Implementation of hierarchical design for manufacture rules in manufacturing processes

In order to shorten the product development cycle time, minimise overall cost and smooth transition into production, early consideration of manufacturing processes is important. Design for Manufacture (DFM) is the practice of designing products with manufacturing issues using an intelligent system, which translates 3D solid models into manufacturable features. Many existing and potential applications, particularly in the field of manufacturing, require various aspects of features technology. In all engineering fields geometric modelling wluch accurately represents the shape of a whole engineering component has become accepted for a wide range of applications. To apply DFM rules or guidelines in manufacturing processes, they have to be systematised and organised into a hierarchical rule system. Rules at the higher level of the hierarchical system are applied to more generic manufacturing features, and specific rules are applied to more detailed features. This enables the number of rules and amount of repetition to be minimsed. Violation of the design for manufacture rules in the features, their characteristics and manufacturing capabilities are further examined in this hierarchical system. Manufacturabillty analysis, such as production type, materials, tolerances, surface finish, feature characteristics and accessibility, are also taken into consideration. Consideration of process capabilities and limitations during the design process is necessary in order to minimise production time and as a result, rnanufactunng cost. The correct selection of manufacturing processes is also important as it is related to the overal cost. As a result of this research, a hierarchical design for manufacture rule system is proposed which would aid designers in avoiding designs that would lead to costly manufacturing processes

The development and implementation of a reverse engineering method for near net shape parts

This research presents a new method for the reverse engineering of Near Net Shape (NNS) parts that bridge the current 3D scanning and Rapid Prototyping technologies. Near Net Shape is a group of manufacturing technologies that includes forging, casting, hot isostatic pressing, and additive manufacturing. This research focuses on casting process and provides a software tool along with the new method for reverse engineering a legacy casting design to the “as was” casted state instead of the “as is” current state, and at the same time, reducing the cost and time for repairing a legacy casting part. The three main objective for this research is to 1.Create a new reverse engineering method 2.Develop a software tool that is designed for feature free model editing 3.Validate the process through metal casting. The Point Cloud Library is applied for assisting point cloud processing and feature free model editing. A series of algorithms is developed for draft adding and pattern generation for the process of casting. The Rapid Pattern Manufacturing system developed in Iowa State University, Rapid Manufacturing and Prototyping Lab is applied for pattern manufacturing. This method is validated to be correct and able to reverse engineer legacy casting parts rapidly and economically through a metal casting process. The layout of this thesis is as follows: Chapter 1: provides introduction, background, research problem statement and objective of this research. Chapter 2: a literature review for the current reverse engineering method and introduces the modules of point cloud library that are used in this research. Chapter 3: presents the overview of method and algorithms that developed for this method in detail. Chapter 4: presents the implementation of this method and gives the analysis of the demo metal casting process. Chapter 5: provides future work and conclusions

A knowledge-based approach for the extraction of machining features from solid models

Computer understanding of machining features such as holes and pockets is essential for bridging the communication gap between Computer Aided Design and Computer Aided Manufacture. This thesis describes a prototype machining feature extraction system that is implemented by integrating the VAX-OPS5 rule-based artificial intelligence environment with the PADL-2 solid modeller. Specification of original stock and finished part geometry within the solid modeller is followed by determination of the nominal surface boundary of the corresponding cavity volume model by means of Boolean subtraction and boundary evaluation. The boundary model of the cavity volume is managed by using winged-edge and frame-based data structures. Machining features are extracted using two methods : (1) automatic feature recognition, and (2) machine learning of features for subsequent recognition. [Continues.

Advanced Manufacturing Using Linked Processes: Hybrid Manufacturing

Hybrid Manufacturing Processes (HMP) can significantly reduce time to customer, waste, and tooling costs per part, while increasing possible part geometric complexity for small batch parts. In the following chapter, HMP is defined by the production of parts produced first with a near-net shape process using methods including: additive manufacturing, casting, injection molding, etc., which is then coupled with multi-axis computer numerical control (CNC) subtractive machining or some other secondary material removal process. Creating process plans for such hybrid manufacturing processes typically takes weeks rather than hours or days. This chapter outlines several hybrid manufacturing processes and the intricacies required to develop process plans for these complex linked processes. A feature-based advanced hybrid manufacturing process planning system (FAH-PS) uses feature-specific geometric, tolerance, and material data inputs to generate automated process plans based on user-specified feature precedence for additive-subtractive hybrid manufacturing. Plans generated by FAH-PS can optimize process plans to minimize tool changes, orientation changes, etc., to improve process times. A case study of additive-subtractive methods for a patient-specific bone plate, demonstrates system capabilities and processing time reductions as compared to the current manual process planning for hybrid manufacturing methodologies. Using the generated FAH-PS process plan resulted in a 35% reduction in machining time from the current hybrid manufacturing strategy

Ceramic applications in turbine engines

Ceramic material characterization and testing of ceramic nozzle vanes, turbine tip shrouds, and regenerators disks at 36 C above the baseline engine TIT and the design, analysis, fabrication and development activities are described. The design of ceramic components for the next generation engine to be operated at 2070 F was completed. Coupons simulating the critical 2070 F rotor blade was hot spin tested for failure with sufficient margin to quality sintered silicon nitride and sintered silicon carbide, validating both the attachment design and finite element strength. Progress made in increasing strength, minimizing variability, and developing nondestructive evaluation techniques is reported

Valukappaleiden parametrinen mallinnus ja laadunvarmistus

Even though 3D modelling and 3D scanning have been industry standards in casting design and measurement for a long time, casting tolerance standards still usually rely on complete definition of castings in 2D drawings and linear dimensional tolerances. ISO 8062-4, published in 2017, is based on a general surface profile tolerance instead of separate dimensional tolerances, thus forming a logical connection between 3D modelling, tolerancing and 3D scanning. As the contemporary 3D methods are prominently used, the outdated ISO 8062-3 should be replaced with the new standard in casting tolerance definition. In this thesis, possibilities to include casting tolerances in casting CAD models are examined. The aim is to create dependent but separate 3D models that depict the allowed minimum and maximum state of the casting as allowed by the casting tolerance. The benefits of these tolerance models are evaluated considering quality verification, strength calculations and collision detection. ISO 8062-4 casting tolerance and a traction sheave from an NMX hoisting machine are used for modelling case study. In addition, different measurement methods are reviewed to determine guidelines for casting measurement based on contemporary methods and standards. The case study revealed that tolerance model construction is difficult and time-consuming compared to the achieved benefits. Therefore, no implementation to every casting by default is recommended. Attention was also paid to modelling techniques and conventions that should be followed regardless of the tolerance models. 3D scanning should be utilised in casting quality verification because of its coverage, speed and ability to compare scanned 3D model directly to the nominal model. Measurement instructions were determined considering the requirements of ISO 8062-4 and the possibilities and restrictions of 3D scanning. An exemplary casting drawing of the traction sheave was created according to ISO 8062-4. Digital 3D product definition and 3D scanning were taken into account when determining the drawing indication.Vaikka 3D-mallinnus sekä 3D-skannaus ovat jo pitkään olleet vallitsevat suunnittelu- ja mittausmenetelmät valuteollisuudessa, valutoleranssistandardit nojaavat pitkälti vielä valujen täydelliseen esittämiseen 2D-kuvissa sekä lineaaristen mittojen tolerointiin. Vuonna 2017 julkaistu ISO 8062-4 perustuu yleiseen pinnanmuototoleranssiin yksittäisten mittojen toleroinnin sijaan, jolloin uusi standardi muodostaa ehyen ja loogisen jatkumon 3D-mallinnuksen ja 3D-skannauksen kanssa. Nykyaikaisia menetelmiä käytettäessä onkin syytä korvata vanhentuneisiin työkaluihin perustuva ISO 8062-3 uudella standardilla valutoleranssien määrityksessä. Tässä työssä selvitetään, miten valutoleranssin saa parametrisesti sisällytettyä valukappaleen CAD-malliin, jolloin erilliset mallit kuvaisivat toleranssin sallimia valun minimi- ja maksimitiloja. Minimi- ja maksimitilojen mallien hyötyjä arvioidaan laadunvarmistuksen, lujuuslaskennan ja törmäystarkasteluiden kannalta. Toleranssimallien luonnissa käytetään standardin ISO 8062-4 mukaisia toleransseja sekä malliesimerkkinä NMX-hissimoottorin vetopyörää. Lisäksi tarkastellaan eri mittausmenetelmiä, ja pyritään määrittämään suuntaviivat nykyaikaisiin menetelmiin ja standardeihin perustuvaa mittausohjetta varten. Tarkasteluissa havaittiin toleranssimallien mallinnuksen olevan työlästä saatavaan hyötyyn nähden, jolloin niiden sisällyttäminen oletuksena jokaiseen valuun ei ole järkevää. Tarkastelun yhteydessä kiinnitettiin huomiota myös mallinnustekniikkaan ja tapoihin, joita tulisi valusuunnittelussa noudattaa riippumatta toleranssimallien käytöstä. Valujen mittaamisessa tulisi ensisijaisesti hyödyntää 3D-skannausta, jossa nimellistä CAD-mallia verrataan skannattuun 3D-malliin, ja joka kattavuutensa ja nopeutensa ansiosta onkin yleisesti käytössä valuteollisuudessa. Mittausprosessin kulku määritettiin samalla huomioiden standardin ISO 8062-4 vaatimukset sekä 3D-skannauksen mahdollisuudet ja rajoitteet. Malliesimerkkinä käytetystä vetopyörästä laadittiin ISO 8062-4:n mukainen valupiirustus, jossa huomioidaan myös nimellisen muodon määritys CAD-mallilla sekä 3Dskannauksen käyttö laadunvarmistuksessa

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

A design-with-features approach for rotational machined components

A major problem in integrating Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) arises from the difference in thinking between the design and manufacturing people. Designers think of designing a new product in terms of its intended function whereas manufacturing engineers think in terms of decomposing a product design into a set of manufacturing operations. Feature Recognition and Designing with Features have been recognised as alternative approaches to the integration of design and manufacturing functions. In this thesis the second approach has been investigated by developing a feature-based front-end to a CAD solid modeller. This produces the geometric representation of the component in terms of manufacturing features and processes, and simultaneously captures this information in a form suitable for an outline process plan. [Continues.

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