通管零件注塑模具設計【一模兩腔】【側抽芯】【說明書+CAD】,一模兩腔,側抽芯,說明書+CAD,通管零件注塑模具設計【一模兩腔】【側抽芯】【說明書+CAD】,零件,注塑,模具設計,說明書,仿單,cad Fundamentals of Manufacturing Accuracy Manufacturing can be defined as the transformation of raw materials into useful products through the use of the easiest and least-expensive methods. It is not enough, therefore, to process some raw materials and obtain the desired product. It is, in fact, of major importance to achieve that goal through employing the easiest, fastest, and most efficient methods. If less efficient techniques are used, the production cost of the manufactured part will be high, and the part will not be as competitive as similar parts produced by other manufacturers. Also, the production time should be as short as possible to enable capturing a larger market share. Modern industries can be classified in different ways. There include classification by process, classification by product, and classification based on the production volume and the diversity of products. The classification by process is exemplified by casting industries, stamping industries, and the like. When classifying by product, industries may belong to the automotive, aerospace, and electronics groups. The third method, i.e., classification based on production volume, identifies three main distinct types of production, mass, job shop, and moderate. Let us briefly discuss the features and characteristics of each type. Mass production is characterized by the high production volume of the same (or very similar) parts for a prolonged period of time. An annual production volume of less than 50 000 pieces cannot certainly be considered as mass production. As you may expect, the production volume is based upon an established or anticipated sales volume and is not directly affected by the daily or monthly orders. The typical example of mass-produced goods is automobiles. Job-shop production is based on sales orders for a variety of small lots. Each lot may consist of 20 up to 200 or more similar parts, depending upon the customers` needs. It is obvious that this type of production is most suitable for subcontractors who produce varying components to supply various industries. The machines employed must be flexible to handle variations in the configuration of the ordered components ,which are usually frequent. Also, the employed personnel must be highly skilled in order to handle a variety of tasks, which differ for the different parts that are manufactured. Moderate production is an intermediate phase between the job-shop and the mass-production types. The production volume ranges between 10 000 to 20 000 parts, and the machines employed are flexible and multipurpose. This type of production is gaining popularity in industry because of an increasing market demand for customized products. A very important fact of the manufacturing science is that it is almost impossible to obtain the desired nominal dimension when processing a workpiece. This is actually caused by the inevitable, though very slight, inaccuracies inherent in the machine tool as well as by various complicated factors like the elastic deformation and recovery of the workpiece and/or the fixture, temperature effects during processing, and sometimes the skill of the operator. Since it is very difficult to analyze and completely eliminate the effects of these factors, it is more feasible to establish a permissible degree of inaccuracy or a permissible deviation from the nominal dimension that would not affect the proper functioning of the manufactured part in a detrimental way. According to the ISO (International Standardization Organization) system, the nominal dimension is referred to as the basic size of the part. The deviations from the basic size to each side (i.e. , positive or negative ) determine the high and the low limits, respectively, and the difference between those two limits of size is called the tolerance. The tolerance is an absolute value without a sign. As you may expect, the magnitude of the tolerance is dependent upon the basic size and is designated by an alphanumeric symbol called the grade. There are eighteen standard grades of tolerance in the ISO system, and the tolerances can be obtained from the formulas or the tables published by the ISO. It is obvious that smaller tolerances require the use of high-precision machine tools in manufacturing the parts and therefore increase production costs. Before two components are assembled together, the relationship between the dimensions of the mating surfaces must be specified. In other words, the location of the zero line to which deviations are referred must be established for each of the two mating surfaces. This actually determines the degree of tightness or freedom for relative motion between the mating surfaces. There are basically three types of fits, namely, clearance fit, transition fit, and interference fit. In all cases of clearance fit, the upper limit of the shaft is always smaller than the lower limit of the mating hole. This is not the case in interference fit, where the lower limit of the shaft is always larger than the upper limit of the hole. The transition fit, as the name suggests, is an intermediate fit. According to ISO, the internal enveloped part is always referred to as the shaft, whereas the surrounding surface is referred to as the hole. Accordingly, from the fits point of view, a key is referred to as the shaft and the keyway as the hole. There are two ways for specifying and expressing the various types of fits, the shaft basis and the hole basis systems. The location of the tolerance zone with respect to the zero line is indicated by a letter, which is always capital for holes and lowercase for shafts, whereas the tolerance grade is indicated by a number, as previously explained. Therefore, a fit designation can be H7/h6, F6/g5, or any other similar form. When the service life of an electric bulb is over, all you do is buy a new one and replace the bulb. This easy operation, which does not need a fitter or a technician, would not be possible without two main concepts, interchangeability and standardization. Interchangeability means that identical parts must be interchangeable, i.e. , able to replace each other, whether during assembly or subsequent maintenance work; without the need for any fitting operations. As you can easily see, interchangeability is achieved by establishing a permissible tolerance, beyond which any further deviation from the nominal dimension of the part is not allowed. 影響加工精度的基本因素 制造業(yè)可以看作是通過使用最簡便、最便宜的方法，把原材料轉化為有用的產品的方法，但這顯然還不夠準確,它應該是通過對原材料的加工,進而獲得所期望得到的產品。 實際上，通過采用最簡單、最快捷和最有效的方法來達到目標是非常重要的。 如果不能采用先進而有效的方法來加工，則產品的制造費用將增高，在與其他類似的產品制造商競爭時產品將會變得沒有競爭力。 此外, 為了獲取更大的市場份額，產品生產的時間也應盡可能短。 現(xiàn)代工業(yè)可以使用很多不同的方法來分類，包括按加工方式分類，按產品的類型分類，按產品生產的數(shù)量和產品的差異性分類。按產品的加工方式來分類，在鑄造行業(yè)及沖壓行業(yè)中被廣泛采用。而按產品的類型來分類的方法，則主要在汽車制造業(yè)、飛機制造業(yè)及電氣業(yè)中采用。第三種方法,即按產品的生產量來分類的方法，確定了三種主要的生產方法：大批量生產、單件小批量生產、中批量生產。下面讓我們來詳細的討論每種生產方式的特點。 大批量生產的特點是長時間的生產同一種（或者非常類似的）產品，如果一件產品的年生產量小于50000件則不能被視為大批量生產。正如你所能想到的，產品生產的數(shù)量是根據(jù)一個既定或預期的銷售數(shù)量來決定的，而不是由一天或一個月的訂單量來決定。一個典型的例子就是汽車的大規(guī)模生產。 單件小批量生產主要是按種類多而批量小的銷售訂單來生產，每個批量在20件到200件或者更多，主要決定于客戶的需求。顯而易見，這種類型的生產最適合分包商，生產不同的零件來供應各類不同的行業(yè)需求。所采用的機器必須具有足夠的柔性，以適應按訂單生產的零件的外形變化，而這種變化是經(jīng)常發(fā)生的。另外，操作機器的工人也必須掌握比較高的技術水平，這樣才能成功的完成各種不同的任務，加工不同的零件。 中批量生產是介于大批量生產和單件小批量生產之間的一種類型，生產量介于10000至20000件之間，而采用的機器也必須很靈活和多功能化。由于按客戶需求制造的產品的市場日益增長，這類類型的應用越來越多。 在制造科學中，有一個非常重要的事實是：加工一個工件時要想獲得理想的名義尺寸幾乎是不可能的。其實，雖然誤差可能非常的小，但這是不可避免的，因為很多復雜的因素造成機器上的刀具存在有固有的誤差。比如工件的彈性變形及其回彈，又或者工件的裝夾、加工過程中溫度的影響，有時還包括操作人員的操作技能。由于準確的分析并完全消除這些因素的影響是非常困難的，于是在名義尺寸之上建立一個允許的誤差或允許的偏差范圍更為可行，而這也不會影響工件的正常運作。按照ISO (國際標準化組織)體系，公稱尺寸被稱為零件的基本尺寸，從基本尺寸向每一側的偏差（正或負）分別決定了上限和下限，而二者之間的差值稱為公差。公差是一個沒有標志的絕對值，正如你可以想到的，公差的大小決定于基本尺寸的大小，而由一個指定的字母數(shù)字符號來表示，稱為等級。在ISO質量管理體系中，一共設有18個標準等級，公差可從公式算出或從ISO出版的表中查出來。顯然，公差較小的零件需要利用高精密機床來制造，而由此會導致產品成本的增加。 在兩個零件組裝在一起之前，尺寸的配合關系必須指定。換句話說，必須在兩個尺寸之間指定零線的位置。這其實是確定兩個物體配合的緊密或能自由運動的范圍?；旧峡梢苑譃槿N配合，即間隙配合，過渡配合，過盈配合。在所有的間隙配合中，軸的上極限尺寸常常比與其配合的孔的下極限尺寸還小；這與過盈配合不同，在過盈配合中軸的下極限尺寸通常比孔的上極限尺寸大；過渡配合,顧名思義,是一個中級的配合。按國際標準化組織的規(guī)定，被包圍在里面的部分常稱之為軸，而包圍的表面則稱之為孔。因此，從配合的觀點來說，鍵被稱為軸，鍵槽被稱為孔。 有兩種方式來指定和表示各種不同的配合，基軸制和基孔制。公差帶相對于基準線的位置是用一個字母來表示的，總是用大寫字母表示孔，用小寫字母表示軸；而公差等級則如前所述用數(shù)字表示。正如先前解釋的， H7/h6，F(xiàn)6/g5都是正確的表示方式，其他類似的形式也是對的。 當一個電氣部件的使用壽命結束時，所有你能做的就是去買一個新的來代替它。這是一件非常容易的事情，不需要任何鉗工或技術員，然而如果沒有兩個概念：互換性和標準化，這一切將不可能?；Q性意味著在相同的零件之間必須能夠進行互換。無論是在裝配時還是在其后的維修中，這些零件都可以互相取代而不需任何修配工作。你不難看出,互換性是通過建立一個允許的公差來達到目的的，然而任何超過范圍的基本尺寸的偏差都是不允許的。 7