Andris Ratkus

In Situ Laser Build-Up Welding of Shipboard Crankshafts

Renovation of marine diesel engine crankshaft main and crankpin journals surfaces is usually done when ships engine is undergoing repairs. Often heavy working conditions and intensive wear accompanied with lubrication failures require a complete renovation of these worn-out surfaces. In most of the cases these repairs are done in the workshop, by removing crankshaft from engine and subsequently performing journal grinding. Where it is necessary also various types of build-up operations are carried out. Final technical requirements for these repairs are demanding: fine surface quality, geometrical accuracy and high surface roughness (texture) parameters have to be ensured. Although available technologies are able to deliver these results, they are very expensive, time consuming and usually can be done only in workshop conditions by highly sophisticated and expensive grinding machinery. This article describes novel technology which has been developed to perform crankshaft crankpin journal surfaces grinding operations directly in engine housing. Furthermore, a comprehensive study of laser build-up techniques and their potential applications for marine crankshaft specifics is outlined. Study confirmed that previously adopted grinding platform can be extended to laser cladding technology. It suites well shipboard crankshaft surface renovation needs and opens an entirely new industrial application dimension to the laser cladding technologies. Combination of these in-situ grinding and laser cladding technologies can bring considerable economic benefits and save the valuable marine diesel engine repair time.

The Application of Laser Cladding to Marine Crankshaft Journal Repair and Renovation

This article presents the development and design of a laser cladding machine for in-situ marine diesel engine crankshaft repairs. The described technology and device is designed to perform crankpin journal renovation operations directly in the engine housing, without removing the crankshaft from the engine. This paper outlines the novel, in-situ concept of applying laser cladding to marine crankshaft repairs. Laser cladding technology is described along with the state of laser cladding implementation in modern production engineering. The principal design of the in-situ laser cladding machine is presented and accompanied by a detailed description of the in-situ laser cladding machine construction. Arguments for the selection of appropriate laser nozzles are provided based on state-of-the-art technology. Technological challenges deriving from the industrial use of the laser equipment are outlined. The proposed device and method satisfy ship-board crankshaft surface renovation needs and open up an entirely new dimension for the industrial application of laser cladding technologies. This technology provides clear economic benefits and many technological advantages.Copyright

A Study on how Grinding Technology Parameters Affect the Surface Texture Formation of Marine Diesel Engine Crankshafts

New technology has been developed to permit repair work on one of the main and most important components of shipboard diesel engines—the crankshaft—without removing it from engine. It is no longer necessary to dismantle the whole engine and as such, this innovative technology significantly reduces repair costs. However, the impact of this novel grinding technology on the surface roughness parameters is not yet clear and requires additional scientific analysis. Machining technology and cutting regimes, as well as the material of the tool being used, all have a direct impact on the surface texture and consequently on the quality of the repair as a whole. Therefore, to realise this innovation, it is necessary to carry out additional research into the impact of grinding technology parameters on the surface formation of the crankshaft main and crankpin bearings (journals). Current roughness research is usually restricted to two-dimensional surface roughness parameters—simple profile analysis. Nevertheless, in practice any surface has three dimensions, which give it a characteristic texture. It is therefore also necessary to create a new theoretical 3-D surface model for crankshaft bearings surfaces. This will allow us to analyse the full-scale impact of technological grinding regimes on the actual three-dimensional surface. This study revealed that optimal 3-D surface roughness (texture) parameters for crankshafts depend upon: the mean arithmetical deviation of the surface, RaT, and two perpendicular surface spacing parameters between the peaks Sm1 and Sm2. Multifactorial research shows individual significance of each technological regime and overall impact on the 3-D parameter RaT, Sm1 and Sm2. The approach and methodology adopted for the experiments enabled us to identify the optimal and most appropriate grinding technology parameters.

New In-Situ Technology for Marine Diesel Engine Crankshaft Renovation and its 3D Surface Texture Model

Repairing marine diesel engine crankshafts is a significant part of overall engine repairs and thus is very important for the ship building and ship repair industry. When a ship’s diesel engine is repaired, crankshaft journal surfaces must be renewed according to very precise geometrical and surface roughness requirements. Although current technologies are sufficient to meet these requirements, they are very time consuming and consequently expensive. A comprehensive research into the surface machining of marine diesel engine crankshaft journals allowed to improve technological processes and to identify respective surface roughness parameters, as well as to provide appropriate technological recommendations. It is important to note that crankshaft journal surfaces must be seen as 3D objects, whose micro-topographical surface roughness parameters have to be defined so that they reflect the actual surface. To summarize all available scientific research in this field, we can state that there has been no analysis into the impact of technological regimes on the surface micro-topography of marine engine crankshaft journals. Bearing in mind the aforementioned arguments a study has been launched to develop a novel grinding technology, enabling diesel engine crankshafts with medium-sized crankpin journals to be repaired directly inside the engine housing. This paper covers the following issues: 1) Description of the novel technological equipment for crankshaft journal grinding; 2) 3D roughness model of the crankshaft journal surface; 3) calculation of 3D parameters based on practical metrological and technological characteristics. This technology saves significant financial resources as well as reduces engine repair time. By solving problems related to surface accuracy, it is possible to considerably improve the crankshaft machining process, along with the performance of maintenance operations and consequently the overall quality of repair work. In this paper, the crankshaft journal surfaces will be defined using 3D surface roughness parameters.Copyright

Mathematical Model of the Influence of Process Parameters on Geometrical Values and Shape in MIG/MAG Multi-Track Cladding

The cladding process in the present case contributes to a repair technology, in which a new layer of material is created by using Metal Inert Gas/Metal Active Gas technology on inner cylindrical surfaces, e.g. bucket bores or hydro cylinders. The cladded layer is subsequently subjected to mechanical processing. Although cladding technology itself is well known, its results are hardly ever predicted with regard to inner surface renewal. In this paper, we explore the influence of cladding technological process parameters on geometrical values: the thickness, cross-section areas and shape of the newly cladded layer are established. Current research provided significant information which enabled mathematical models to be developed for inner surface cladding. Polynomial regression was used to create a mathematical model, where coefficients established with the SYSTAT software and their adequacy was checked using the analysis of variance technique. Thus an equation was obtained to help identify the effects of parameters on the final result. The most significant factor identified in cladding geometry is the amount of material that is supplied to the melting pool, followed by the process speed and heat input. The obtained coefficient describing the amount of material is presented, together with equations for calculating minimal thickness, efficient thickness and the multi-track cladding shape.Copyright

Analysis of the Impact of In Situ Repair Technology on the Surface Integrity of Excavator Bucket Bores

The aim of this article is to outline the progress of research into how to develop economically and scientifically justified backhoe bucket borehole renewal technology using mobile on-site manufacturing equipment. The novel boring machine is deployed directly on the excavator bucket and thus does not require the complete dismantling of the damaged unit. These machining operations should achieve superior results: the repair quality must be equivalent to the new product. Surface roughness, shape and tolerances should correspond to the manufacturer’s requirements. Comprehensive analysis is therefore required of the technological regime’s impact on surface integrity, supported by clear recommendations for the optimal choice of the technological regimes.