Hiukkasilmaisimen tukirakenteen toleranssianalyysi ja laadunvarmistus

Particle detectors are some of the largest and most complicated devices ever built, that are used to study the smallest building blocks of our universe. Design and construction can take years and engineers and physicists have to guarantee that the detectors finally operate as required. The Large Hadron Collider (LHC) at CERN is being updated to operate at higher luminosities. Consequently, many of the detectors that study the collisions produced by the LHC are being upgraded. In this thesis, an abstracted feature based model is presented for allocating geometric tolerances for a novel support structure of the future tracking detector of the Compact Muon Solenoid (CMS) experiment. This new tracking detector will have a unique section where silicon sensors are mounted in different angular orientations, providing unparalleled track reconstruction efficiency while lowering costs tremendously. The tolerance analysis is based on the functional requirement of hermeticity in the CMS tracker: silicon sensors within each of the tracker’s layers must overlap slightly so that particles cannot traverse a layer without hitting at least one active sensor surface. Imprecisions in the tracker’s real construction geometry cause the sensors to deviate from their nominal positions. This may generate gaps through which particles can traverse without hitting a sensor. Because the CMS tracker is a first-time-right production, with limited or even no possibilities for corrections in the mechanical construction, the composed model of the tolerances is based on worst-case analysis. The second part of this thesis is dedicated to quality assurance; the simulated geometric tolerances are utilized to develop accuracy requirements for dimensional measurements. Dimensional measurement plans are presented for the various assembly stages of the studied sub-detector. The chosen measurement methods utilize either a coordinate measurement machine (CMM) when the geometry and dimensions allow it, or photogrammetry. In case of photogrammetry, detailed descriptions are provided as where to position photogrammetric targets to achieve the required measurement accuracies. As a result, it is shown that an abstracted feature based model is suitable for synthesizing tolerances of the CMS trackers support structures. Such model can also be integrated into existing software at CERN, to allocate tolerances for other support structures. Additionally, comprehensive dimensional measurement plans have been developed for the quality assurance of the sub-detector.Hiukkasilmaisimet ovat yksiä suurimmista ja monimutkaisimmista laitteista joita on koskaan rakennettu. Niitä käytetään tutkimaan universumimme pienimpiä ja perustavanlaatuisimpia palasia. Hiukkasilmaisimien rakentaminen vie usein vuosia, ja niinpä niitä rakentavien insinöörien ja fyysikoiden tulee olla varmoja, että ne toimivat ennalta määritetyllä tavalla valmistuttuaan. CERN:issä sijaitsevaa suurta hadronitörmäytintä valmistellaan uudistukseen, jonka jälkeen se toimii korkeammalla luminositeetillä. Tästä johtuen useat ilmaisimet jotka tutkivat törmäyttimen tuottamia törmäyksiä uudistetaan myös. Tässä työssä esitellään abstrakteihin piirteisiin perustuva malli, jonka avulla asetetaan toleransseja kompaktin myonisolenoidin uuden jäljittimen tukirakenteisiin. Mallin toleranssianalyysi pohjautuu jäljittimen hermeettisyyteen liittyvään toiminnalliseen vaatimukseen: jäljittimen kerroksissa olevien piisensoreiden tulee limittyä hieman päällekkäin, jotta partikkelit eivät pääse kulkeutumaan kerroksen läpi osumatta ainakin yhden piisensorin aktiiviseen pintaan. Tukirakenteen toleranssit aiheuttavat näiden sensoreiden paikaan poikkeavuutta niiden nominaalisesta sijainnista, jolloin kerroksiin voi syntyä rakoja joista partikkelit pääsevät läpi. Koska uusi jäljitin rakennetaan vain kerran, toleranssianalyysimalli ratkaisee toleranssit pahimman mahdollisen skenaarion menetelmällä. Työn toisessa osassa hyödynnetään laskettuja toleransseja määrittelemällä niiden perusteella tarkkuusvaatimukset tukirakenteen dimensionaaliselle mittaukselle. Dimensionaalisen mittauksen suunnitelmat esitellään jäljittimelle sen kokoamisen eri vaiheissa. Valitut mittaustavat käyttävät hyödyksi joko koordinaattimittauskonetta, tai fotogrammetriaa. Fotogrammetrian tapauksessa keskitytään fotogrammetristen maalien paikkoihin, jotta mittauksen tarkkuusvaatimukset toteutuisivat. Työn tuloksena näytetään, että esitelty abstrakteihin piirteisiin perustuva malli soveltuu kompaktin myonisolenoidin jäljittimen tukirakenteiden toleranssisynteesiin. Malli voidaan myös integroida jo CERN:issä käytössä oleviin ohjelmiin, jolloin toleranssit voi asetta muillekin tukirakenteille kuin tässä työssä tutkitulle. Tukirakenteelle lasketut toleranssit esitellään taulukkomuodossa. Lisäksi, työssä suunniteltiin kattavat dimensionaalisen mittauksen menetelmät tutkittavan tukirakenteen laadun varmistamiseksi

A precision analysis method for the kinematic assembly of complex products based on equivalence of deviation source

Purpose: The assembly quality of complex products is pivotal to their lifecycle performance. Assembly precision analysis (APA) is an effective method used to check the feasibility and quality of assembly. However, there is still a need for a systematic approach to be developed for APA of kinematic mechanisms. To achieve more accurate analysis of kinematic assembly, this paper aims to propose a precision analysis method based on equivalence of the deviation source. Design/methodology/approach: A unified deviation vector representation model is adopted by considering dimension deviation, geometric deviation, joint clearance and assembly deformation. Then, vector loops and vector equations are constructed, according to joint type and deviation propagation path. A combined method, using deviation accumulation and sensitivity modeling, is applied to solve the kinematic APA of complex products. Findings: When using the presented method, geometric form deviation, joint clearance and assembly deformation are considered selectively during tolerance modeling. In particular, the proposed virtual link model and its orientation angle are developed to determine joint deviation. Finally, vector loops and vector equations are modeled to express deviation accumulation. Originality/value: The proposed method provides a new means for the APA of complex products, considering joint clearance and assembly deformation while improving the accuracy of APA, as much as possible.Natural Science Basic Research Project of Shaanxi Province, China (Grant Nos. 2019JM-435 and 2019JM-073), the China Postdoctoral Science Foundation (Grant No. 2018M633439) and the Key Laboratory of Road Construction Technology and Equipment (Chang’an University), MOE (Grant No. 300102258506)

TOLERANCE ALLOCATION FOR KINEMATIC SYSTEMS

A method for allocating tolerances to exactly constrained assemblies is developed. The procedure is established as an optimization subject to constraints. The objective is to minimize the manufacturing cost of the assembly while respecting an acceptable level of performance. This method is particularly interesting for exactly constrained components that should be mass-produced. This thesis presents the different concepts used to develop the method. It describes exact constraint theory, manufacturing variations, optimization concepts, and the related mathematical tools. Then it explains how to relate these different topics in order to perform a tolerance allocation. The developed method is applied on two relevant exactly constrained examples: multi-fiber connectors, and kinematic coupling. Every time a mathematical model of the system and its corresponding manufacturing variations is established. Then an optimization procedure uses this model to minimize the manufacturing cost of the system while respecting its functional requirements. The results of the tolerance allocation are verified with Monte Carlo simulation

Review of research in feature-based design

Research in feature-based design is reviewed. Feature-based design is regarded as a key factor towards CAD/CAPP integration from a process planning point of view. From a design point of view, feature-based design offers possibilities for supporting the design process better than current CAD systems do. The evolution of feature definitions is briefly discussed. Features and their role in the design process and as representatives of design-objects and design-object knowledge are discussed. The main research issues related to feature-based design are outlined. These are: feature representation, features and tolerances, feature validation, multiple viewpoints towards features, features and standardization, and features and languages. An overview of some academic feature-based design systems is provided. Future research issues in feature-based design are outlined. The conclusion is that feature-based design is still in its infancy, and that more research is needed for a better support of the design process and better integration with manufacturing, although major advances have already been made

Manufacturing variation models in multi-station machining systems

In product design and quality improvement fields, the development of reliable 3D machining variation models for multi-station machining processes is a key issue to estimate the resulting geometrical and dimensional quality of manufactured parts, generate robust process plans, eliminate downstream manufacturing problems, and reduce ramp-up times. In the literature, two main 3D machining variation models have been studied: the stream of variation model, oriented to product quality improvement (fault diagnosis, process planning evaluation and selection, etc.), and the model of the manufactured part, oriented to product and manufacturing design activities (manufacturing and product tolerance analysis and synthesis). This paper reviews the fundamentals of each model and describes step by step how to derive them using a simple case study. The paper analyzes both models and compares their main characteristics and applications. A discussion about the drawbacks and limitations of each model and some potential research lines in this field are also presented

Microassembly technology for modular, polymer microfluidic devices

Assembly of modular, polymer microfluidic devices with different functions to obtain more capable instruments may significantly expand the options available for detection and diagnosis of disease through DNA analysis and proteomics. For connecting modular devices, precise, passive alignment structures can be used to prevent infinitesimal motions between the devices and minimize misalignment. The motion and constraint of passive alignment structures were analyzed using screw theory. A combination of three v-groove and hemisphere-tipped post joints constrained all degrees of freedom of the two mating modules without overconstraint. Simulations and experiments were performed to assess the predictability of dimensional and location variations of injection molded components. A center-gated disk with micro scale assembly features was replicated. Simulations using a commercial package (Moldflow) overestimated replication fidelity. Mold surface temperatures and injection speeds significantly affected the experimental replication fidelity. The location of features for better replication, at each mold surface temperature, moved from the edge of the mold cavity to the injection point as the mold surface temperature increased from 100˚C to 150˚C. Prototype modular devices were replicated using double-sided injection molding for the experimental demonstration. Dimensional and location variations of the assembly features and alignment standards were quantified for an assembly tolerance analysis. Monte Carlo methods were applied to the assembly tolerance analysis to simulate propagation and accumulation of variation in the assembly. In simulations, mean mismatches with standard deviations ranged from 115±29 to 118±30 µm and from 17±11 to 19±13 µm along the X- and Y-axes, respectively. Vertical gaps with standard deviations at the X- and Y-axes were 312±37~319±37 µm, compared to the designed value of 287µm. The measured lateral mismatches were 103±7~116±11 µm and 15±9~20±6 µm along the X- and Y-axes, respectively. The vertical gaps ranged from 277±4 µm to 321±7 µm at the X- and Y-axes, respectively. The present study combined an investigation of microassembly technology with a better understanding of the micro injection molding process, to assist in realizing cost-effective mass production of modular, polymer microfluidic devices enabling biochemical analysis

Tolerance optimization with statistical approach in the CAT environment

Nowadays, product development in all its phases plays a fundamental role in the industrial chain. The need for a company to compete at high levels, the need to be quick in responding to market demands and therefore to be able to engineer the product quickly and with a high level of quality, has led to the need to get involved in new more advanced methods/ processes. In recent years, we are moving away from the concept of 2D-based design and production and approaching the concept of Model Based Definition. By using this approach, increasingly complex systems turn out to be easier to deal with but above all cheaper in obtaining them. Thanks to the Model Based Definition it is possible to share data in a lean and simple way to the entire engineering and production chain of the product. The great advantage of this approach is precisely the uniqueness of the information. In this specific thesis work, this approach has been exploited in the context of tolerances with the aid of CAD / CAT software. Tolerance analysis or dimensional variation analysis is a way to understand how sources of variation in part size and assembly constraints propagate between parts and assemblies and how that range affects the ability of a project to meet its requirements. It is critically important to note how tolerance directly affects the cost and performance of products. Worst Case Analysis (WCA) and Statistical analysis (RSS) are the two principal methods in DVA. The thesis aims to show the advantages of using statistical dimensional analysis by creating and examining various case studies, using PTC CREO software for CAD modeling and CETOL 6σ for tolerance analysis. Moreover, it will be provided a comparison between manual and 3D analysis, focusing the attention to the information lost in the 1D case. The results obtained allow us to highlight the need to use this approach from the early stages of the product design cycle

Virtual reality for assembly methods prototyping: a review

Assembly planning and evaluation is an important component of the product design process in which details about how parts of a new product will be put together are formalized. A well designed assembly process should take into account various factors such as optimum assembly time and sequence, tooling and fixture requirements, ergonomics, operator safety, and accessibility, among others. Existing computer-based tools to support virtual assembly either concentrate solely on representation of the geometry of parts and fixtures and evaluation of clearances and tolerances or use simulated human mannequins to approximate human interaction in the assembly process. Virtual reality technology has the potential to support integration of natural human motions into the computer aided assembly planning environment (Ritchie et al. in Proc I MECH E Part B J Eng 213(5):461–474, 1999). This would allow evaluations of an assembler’s ability to manipulate and assemble parts and result in reduced time and cost for product design. This paper provides a review of the research in virtual assembly and categorizes the different approaches. Finally, critical requirements and directions for future research are presented

Design method of a modular electronic printed circuit board testing system

Thesis: M. Eng. in Manufacturing, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 52-54).The failure rate of the printed circuit board electronic testing process is higher than acceptable at a Lenze Americas factory. This thesis will understand the root causes of failure, and use system engineering methods to decide what course of action should be taken. A Tradespace analysis is used to help decompose some of the complexity into a visualization that simplifies the decision process. The Tradespace analysis suggests that more utility can be achieved by upgrading the design of existing test fixtures versus purchasing off of the shelf solutions. The second phase will identify a design concept, offer specific design solutions, and finally a fully designed system that is capable of improving the performance of the test fixtures in electronic board test area by 50%. The system is then upgradable with in-line conveyors to run autonomously decoupling the operator from the process.by David McCalib, Jr.M. Eng. in Manufacturin