Search results

Outlines development work on the surfing hopper, a new parts feeding system where chain conveyors with free rollers are driven by a variable‐speed motor and a flexible belt is pushed up partly by the free rollers to generate a wave in the belt. Describes how the wave effect keeps the stacked parts level and how experiments were carried out using different parts materials such as small water‐filled bottles and nuts made of steel. Looks at studies carried out on feeding correctly orientated parts to the assembly station and experiments on surfing feeding system with regard to part separation on the belt. Concludes that the surfing hopper can supply heavy parts intermittently at a rough definite supply ratio, without jamming and entangling the parts and without damage to the belt.

The purpose of this paper is to investigate the process of jamming of the hollow parts on the shaft and to derive a mathematical model for jamming in an assembly process.

The mathematical model for jamming of parts on the shaft in an assembly process is based on the sizes, geometry, angular declination of part and shaft axes, and the frictional factor.

The equation for angular positional tolerance of coaxial parts and shafts, based on their geometry and sizes and leading to jamming, was derived.

A mathematical model of parts jamming on the shaft is developed for assembly mechanisms. This research does not consider flexible deformations of components in assembly mechanisms, which results in the axis concentricity of part and shaft in the assembly process.

The results presented in the form of angular positional tolerance for coaxial parts and shafts based on their geometry and sizes make it possible to avoid the jamming of the parts. The results allow for formulating the angular positional tolerance of the assembly mechanisms that clamp the parts.

The proposed method for calculating the angular positional tolerance of coaxial parts and shafts for the assembly process should allow for increasing the reliability of the assembly process in the manufacturing industry.

The purpose of this research is working out of a new forming technology of flat parts with ribs from magnesium alloys with the application of a three-slide forging press (TSFP) for the aircraft industry.

New possibilities of forming aviation parts with ribs gives the application of a prototype TSFP. This press consists of three moveable tools and has wider technological possibilities than typical forging machines. It was assumed that this machine (press) application would allow for obtaining ribbed flat forgings from magnesium alloys of good functional and resistance qualities. A characteristic feature of such forgings forming is the working movement of two side tools, which upset the billet in the form of a plate; the result of their action is forming of one or more ribs in the plane central part. It is possible to use the upper punch to form appropriate rib outline. Theoretical research works based on simulations by means of finite element method were conducted for three cases of the process: semi-free forging of parts with one rib, semi-free forming of forgings with two ribs and forging in closed impression of parts with one rib of triangular outline. The first experimental tests were made on a TSFP for the variant of semi-free forging of parts with one rib.

Research results show that there exists the possibility of realization of forming process of parts with ribs according to the conception assumed by the authors. Positive results of theoretical analyses justify the purposefulness of conducting experimental verification for the proposed theoretical solutions of the forging processes of parts with one rib of triangular outline and with two ribs.

Production of flat parts with ribs from magnesium alloys basing on the worked out by the authors’ technology will allow for improving functional and mechanical properties of parts and for lowering their manufacturing costs. At present, such aviation parts are imported to Poland in the form of casts, which are expensive and not always fulfill the requirements. Additionally, large amount of machining at manufacturing of this type of parts generate larger price at their production.

Forging technology of parts with ribs in a TSFP is unique on a world scale. The advantages of this technology are the process material savings and better resistance properties of the formed forgings with ribs than parts obtained in a traditional way.

We study a programmable robotic part feeder that relies on a sequence of three conveyor belts to singulate and re‐circulate parts. In industrial practice, belt speeds are set in an ad hoc fashion. Experience with real feeders reveals that throughput can suffer owing to: starvation where no parts are visible to the camera; and saturation, where too many parts are visible, which prevents identifying part pose or grasping due to obstruction by nearby parts. This motivates our search for a systematic approach to setting belt speeds. Our goal is to optimize throughput, measured in terms of how many parts per second are delivered from the robotic feeder. We describe a 1D model of the belts with a Poisson arrival process to stochastically model how belt speeds affect throughput. Initially, we study the finite case where N parts are placed into the feeder and re‐circulated until they are all delivered by the robot. Our first insight is that the vision belt should be run at maximum achievable velocity. We run simulations to empirically determine optimal buffer belt velocity as a function of lot size. Finally, we develop a theoretical model for the case where N = ∞ which approximates common usage where the buffer is replenished before it becomes empty. From this model, we derive the optimal buffer belt velocity and show that it produces throughput five times greater than that achieved with ad hoc settings.

The paper aims to investigate theoretically and experimentally vibrational alignment of parts in an assembly position under kinematical excitement of the movably based part.

Presents developed mathematical model for vibrational alignment when the kinematical excitement of movable part is applied along the insertion axis. Dependencies of alignment duration on stiffness of basing elements and excitation frequency were defined numerically solving the mobile‐based part alignment equations. Alignment experiments of rectangular cross‐section and cylindrical parts under kinematical excitement were carried out.

The mathematical model and the experiments have demonstrated that alignment of the parts being assembled happens due to directed displacement of the movable part resulted by certain parameters of the system and excitement. In the course of the displacement, mating surfaces are aligned and the final mutual orientation of the parts before insertion is realized. Experiments have proved validity of the developed mathematical model. This process reduces allowable axial non‐coincidence and angular misfit of the parts to be assembled.

Impact and non‐impact regimes of the displacement exist depending on the excitement amplitude and initial contact force between the parts. Also, during the vibrational alignment it is possible to control dry friction force between parts by additional high frequency vibrations. Besides, the vibrational excitement can be not only harmonic, but also impulse, bi‐harmonic, etc. Only non‐impact regime of the motion without dry friction force control was investigated and presented in the paper.

The paper investigates the vibrational alignment method based on the directed vibrational displacement of the connecting part, which does not require high preciseness of the interdependent position of the parts in the assembly position.

Vibrational assembly devices of directional action enable compensation of errors of the parts' mutual positioning without use of sensors, feedback systems and control algorithms.

Metal laser-powder-bed-fusion using laser-beam parts are particularly susceptible to contamination due to particles attached to the surface. This may compromise so-called technical cleanliness (e.g. in NASA RPTSTD-8070, ASTM G93, ISO 14952 or ISO 16232), which is important for many 3D-printed components, such as implants or liquid rocket engines. The purpose of the presented comparative study is to show how cleanliness is improved by design and different surface treatment methods.

Convex and concave test parts were designed, built and surface-treated by combinations of media blasting, electroless nickel plating and electrochemical polishing. After cleaning and analysing the technical cleanliness according to ASTM and ISO standards, effects on particle contamination, appearance, mass and dimensional accuracy are presented.

Contamination reduction factors are introduced for different particle sizes and surface treatment methods. Surface treatments were more effective for concave design features, however, the initial and resulting absolute particle contamination was higher. Results further indicate that there are trade-offs between cleanliness and other objectives in design. Design guidelines are introduced to solve conflicts in design when requirements for cleanliness exist.

This paper recommends designing parts and corresponding process chains for manufacturing simultaneously. Incorporating post-processing characteristics into the design phase is both feasible and essential. In the experimental study, electroless nickel plating in combination with prior glass bead blasting resulted in the lowest total remaining particle contamination. This process applied for cleanliness is a novelty, as well as a comparison between the different surface treatment methods.

Fused Filament Fabrication (FFF) is one of the growing technologies in additive manufacturing, that can be used in a number of applications. In this method, process parameters can be customized and their simultaneous variation has conflicting impacts on various properties of printed parts such as dimensional accuracy (DA) and surface finish. These properties could be improved by optimizing the values of these parameters.

In this paper, four process parameters, namely, print speed, build orientation, raster width, and layer height which are referred to as “input variables” were investigated. The conflicting influence of their simultaneous variations on the DA of printed parts was investigated and predicated. To achieve this goal, a hybrid Genetic Algorithm – Artificial Neural Network (GA-ANN) model, was developed in C#.net, and three geometries, namely, U-shape, cube and cylinder were selected. To investigate the DA of printed parts, samples were printed with a central through hole. Design of Experiments (DoE), specifically the Rotational Central Composite Design method was adopted to establish the number of parts to be printed (30 for each selected geometry) and also the value of each input process parameter. The dimensions of printed parts were accurately measured by a shadowgraph and were used as an input data set for the training phase of the developed ANN to predict the behavior of process parameters. Then the predicted values were used as input to the Desirability Function tool which resulted in a mathematical model that optimizes the input process variables for selected geometries. The mean square error of 0.0528 was achieved, which is indicative of the accuracy of the developed model.

The results showed that print speed is the most dominant input variable compared to others, and by increasing its value, considerable variations resulted in DA. The inaccuracy increased, especially with parts of circular cross section. In addition, if there is no need to print parts in vertical position, the build orientation should be set at 0° to achieve the highest DA. Finally, optimized values of raster width and layer height improved the DA especially when the print speed was set at a high value.

By using ANN, it is possible to investigate the impact of simultaneous variations of FFF machines’ input process parameters on the DA of printed parts. By their optimization, parts of highly accurate dimensions could be printed. These findings will be of significant value to those industries that need to produce parts of high DA on FFF machines.

For many types of automated manufacturing equipment there is a requirement to supply the equipment with parts which invariably need to be presented in a single orientation. For metal cutting and forming work there is limited applicability and invariably the parts to be presented are simple shapes. For assembly, many different and sometimes complex shapes need to be presented and it is in this activity that small parts feeding has its biggest application.

This paper aims to focus on the novel design and development of an automatic feeding system which is capable of feeding cylindrical parts which are fragile and powdery in nature and possess asymmetrical features such as a groove near to one end.

It is an active feeder, performing its task without having to reject any feeding part by performing active orientation of feeding parts that are in the undesired orientation. This design incorporating active orientating capability is aimed at 100 percent feeding efficiency. The system is controlled and driven by a programmable logic controller and electropneumatics.

System evaluation results showed that the average jam rate is below 5 percent and the percentage of correctly orientated parts is above 95 percent. With enhancement and fine tuning, the system could become a very useful feeder for industry in the future.

The scope of this paper focuses on presentation of the design concept, development and evaluation of the feeder only and design calculations are not included.

This paper is of value to those who are involved in the manufacturing of small delicate and powdery engineering parts such as those providing performs to the semiconductor industry for encapsulation of integrated circuit chips.