Mobile, Modular and Adaptive Assembly Jigs for Large-Scale Products

The assembly of products is often supported by jigs. Especially for large dimensional products, jigs and fixtures are used to align the components and ensure the stability of the assembly until all parts are firmly mounted. This paper describes the development of mobile, modular and adaptive assembly jigs, which are designed to support ergonomic working in the production of high-lift systems for civil aircrafts. The jig supports the workers to adapt the position and orientation of the product to the current assembly operation. The fundamentals of the development are explained and the features of a concept, called assembly wheel, are presented. The assembly wheel consists of two or more robot arms on a circular seventh axis. The robot arms hold and position the components to be assembled so that all joining spots are freely accessible to the worker. The ergonomic benefits of the concept were examined in a study using a 3D model of the jig. A demonstrator on a scale of 1:2 was set up, with which real experiments with an adaptive jig can be conducted for evaluation.

Computer-Aided Design of Traditional Jigs and Fixtures

Conventional design of jigs and fixtures has become unsuitable given the requirements of modern technology and complexity and diversity in the production with the rapid update of products. Computer-aided design (CAD) of jigs and fixtures is an effective solution in this direction. The current paper focuses on a computer-aided design of the traditional jigs and fixtures and developed a system containing tailor-made software, created using the Visual Basic programming language and installed on it the viewer screen to show the part. The developed system has been built by connecting Visual Basic programming language to the SolidWorks software on which the part is drawn and saved as STEP AP-203 file format, and the system reads and extracts the data from the STEP AP-203 file. Heuristic rules of feature recognition are pre-prepared for checking the extracted geometric data and deciding which data shape will represent the machining feature; then, the system provides the optimum design of the traditional jigs and fixtures for a group of hollow cylindrical parts that contain a group of cross-holes on the cylinder body, whether perpendicular or offset from the cylinder’s axis, (inclined or inclined offset, or blind or through, by applying pre-prepared heuristic rules for the design of traditional jigs and fixtures.

The Effect of Annealing on Additive Manufactured ULTEM™ 9085 Mechanical Properties

Fused filament fabrication (FFF) is increasingly adopted for direct manufacturing of end use parts in an aviation industry. However, the application of FFF technique is still restricted to manufacturing low criticality lightly loaded parts, due to poor mechanical performance. To alleviate the mechanical performance issue, thermal annealing process is frequently utilized. However, problems such as distortion issues and the need for jigs and fixtures limit the effectiveness of the thermal annealing process, especially for low volume complex FFF parts. In this research, a novel low temperature thermal annealing is proposed to address the limitations in conventional annealing. A modified orthogonal array design is applied to investigate the performance of ULTEM™ 9085 FFF coupons. Further, the coupons are annealed with specialized support structures, which are co-printed with the coupons during the manufacturing process. Once the annealing process is completed, multiscale characterizations are performed to identify the mechanical properties of the specimens. Geometrical measurement of post annealed specimens indicates an expansion in the layering direction, which indicates relief of thermal stresses. Moreover, annealed coupons show an improvement in tensile strength and reduction in strain concentration. Mesostructure and fracture surface analysis indicate an increase in ductility and enhanced coalescence. This research shows that the proposed annealing methodology can be applied to enhance the mechanical performance of FFF parts without significant distortion.

The study of the curvature of the axis of the processed shaft when based in the centers using a steady rest

This paper presents the analysis and results of the study of a two-stage shaft fixed in dead centers and a rest device. Cutting forces act on the shaft, causing a bending moment. The analysis of the curvature of the axis of the workpiece, processed on a lathe when based in the centers, using a rest device, is carried out. The formula of elastic displacement of the workpiece axis at the place of the resulting cutting force is obtained. Diagrams of the stresses of the shaft axis displacements are constructed and a conclusion is made. The analysis showed that the greatest deflection is at the point of the cutting forces acting on the shaft. The quality of the part obtained after processing is characterized by accuracy. The parts mating in the product and, as a result, the overall reliability depends on how accurately the size and shape of the part will be maintained during processing. Parts with length of 10 to 12 times larger than the diameter are bent under the action of their own weight and cutting forces, as a result of which they get a barrel-like shape. It is possible to eliminate this by applying special devices for the machine. When processing long nonrigid workpieces, the tools, jigs and fixtures must evenly distribute the clamping force over the surface of the part. These conditions are well provided by technological equipment with pneumatic, hydraulic clamping devices, as well as with various collet clamps, split bushings, diaphragm or cartridges. When processing long non-rigid shafts, rest devices are used. The rest device plays the role of the main or secondary support when working with workpieces; it creates support for large, long parts during processing. It helps to avoid the risk of damage and deformation of the workpiece or the cutting elements of the machine, by giving the workpiece additional stability

Increasing the productivity of automated technological complexes by using multipiece devices

This article deals with the issue of increasing the productivity of automated technological complexes of mechanical processing by reducing off-cycle time losses. The time for adjustment of tools, jigs and fixtures is considered the most significant type of losses for flexible machining cells. The most effective solution for reducing the adjustment time to increase the productivity of technological complexes of mechanical processing is the use of multipiece devices. Multipiece devices refer to machine retaining devices that allow installing workpieces of different standard sizes without readjustment or with minimal readjustment. The effectiveness of such devices depends on the number of installed parts of different standard sizes, and the greater this number is, the higher the effectiveness of the device is. The article proposes to divide the total time of adjustment of a multipiece device into components that take into account the time for installation and adjustment of the device and the time for changing the adjustment of the device when switching to the production of the next batch of parts. The division of the total adjustment time allows taking into account the loss of adjustment time for each part in the conditions of using a multipiece device. The time for changing the adjustment before making a new batch of parts is divided into the entire batch or several batches, if several batches of parts are made during the same adjustment. The time of installation and adjustment of the device is divided into all the batches processed on this device. With a strict schedule for the operation of an automated technological complex within a certain period of time, such a calculation shows an accurate result. However, for technological complexes with a flexible schedule, analytical calculation becomes impossible. Therefore, the task is to obtain the value of the adjustment time of the device, which falls on one processed part by conducting simulation modeling on an automated technological complex. A simulation experiment is conducted to determine the performance of the complex, depending on the device used.