夾具類外文翻譯-為持續(xù)提高夾具精度的安裝方法【中文3460字】【PDF+中文WORD】,中文3460字,PDF+中文WORD,夾具,外文,翻譯,持續(xù),提高,精度,安裝,方法,中文,3460,PDF,WORD 【中文3460字】 可持續(xù)夾具的高精度安裝方法 詹姆斯迪Maropoulos 英國巴斯大學機械工程系 摘要 精確安裝時的測量夾具組件的能力決定了他們的精度，特別是對于大尺寸的產品和應用。這件事是至關重要的質量定制的產品和部件設計中的各種小批量生產。產品質量應與快速轉換哲學和諧作為妥協(xié)的質量速度不可原諒的敏感部件和組件，如在航空航天工業(yè)，見。它是對夾具以減少使用高度精確安裝必要的容差預算由于變化的夾具定位。對夾具的主要費用特是在航空航天工業(yè)，導致柔性和可重構夾具概念的發(fā)展夾具。可重構夾具的可重用性，使他有吸引力的可持續(xù)解決方案。他們的組件可以重復使用的產品或組件的幾個變種。這種類型的主要缺點夾具的精度和可靠性已經成為他們的貧窮。在本文中，精確定位的關鍵可持續(xù)的具元件的研究。對影響夾具性能的因素夾具的安裝階段審查。本文介紹了用于最小化的方法在柔性夾具的夾持和定位的不確定性。 關鍵詞：可持續(xù)的夾具，夾具的安裝，校準的不確定性，夾具的監(jiān)測，計量，可重復使用的夾具 1簡介 質量和可靠性等因素早已轉化為新產品的隱含特征。最近的市場趨勢迫使制造業(yè)在其產品和服務范圍內進行大規(guī)模定制。新產品設計的變化越來越大，子組件和組件級別的第二波變化波幅較大。 最先進的制造系統(tǒng)和技術提供了更多的靈活性，使設計人員能夠更自由地思考。例如，在過去幾年開發(fā)的新的大容積測量系統(tǒng)能夠測量幾個分層距離。這些技術有助于驗證過去由幾個組裝部件制造的大尺寸部件。 大尺寸產品的制造需要專門的夾具和夾具，以便在構建和組裝期間將其部件保持在所需的方向。這需要主要的間接成本，這在某些情況下只能通過批量生產來證明，否則成品的成本可能非常高。這個問題與客戶不斷尋求更高價值的市場趨勢相矛盾。在一個典型的產品中，產品的變化創(chuàng)造了一個更可持續(xù)的業(yè)務，因為它可以滿足相對較大市場的需求。 可以形成不同形狀以支持不同產品變化的靈活和可重新配置的夾具和夾具是上述挑戰(zhàn)的關鍵解決方案。靈活夾具的概念在研究領域已存在多年[1]。然而，它們在很大程度上在實際的生產設備中并沒有被充分利用，特別是對于大型產品制造商如航空航天。這是由于與其初始安裝相關的挑戰(zhàn)，校準差和重復性常常超過公差要求。從高質量的關鍵部件制造這些夾具和夾具，以及與大容量計量系統(tǒng)的集成可以減少上述限制。 本文介紹與柔性夾具和夾具的安裝和校準相關的計量問題以及在使用過程中的監(jiān)控。 2 相關工作 2.1大型零件的制造和裝配 通常在精密制造機械部件之前，將原材料移至機臺，必須進行粗切割，然后精確對準和夾緊。在這個階段，該零件準備加工其高精度關鍵特征。然而，對于大尺寸和/或重組件來說，這并不總是可能的。大規(guī)模產品是指在經濟上無法在工廠中處理或移動的組件，用于制造和組裝目的[2]。這些部件的制造和組裝過程包括機器和系統(tǒng)相對于這些部件移動到期望的位置和取向。這些部件通常使用大尺寸的夾具和夾具保持在它們的位置。如果這些部件是以小批量生產的，就是航空航天工業(yè)的情況，則會產生每個產品的高架空成本。已經有許多設計和制造夾具和固定裝置的嘗試，使得它們可以容納許多組件的變型[3,4]。然而，由于其高精度要求，這種方法對于具有敏感或關鍵特征的部件是不可行的?？烧{節(jié)，可重構的夾具和夾具與固定夾具相比，隨著時間的推移產生較低的重復性。固定夾具具有通過焊接或鉚接的永久接頭實現(xiàn)的永久拓撲結構。這些夾具和夾具的機械故障，例如疲勞和塑性變形，是終止其使用并將其送回回收的主要原因。對于小批量制造要求，現(xiàn)在常常要退出一個符合要求的夾具，因為其使用壽命取決于產品的使用壽命。換句話說，在制造零件變體后不久， 大量的制造時間是固定夾具和固定裝置的另一個主要缺點。這些夾具應在任何制造工藝之前進行訂購。這可能會在生產計劃和產品上市時間上帶來額外的復雜性。 不管它們的類型如何，大規(guī)模夾具具有許多共同的元件，包括一個主框架，一個或多個內框架，潛在地一個或多個移動機構，以及較小的部件，例如夾具，襯套，拾取器和可調螺釘（圖1）。 Inner frame Adjustable holds Clamp Component Main frame Moving mechanisms 圖1：大型夾具的典型組件（圖片由Electroimpact提供） 2.2靈活的夾具和夾具 開發(fā)靈活的夾具和夾具的概念是為了提高可持續(xù)性，快速切換以及低成本?，F(xiàn)在可以使用現(xiàn)成的模塊和夾具進行夾具??和夾具的設計和組裝。根據(jù)要求，可能需要定制設計和制造用于夾具和固定裝置的少量專用部件。在這個概念中，大多數(shù)批量零件，附件中的接頭用于特定應用。一旦完全制造了產品設計變體，就可以拆卸上述組件，并將其重新組裝在一個新的拓撲結構中，以配合下一個設計變體?？梢栽谙嚓P的夾具上重復該循環(huán)，并且夾具變得多余。即使夾具仍處于工作狀態(tài)，也必須報廢并送回回收。這種方法帶來高耗能的回收利用。即使對于固定夾具和固定裝置，大尺寸零件和夾具中的漂移也會影響大尺寸裝配的精度[5]。已經開發(fā)了幾種分析夾具剛度的方法[6]來評估振動對大尺寸夾具的影響。無論如何，只有通過替代解決方案才能實現(xiàn)更可持續(xù)的制造。 大量次數(shù)導致夾具和夾具的間接成本降低。不用說提到拆卸時間，復位時間等其他因素，運行時間應考慮用于評估使用這種夾具和夾具的實際成本效益。這種方法最大限度地降低了組裝的夾具和夾具的成本以及設計相當接近的部件范圍。 取決于組件的變化程度以及需要重新布置的每個不同百分比的撓性夾具所需的工作類型。在設計階段考慮這個問題至關重要，以增加使用這種夾具和夾具的好處。例如，在可能的情況下，拾音器和組件的不同變體上的拾取器和夾具的位置和3D定位甚至完全不同的部分應該靠近以增加夾具和固定裝置的子系統(tǒng)的兼容性和互換性。收集夾具的關鍵部件可以在短時間內保證所需夾具的可用性。除此之外，夾具的存放需要更少的空間，因為可以拆卸通常以腳手架形式放置的所有模塊，并將它們放置在彼此之間。一些汽車公司目前使用靈活的夾具（圖2），因為它們的精度水平對于該部門來說是足夠的。盡管有以上的好處 航空航天工廠等大型制造設施中沒有許多靈活的夾具運行。定位銷的精度和不確定性，夾具的重復性和夾具結構的漂移都有助于大容量計量系統(tǒng)和技術的許多新發(fā)展?，F(xiàn)代激光測量系統(tǒng)和技術現(xiàn)在能夠以可接受的精度測量高達幾個分辨率的大尺寸產品。這些系統(tǒng)可用于在其安裝和初始設置期間精確定位夾具的關鍵部件的安裝。 夾具和固定裝置的安裝通常從其基座或主框架開始，然后大的部件逐漸向較小的部件（例如拾取器和夾具）開始。測量系統(tǒng)可用于安裝柔性夾具主框架及其內框架，以確保每個部件的正確定位。表1顯示了這些大型測量系統(tǒng)中的一些。對于這些系統(tǒng)的技術審查，參見[7]。能夠測量參考點的激光跟蹤系統(tǒng)是用于此目的的最適合的測量系統(tǒng)之一。儀器跟蹤一個球形反射鏡（SMR）目標，其位置可以在三維空間中注冊。 SMR可以直接與目標對象聯(lián)系起來，以提供幾何位置信息，或者可以在稱為激光跟蹤器目標的機械可重復的SMR嵌套中使用，或者在此點上用于短目標。像任何其他測量儀器一樣的激光跟蹤器具有在夾具安裝過程中需要考慮的不確定度水平。還應考慮激光跟蹤器及其目標點之間的視線問題，如果需要，應使用多個跟蹤器位置。在實際測量活動中，結果必須伴隨著不確定性的陳述。這種說法表明，合理地，這些夾具不能滿足發(fā)電和航空航天工業(yè)的公差要求的值的分散。一旦精度問題解決，這些夾具在上述行業(yè)中具有很高的利用潛力。 Component Main frame Clamp Inner frame 圖2：汽車行業(yè)可重構組件的夾具（圖片由Witte提供） 歸因于被測量[8]。對于任何夾具或夾具的安裝和后續(xù)驗證，此問題是相同的。這個知識闡明了給定定位和裝配任務的夾具能力。換句話說，它表示一個夾具是否可以滿足其相關過程的公差要求。 2.3夾具理論的比較 在不同的制造和組裝應用的不同公司中有大量不同形狀和設計的夾具和夾具。這些夾具和夾具中的一些可以以標準形式容易地獲得，而一些夾具和固定裝置特定于特定部件和任務而設計和制造?；诋a品的復雜性和規(guī)模，后者可能非常昂貴[9]。 無論成本和目的如何，可以使用沒有夾具，固定框架夾具或可重新配置或靈活的夾具進行制造或組裝過程。表2提供了這些方法與其典型應用的比較。 固定框架夾具通常用于重型應用。它們更適用于具有大量產品的應用，可以放松夾具的間接成本。 在大型和復雜產品的制造和組裝中應用柔性夾具和固定裝置有幾個優(yōu)點。特別是對于研發(fā)工作，以及制造小批量產品的情況，靈活的夾具和夾具可以非常有益。除了時間和金錢節(jié)省的好處，由于改變了夾具整體拓撲結構的直接和經常性成本，使用柔性夾具的可能性使設計，制造和組裝過程更加自由。與常規(guī)夾具相比，柔性夾具的重新配置和可重用性是這種夾具的主要優(yōu)點。這是特別重要的，因為它符合循環(huán)綠色制造業(yè)的行業(yè)方向來自二手系統(tǒng)的組件，減少了相關項目的加工費用的項目成本。 5 Methodology for High Accuracy Installation of Sustainable Jigs and Fixtures J. Jamshidi, P.G. Maropoulos Department of Mechanical Engineering, University of Bath, UK Abstract The ability to accurately measure the components of jigs and fixtures during their installation determines the state of their precision, especially for large size products and applications. This matter is crucial in mass customisation where small batches of products and components with high variety in design are manufactured. Product quality should be in harmony with rapid changeover philosophy as compromising quality for speed is not forgivable for sensitive components and assemblies such as those seen in the aerospace industry. It is necessary for the installation of the jigs and fixtures to be highly accurate in order to minimise the use of tolerance budget due to variations in jigs and fixture positioning. Major overhead costs for jigs and fixtures particularly in the aerospace industry led to the development of the concept of flexible and reconfigurable jigs and fixtures. Reusability of reconfigurable jigs and fixtures makes them attractive for sustainable solutions as their components can be reused for several variant of a product or assembly. The main drawbacks of this type of jigs and fixtures have been their poor accuracy and reliability. In this paper accurate positioning of the key components of sustainable jigs and fixtures is investigated. The factors affecting the performance of the jigs and fixtures are reviewed from the installation stage. The paper introduces a methodology for minimising uncertainties in positioning of the holds and clamps for flexible jigs and fixtures. Keywords: Sustainable Jig, Jig installation, Calibration Uncertainty, Jig Monitoring, Metrology, Reusable Jig 1 INTRODUCTION Factors such as quality and reliability have long converted to implicit characteristics of the new products. Recent market trends have forced manufacturing industries to move towards mass customisation in their products and service range. Increased variation in the design of new products is followed by a second wave of variation with higher amplitude at subassemblies and component level. State of the art manufacturing systems and technologies have provided more flexibility, enabling designers to think more freely. For instance new large volume measurement systems, developed in the past few years, are capable of measuring several decametre distances. Such technologies facilitate the verification of large size components that used to be manufactured from several assembled components. The manufacturing of large size products requires specialist jigs and fixtures in order for their components to be held in the desired orientation during build and assembly. This requires major overhead cost that can only be justified by mass production in some cases or otherwise the cost of finished products can be very high. This issue contradicts with the market trends where customers are constantly looking for higher value for their money. In a typical product the variation in the product creates a more sustainable business as it can fulfil the needs of a relatively larger market. Flexible and reconfigurable jigs and fixture that can be formed in different shapes to support different variation of products is a key solution for the above challenges. The concept of flexible jig existed for several years in the research domain [1]. However, they are not fully utilised to a great extent in real production facilities especially for large size product manufacturers, such as aerospace. This is due to the challenges related to their initial installation, poor calibration, and repeatability that often exceed the tolerance requirement. The manufacturing of these jigs and fixtures from high quality key components as well as their integration with large volume metrology systems can reduce the above limitations. This paper covers metrology issues related to the installation and calibration of flexible jigs and fixtures as well as their monitoring during service. 2 RELATED WORK 2.1 Manufacturing and assembly of large scale parts Typically prior to precision manufacturing of mechanical parts it is essential to move the raw material to the machine bench, proceed with rough cutting then fine alignment and clamping. At this stage the part is ready for machining of its high precision key features. However, this is not always possible for large size and/or heavy components. Large scale products refer to those with components that are not economically possible to handle or move around in the factory for fabrication and assembly purposes [2]. The manufacturing and assembly processes of these parts encompass movement of the machines and systems to the desired location and orientation with respect to these parts. Such parts are normally held in their positions using large size jigs and fixtures. If these parts are produced in small batch sizes that is the case for aerospace industries, high overhead cost per product will occur. There have been many attempts to design and manufacture jigs and fixtures so that they can hold a number of variants of components [3, 4]. However, this approach is not feasible for parts with sensitive or key features due to their high accuracy requirements. G. Seliger et al. (eds.), Advances in Sustainable Manufacturing: Proceedings of the 8th Global Conference 149 on Sustainable Manufacturing, DOI 10.1007/978-3-642-20183-7_22, ? Springer-Verlag Berlin Heidelberg 2011 Methodology for High Accuracy Installation of Sustainable Jigs and Fixtures 155 Adjustable, reconfigurable jigs and fixtures produce lower repeatability over time compared to fixed ones. Fixed jigs have permanent topology achieved through their permanent joints that are welded or riveted. Mechanical failure of these jigs and fixtures for example due to fatigue and plastic deformation is a main cause of terminating their service and sending them for recycling. With small batch manufacturing requirements it is now common to retire a conforming jig as their service life depends on the life of products. In other words soon after the cease of manufacturing a part’s variant, the associated jigs and fixtures become redundant. Even if the jigs are still in working order, they have to be scrapped and sent for recycling. This method brings the burden of high energy consumption for recycling. Even for the fixed jigs and fixtures the drift in the large size parts and jig can affect the accuracy of a large size assembly [5]. Several methods for analysing jig rigidity have been developed [6] to evaluate the impact of vibration on large size jigs. In any case a more sustainable manufacturing can only be achieved by alternative solutions. Inner frame Adjustable holds Clamp Component Main frame Moving mechanisms Figure 1: Typical components of large scale jig (image courtesy of Electroimpact http://www.electroimpact.com/G150TFIX/gallery.asp) Extensive lead time to manufacture is another major drawback for fixed jigs and fixtures. These jigs should be ordered well in advance of any manufacturing processes. This can create additional complexity in production planning and product time to market. Regardless of their type, large scale jigs have a number of common elements including one main frame, one or a number of inner frames, potentially one or a number of moving mechanisms, and smaller components such as clamps, bushings, pickups and adjustable screws (Figure 1). 2.2 Flexible jigs and fixtures The concept of flexible jigs and fixtures is developed for increased sustainability, rapid changeover as well as low cost. It is now possible to use off the shelf modules and clamps for jigs and fixtures design and assembly. Depending on the requirement only a handful of specialised components for the jigs and fixtures might be needed to be custom designed and manufactured. In this concept the majority of bulk components, joints at the attachments are used in for a specific application. Once the product design variant is fully manufactured it is then possible to disassemble the above components and reassemble them in a new topology to suite the next design variant. This cycle can be repeated over a  large number of times resulting in reduced overhead cost for jigs and fixtures. Needless to mention the other factors such as disassembly time, resetting time, operators’ time should be considered for evaluating the real cost benefit of using this type of jigs and fixtures. This approach best reduces the cost of jigs and fixtures for the assembly and component ranges that are fairly close in design. Depending on the level of variations in the components and the type of work required on each a different percentage of the flexible jigs need to be rearranged. This matter is crucial to be considered at design stage in order to increase the benefit of using this type of jigs and fixtures. For example, when possible, the location and 3D positioning of pickups and clamps on different variants of the component or even totally different parts should be in close proximity to increase compatibility and inter-changeability of sub-systems of jigs and fixtures. Having a collection of the key components of the jigs can guarantee the availability of the desired jigs in a short time. In addition to this the storage of the jigs required less space as it is possible to dismantle all the modules that are typically in the form of scaffolding and place them next to each other. Flexible jigs are currently utilised in some of the automotive companies (Figure 2) as their accuracy level is sufficient for this sector. Despite the above benefits there are not many flexible jigs in operation in large size manufacturing facilities such as aerospace factories. Accuracy and uncertainty of positioning pins, repeatability of the clamps and drift of the jig structure are all contributing to the fact that these jigs cannot meet the tolerance requirements of the power generation and aerospace industries. These jigs have high potentials for utilisation in the above industries once their accuracy problems are resolved. Figure 2: Fixture with reconfigurable components for automotive industry (image courtesy of Witte http://www.horst-witte.de/en/) Component Main frame Clamp Inner frame There has been a number of new developments in large volume metrology systems and technologies. Modern laser based metrology systems and technologies are now capable of measuring large size products up to several decametres with acceptable accuracy. These systems can be used to accurately position mountings of the key components of the jig during its installation and initial setup. The installation of jigs and fixtures typically starts form its base or main frame then large components and gradually to the smaller components such as pickups and clamps. Metrology systems can be used for the installation of flexible jig main frame and its inner frames to guarantee the correct positioning of each and every component. Table 1 shows a few of these large scale measurement systems. For technological review of these systems see [7]. Laser tracker systems capable of measuring reference points, are among the most suitable measurement systems for this purpose. The instrument tracks a Spherically Mounted Retroreflector (SMR) target the position of which can be registered in three dimensional space. SMR can be contacted directly with the target object to provide geometrical positional information or can be used within a mechanically repeatable SMR nest known as Laser tracker target or in short target from this point on. Laser trackers like any other measurement instrument have a level of uncertainty that need to be accounted for during the jig installation process. Also the line of sight issues between the laser tracker and its target point should be considered and if necessary multiple tracker positions should be used. In real measurement activity the result must be accompanied with a statement of uncertainty. Such statement characterises the dispersion of the values that are reasonably attributed to the measurand [8]. This issue is the same for the installation and later verification of any jig or fixture. This knowledge clarifies the jig capability of a given positioning and assembly task. In other word it indicates if a jig can meet the tolerance requirements for its related processes. 2.3 Comparison of jig philosophies There are a large number of different shape and design jigs and fixtures in different companies for various manufacturing and assembly applications. Some of these jigs and fixtures are readily available in standard forms, while some are designed and manufactured specific to particular parts and tasks. The latter can be very expensive based on the complexity and scale of the products [9]. Regardless of cost and purpose a manufacturing or assembly process can be performed using with no jig, with fixed frame jigs, or with reconfigurable or flexible jigs. Table 2 provides a comparison of these methods with their typical applications. Fixed frame jigs are typically for heavy duty applications. They are more suitable for applications with a large number of products that can relax the overhead cost of the jig. There are several advantages in the application of flexible jigs and fixtures for the manufacturing and assembly of large and complex products. In particular for research and development work, as well as for cases where low volume products are manufactured flexible jig and fixture can be very beneficial. In addition to time and money saving benefits the possibility of having a flexible jig gives more freedom to the design, manufacturing and assembly processes due to the low direct and recurrent cost of changing the overall topology of the jig. Reconfigurability and reusability of flexible jig is a main advantage for this type of jig compared to conventional jigs. This is particularly important as it is in line with the industry direction in terms of green manufacturing by recycling components from a used system, reducing project costs with regards to expenses for tooling of associated items. Table 1: Examples of large volume/portable measurement instruments for jig verification Instrument Auxiliary components Measurement type Image Contact Non-contact Laser Tracker SMR probe ／ T-probe ／ Laser Radar Spherical targets ／ Photogrammetry Targets ／ Light projection ／ Articulated Arm CMM Laser based scanning head ／ Contact probe ／ 3 FLEXIBLE JIG INSTALLATION The issues and concerns that need to be considered in the jig installation procedure are described in this section. The installation of the jig components in the right position can be a challenging especially when the positioning tolerances are tights. Flexible jigs should also be monitored in order to exploit and compare their rigidity with that of the conventional ones. Stage by stage measurement instruction for the jig installation based on the results of an initial jig setup in the simulation software environment and practical experiment of a large size jig with dimensions of 5m x 4m x3m is given in a generic description. This is regardless of whether the jig is in first time installation or it is a change of an existing jig topology into a new shape, for holding a different component. Depending on the complexity a typical large size jig has between three to five levels of frames. Apart from the base level with normally one main frame, at each level there can be one or several frames. These frames are interrelated with reference to the jig datum in order to facilitate the positioning and functionality required. In an automated, fixed platform, robotic systems carry out several tasks such as part positioning, machining and assembly. The robot working datum therefore is linked with the working frame of the jig. Careful consideration of jig datuming strategy and its subsequent installation can secure achieving the desired tolerance. 3.1 Measurement assisted flexible jig installation There are several stages for the installation of flexible jigs that can be carried out in first simulation and then real world. The use of simulation exercise can reduce the number of potential errors and rework during this process. The process of measurement assisted installation is similar to tracking objects to position that is common for large size assemblies. In this approach the components of the jig are roughly positioned, within 1mm tolerance from the target position, at first. Then when all of the jig components are attached into their designated positions, within 0.1mm to 0.15mm tolerance, they are tightened using the appropriate torque. The typical stages of metrology assisted flexible jig installation are given below: 1. setting initial reference frames in the factory 2. measurement of initial reference frame 3. installation of base or main frame in its position 4. installation of inner frames offline 5. installation of holding and positioning brackets 6. installation of clamps, bushings and pickups in their rough position on inner frames and main frame 7. installation of inner frame on the base frame 8. fine adjustment and fastening of key locating components 9. verification of reference frames and clamps 10. in service monitoring of key positions on the jig These stages are related to the complete installation of the jig from the scratch. Needless to mention that in case of slight change in design variation some of the following operations will be omitted. Table 2: A brief comparison between different jig philosophies Typical characteristic Fixed frame Flexible jig Jig-less Application Large volume production Low volume production Prototyping Pros Uniqueness Repeatable Reconfigurable Cost effectiveness Durability Very high High Low Rigidity Very high Uncertainty rigidity Low Cons Weight Heavy Medium Low Portability Non-portable Difficult component positioning in each setup Difficult to program Cost Very high Medium Low Manufacturing time Long Medium Short 3.2 Algorithm for flexible jig installation The installation processes for flexible jigs take the following main stages: 1. the installation of main frame of the jig 2. the assembly of moving units and sub-systems 3. the installation of the jig inner frames on the jig assembly 4. the assembly of pickups and clamps on the jig. The main frame is the backbone of the jig that is typically fixed for a large number of jig topology and design variations. Therefore it does not change in shape as regularly as the inner frame or the smaller elements of the jig such as bushings, pickups and clamps. Careful consideration of the manufacturing process can reduce the necessity of rearranging larger elements of the jig components resulting in further time and money saving. Figure 3 in three separate groups of activities shows the processes of flexible jig installation. In this process it is assumed that the standard parts of the jig are selected from the available, off the shelf sections and components. Then in advance of the physical installation a number of tests and trials are carried out to plan the jig installation in such a way that the uncertainty of measurement is reduced. Once the acceptable level of uncertainty is achieved the physical installation can take place. Figure 3: Measurement assisted installation procedure for flexible jig In jig installation process it might be required to use