Rafał Kluz

The repeatability positioning analysis of the industrial robot arm

Purpose – The purpose of the following work was to work out the dependency to allow for the determination of the repeatability positioning error value of the robot at any given point in its workspace, without the necessity of conducting time-consuming measurements while routing a precise surface of repeatability positioning. Design/methodology/approach – The presented dependency permits for the possibility to determine, even at the planning phase, the optimal connection point in the workspace, ensuring the best parameters for the process of machine assembly, without needless overestimation of precision of the utilized equipment. To solve the task the sequential quadratic programming (SQP) method implemented in the MATLAB(R) environment was used. To verify the hypothesis of the compatibility of the empirical distribution with the hypothetical distribution of the robot’s positioning error, the Kolmogorov test was used. Findings – In this paper, it has been demonstrated theoretically and experimentally that ...

Analysis of the optimal orientation of robot gripper for an improved capability assembly process

The objective of the article is to increase the probability of achieving a joint of cylindrical machine parts, through appropriate orientation of the robot gripper of the assembly robot, while ensuring the best parameters of the assembly process and the required process capability, without unnecessarily increasing the accuracy of the assembly workstation equipment. The presented methodology for the summation of errors, besides its simplicity, has an additional advantage compared with the method of the summation of variance or error vectors separately in regard to each axis of the adopted coordinate system, because it takes into account the nature of the relationships between variables (covariance). The analysis showed that by rotation of the gripper around an oriented axis of the machine cylindrical part, the probability of the joint and process capability index C p value can be increased from C p = 1.17 to C p = 1.33 . The optimal orientation of the robot gripper enables the clearance fit between mating parts to be reduced by 8% and 19% with respect to its extreme unfavourable setting. However, this setting of the robot gripper reduces the sensitivity of the system to the effects of systematic errors. We presents the method of determining the optimal angle of rotation of the robot gripper.By the suitable rotation of the robot gripper, the probability of joint is increased.The proposed method allows to increasing the value of process capability index C p .Optimum setting of the gripper enables the reduction of clearance fit between mating parts.

Investigating the influence of the chamfer and fillet on the high-cyclic fatigue strength of adhesive joints of steel parts

Abstract This paper presents the results of research undertaken to determine the possibility of improving the fatigue properties of peel-loaded adhesive-bonded joints by the constructional modification of the adherend. Fatigue strength tests were carried out on the electromagnetic inductor at the resonance frequency of the adhesive-bonded joint specimens. The tests were carried out on the specimens bonded by means of Bison Epoxy and Epidian 57 epoxy compositions with poly-aluminium chloride hardener. The joined elements were modified by making the chamfer or fillet to enlarge the thickness of the adhesive layer with the aim of reducing the stress concentration in the frontal part of the joint. This modification is the result of a research that confirms the existence of a stress concentration on the short section of the frontal part of an adhesive joint. This phenomenon can lead to the rapid initiation of adhesive joint destruction. The fatigue strength tests revealed a significant improvement in fatigue endurance.

Grindability of selected grades of low-alloy high-speed steel

In this paper, we presents the results of investigations studied the cutting ability and grindability of selected high-speed steels. We analysed the effect of the austenitization temperature on the grain size, the amount of retained austenite and percentage of retained austenite in HS3-1-1 steel. Furthermore, the investigations concerned on the efficiency of the keyway broaches during the whole period of operation were carried out. It was found that the value of average roughness parameter increases together with increases in the grinding depth. The investigations also show the influence of tempering conditions on the volume of carbide phases in HS3-1-1 steel.

Forecasting the Mountability Level of a Robotized Assembly Station

This article presents the problem of determining the mountability level of the assembly station using an artificial neural network (ANN). The results of ANN modelling were compared with the results of experimental research and classical mathematical modelling. It was found that the error in predicting the mountability level using the artificial neural network is about two-fold lower than in the case of the error determined by classical mathematical modelling. Although the neural network ensures a lower prediction error, to obtain a good prediction it is necessary to conduct many experiments in the whole workspace of the robots to build a training set. Despite the worst prediction, a mathematical model of the mountability level only requires an analytical description of the kinematic structure of the assembly robot, so in industrial applications this is preferred due to the lower labour requirement.

The Effect of Plunge Depth on the Strength Properties of Friction Welded Joints Using the RFSSW Method

In the field of joining metal elements, there has been a considerable improvement in the quality and increase the quantity of joining methods over the past few years. One of the more frequently used methods in recent years is Friction Stir Welding (FSW). This method is the subject of intensive research [1, 13, 16, 21]. Friction Stir Spot Welding (FSSW) is one of the variants of friction welding gaining wider use in the automotive [10, 12] and aviation industries [12, 16]. The difficulties of making high quality welded joints using traditional methods have been partially overcome by FSSW technology in the automotive industry. In turn, the aviation industry demands the development of an inexpensive method of joining precipitation hardened aluminium alloys, which can ensure high joint strength while lowering the work load of the process in comparison to traditional methods. Friction stir spot welding is an alternative to resistance welding, riveting, and adhesive bonding of lightweight alloys and it has many benefits [8, 14, 20, 23, 26, 27]. The FSSW method can also combine materials with various properties [2, 3, 5, 25]. The quality of the joint is affected by the process parameters like rotational speed, tool plunge speed, tool plunge time and tool exit time [6, 22]. The main flaw of the FSSW method is the hole that results from the welding process that significantly weakens the strength of the joint [19]. This flaw is eliminated by a following method based on FSSW, in which the hole left from the tool is filled using different process kinematics. Refill Friction Stir Spot Welding (FRSSW) consists of welding two pieces of sheet metal using a tool made of pin and a sleeve. A diagram of the friction welding process is presented in Fig. 1. This method is based on local (spot) friction heating in the area of the joint by a rotating tool. Initially, the sleeve plunges into the material and pushes it into the place of the receded pin. Next, the sleeve recedes from the material leaving room for material extrude by the pin. The use of a divided tool to weld in the RFSSW method changes the kinematics of creating a joint, the connection is homogenous and THE EFFECT OF PLUNGE DEPTH ON THE STRENGTH PROPERTIES OF FRICTION WELDED JOINTS USING THE RFSSW METHOD

THE EFFECT OF RFSSW PARAMETERS ON THE LOAD BEARING CAPACITY OF ALUMINUM 7075-T6 SHEET METAL JOINTS

Friction Stir Spot Welding is one of the most contemporary methods of joining metals and alloys in their solid state. The ability to join elements made of aluminum alloys allows for utilizing this method in the manufacturing of aircraft structures while lowering the work load, costs, and weight, without sacrificing or even having better strength parameters than classic methods of joining elements. It ensures constant joint parameters, however it requires the use of optimal welding parameters such as: the rotational speed of the tool, tool delve depth, and welding time. The work presents the results of experiments conducted on 7074 aluminum sheet metal that was 1.8 and 0.8 mm thick, which conducted in accordance with the PS/DK32 research plan. The welding tests were done on a dedicated spot welding machine, while the strength tests consisted of static tensile strength tests. In the final part of the article contains an analysis and interpretation of the results.

Optimization of Selected Parameters of Modular Assembly Robot

An important task of designing the robotic assembly stand is to ensure the reliability and accuracy of the parts mating process. This can be achieved by selection of the appropriate method of assembling and by providing the required accuracy of the devices in the kinematic chain of assembly operation. Using high accuracy equipment and instrumentation leads to an increasing of the probability of correct realization of the process of parts mating, but this greatly increases the cost of assembly stand. The use of too precise and complex equipment to robotize the assembly process can be highly uneconomical. This paper presents a mathematical model that allows the selection of the parameters of the modular assembly robot performing the process of mating parts with flat and cylindrical surfaces, which represent the largest share among all the assembled parts. The presented model allows for the optimal selection of the accuracy of each robot modules which ensures reliable realization of assembly process without unnecessary increasing their accuracy, and therefore the stand cost. In the final part of the paper, the results of the model solution have been presented.