matte and rough.
- Wear: The entirety of surface damage to the raceways, rolling elements, ribs, roller end faces, and cage pockets, which are usually caused by sliding friction.
- Fretting corrosion: Wear that is triggered by micromovements between roller bearing rings and the mating surface on the shaft or housing.
- Stationary marks: Characterized by trough-like patches and form due to oscillations in the rolling contact, usually in the spacing of the rolling element.
- Creeping of the bearing rings: This can only occur on a roller bearing’s rings. It involves relative slippage between the mating surfaces and the formation of play between the surfaces. Creeping results in shiny surfaces.
- Blocking: Sudden overheating causes the rings and rolling element to expand, press against each other, and block the roller bearing as a consequence.
- Electrical corrosion: When an electric current flows through a roller bearing, it causes electric arcs and burns. Fluting occurs due to localized melting.
- Rust and corrosion: Both cause red or black dimples on the surfaces of the bearing rings and rolling elements.
- Discoloration: Discoloration in roller bearings occurs due to high temperatures and reactions with lubricant.
Constructive and tribological damage diagnosis
The characteristics documented in this manner are subsequently assessed. Findling Wälzlager makes a distinction between two service areas: The structural damage analysis examines whether the roller bearing position was incorrectly designed. It is often supported by numerical calculations using special software. The experts are able to accurately illustrate the bearing position, calculate the service life, and simulate design changes. By contrast, the tribological assessment deals with roller bearing damage caused by increased friction, wear, and defective lubricants. Unsuitable, old or sparsely used lubricants are the most frequent causes of damage.
Damage analysis application example
A practical example from 2015 shows how important professional expertise in application technology is: A company specialized in power transmission engineering purchased deep-groove ball bearings from a brand-name manufacturer. During the endurance test of the preproduction series at the end customer’s location, roller bearing damage already occurred in two cases after about 5,000 operating hours. The company commissioned Findling Wälzlager with the task of performing a damage appraisal, including suggestions for improvement. The result of the investigation and detailed grease analysis: In this case, the wrong fit was selected, and the lubricant was contaminated for design reasons. It was possible to successfully conclude the test once these defects were eliminated.
Application example for damage analysis and product development
Cage fracturing – this was the diagnosis given by the damage analysis, which Findling Wälzlager carried out on behalf of a renowned robot manufacturer. The background: Despite extremely high acceleration, deep-groove ball bearings with standard cages made of steel sheet, which consisted of two halves riveted together, were installed in the robots. This is totally sufficient for most applications. However, the more extreme the operating conditions are, the more the individual components of a roller bearing have to be adapted to these operating conditions. In this case, the cage and rivets had a more robust and solid design, which permanently solved the problems during operation.
