Spline-Locking Screw Fastening Strategy (SLSFS)

A fastener was developed by NASA Goddard for efficiently performing assembly, maintenance, and equipment replacement functions in space using either robotic or astronaut means. This fastener, the 'Spline Locking Screw' (SLS) would also have significant commercial value in advanced manufacturing. Commercial (or DoD) products could be manufactured in such a way that their prime subassemblies would be assembled using SLS fasteners. This would permit machines and robots to disconnect and replace these modules/parts with ease, greatly reducing life cycle costs of the products and greatly enhancing the quality, timeliness, and consistency of repairs, upgrades, and remanufacturing. The operation of the basic SLS fastener is detailed, including hardware and test results. Its extension into a comprehensive fastening strategy for NASA use in space is also outlined. Following this, the discussion turns toward potential commercial and government applications and the potential market significance of same

Development of a truss joint for robotic assembly of space structures

This report presents the results of a detailed study of mechanical fasteners which were designed to facilitate robotic assembly of structures. Design requirements for robotic structural assembly were developed, taking into account structural properties and overall system design, and four candidate fasteners were designed to meet them. These fasteners were built and evaluated in the laboratory, and the Hammer-Head joint was chosen as superior overall. It had a high reliability of fastening under misalignments of 2.54 mm (0.1 in) and 3 deg, the highest end fixity (2.18), the simplest end effector, an integral capture guide, good visual verification, and the lightest weight (782 g, 1.72 lb). The study found that a good design should incorporate chamfers sliding on chamfers, cylinders sliding on chamfers, and hard surface finishes on sliding surfaces. The study also comments on robot flexibility, sag, hysteresis, thermal expansion, and friction which were observed during the testing

Spline screw payload fastening system

A system for coupling an orbital replacement unit (ORU) to a space station structure via the actions of a robot and/or astronaut is described. This system provides mechanical and electrical connections both between the ORU and the space station structure and between the ORU and the ORU and the robot/astronaut hand tool. Alignment and timing features ensure safe, sure handling and precision coupling. This includes a first female type spline connector selectively located on the space station structure, a male type spline connector positioned on the orbital replacement unit so as to mate with and connect to the first female type spline connector, and a second female type spline connector located on the orbital replacement unit. A compliant drive rod interconnects the second female type spline connector and the male type spline connector. A robotic special end effector is used for mating with and driving the second female type spline connector. Also included are alignment tabs exteriorally located on the orbital replacement unit for berthing with the space station structure. The first and second female type spline connectors each include a threaded bolt member having a captured nut member located thereon which can translate up and down the bolt but are constrained from rotation thereabout, the nut member having a mounting surface with at least one first type electrical connector located on the mounting surface for translating with the nut member. At least one complementary second type electrical connector on the orbital replacement unit mates with at least one first type electrical connector on the mounting surface of the nut member. When the driver on the robotic end effector mates with the second female type spline connector and rotates, the male type spline connector and the first female type spline connector lock together, the driver and the second female type spline connector lock together, and the nut members translate up the threaded bolt members carrying the first type electrical connector up to the complementary second type connector for interconnection therewith

Force and effort analysis of unfastening actions in disassembly processes

Fastening is the process of connecting one or more parts together with the aid of fastening elements. Unfastening, the reverse of fastening, is the process of separating components from each other by removing or detaching fastening elements. So far, the unfastening process is not well understood, and the analysis about it is not very extensive. However, the need for disassembly is currently increasing. First, parts have to be taken apart for service and repair, and secondly, for the recycling process. Therefore, there is a need to consider unfastening during the design process in order to enable efficient disassemblies. The purpose of this dissertation is to develop an analytical model, which enables unfastening analysis during the design of new products. Specifically, (i) a standard nomenclature for defining unfastening related parameters and variables is introduced, (ii) the U-Effort model for deriving the unfastening effort for a variety of commonly used fasteners is developed, (iii) the U-Effort model to model unfastening motion and hence estimate disassembly complexity is extended, and (iv) the U-Force model for estimating the required unfastening force in the case of cantilever and cylindrical snap fits is developed. The U-Effort model is a detailed study about the unfastening effort and the design attributes of commonly used fasteners. There is a difference between unfastening effort and unfastening force. Unfastening effort depends on several influencing factors, whereas the unfastening force is a more direct calculated value. The influencing attributes for the unfastening effort include the geometry and shape of the fastener and the condition at the end-of-life of the product. In the U-Force model, unfastening considerations are included in the design phase, mainly through the calculation of unfastening forces. The U-Force model is applied to the cantilever and cylindrical snap fit integral attachments. The U-Effort and the U-Force models can be used by designers to evaluate the unfastening suitability of new and existing product designs. Fastening elements can be selected based on functionality and the least unfastening effort. The developed models can assist industrial companies engaged in demanufacturing plan their recycling and reuse activities

Automated freeform assembly of threaded fasteners

Over the past two decades, a major part of the manufacturing and assembly market has been driven by its customer requirements. Increasing customer demand for personalised products create the demand for smaller batch sizes, shorter production times, lower costs, and the flexibility to produce families of products - or different parts - with the same sets of equipment. Consequently, manufacturing companies have deployed various automation systems and production strategies to improve their resource efficiency and move towards right-first-time production. However, many of these automated systems, which are involved with robot-based, repeatable assembly automation, require component- specific fixtures for accurate positioning and extensive robot programming, to achieve flexibility in their production. Threaded fastening operations are widely used in assembly. In high-volume production, the fastening processes are commonly automated using jigs, fixtures, and semi-automated tools. This form of automation delivers reliable assembly results at the expense of flexibility and requires component variability to be adequately controlled. On the other hand, in low- volume, high- value manufacturing, fastening processes are typically carried out manually by skilled workers. This research is aimed at addressing the aforementioned issues by developing a freeform automated threaded fastener assembly system that uses 3D visual guidance. The proof-of-concept system developed focuses on picking up fasteners from clutter, identifying a hole feature in an imprecisely positioned target component and carry out torque-controlled fastening. This approach has achieved flexibility and adaptability without the use of dedicated fixtures and robot programming. This research also investigates and evaluates different 3D imaging technology to identify the suitable technology required for fastener assembly in a non-structured industrial environment. The proposed solution utilises the commercially available technologies to enhance the precision and speed of identification of components for assembly processes, thereby improving and validating the possibility of reliably implementing this solution for industrial applications. As a part of this research, a number of novel algorithms are developed to robustly identify assembly components located in a random environment by enhancing the existing methods and technologies within the domain of the fastening processes. A bolt identification algorithm was developed to identify bolts located in a random clutter by enhancing the existing surface-based matching algorithm. A novel hole feature identification algorithm was developed to detect threaded holes and identify its size and location in 3D. The developed bolt and feature identification algorithms are robust and has sub-millimetre accuracy required to perform successful fastener assembly in industrial conditions. In addition, the processing time required for these identification algorithms - to identify and localise bolts and hole features - is less than a second, thereby increasing the speed of fastener assembly

Interference Fit Fastener Inspection using Sonic Thermography

This paper reports on an experimental study addressing the application of sonic thermography to the characterisation of interference fit levels in fastened metallic plates. The technique uses high intensity acoustic waves to induce frictional heating at defect locations. In the case of poorly fitted interference fasteners, the acoustic waves induce relative motion between the fastener and host, causing frictional heating which is detected with a thermal imaging system. Results are shown to demonstrate the efficacy of the approach

Vibration-induced rotation

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.This thesis presents, explores, and documents the validation of a mechanical mechanism dubbed Vibration-Induced Rotation, or VIR. The tendency of threaded fasteners to move under the influence of vibrations is well known, but never before has the root cause been identified and investigated in search of beneficial consequences. The sense of rotation, speed, and force with which a threaded body moves in an appropriately vibrated medium is a function of the excitation. The principal kinematic and dynamic relationships governing VIR have been developed and experimentally affirmed. There is evidence for more complex modes of motion, but pure VIR remains the dominant response under a wide variety of conditions. Simplicity, robustness, and uniqueness suggest a multitude of possible applications, particularly in the areas of product assembly and fastener insertion. This thesis should provide a cornerstone in a new and promising field of application-oriented research.by Patrick Andreas Petri.S.B

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 40)

Abstracts are provided for 181 patents and patent applications entered into the NASA scientific and technical information system during the period July 1991 through December 1991. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or patent application

Design of a test apparatus to study a proposed dynamic tissue puncture model

Thesis (S.B.)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (page 22).Two test apparatuses were designed, built, and evaluated in order to study a proposed dynamic tissue puncture model. The test apparatuses were designed to improve existing experiments used previously to experimentally verify tissue models. These models are incomplete due to the small range of velocities tested (up to 250 mm/s) and because they do not account for the complex interactions between tissue and needle during deep puncture. The first test apparatus is based on a vertical drop test. This apparatus was modeled, built, and evaluated for its performance based on the speeds achieved in the region of impact. Based on improvements from this apparatus, a second test apparatus was modeled and will be built in the future. The second apparatus is a modified drop test; however, it is on an inclined plane in order to reduce the effects of gravity when attempting to achieve lower speeds.by Kathleen Marie Inman.S.B