Artis Kromanis

Additive Manufacturing and Casting Technology Comparison: Mechanical Properties, Productivity and Cost Benchmark

Abstract The casting technology is one of the oldest production technologies in the world but in the recent years metal additive manufacturing also known as metal 3D printing has been evolving with huge steps. Both technologies have capabilities to produce parts with internal holes and at first glance surface roughness is similar for both technologies, which means that for precise dimensions parts have to be machined in places where precise fit is necessary. Benchmark tests have been made to find out if parts which are produced with metal additive manufacturing can be used to replace parts which are produced with casting technology. Most of the comparative tests have been made with GJS-400-15 grade which is one of the most popular cast iron grades. To compare mechanical properties samples have been produced using additive manufacturing and tested for tensile strength, hardness, surface roughness and microstructure and then the results have been compared with the samples produced with casting technology. In addition, both technologies have been compared in terms of the production time and production costs to see if additive manufacturing is competitive with the casting technology. The original paper has been written in the Latvian language as part of the Master Thesis within the framework of the production technology study programme at Riga Technical University.

The Effect of the Cutting Parameters on the Machined Surface Roughness

From the invention of turning machine or lathe, some engineers are trying to increase the turning productivity. The increase of productivity is following after the breakout in instrumental area, such as the hard alloy instrument and resistance to wear cutting surfaces. The potential of cutting speed has a certain limit. New steel marks and cutting surfaces types allow significantly increase cutting and turning speeds. For the most operation types the productivity increase begins from the feeding increase. But the increase of feeding goes together with machined surface result decreasement. Metal cutting with high feeding is one of the most actual problems in the increasing of manufacturing volume but there are some problems one of them is the cutting forces increasement and larger metal removal rate, which decrease the cutting tool life significantly. Increasing of manufacturing volume, going together with the cutting instrument technology and material evolution, such as the invention of the carbide cutting materials and wear resistant coatings such as TiC and Ti(C,N). Each of these coating have its own properties and functions in the metal cutting process. Together with this evolution the cutting tool geometry and machining parameters dependencies are researched. Traditionally for the decreasing the machining time of one part, the cutting parameters were increased, decreasing by this way the machining operation quantity. In our days the wear resistance of the cutting tools increasing and it is mostly used one or two machining operations (medium and fine finishing). The purpose of the topic is to represent the experimental results of the stainless steel turning process, using increased cutting speeds and feeding values, to develop advanced processing technology, using new modern coated cutting tools by CVD and PVD methods. After investigation of the machined surface roughness results, develop the mathematical model of the cutting process using higher values of the cutting parameters.

Influence of Machining Parameters on 3D Surface Roughness of Powder Bushings

The paper presents the results on research of machining anti-friction bushings of lever brake systems of rail transport, wherein the bushings are made of powder material based on iron and copper. Powder composition contains Fe-C-Cu with Ni and Mo content of less than 0.3%, and with reduced phosphorus content. The porosity of the bushings were in the range of 15 – 20 %. The main objective of the work was to determine the optimal machining parameters, as well as to evaluate the quality of the machined surface. The bushing were machined with cutting speed in the range of 130 – 150 m/min. To assess the quality of the machined surfaces the 3D roughness parameters were used, which allow to asses the surface roughness in more accurate details. The microstructure of the samples indicated the presence of pores onto the machined surfaces. It was found that to improve the quality of the surface it is necessary to adjust the parameters of the powder processing of parts with high porosity in the direction of their reduction. Studies of the microstructure and morphology of chips showed that the shape and structure of the chip is highly dependent on the porosity of the material and its processing conditions.

Influence of Casting Velocity on Mechanical Properties and Macro-Structure of Tin Bronzes

Continuous casting is the most productive method of casting. Manufacturers often tend to increase casting velocity without taking into account the fact that it can cause latent defects within the casting and accordingly lead to a deterioration of the mechanical properties of product. The casting process of tin bronzes encumbers high shrinkage and high segregation in the cross section of the castings. The research was performed on three types of tin bronze alloys CuSn12-C, CuSn5Zn5Pb2-C, and CuSn7Zn3Pb7-C (EN 1982:2008). Influence of casting velocity on mechanical properties and macrostructure was studied and optimal velocity parameters were given. The following study revealed a significant effect of the velocity of continuous casting on the mechanical properties of tin bronze, which was also reflected in the macrostructure of the selected samples. Based on the results of the study the recommendations about the optimal casting parameters to increase a quality of end-product were given. The recommendations were later implemented in the manufacturing confirming the value of this study.