From computer-aided to intelligent machining: Recent advances in computer numerical control machining research

The aim of this paper is to provide an introduction and overview of recent advances in the key technologies and the supporting computerized systems, and to indicate the trend of research and development in the area of computational numerical control machining. Three main themes of recent research in CNC machining are simulation, optimization and automation, which form the key aspects of intelligent manufacturing in the digital and knowledge based manufacturing era. As the information and knowledge carrier, feature is the efficacious way to achieve intelligent manufacturing. From the regular shaped feature to freeform surface feature, the feature technology has been used in manufacturing of complex parts, such as aircraft structural parts. The authors’ latest research in intelligent machining is presented through a new concept of multi-perspective dynamic feature (MpDF), for future discussion and communication with readers of this special issue. The MpDF concept has been implemented and tested in real examples from the aerospace industry, and has the potential to make promising impact on the future research in the new paradigm of intelligent machining. The authors of this paper are the guest editors of this special issue on computational numerical control machining. The guest editors have extensive and complementary experiences in both academia and industry, gained in China, USA and UK

Feature technology and its applications in computer integrated manufacturing

A Thesis submitted for the degree of Doctor of Philosophy of University of LutonComputer aided design and manufacturing (CAD/CAM) has been a focal research area for the manufacturing industry. Genuine CAD/CAM integration is necessary to make products of higher quality with lower cost and shorter lead times. Although CAD and CAM have been extensively used in industry, effective CAD/CAM integration has not been implemented. The major obstacles of CAD/CAM integration are the representation of design and process knowledge and the adaptive ability of computer aided process planning (CAPP). This research is aimed to develop a feature-based CAD/CAM integration methodology. Artificial intelligent techniques such as neural networks, heuristic algorithms, genetic algorithms and fuzzy logics are used to tackle problems. The activities considered include: 1) Component design based on a number of standard feature classes with validity check. A feature classification for machining application is defined adopting ISO 10303-STEP AP224 from a multi-viewpoint of design and manufacture. 2) Search of interacting features and identification of features relationships. A heuristic algorithm has been proposed in order to resolve interacting features. The algorithm analyses the interacting entity between each feature pair, making the process simpler and more efficient. 3) Recognition of new features formed by interacting features. A novel neural network-based technique for feature recognition has been designed, which solves the problems of ambiguity and overlaps. 4) Production of a feature based model for the component. 5) Generation of a suitable process plan covering selection of machining operations, grouping of machining operations and process sequencing. A hybrid feature-based CAPP has been developed using neural network, genetic algorithm and fuzzy evaluating techniques

Development of a manufacturing feature-based design system

Traditional CAD systems are based on the serial approach of the product development cycle: the design process is not integrated with other activities and thus it can not provide information for subsequent phases of product development. In order to eliminate this problem, many modern CAD systems allow the composition of designs from building blocks of higher level of abstraction called features. Although features used in current systems tend to be named after manufacturing processes, they do not, in reality, provide valuable manufacturing data. Apart from the obvious disadvantage that process engineers need to re-evaluate the design and capture the intent of the designer, this approach also prohibits early detection of possible manufacturing problems. This research attempts to bring the design and manufacturing phases together by implementing manufacturing features. A design is composed entirely in a bottom-up manner using manufacturable entities in the same way as they would be produced during the manufacturing phase. Each feature consists of parameterised geometry, manufacturing information (including machine tool, cutting tools, cutting conditions, fixtures, and relative cost information), design limitations, functionality rules, and design-for-manufacture rules. The designer selects features from a hierarchical feature library. Upon insertion of a feature, the system ensures that no functionality or manufacturing rules are violated. If a feature is modified, the system validates the feature by making sure that it remains consistent with its original functionality and design-for-manufacture rules are re-applied. The system also allows analysis of designs, from a manufacturing point of view, that were not composed using features. In order to reduce the complexity of the system, design functionality and design-for manufacture rules are organised into a hierarchical system and are pointed to the appropriate entries of the feature hierarchy. The system makes it possible to avoid costly designs by eliminating possible manufacturing problems early in the product development cycle. It also makes computer-aided process planning feasible. The system is developed as an extension of a commercially available CAD/CAM system (Pro/Engineer), and at its current stage only deals with machining features. However, using the same principles, it can be expanded to cover other kinds of manufacturing processes

CAD/CAM integration based on machining features for prismatic parts

The development of CAD and CAM technology has significantly increased efficiency in each individual area. The independent development, however, greatly restrained the improvement of overall efficiency from design to manufacturing. The simple integration between CAD and CAM systems has been achieved. Current integrated CAD/CAM systems can share the same geometry model of a product in a neutral or proprietary format. However, the process plan information of the product from CAPP systems cannot serve as a starting point for CAM systems to generate tool paths and NC programs. The user still needs to manually create the machining operations and define geometry, cutting tool, and various parameters for each operation. Features play an important role in the recent research on CAD/CAM integration. This thesis investigated the integration of CAD/CAM systems based on machining features. The focus of the research is to connect CAPP systems and CAM systems by machining features, to reduce the unnecessary user interface and to automate the process of tool path preparation. Machining features are utilized to define machining geometries and eliminate the necessity of user interventions in UG. A prototype is developed to demonstrate the CAD/CAM integration based on machining features for prismatic parts. The prototype integration layer is implemented in conjunction with an existing CAPP system, FBMach, and a commercial CAD/CAM system, Unigraphics. Not only geometry information of the product but also the process plan information and machining feature information are directly available to the CAM system and tool paths can be automatically generated from solid models and process plans

Effect of grain size and density of abrasive on surface roughness, material removal rate and acoustic emission signal in rough honing processes

Honing processes provide a special cross-hatch pattern to the internal surface of cylinders that favors oil flow. However, along honing operation the abrasive grains wear out and lose their ability to cut material. The honing chips mixed with oil fill the pores of the abrasives and they start cutting in an incorrect way, leading to clogging. In the present paper, honing experiments were carried out according to a 32 factorial design, with different grain size and density of abrasive grains. Roughness, material removal rate, and tool wear were determined. Acoustic emissions were also measured and the chirplet concept was applied in order to detect differences between correct and incorrect cutting operations. As a general trend roughness and material removal rate increase with grain size and with density of abrasive. However, when clogging occurs roughness and material removal rate decrease, because the abrasive grains tend to deform the material instead of cutting it. When the honing process is working appropriately, the chirplet diagram of the harmonic part of the signal shows constant marks. On the contrary, when it does not work properly, marks disappear with time and their frequencies decrease. The results of the present paper will allow monitoring the honing process in order to change the abrasives when they are not working properly.Peer ReviewedPostprint (published version

Knowledge-based automatic tolerance analysis system

Tolerance measure is an important part of engineering, however, to date the system of applying this important technology has been left to the assessment of the engineer using appropriate guidelines. This work offers a major departure from the trial and error or random number generation techniques that have been used previously by using a knowledge-based system to ensure the intelligent optimisation within the manufacturing system. A system to optimise manufacturing tolerance allocation to a part known as Knowledge-based Automatic Tolerance Analysis (KATA) has been developed. KATA is a knowledge-based system shell built within AutoCAD. It has the ability for geometry creation in CAD and the capability to optimise the tolerance heuristically as an expert system. Besides the worst-case tolerancing equation to optimise the tolerance allocation, KATA's algorithm is supported by actual production information such as machine capability, types of cutting tools, materials, process capabilities etc. KATA's prototype is currently able to analyse a cylindrical shape workpiece and a simple prismatic part. Analyses of tolerance include dimensional tolerance and geometrical tolerance. KATA is also able to do angular cuts such as tapers and chamfers. The investigation has also led to the significant development of the single tolerance reference technique. This method departs from the common practice of multiple tolerance referencing technique to optimise tolerance allocation. Utilisation of this new technique has eradicated the error of tolerance stackup. The retests have been undertaken, two of which are cylindrical parts meant to test dimensional tolerance and an angular cut. The third is a simple prismatic part to experiment with the geometrical tolerance analysis. The ability to optimise tolerance allocation is based on real production data and not imaginary or random number generation and has improved the accuracy of the expected result after manufacturing. Any failure caused by machining parameters is cautioned at an early stage before an actual production run has commenced. Thus, the manufacturer is assured that the product manufactured will be within the required tolerance limits. Being the central database for all production capability information enables KATA to opt for several approaches and techniques of processing. Hence, giving the user flexibility of selecting the process plan best suited for any required situation

STEP COMPLIANT APPROACH FOR TURN-MILL OPERATIONS

Current machine tools have incurred challenges on limitation such as part programming complexity of G and M code, weak integration of digital machine tools and coverage of universal data modeling for product and manufacturing resources. In response to this manufacturing system requirement, Standard for Exchange of Product data (STEP) and its implementation on developing an interface for the next generation of machine tool controllers (STEP-NC) has become a concern of research interest and performed on basic manufacturing technology limited to a unit domain such as turning, milling or Wire EDM. Therefore; extending this STEP implementation on multipurpose machine tools such as turn-mill machines is mandatory since the machines are the main component in these industries. The research work offers a STEP-NC compliant interface supporting turn-mill machining environment identified as SCSTMO

Characterization and improvement of copper / glass adhesion

The development of glass substrates for use as an alternative to printed circuit boards (PCBs) attracts significant industrial attention, because of the potential for low cost but high performance interconnects and optical connection. Electroless plating is currently used to deposit conductive tracks on glass substrates and the quality of copper / glass adhesion is a key functional issue. Without adequate adhesive strength the copper plating will prematurely fail. Existing studies have covered the relationship between surface roughness and adhesion performance, but few of them have considered the detail of surface topography in any depth. This research is specifically considering the mechanical contribution of the glass surface texture to the copper / glass adhesive bond, and attempting to isolate new ISO 25178 areal surface texture parameters that can describe these surfaces. Excimer laser machining has been developed and used to create a range of micro pattern structured surfaces on CMG glass substrates. Excimer mask dimensions and laser operation parameters have been varied and optimized according to surface topography and adhesion performance of the samples. Non-contact surface measurement equipment (Zygo NewView 5000 coherence scanning interferometry) has been utilized to measure and parameterize (ISO 25178) the surface texture of the glass substrates before electroless copper metallization. Copper adhesion quality has been tested using quantitative scratch testing techniques, providing an identification of the critical load of failure for different plated substrates. This research is establishing the statistical quality of correlation between the critical load values and the associated areal parameters. In this thesis, the optimal laser processing parameter settings for CMG glass substrate machining and the topographic images of structured surfaces for achieving strong copper / glass plating adhesion are identified. The experimental relationships between critical load and areal surface parameters, as well as the discussions of a theoretical approach are presented. It is more significant to consider Sq, Sdq, Sdr, Sxp, Vv, Vmc and Vvc to describe glass substrate surface topography and the recommended data value ranges for each parameter have been identified to predict copper / plating adhesion performance

Process planning for the rapid machining of custom bone implants

This thesis proposes a new process planning methodology for rapid machining of bone implants with customized surface characteristics. Bone implants are used in patients to replace voids in the fractured bones created during accident or trauma. Use of bone implants allow better fracture healing in the patients and restore the original bone strength. The manufacturing process used for creating bone implants in this thesis is highly automated CNC-RP invented at Rapid Manufacturing and Prototyping Lab (RMPL) at Iowa State University. CNC-RP is a 4th axis rapid machining process where the part is machined using cylindrical stock fixed between two opposing chucks. In addition to conventional 3 axes, the chucks provide 4th rotary axis that allows automated fixturing setups for machining the part. The process planning steps for CNC-RP therefore includes calculating minimum number of setup orientations required to create the part about the rotary axis. The algorithms developed in this thesis work towards calculating a minimum number of orientations required to create bone implant with their respective surface characteristics. Usually bone implants may have up to 3 types of surfaces (articular/periosteal/fractured) with (high/medium/low) finish. Currently CNC-RP is capable of creating accurate bone implants from different clinically relevant materials with same surface finish on all of the implant surfaces. However in order to enhance the functionality of the bone implants in the biological environment, it is usually advisable to create implant surfaces with their respective characteristics. This can be achieved by using setup orientations that would generally isolate implant surfaces and machine them with individual finishes. This thesis therefore focuses on developing process planning algorithms for calculating minimum number of orientations required to create customized implant surfaces and control related issues. The bone implants created using new customization algorithms would have enhanced functionality. This would reduce the fracture healing time for the patient and restore the original bone strength. The software package created using new algorithms will be termed as CNC-RPbio throughout in this thesis The three main tasks in this thesis are a) calculating setup orientations in a specific sequence for implant surfaces b) Algorithms for calculating a minimum number of setup orientations to create implant surfaces c) Machining operation sequence. These three research tasks are explained in details in chapter 4 of this thesis. The layout of this thesis is as follows. Chapter 1 provides introduction, background and motivation to the research in this thesis. Chapter 2 provides a literature review explaining different researches conducted to study the effects of different surface finish on the bone implants on their functionality. It also presents different non-traditional and RP techniques used to create bone implant geometries with customized surfaces, their advantages and limitations. Chapter 3 gives the overview of process planning algorithms used for CNC-RP and those needed for CNC-RPbio. Chapter 4 is the main chapter of the thesis including process planning algorithms for rapid machining of bone implants with customized surfaces using CNC-RP in details, while Chapter 5 provides Conclusions and Future work