水电厂进水口闸门单吊液压启闭机设计含CAD图
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附录一11.2.2 进行成本估计工程师的责任是知道设计组件的制造成本。能够使这些估计与经验和帮助来自经验丰富的团队成员和供应商。在许多公司成本估计是通过专业专攻确定组件的成本是否在房子或从供应商购买。这个人必须在他或她的尽可能准确的估计, 关于产品的重大决策都是基于这些成本。成本估计需要很详细的信息来执行他们的工作。是不现实的设计师给成本估计 20 概念设计草图,并期望任何形式的合作。在大多数小公司,成本估计都是由工程师来完成。第一估计应该在产品设计的早期阶段,足够精确的决策中使用哪些设计消除继续精炼的考虑和设计。在这个阶段的过程中,最后直接成本在成本估计的 30% 是可能的。我们的目标是让这个估计提高设计的准确性向最终产品精制。初步估计越准确，更有估计类似产品的经验。成本计算过程取决于产品中的组件。获取组件有三种可能的选择:从供应商购买成品,有一个供应商生产组件设计的房子,或制造组件的房子。正如 Chap.9 中讨论的,有强大的动力去从供应商购买现有组件。如果购买的数量足够大,大多数供应商将与产品设计师修改现有的组件,以满足新产品的需求。如果现有的组件或修改组件不可用,然后他们必须生产,在这种情况下,必须做出决定是否应该由供应商或制造的房子。这是典型的制造或购买的决定,一个复杂的决定,是基于组件的成本涉及广告设备的资本,投资生产人员,公司计划在未来使用类似的制造设备。无论组件制造或购买,成本估算是至关重要的。我们现在有两个主要制造工艺成本估算:加工和注塑。11.2.3 机加工零部件的成本加工生产的组件是去除不想要的部分材料。因此,加工成本主要是依赖于材料的成本和形状,如何准确删除材料的数量和形状,这三个领域可以进一步分解成七个重要的控制因素,确定加工成本的组件:1. 从组件要加工什么材料?材料影响成本在三个方面:原材料的成本,产生的废料的价值,可以加工的材料。前两个是直接材料成本,最后影响加工的劳动量，加工的时间，选择制造组件的机器。2. 什么类型的机器是用来生产的组件?机床的类型,水平,垂直,所以使用什么机器在影响组件的成本。对于每种类型,不仅是机器时间本身的成本,还需要的工具和设备的成本。3. 组件的主要维度是什么?这个因素有助于确定需要多大类型的机器生产的组 件。每台机器在一个生产设备都有不同的使用成本,根据机器的初始成本和它的年龄。4. 有多少加工表面,材料要删除多少?只知道表面的数量和材料移除率(最终组件体积之比初始体积)可以帮助给予机器使用时间的一个好的估计。估计更准确需要知道什么将用于每个削减加工操作。5. 组件数量的多少?一批组件的数量对成本有很大的影响。很小一块夹具,几块简单的装置长时间设置和调整是必需的。高容量,生产过程自动化,广泛的夹具和数控加工。6. 需要哪些尺寸和表面装饰?更严格的公差和表面光洁度要求,需要更多的时间和设备制造。7. 机械师的劳动率是什么?举一个例子,这七个因素如何影响机加工零部件的成本,考虑 Fig.11.6 中的组件,这个组件的七个重要的影响因素是成本1. 材料是 1020 低碳钢。2. 主要制造机是一种车床。两个额外的机器需要用来磨平表面和钻洞。3. 主要长度尺寸是直径57.15 毫米和100 毫米。最初的原材料必须大于这些维度。4. 有三个表面和其他七个表面。最后一个组件是大约 32%的体积。5. 讨论了组件的数量,在接下来的段落。6. 在不同的表面组件的容忍度不同。名义上的是在大多数表面,但是在直径,这是一个配合公差。表面光洁度,8 度被认为是中间。7. 使用的劳动率是每小时 35 美元;这包括开销和附加福利。图 11.7 显示了该组件的成本为各种生产卷。每个组件值总生产成本。材料/ 组件的成本仍然相当恒定在 1.48 美元,但劳动小时数,因此体积的劳动力成本下降。因为使用计算机辅助制造,凸轮。加工零部件,成本依赖体积很小数量超过10。制造成本的依赖在其他变量如表 11.1 所示,在宽度、完成,材料是多种多样的。前三行显示的变化与宽度。宽度是罚款用于数据在图 11.7 和 1 号线所示。宽度是放松的名义(2),然后粗糙(3),成本下降。第四和第五行显示表面光洁度对生产成本的影响。图纸中指定 Fig.11.7 中的数据是基于一个中间表面光洁度,。这是改善(4),生产成本上涨,这是减少到(5),成本大幅下降。表 11.1 所示是改变材料的影响从低碳钢、高碳钢(6),双打的成本相比,1 号线部分原因是材料成本的增加(+ 4.00 美元)和增加加工时间。11.2.4 生产出成型组件的成本最受欢迎的大容量产品的制造方法可能是塑料注射成型。在组件的形状,生产数量超过 10000,id 通常成本效益上这种方法有很大的灵活性。在粗级别,所有加工组件的影响成本的因素也会影响射出成型组件的成本。唯一的区别是,只有一种类型的机器,一个注塑成型机器,修改关于几何的问题。除了组件的主要维度, 重要的是要知道壁厚和组件复杂性为了确定成型机的大小需要时间组件冷却充 分的弹射机、蛀牙在模具的数量,和模具的成本。展示的影响因素,我们展示一段的费用,Fig.11.8 所示。影响成本的重要因素1. 外形尺寸是 9.46 厘米的模具平面 4.52 厘米和 4.52 厘米深。2. 壁厚为 3.2 毫米。3. 组件生产的数量是 100 万。4. 每小时劳动率是 35 美元。5. 宽容度是中间。6. 表面光洁度不重要。生产成本的组件在图 11.8 中所示图 11.9 不同产量。制作模具的资本成本足够高控制组件的成本较低。这就是为什么生产只有 1000 注塑塑料零件将是非常昂贵的。经验法则是,如果制造体积小于 10000,塑料注塑成本可能是被禁止的。制造成本会影响壁厚。图纸的厚度是 3.2 毫米。如果将图纸的厚度降至 2.5毫米,部分成本将会下降大约 18%。这主要是因为模具冷却所需的时间从 18 秒下降到 13 秒,节省了周期时间。附录二11.2.2 Making a Cost EstimateIt is responsibility of the engineer to know the manufacturing cost of components designed. The ability to make these estimations comes with experience and with help from experienced team members and vendors. In many companies cost estimating is accomplished by a professional who specializes in determining the cost of a component whether it is made in house or purchased from a vendor. This person must be as accurate as possible in his or her estimates,as major decisions about the product are based on these costs. Cost estimators need fairly detailed information to perform their job. It is unrealistic for the designer to give the cost estimator 20 conceptual designs in the form of rough sketches and expect any cooperation in return. In most small companies, all cost estimations are done by the engineer.The first estimations should be made early in the product design phase and be precise enough to be of use in making decisions about which designs to eliminate from consideration and which designs to continue refining. At this stage of the process,cost estimates within 30% of the final direct cost are possible. The goal is to have the accuracy of this estimate improve as the design is refined toward the final product. The more experience one has in estimating similar products,the more accurate the early estimates will be.The cost-estimating procedure depends on the components in the product. There are three possible options for obtaining the components:purchase finished components from a vendor,have a vendor produce components designed in house,or manufacture components in house.As discussed in Chap.9,there are strong incentives to buy existing components from vendors.If the quantity to be purchased is large enough,most vendors will work with the product designer and modify existing components to meet the needs of the new product.If existing components or modified components are not available off the shelf,then they must be produced,in which case a decision must be made as to whetherthey should be produced by a vendor or made in house. This is the classic make or buy decision, a complex decision that is based on the cost of the component involved as well ad the capitalization of equipment, the investment in manufacturing personnel,and plans by the company to use similar manufacturing equipment in the future.Regardless of whether the component is to be made or bought,cost estimates are vital. We look now at cost estimating for two primary manufacturing processes:machining and injection molding.11.2.3 The Cost of Machined ComponentsMachined components are manufactured by removing portions of the material not wanted. Thus, the costs for machining are primarily dependent on the cost and shape of the stock material,the amount and shape of the material that needs to be removed,and how accurately it must be removed.These three areas can be further decomposed into seven significant control factors that determine the cost of a machined component:1. From what material is the component to be machined? The material affects the cost in three ways:the cost of the raw material,the value of the scrap produced,and the ease with which the material can be machined. The first two are direct material costs,and the last affects the amount of labor, the amount of time,and the choice of machines that are used manufacturing the component.2. What type of machine is used to manufacture the component?The type of machine-lathe,horizontal mill,vertical mill,and so on-used in manufacture affects the cost of the component.For each type,there is not only the cost of the machine time itself but also the cost of the tools and fixtures needed.3. What are the major dimensions of the component?This factor helps determine what size of machines of each type will be required to manufacture the component. Each machine in a manufacturing facility has a different cost for use, depending on the initial cost of the machine and its age.4. How many machined surfaces are there, and how much material is to be removed? Just knowing the number of surfaces and the material removal ratio (theratio of the final component volume to the initial volume) can aid in giving a good estimate for time required to machine the part. Estimates that are more accurate require knowing exactly what machining operations will be used to make each cut.5. How many components are made? The number of components in a batch has a great effect on the cost. For one piece,fixturing is minimal,though long setup and alignment times are required. For a few pieces,simple fixtures are made. For a high volume,the manufacturing process is automated,with extensive fixturing and numerically controlled machining.6. What tolerance and surface finishes are required? The tighter the tolerance and surface finish requirements,the more time and equipment are needed in manufacture.7. What is the labor rate for machinists?As an example of how these seven factors affect the cost of machined components,consider the component in Fig.11.6,For this component the seven significant factors affecting cost are1. The material is 1020 low-carbon steel.2. The major manufacturing machine is a lathe. Two additional machines need to be used to mill the flat surfaces and drill the hole.3. The major dimensions are a 57.15-mm diameter and a 100-mm length. The initial raw material must be larger than these dimensions.4. There are three turned surfaces and seven other surfaces to be made. The final component is approximately 32% the volume of the original.5. The number of components to be made is discussed in the next paragraph. 6.The tolerance varies over the different surfaces of the component. On mostsurfaces,it is nominal,but on the diameters,it is a fit tolerance. The surface finish,8 um,is considered intermediate.7.The labor rate used is $35 per hour;this includes overhead and fringe benefits.Figure 11.7 shows the cost of this component for various manufacturing volumes. The values are the total manufacturing cost per component. The cost of materials per component remains fairly constant at $1.48,but the labor hours and thus the cost of labor drop with volume. For machined components,the cost dependence on volume is small in quantities above 10 because of the use of Computer-Aided Manufacturing,CAM.The dependence of the manufacturing cost on other variables is shown in Table 11.1,in which the tolerance,finish,and material are varied. The first three lines show the change with tolerance. A fine tolerance was used for the data in Fig. 11.7 and is shown in line 1. As the tolerance was relaxed to nominal(2) and then to rough(3) ,the cost dropped.The fourth and fifth lines show the effect of surface finish on the manufacturing cost. The data in Fig.11.7 were based on an intermediate surface finish,as specified in the drawing. As this was improved(4),the manufacturing cost rose, and as it was reduced to as turned (5),the cost dropped dramatically. Also shown in Table 11.1 is the effect of changing the material from low-carbon steel to high carbon steel (6) ,which doubles the cost when compared to line 1 in part because of an increase in material cost (+$4.00) and an increase in the machining time.11.2.4 The Cost of Injection-Molded ComponentsProbably the most popular manufacturing method for high-volume products is plastic injection molding. This method allows for great flexibility in the shape of the components and,for manufacturing volumes over 10000,id usually cost effective. On a coarse level,all the factors that affect the cost of machined components also affect the cost of injection-molded components.The only differences are that there is only one type of machine,an injection-molding machine,and the questions concerning geometry are modified. Besides the major dimensions of the component, it isimportant to know the wall thickness and component complexity in order to determine the size of the molding machine needed, the time it will take the components to cool sufficiently for ejection from the machin
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