Tomasz Trzepieciński

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.

Study of Frictional Properties of AMS Nickel-Chromium Alloys

The research reported in this article has considered the frictional characteristics of three kinds of AMS nickel-chromium alloys that are commonly used in aerospace industry. These are alloys with additions of titanium and aluminum AMS5542, nickel-chromium alloy AMS5596, and non-magnetic, corrosion and oxidation resistant, nickel-chromium alloy AMS5599. To determine the friction coefficient two tribological tests, a strip drawing test and a pin-on-disc tribometer have been conducted. Three different friction conditions were considered, dry friction, lubrication conditions using two grades of oils used in sheet metal forming of AMS alloys. The experimental results have ascertained several relationships showing the effect of sheet metal surface roughness, lubricant conditions and sheet orientation on the value of friction coefficient in sheet metal forming processes. Different levels of normal pressure were also used in friction tests. The results further showed that the surface topography and sample orientation in the rolling direction of the sheet are significant factors that influence the friction coefficient. It has been observed that the tested AMS alloys, selected from aerospace industry applications, exhibit anisotropic resistance to the friction corresponding to the measured orientation in relation to the rolling direction of the sheet.

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.

Effect of Activation Function and Post Synaptic Potential on Response of Artificial Neural Network to Predict Frictional Resistance of Aluminium Alloy Sheets

Many technological factors affect the friction phenomenon in sheet metal forming process. As a result, the determination of the analytical model describing the frictional resistance is very difficult. In this paper, a friction model was built based on the experimental results of strip drawing tests. Friction tests were carried out in order to determine the effect of surface and tool roughness parameters, the pressure force and mechanical parameters of the sheets on the value of coefficient of friction. The strip drawing friction tests were conducted on aluminium alloy sheets: AA5251-H14, AA5754-H14, AA5754-H18, AA5754-H24. The surface topography of the sheets was measured using Taylor Hobson Surtronic 3+ instrument. In order to describe complex relations between friction and factors influencing tribological conditions of sheet metal forming, the multilayer artificial network was built in Statistica Neural Network program. The effect of activation function and post synaptic potential function on the sensitivity of multilayer neural network to predict the friction coefficient value is presented. It has been found that the difference in the prediction of error of neural network for different approaches can reach 400%. So, the proper selection of activation and post synaptic potential functions is crucial in neural network modelling.

Effect of tool material on tool wear and delamination during machining of particleboard

The tool material and the parameters of machining are the main conditions which decide the quality of particleboard surface. The objective of the study was to investigate the wear of a carbide cemented bit and high-speed steel bit during machining of melamine-faced particleboard. Analysis of variance (ANOVA) was implemented to find the significance of the effect of machining parameters and tool wear on the value of the delamination factor Adel. The delamination factor Adel is defined as the ratio of area of delamination (mm2) to the measured length of the test piece (cm). To determine the durability of the cutting tool a geometric criterion was adopted, i.e., maximum wear of the tool flank. We observed a clear impact of cutting speed on the length of the tool life. This relation was manifested as a decrease in the tool life with increasing cutting speed. It was also found that a reduction in the cutting speed increases the area of delamination, leading to an increase in the value of the Adel factor. It was especially visible for higher values of tool wear. In the case of feed per tooth we observed no clear effect on intensifying the delamination phenomenon.

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.

METHOD OF FERTILIZATION OF ENERGY WILLOW PLANTATION USING SEWAGE SLUDGE

Sewage sludge deriving from biofiltration of municipal waste abound in soil processed organic substances and mineral fertilization components which may be used for fertilization of energy willow plantations. In the article the potential of natural utilization of sewage sludge and the patented device for injection dosage of sludge has been presented. The device enables putting into soil mineral and organic fertilizers with loose consistency and their immediate covering by soil in order to reduce unpleasant smell and limit loss of volatile components of fertilizer.

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.

Fracture Prediction of Piezoelectric Ceramic by the 2-D Boundary Element Analysis

Piezoelectric ceramics are widely used as sensors and multilayer actuators in many areas of industry [1], despite the absence of a fundamental understanding of their fracture behaviour [2]. Piezoelectricity is a linear effect that is related to the microscopic structure of the solid. Among piezoelectric materials, barium titanate is the most often used as a ceramic material. Barium titanate is a ferroelectric classic perovskite structure with wide-ranging material properties that depend on its composition [3, 4]. The perovskite structure ABO3 (Fig. 1) is the arrangement where the corner-sharing oxygen octahedra are linked together in a regular cubic array with smaller cations (Ti, Zr, Sn, Nb, etc.) occupying the central octahedral B-site, and larger cations (Pb, Ba, Sr, Ca, Na, etc.) filling the interstices between octahedra in the larger A-site [5]. Several studies have been carry out in order to study the influence of compositionally modified ceramic bodies and the sintering conditions on the properties of ceramic [6]. The ceramic material which is composed of the random orientation of these piezoelectric crystallites, is inactive, i.e., the effects from the individual crystals cancel each other and no discernable piezoelectricity is present [5]. The domains are the regions of equally oriented polarization vectors. To orient the domains the pooling method can be used. This technique consist in polarizing the ceramic through the application of a static electric field. Open image in new window Fig. 1 Perovskite structure