The rapid development of manufacturing in recent years has led to a significant expansion of the technological capabilities of modern metal-cutting equipment. Therefore, the modern approach to intensifying production requires an advanced fixture design. Design and manufacture of flexible fixtures capable of machining similar shapes and sizes of complex geometry parts reduce setup time. The article aims to design flexible fixtures for parts such as one-piece connecting rods under incomplete locating conditions. The advantages are the minimum number of parts and tool availability for multi-axis machining connecting rods in one setup. This approach, combined with up-to-date machining centers and industrial robots, can increase the production efficiency of manufacturing non-removable connecting rods. This effectiveness is in a decrease in the number of operations by 5–7 times, fixtures—by 3–4 times, and machine tools—by 3–5 times, depending on the type of a non-removable connecting rod and its design features. The numerical simulation results of the proposed fixture design confirmed the comprehensive technological capabilities and dynamic characteristics. Particularly, a decrease in displacements and oscillation amplitudes up to 7% compared to the full-basing locating chart was provided. It is determined that the system “fixture–workpiece” entirely meets all the strength, accuracy, and rigidity parameters, which allows you to perform machining with intensive cutting modes. The amplitudes of oscillations do not exceed the tolerances on the dimensions of these surfaces, established by requirements for non-removable connecting rods, and all displacements are elastic. During numerical simulation, the workpiece position remained stable at all machining steps.
Modern manufacturing engineering requires quick and reasonable solutions during the production planning stage, ensuring production efficiency and cost reduction. This research aims to create a scientific approach to the rational choice of a locating chart for complexly shaped parts. It is an important stage during the manufacturing technology and fixture design process. The systematization of the designed and technological features of complexly shaped parts and the definition of the features that impact a locating chart create the fundamentals for justification. A scientific approach has been developed using the complex combination of the part’s features and a decision-making approach using the example of bracket-type parts. The matrix of design and technological features of parts was developed including steel AISI 3135 and cast iron DIN 1691. The classification of locating charts for bracket-type parts was defined. A mathematical model of the rational choice of the locating chart according to the structural code of the workpiece was verified in case studies from the practice. As a result, a decision-making approach was applied to the rational choice of the locating chart for any bracket-type part. The proposed solutions improve the production planning stage for machine building, automotive, and other industries.
The analysis of various methods of machining of rope internal thread ISO 10208, DIN 20317 has been carried out and the criteria of high-efficiency machining have been formulated. The concept of the method has been developed, which supposes the designing of the construction of noncore tool and the calculation of the parameters of mechanical trajectory with the purpose of ensuring the machining per one pass on the computer numerical control (CNC) milling machine. The compensation procedure of dimensional wear of insert has been developed. While machining the production batch of the parts in an experimental way, the optimum cutting conditions have been determined which allow ensuring the maximum efficiency on reaching the required roughness and the dimensional accuracy of the profile of rope thread. The performed statistical analysis of the machined parts allowed to establish that dispersions of the actual values of profiles' roughness follow Gauss' law. In an experimental way, it has been proved that the application of the proposed method increased the efficiency of machining of the internal rope thread by 2.5 times. On the basis of comparison of engineering-and-economical performance, the efficient fields of application of high-efficient method of machining of the rope threads have been determined.
In the frame of injection moulding production process not all raw material creates the final products and a waste material is generated (defective and rejected products, cold runners, etc.). This technological waste is very often reused in production, which reduces the final production costs, however, this regrind or regranulated material affects the final properties of the part. The negative impact of recycled material presence depends on the degree of chain cleavage of the polymer macromolecules caused by high temperature load. The deterioration of the product end-use properties does not have to be demonstrated immediately (or in a short time period) after the removal of the part from injection mould. However, the product service life can be dramatically reduced which is simulated in the technical practice as exposure of the product to elevated temperature for prolonged time periods. This paper is focused on experimental methods for detection of heat-damaged recycled material incorporated to the non-filled moulded parts made of polypropylene. For the purpose of the analyses the multipurpose test specimens type A (specified by ISO 3167 standard) were prepared under the conditions defined in ISO 1873-2 and ISO 294-1 standard (melt temperature, mould temperature, injection rate, holding time, cycle time, etc.). Subsequently, the melt was overheated within the injection unit which caused the heat-induced macromolecule cleavage. This material was used for production another specimens that were then grinded and added to the original (virgin) raw material in the wide range of concentrations (from 10 to 100 wt%). These final specimens were analyzed using the physical methods modified for engineering practice to determine morphological, rheological, thermal and physical-mechanical properties of the moulded parts.
This article is focused on the prediction model of surface roughness parameters of structural steel created by plasma arc cutting. Optimization of the cutting process is very important from both quality and economy point of view. The presented paper shows the carrying out of the experiment with the specification of the design of experiments method. In these experiments, the influence of three factors ‐ the plasma current, the traverse speed, and plasma gas pressure was observed. Experimental material was selected structural steel S355. Along with the influence of controllable process factors was observed the influence of different plasma gasses. Application of different plasma gas significantly changes surface quality. The result of each experiment series is a regression function that can predict the Rz values according to the process parameters at given intervals. Presented equations can be applied in the production process for adjusting the plasma cutting process in order to achieve required surface quality.
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