全自動咖啡機(jī)的機(jī)械設(shè)計【含CAD圖紙、說明書】
全自動咖啡機(jī)的機(jī)械設(shè)計【含CAD圖紙、說明書】,含CAD圖紙、說明書,全自動,咖啡機(jī),機(jī)械設(shè)計,cad,圖紙,說明書,仿單
外文翻譯
Failure evaluation of coffee maker
ABSTRACT:The coffee maker was disassembled, and the characteristics, working principle and process of each unit and component were investigated in this paper. The response of the system under abnormal operation conditions was found through simulating test. And the failure modes of each unit failing in the test were analyzed based on the characteristics of mate-rial, structure and service condition. The failure evaluation of the coffee maker system was made using the reliability analysis methods such as failure mode and effect analysis, fault tree analysis etc. The results show that the coffee maker can basically meet the demands for functionality. However, the hidden hazard caused by design exists for the pressure relief pipeline, which needs further improving. In?ammation and explosion etc. can hardly occur to the coffee maker, but leakage of steam may take place, which should be avoided. The quality of some units in the coffee maker are poor, which is detrimental to safe use of long term, and improved processing are needed.
1. Introduction
The main objective of this study is to evaluate whether the designed function of one kind of coffee maker can realized and is safe enough or not in the work process when it is abnormally or improperly operated. First, the components and units of every subsystem were disassembled. Then possible failure modes of each unit were analyzed based on the characteristics of material, structure and service conditions. The possible failure modes of each component were inferred from the combina-tion of the in?uence of unit failure on components and simulation test demonstration. Finally, security and reliability of the whole system were evaluated based on the results on the components.
2. Structural features and analysis of system functions
2.1. Classi?cation of subsystems
Structural features and analysis of system functions are fundamental to both failure and system safety evaluation [1,2]. According to function characteristic, the coffee maker can be separated into three relatively independent subsystems. (1) Water circulation system. It is the center working system of the coffee maker which accomplished by supply, drawing, heat-ing and output process. This circulation system consists of the following components, water reservoir, ?ow meter, pump, heater, trifurcate tube connector, brew basket, pod holder, relief valve, check valve and tube. (2) Electric control system. The electric control system acts as a nerve center (cerebrum) of the coffee maker, carrying out automation control by program including working process control and error response management etc. According to function, the electric control system is composed of in-out circuit, processor and electric support circuit. Main parts of in-out circuit include negative temperature coef?cient (NTC), thermostat, thermal cut off and beep. The processor refers to the master integrate circuit(IC). The electric support circuit includes capacitance, resistance, inductance, triode, tri-voltage regulator, transformer, wire and plug-in board. (3) Shell structure system. The shell structure system, which composed of front shell, rear shell, chassis, lid and skeleton, is in charge of protecting and supporting the whole system.
2.2. Analysis of working process
Working process of the water circulation system is vital to coffee maker. On the basis tests, we can tentatively infer the working process of water circulation, as shown in Fig. 1. For example, when the coffer maker make coffer of 7oz, at ?rst, the coffee maker is powered on, the heater will preheat itself up to about 65 ?C(149 ?F), the pump then starts pumping water into the heater through the ?ow meter and heated water (not boiled) ?ows out of the spout. As soon as the ?ow meter reads 7oz (7oz mode), the pump stops. The water left in the heater will be boiled so that the steam spurts from the spout. However, when the steam pressure is too high, the relief valve turns on and excess steam is released in the chassis. In contrast, when the steam pressure is lower than 1 atm, air outside will be pressed into the water circulation system through the check valve in order to keep it stable. This is the pressure hazard defense system.
2.3. Overheating hazard protection process
Overheating may be the main cause of burning and explosion of the coffee maker. Its overheating protection is realized by the following three grades, as shown in Fig. 2. Grade I hazard protection is made up of two parallel connected thermal resistances; grade II is a thermostat and grade III is a thermal cut off. When the temperature of the inner shell of the heater or heater spout is too high, the thermal resistance gets to work and the system is prevented from working. The thermostat is controlled by strong electricity. When the heater tube is over-heated, the thermostat works, cutting off the power supply of the heater and the pump to ensure safety. After the temperature returns to normal, the thermostat will re-connect to the power. The thermal cut off is the highest grade of safety protection. When the ?rst two grades fail to work and the temperature of the heater tube exceeds critical temperature, the thermal cut off will sever the power supply of the whole system.
3. Safety evaluation
3.1. Failure mode and effect analysis (FMEA)
FMEA is a qualitative method to analyze the hazards, which gradually analyzes the in?uences of the failure of components and units on the personnel, operation and the whole system and its possible causes [3,4]. The analysis results of some units of water circle subsystem were only given here, as shown in Table 1.
3.2. Fault tree analysis (FTA)
Fault tree analysis adopts logical method to conduct dangerous analyzing work characterized by intuitiveness, straight-forwardness, clear thinking and logic. Both quantitative and qualitative analysis can be conducted, which re?ects the sys-tematically, accuracy and predictability of the systematical project method to research safety problem. It is one of the main analyzing methods of safety system projects. On the basis of FMEA, the failure modes that have the most possibility to occur are leakage of high-temperature and high-pressure water and electricity leakage, the results are shown in Figs. 3 and 4.
4. Simulation test and analysis
Simulation test aims to ?nd out the unknown design fault and validate FMEA conclusions by simulating failure of many kinds of main components. It is a testing way that is closest to the actual conditions. The report is concerned mainly on components in the water circulation system and the hazard protection system. The prefabricated failures often happen in actual service.
4.1. Outlet clogging of creamy pod holder
This clogging often occurs in practical service. If coffee powder is carelessly put into the creamy pod holder, the water will ?ow to the cup through the pressure relief pipe, indicating that the pressure hazard protection system run normally. However, the pod holder is full of hot water. Under pressure the lid cannot be opened immediately so that users would open it forcibly to be scalded. This clogging experiment also holds for the outlet clogging.
4.2. Clogging of waterspout of relief valve
Failure of the simulation test would occur if the relief piston was clogged as the scale deposits lie in the relief discharging outlet in the underpin or the spring is ruptured because of erosion. During the test, the system ran normally and the adhesive plaster clogging the discharging outlet was sunken. Therefore, only under great pressure would the relief pipeline be opened. Despite no signi?cant in?uence of the failure on the system, the failure still makes the pressure hazard protection system in the water-circulating system malfunction, which is hard to be observed. Once the heater pipeline is clogged, it may be ruptured to cause rapid leakage of the hot water and even electric shock or scalding of people because of the dramatically rising pressure.
4.3. Leakage of check valve
The failure of the check valve leakage was simulated in this test, which also holds for any leakage of the outlet pipeline of the heater. As aforementioned, the failure caused by the aging, thermal melting, and hot water leakage possibly occurs for silicone tube, ?rmware, connector in the outlet pipelines in the high-temperature and high-pressure vapor. Once the failure takes place, the leakage of the outlet pipeline may cause the short circuit and scalding of people. Therefore, such leakage is a dangerous mode of failure which occurs commonly. The check valve is an important element for the pressure hazard protection, which can relieve negative pressure of the system. Different from the leakage in the coffee maker, as the inlet of the check valve directly leads to fascia cover in front of the crust, water (steam) with high-temperature and high-pressure will directly ?ow out of the coffee maker if the ?ow direction is reversed. It could cause serious harm to people.
4.4. Replacement of NTC 1#and NTC 2#
This test has conducted a survey of the working situation of the protection system of temperature danger after the NTC 1# and NTC 2#and electromagnetic pump fails to function simultaneously. After the NTC 1#and 2#are invalidated simultaneously, the thermostat should exercise the function of overheating protection at the second level. After the heater reaches the critical temperature during the dry burning process, the thermostat will cut off the chief power. During the simulation test process, although the thermostat at last exercises the function of cutting off the power, the NTC holder has already invalidated in the initial stage, which leads to the leakage of high-temperature vapor in the water-circulating system, as shown in Fig. 5. Such NTC holder suffers from failure for serious distortion of melting and perforation at temperature about 100 C(212 F), as shown in Fig. 6.
The NTC holder is made of PP plastic. PP plastic has good hardness, toughness, high thermal resistance temperature, good
fatigue property, good chemical stability and oxidation resistance. It can endure the high-temperature from 110 C(230 F) to
120 C(248 F), even 150 C(302 F) without force operation. NTC holder has strength much lower than that of trifur connector though they are made of the same PP. NTC holder is of semi-transparent and yellowish color while trifurcate tube connector is of opaque and white color. The obvious difference in color and roughness can be ascribed to different processing qualities. These results show that NTC holder failure is due to the processing of manufacture. In addition, lid lower of the coffee maker was found that material drop by delamination occurred around the screw of the lid, as indicated by the arrow in Fig. 7. The lid is made of PPS (Polyphenylene Sul?de) which has good thermal, in?aming, mechanical, chemical, wearing resistance, and also better dimension stability. It can serve in between 220 and 240 C for long time. Both short-term thermal resistance and long-term thermal stability are superior to any other engineering plastics. Thus, this kind of material is suitable for inner units of the coffee maker. Lid, slider and chassis are all made of PPS. It should be pointed out that delaminating drop may be due to the improper fabrication and installation process of the environment-friendly PPS. The reliability of security of the coffee maker would be guaranteed by adopting the correct fabrication technology of PPS.
5. Analysis and discussion
The coffee maker can basically meet the demands for functionality according to test and analysis above. However, the hidden hazard also exists in design and few parts, which will detailed as follow, and needs further improving.
5.1. Design factor
Design fault is quite serious and unacceptable and thus must be improved in that probability of failure caused by unreasonable design is highest. Test results showed that the main problems existed in design include:
(a) Unreasonable design of the heat tube. For example, the structure of the NTC holder is rather complex and the innerdiameter of tube is small and the wall is too thin such that thermal melting, poring and rupturing are easy to occur.
(b) Hidden hazards in design of the pressure relief pipeline. The exit of the pressure relief pipeline lies inside the chassis. It doesn’t work in normal service. But high-temperature vapor will leak rapidly through this pipeline under anomalous conditions such as overheat and overhigh pressure etc, which would scald people. Therefore, the design of this pipe-line should be further considered. We propose that the pipeline should directly lead to the water reservoir.
(c) The PPS in the cover lower of the brew vessel is subjected to high stress and is the only connector to the shower cap. The aging or delamination of the PPS here will lead the inner bolt and the shower cap to drop off. Therefore, the hot water or steam will leak. This is the un-negligible hidden hazard.
5.2. Manufacture factor
The quality of processing is the important guarantee for the reliability of the coffee maker. The processing quality of NTC holder is poor. Early failure of NTC holder would lead to leakage of water circle subsystem, which may result in scald.
5.3. Unpredictable accident
Accident in service cannot be controlled by designers and manufacturers. By designing a perfect protection system harm would be possibly minimized. These accidents mainly include bulk exotic articles introduced into the water-circulating system, incorrect operation and so on. Test clearly showed that the outlet would be completely clogged if coffee powder is put into the creamy pod holder. Improvement in design is indispensable for this component.
6. Conclusions
(1) Design in system, structure and safety protection of the coffee maker is reasonable. This product satis?es the requirements by safety design and will not fail severely in normal operation for a short term.
(2) The safety protection system of the coffee maker works well to be able to deal with accidents properly and thus ensure that no severe safety events happen in service.
(3) In?ammation and explosion etc. can hardly occur to the coffee maker. However, leakage of steam etc. may take place, which should be avoided.
(4) The processing quality of some particular elements is poor and will impose the hidden hazard on the whole system.
References
[1] Chunhu Tao, Nan Du, Weifang Zhang. Tactic thought about progress of failure analysis. Fail Anal Prevent 2006;1(1):1–5.
[2] Seyed-Hosseini SM, Safaei N, Asgharpour MJ. Reprioritization of failures in a system failure mode and effects analysis by decision making trial and
evaluation laboratory technique. Reliab Eng Syst Safe 2006;91(8):872–81. 1954
[3] Foster, Tandon, Zoghi. Evaluation of failure behavior of transversely loaded unidirectional model composites. Exp Mech 2006;46(2):217–43.
[4] Mosleh A, Parry GW, Zikria AF. An approach to the analysis of common cause failure data for plant-speci?c application. Nucl Eng Des 1999;(150):25–47.
中文翻譯：
咖啡機(jī)的失效評估
摘要：本文對某型咖啡機(jī)做了拆卸，對各個元器件的工作原理、工作過程和特點進(jìn)行了研究。通過模擬實驗，對在異常運(yùn)行情況下的系統(tǒng)響應(yīng)做出監(jiān)測。根據(jù)材料的特點、結(jié)構(gòu)、和工作條件分析測試中每一個失效的單元模式。在咖啡機(jī)失效系統(tǒng)的評估中利用可靠性分析方法，如故障模式和影響分析，故障樹分析等。結(jié)果表明，咖啡機(jī)可滿足基本功能。然而，在設(shè)計中管道壓力隱患問題仍然需要改善。雖然一些爆炸和腐蝕不會發(fā)生在咖啡機(jī)上，但蒸汽泄露時有發(fā)生，應(yīng)該盡力避免?？Х葯C(jī)的一些元器件的質(zhì)量差，不利于長期安全的使用，需要對其進(jìn)行一些改進(jìn)和提升。
1、引言
本研究的目的主要是評估某型咖啡機(jī)在異?；蛘卟徽２僮鞯臅r候是否能正常實現(xiàn)其設(shè)計功能和工作過程中是否安全兩個方面。首先，將整個咖啡機(jī)系統(tǒng)分解為幾個子系統(tǒng)。然后根據(jù)材料特點、結(jié)構(gòu)和工作環(huán)境條件分析每個單元可能的故障模式。在此基礎(chǔ)上，推斷出由元件組成的器件會出現(xiàn)何種失效模式以及失效后的影響，并通過模擬實驗加以驗證。最后，根據(jù)器件分析結(jié)果評估整個咖啡機(jī)系統(tǒng)的安全性和可靠性。
2、結(jié)構(gòu)特點和系統(tǒng)功能分析
2.1子系統(tǒng)分類
系統(tǒng)功能的分析和結(jié)構(gòu)上的特點是失效和系統(tǒng)安全評估的基礎(chǔ)。根據(jù)功能特點，咖啡機(jī)可以分為三個相對獨(dú)立的子系統(tǒng)。（1）水循環(huán)系統(tǒng)。這個工作系統(tǒng)是通過供應(yīng)、汲取、加熱與輸出的開放性循環(huán)系統(tǒng)過程構(gòu)成。這個循環(huán)系統(tǒng)通過一下部分構(gòu)成：水庫、流量計、泵、加熱器、三叉管接頭、咖啡泡制杯、熱熔器、安全閥、止回閥及水管等。（2）電氣控制系統(tǒng)。電氣控制系統(tǒng)是咖啡機(jī)的神經(jīng)中樞，它以程控的方式對咖啡機(jī)進(jìn)行自動化控制，包括工作流程控制和誤差應(yīng)急處理等。該部分包括熱電阻（NTC）、恒溫控制器（Themostat）、熔斷器(ThermalCutOff)和蜂鳴器（Beef）等。該處理器涉及到掌握集成電路。電動輔助電路包括電容，電阻，電感，三極管，三電壓調(diào)節(jié)器，變壓器，導(dǎo)線和插件版。（3）外殼結(jié)構(gòu)體系。殼體結(jié)構(gòu)系統(tǒng)由前殼、后殼、底盤、蓋和骨架組成，發(fā)揮支撐和防護(hù)的功能。
2.2工作過程分析
水循環(huán)系統(tǒng)的工作過程對咖啡機(jī)至關(guān)重要。在一些測試資料的基礎(chǔ)上，我們可以初步推斷水循環(huán)的工作過程，如圖1所示。當(dāng)泡制7盎司的咖啡時，首先開機(jī)后，加熱器開始預(yù)熱，溫度升高到65攝氏度左右，電磁擺動泵開始工作，水通過流量計抽到加熱器中進(jìn)行加熱。加熱后的水從出水口處流出。當(dāng)流量計計算出到達(dá)指定7盎司的水量時，泵停止抽水，加熱器中的存水被繼續(xù)加熱至沸騰，水煮沸成蒸汽從出水口噴出。如果出現(xiàn)管路蒸汽壓力過大，安全閥開啟，多余蒸汽排在底盤內(nèi)。如果由于冷卻作用等原因，蒸汽壓力低于一個大氣壓時，止回閥開啟，將外界空氣抽回至水循環(huán)系統(tǒng)內(nèi)，以此來保持水循環(huán)系統(tǒng)蒸汽壓力的穩(wěn)定。這種設(shè)計構(gòu)成了咖啡機(jī)的壓力危險防護(hù)體系。
圖1 水循環(huán)系統(tǒng)總圖
2.3過熱危險防護(hù)方法
過熱可能是咖啡機(jī)燃燒和爆炸的主要原因。該咖啡壺過熱防護(hù)主要分為三個等級（圖2）I級危險的保護(hù)是由兩個熱電阻并聯(lián)而成。Ⅱ級和Ⅲ級溫控器是一種熱切斷。
當(dāng)加熱器的內(nèi)腔或加熱器的出口溫度過高時，熱電阻發(fā)生作用，系統(tǒng)中斷工作。恒溫控制器由強(qiáng)電控制。當(dāng)加熱管過熱時，溫控器工作，切斷加熱器電源，保證水泵安全。當(dāng)加熱器溫度恢復(fù)正常后，溫控器將重新連接電源。熱切斷是最高的安全等級保護(hù)，在前兩級未能起到作用的情況下，當(dāng)加熱器超過臨街溫度時，熔斷器將切斷全系統(tǒng)的供電。
圖2 咖啡機(jī)過熱防護(hù)體系
3、安全性評估
3.1 失效模式與影響分析
FMEA是一種定性的危險分析方法，是從元器件的失效開始，逐次分析其失效對人員、操作及整個系統(tǒng)的影響和可能產(chǎn)生失效的原因?？Х葯C(jī)水循環(huán)系統(tǒng)及部分元器件的失效模式見表1。
3.2 故障樹分析
故障樹分析的特點是直觀、明了，思路清晰、邏輯性強(qiáng)，可以做定性分析，也可以做定量分析。體現(xiàn)了以系統(tǒng)公曾方法研究安全問題的系統(tǒng)性、準(zhǔn)確性和預(yù)測性，它是安全系統(tǒng)工程的主要分析方法之一。
在對FMEA失效模擬的基礎(chǔ)上，確定咖啡機(jī)最有可能的失效為高溫高壓水蒸汽的泄漏和漏電，繪出故障樹圖3和圖4。
圖3 高溫高壓水蒸氣泄漏
圖4 咖啡機(jī)漏電
4、模擬實驗及分析
失效模擬實驗室通過對各類主要器件的失效模擬，驗證FMEA的結(jié)論，找出設(shè)計中的未知缺陷。它是一種最接近實際情況的測試方式。本報告主要針對水循環(huán)系統(tǒng)和電氣信息輸入系統(tǒng)中的主要器件進(jìn)行失效模擬，這些失效都是在實際使用中容易出現(xiàn)的情況。
4.1 奶油熱熔器出口堵塞
這種堵塞經(jīng)常發(fā)生在實際使用中。如果不小心把咖啡粉放入奶油熱熔器中，這時熱熔器出水口會被堵塞，壓力危險防護(hù)體系啟用，水通過減壓管路，最終流出到杯中。然而由于此時熱熔器中盛滿熱水，導(dǎo)致頂蓋在壓力作用下不能立即開啟，使用者有可能強(qiáng)行開啟造成燙傷。試驗表明，這種堵塞也會發(fā)生在出水管路。
4.2 排水閥堵塞
如果有水垢沉淀堵塞位于底盤中的安全排水口，或因彈簧腐蝕斷裂等原因?qū)踩钊ㄋ?，都會出現(xiàn)模擬試驗的失效情況。試驗過程中系統(tǒng)運(yùn)行正常，排水口堵塞的膠布凹陷，由此可見安全管路只有在壓力較大時才會開啟。雖然這種失效對系統(tǒng)正常工作影響不大，但會導(dǎo)致水循環(huán)系統(tǒng)壓力危險防護(hù)喪失功能，且不易被人發(fā)現(xiàn)，有可能導(dǎo)致管路因壓力急劇升高而破裂，從而引發(fā)高溫水蒸汽的快速泄漏，對人造成燙傷或觸電等傷害。因此該安全閥堵塞問題值得關(guān)注。
4.3 止回閥泄漏
試驗?zāi)M了止回閥泄漏失效，對于加熱器出水管路任一點泄漏均適用。元器件在高溫高壓的蒸汽環(huán)境下有可能發(fā)生老化和熱熔而導(dǎo)致此類泄漏。一旦發(fā)生失效故障，出水管路中的泄漏點流出有可能早恒電氣系統(tǒng)短路和燙傷。因此這一類泄漏是比較危險而又比較容易發(fā)生的失效。止回閥壓力保護(hù)的一個重要功用是減輕系統(tǒng)的壓力負(fù)擔(dān)。與咖啡機(jī)內(nèi)泄漏不同的是，由于止回閥進(jìn)氣端直通外殼前擋板，如果其反向?qū)?，高溫高壓水蒸氣會直接?dǎo)出咖啡壺，有可能造成人員的嚴(yán)重傷害，因此止回閥的質(zhì)量非常值得關(guān)注。
4.4 1＃、2＃熱電阻同時置換模擬實驗
本試驗檢測了1＃和2＃熱電阻同時失效后，溫度危險防護(hù)系統(tǒng)的工作親狂。在1＃和2＃熱電阻同時失效后，恒溫器應(yīng)承擔(dān)起二級過熱防護(hù)的功能，加熱器在干燒過程中達(dá)到臨界溫度后，恒溫器切斷總電源。在模擬試驗過程中雖然最終恒溫器發(fā)揮了作用切斷了電源，但熱電阻保持架在低于正常工作溫度下就發(fā)生了嚴(yán)重的熱熔變形和穿孔失效，導(dǎo)致整個水循環(huán)系統(tǒng)發(fā)生泄漏，其質(zhì)量應(yīng)引起高度關(guān)注。如圖5,和圖6所示。
保持架和三通采用PP塑料，PP塑料具有良好的硬度，韌性，高的熱電阻溫度，良好的抗疲勞性能，優(yōu)良的化學(xué)穩(wěn)定性和抗氧化性。耐熱溫度高，為110攝氏度~120攝氏度，無外力作用時可達(dá)150攝氏度。通過觀察發(fā)現(xiàn)，熱電阻保持架與三通所用材料雖然相同，但可以觀察到熱電阻保持架的顏色為不透明乳白色，而三通的顏色為半透明的米黃色，此外熱電阻保持架表面比三通表面加工粗糙，熱電阻保持架材料強(qiáng)度明顯低于三通，這些現(xiàn)象說明二者在制備工藝的質(zhì)量控制上存在著很大的差距。所以說熱電阻保持架等同質(zhì)器件作為加熱管路中的最容易失效的薄弱環(huán)節(jié)，需要得到重視。
沖泡器采用PPS塑料。PPS塑料具有較好的耐熱、阻燃、機(jī)械、耐化學(xué)腐蝕及耐磨性能，尺寸穩(wěn)定性好，比較適合作咖啡機(jī)的外殼結(jié)構(gòu)結(jié)構(gòu)材料。在實驗分析中發(fā)現(xiàn)，下蓋安裝螺絲釘存在分層脫落，如圖7所示，但其原因可能是由于下蓋采用環(huán)保的再生PPS塑料制備或制備工藝控制不當(dāng)所致。如果采用合理的制備技術(shù)，提高材料質(zhì)量，能夠保證咖啡機(jī)的安全可靠性。
5、分析和探討
根據(jù)測試和分析的結(jié)果，該咖啡機(jī)基本可以滿足所要求的功能，但個別元器件還是存在安全隱患，將具體描述如下，需要進(jìn)一步的提高。
5.1 設(shè)計因素
設(shè)計上出現(xiàn)問題是比較嚴(yán)重和不可接受的，必須加以改進(jìn)。通過試驗與分析，可知該咖啡機(jī)在設(shè)計方面存在的主要問題有：
（a） 加熱管路部分器件結(jié)構(gòu)設(shè)計不當(dāng)。如熱電阻保持架結(jié)構(gòu)比較復(fù)雜，但管路管徑和內(nèi)徑都過小，管壁過薄，容易造成熱熔穿孔或爆裂失效。
（b） 安全減壓管路設(shè)計存在隱患。該咖啡機(jī)的安全減壓管路出口設(shè)計在底盤內(nèi)部。在正常工作過程中，加壓管路并不使用，但在過熱過壓等非正常情況時，加壓管路會快速排泄高溫蒸汽，這些蒸汽從底盤直接排除很有可能造成人員的燙傷。因此，對該管路的設(shè)計還需要進(jìn)一步的考慮，建議排到水容器的冷水中。
（c） 沖泡容器頂蓋中螺孔PPS材料剝層，此處受力較大，又是與金屬密封蓋的唯一連部位，該處的老化或受力剝層可能造成內(nèi)螺栓的脫落，進(jìn)而造成密封蓋的脫落，可能造成熱水的大量泄漏。因此該處為不可忽視的安全隱患。
5.2 加工制造因素
加工質(zhì)量是高品質(zhì)咖啡機(jī)可靠性的重要保證。在本系統(tǒng)內(nèi)電阻保持架的加工質(zhì)量是嚴(yán)重欠缺的，該器件的早期失效導(dǎo)致水循環(huán)系統(tǒng)泄漏，存在燙傷的危害。
5.3 不可預(yù)知因素
使用中出現(xiàn)意外時設(shè)計和生產(chǎn)者無法控制的，只有通過完善的保護(hù)系統(tǒng)來保證在意外發(fā)生時將危害降到最低。這類因素主要指大塊異物進(jìn)入水循環(huán)系統(tǒng)、使用者誤操作等，根據(jù)模擬測試試驗結(jié)果可知，咖啡機(jī)在使用中如果將咖啡粉直接放入奶油沖泡熱熔器，會導(dǎo)致出口的完全堵塞，存在燙傷危害。因此對該器件結(jié)構(gòu)的再設(shè)計是必要的。
6、結(jié)論
（1） 咖啡機(jī)在結(jié)構(gòu)、系統(tǒng)、安全防護(hù)設(shè)計等方面較為合理，總體設(shè)計水平較高，正確使用情況下，短期內(nèi)不會出現(xiàn)嚴(yán)重事故，符合安全設(shè)計準(zhǔn)則。
（2） 咖啡機(jī)的安全保護(hù)系統(tǒng)運(yùn)作良好，在使用中能夠正確處理事故確保安全運(yùn)行。
（3） 咖啡機(jī)發(fā)生燃燒、爆炸等安全爆炸的幾率較小，但存在蒸汽泄漏等需要改進(jìn)的地方。
一些特定元器件的加工質(zhì)量差，將對整個系統(tǒng)產(chǎn)生隱患。
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