【正文】 模式的特定的根本原因 問題的分支 問題 問題的原因 系統(tǒng) 設計 制程 零件 子系統(tǒng) 主系統(tǒng) 人員 機器 方法 物料 測量 環(huán)境 零件 子系統(tǒng) 主系統(tǒng) 把系統(tǒng)失效模式的后果最小化 焦點 把設計的失效模式的后果最小化 焦點 最大化系統(tǒng)的質(zhì)量，可靠性，成本和可維護性 目標 最大化設計的質(zhì)量，可靠性，成本和可維護性 目標 機器 工具， 工作崗位，生產(chǎn)線，員工培訓，制程，量具 把整個制程的失效模式的后果最小化 焦點 最大化整個制程的質(zhì)量，可靠性，成本和可維護性 目標 三種 FMEA之間的關系 典型的汽車產(chǎn)品發(fā)展的三步曲 產(chǎn)品流程圖和產(chǎn)品的工程規(guī)格 PFMEA 控制計劃 輸入 輸出 過程 客戶的要求是什么？？ 典型的汽車產(chǎn)品發(fā)展的三步曲 PFMEA （包括所有的過程） 關鍵特性和失效的后果 DFMEA 過程的控制計劃 （來自 PFMEA的關鍵過程） 關鍵特性和特性的控制 流程圖 （包括所有的過程） APQP時間表 典型的汽車產(chǎn)品發(fā)展的三步曲 過程的流向及清單 檢查客戶的要求 選擇每一個“關鍵”的過程到FMEA表中 評估每一個過程的 FMEA項目 發(fā)展包含了特殊特性的控制計劃 仔細考慮所選的“關鍵”過程 用適當?shù)?RPN數(shù)值和一些別的意見來決定關鍵的特性 （過程） 發(fā)展針對特殊特性的控制機制 仔細考慮控制計劃的各個階段： －樣板 －試產(chǎn) －量產(chǎn) 注意： FMEA＝還應當包含對產(chǎn)品特殊特性的評估。 特殊特性 ?過程的特殊特性 –可能產(chǎn)品的影響產(chǎn)品的功能，可靠性，壽命，耐用性，安全性，或可能影響法律法規(guī)的符合性或產(chǎn)品后續(xù)生產(chǎn)過程的制造過程參數(shù)。這些缺陷可能是功能，裝配，外形方面的問題，對客戶滿意度有不同程度的影響。 怎樣用 FMEA評估過程的風險？ 1. 失效模式的嚴重度 （ S） S（嚴重度）來表示產(chǎn)品的缺陷對最終使用，或下道工序，以及客戶滿意度的影響程度。 O最小為 1， 最大是 10。 D越大，產(chǎn)品的缺陷越難以被探測到的可能性越小。 ，以確保領會客戶的要求。把 對下道工序有影響的工序 標出來，這些過程也應當優(yōu)先評估。 對下道工序有影響的工序 標出來，這些過程也應當優(yōu)先評估。 2. 8. 評估每一個缺陷可能造成的后果，根據(jù) FMEA的規(guī)則對后果進行評分。 however, loss of mobility is obviously a much more severe fault than losing air conditioning. Fault Tree Fundamentals (Continued 1) 2. Defining Types of Faults Faults fall into two basic categories: operational and ponent. Operation Fault The operational fault is one which occurs when a ponent is operating as it was designed to, but at an inappropriate time or place. An example is a failure of a control valve to close or to interrupt the introduction of a reactant into a chemical process due to an inappropriate signal from another device. Component Fault The ponent fault can be further divided into two subcategories: primary and secondary. A Primary ponent fault occurs when a ponent fails to function in its intended environment. Example: A radar unit designed for use in aircraft which fails due to vibration. A Secondary ponent failure occurs when a ponent fails to function in an environment other than the environment for which it is intended. Example: A radar unit designed for a cargo aircraft fails in a fighter aircraft due to vibration. Fault Tree Fundamentals (Continued 2) 3. Comparison of Fault Occurrence and Fault Existence The term Fault Occurrence refers to the fact that an undesired event has taken place and may or may not still exist. Fault Existence, however, implies that the fault has occurred and continues to exist. Therefore, the fault can be described as being either transient or permanent. During the construction of the fault tree, all systems analysts should use Fault Occurrence, rather than Fault Existence, as the focus of interest. 4. Comparison of Failure Causes and Fault Effects A failure is considered to be an inability to perform a normal function. Example: Valve does not open. A fault is a higher level Occurrence which is usually preceded by a lowerlevel failure, such as a casing cracking due to overheating because of a lack of coolant induction due to an inoperable valve (lower level of failure). However, a fault may also occur when no failure is present. Example: Coolant valve operates properly, but the signal to operate it encounters a delay. A fault has occurred, but there is no valve failure. Because of this, it can be stated that any failure causes a fault, but not every fault is caused by a failure. Failure Categories: a. Component, b. Environment, c. Human, d. Software. Fault Tree Construction Steps Summary ? Determine the level to which the examination should be constructed ? Begin with the systemlevel fault ? Fully describe all events which immediately cause this event ? With each lowerlevel fault, continue describing its immediate causes until a ponent level failure or human error can be attributed to the fault Fault Tree Construction Steps Summary (continued) ? Fully define each branch of the tree before beginning another branch ? During the construction of the tree, it is advisable to use a block diagram of the system to simplify determining the main branches ? If the results of the FMECA on the system are available at the time of the FTA it is advisable to use the results in defining the top event(s) Analyzing the Fault Tree 1. Determine the minimal cutsets to simplify the tree (qualitative analysis).