| The safety design of machine is to adopt the advanced safety techniques, identifying, analyzing and evaluating the mighty danger from the inner construction of the machine, in order to control any mighty incident and extend the machine's life span. The safety design, consisting of safety analysis, safety evaluation and safety design, is a systematic project, which makes the quality and quantity analysis to the factors that possibly cause danger, in order to figure out the optimum design scheme with minimum risk. 1 The safety goal and requirement for the engine crankshaft's mechanical manufacturing system design. The ideal safety system must be able to insure that all the functions can be carried out normally under the conditions illustrated in the manual, and make sure no damage to people or the machine system will happen in any section during its life span, including transportation, installation, adjustment, use and maintenance , dismantle and scrap rear handling. And also, it should be safe even if it were operated in a wrong way that can be foreseen. To fulfill the safety requirement in all sections during its life span, we should put forward safety request to every section before the engine crankshaft's mechanical manufacturing system safety design. For example, when the system runs smoothly, the high-speed revolving parts in the system should be in a stage of static balancing and dynamic balancing when it comes to operation, the hand-controlling structure should be convenient to handle and should keep hands away from the other machine parts and machine bed; during the process installing clips, the clip devices should enable operators to work beyond the reach of the dangerous parts; when it is necessary to repair any part, the mechanical manufacturing equipment, along with its subsidiaries should satisfy the dismantling requirement. 2 The safety-risk evaluation of the engine crankshaft's mechanical manufacturing system. The process of this evaluation divides into two stages. The first stage was named risk analysis. On the basis that we've already known the safety goal and requirement, we should now check and find out the shortage compared to the formal target and request by analyzing its main sub-system and the whole system. The second stage is risk evaluation. Here we evaluate the goal and the requirement according to the risk analysis. 2.1 The elementary risk analysis We can catalogue the engine crankshaft's mechanical manufacturing system in terms of craft equipment as below: cut subsystem, grinding subsystem, turning subsystem, milling subsystem, the subsystem of heat treatment and other subsystems. The elementary risk analysis includes the damage form and risky status of the sub-system's revolving parts, back-and-forth parts, passing parts, liquid-pressure system, cooling-off system, clip system, electrical system, etc. Thus we conclude that back-and-forth parts, revolving parts and cooling-off parts in the systems have rather great possibility to suffer from danger, which is in need of further risk evaluation. . 2.2 Risk evaluation We apply scoring method to the further analysis of the engine crankshaft's sub-system, concluding that: grinding in high danger badly need improvement. In the same way we make an elementary quantity analysis of the back-and-forth parts, revolving parts and cooling-off parts, the result of which indicates that revolving parts exist safety problem, requiring for another further analysis.Among the grinding system's revolving parts the emery wheels run at the highest speed. Take an example for the accident caused by the smashed emery wheel of the grinding-bed system, we apply so-called incident tree to make quality and quantity analysis。According to the quality analysis of the ordinary emery wheel hurting incident in the incident tree acquire the important sequence of the basic incident's structure. the protection device's invalidity is the most basic incident, fixing pressure is too much and flange plate is too little,, the hole of emery wheel and axle gap exceptional , the working table of emery wheel is wrong, feed exceptional and feed speed exceptional, the specified operation and work piece of rotational speed that exceeds emery wheel pack lined unsuitable is the second important, the specifications of emery wheel model option unsuitable and flange plate is too little, the hole of emery wheel and axle gap exceptional , the working table of emery wheel is wrong, feed exceptional and feed speed exceptional , the specified operation and workpiece of rotational speed that exceeds emery wheel pack lined unsuitable is the second important, in adequate examination to the emery wheel is the third important, the quantity problem of the emery wheel, serious moist, split of split because of shaking is the forth important. Through quantitative analysis reach the incident to occur on top probability explains for perfect protective structure grinding machine per working hour the possibility of incident that wound personnel is 0.000007172 times per hour. We know then if the protection device goes invalid, the possibility is 0.01793 per hour, as is 2500 times higher than that in the protection device's perfect condition. This further indicates that whether the protection device is invalid plays a very important role in the safety aspect.3. The safety measure design The purpose of the system's risk analysis and risk evaluation is to support the safety measure. Any danger may happen to the operator during the cause of transportation, installation, adjustment, use and maintenance, and dismantle。Hence, what safety measures should we take to avoid or reduce such danger to insure people's health and safety? The designer should follow the following three aspects: reduce risk through the design process, design safety protection device and make use of message that informs and warns users or operators the possible risks. According to the risk analysis of the engine crankshaft's mechanical manufacturing system in Chap.3 we know that whet sub-system in the system owns high possibility of danger, and yet the most basic way to insure the sub-system safety relys on the protection devices. Therefore, as long as we high-level the dependability of the protection devices, the safety of the emery wheel can be effectively improved consequently. As a result, all the emery wheels in the whet sub-system should be equipped with protection devices. And the devices should be in proper dimensions and fixed tightly, which is forbidden to dismantle and discard randomly. To apply the dependable protection device to grinding sub-system is a way to reduce the accident happening to the engine stalk's mechanical manufacturing system. Similarly, dependable devices should be applied to turning and milling system. In the process, with proper marching speed, marching quantity and right-position clipping, it can reduce the possibility of the accident. All these are requirement to the workers. So if the capital allows, to bring in mass numerical control machine beds can be considered as an advisable idea to keep in breast with the high-tech development currency. Besides, to strengthen the skill training and safety education is another wayto lower the mistakes and possibility of incidents. The safety system engineering principle is applied in this essay to introduce and study safety design of the mechanical manufacturing system, and further put forward a comparably perfect safety method to design the engine stalk's mechanical manustructuring system, which therefore has certain referring values for the safety system engineering in the practical production of the processing industry. |
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