<P><FONT face="Arial Unicode MS"><FONT size=3><B>2. The quantifiable attributes</B> </FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>可量化性能</FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>The quantifiable attributes are usually found in the specification of a PIMM. They should be considered together instead of individually in considering a selection. The significance of each is explained below. In short, this section steps the readers through how to read a PIMM's sspecification table. </FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>这些性能可以从注塑机的规格说明获得，选择时应综合考虑，且勿单一分割。每一项的意义将在以下叙及。简言之，这部分将引导读者如何去阅读注塑机的说明书。</FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>Most quantifiable attributes in a specification table are the maximum the machine is capable of. If so, a value at or below the maximum could be used. Table 1 lists the quantifiable attributes and whether they are specified as a maximum in a specification table. </FONT>
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<P><FONT face="Arial Unicode MS" size=3>说明书上的大多数可量化性能指标指的是注塑机的最大能力。因此，小于或等于该值是可用的。表1列出的是说明书中的可量化性能以及是否指定为最大值。</FONT></P>
<P><FONT face="Arial Unicode MS"><FONT size=3><B>2.1 Shot weight</B> 射出重量</FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>Shot weight is an important attribute of the injection unit of a PIMM. Expressed in ounces or grams, this is by far the most commonly used single attribute to select a plastic injection moulding machine. It is not unreasonable to say that it has been abused. </FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>射出重量是注塑机注射单元中非常重要的性能，单位是盎司(ounces)或克(g)，这是迄今为止选择PIMM最普遍的性能。说它过时是没道理的。</FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>The reason is simple. A moulder has an article at hand to be moulded. Once the plastic material is selected, it has a weight. A PIMM with sufficient shot weight is then selected. </FONT>
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<P><FONT size=3></FONT></P><FONT size=3>原因很简单，任何产品都有重量，因此要选择有足够注射量的PIMM。</FONT>
<P><FONT face="Arial Unicode MS"><FONT size=3><B>2.1.1 Definition of shot weight</B> 射出重量的定义</FONT>
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<P><FONT face="Arial Unicode MS"><FONT size=3>The shot weight is the measured (therefore actual) weight of the plastic 'injected' when the nozzle is free- standing (not held against the mould). The plastic used is usually polystyrene with a specific gravity (S.G.) of 1.05. This is specified in the specification as PS. </FONT>
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<P><FONT size=3></FONT></P><FONT size=3>射出重量是指射出的塑料的实际重量，通常规范使用的塑料为比重1.05的PS。</FONT>
<P><FONT face="Arial Unicode MS"><B>2.1.2 Shot weight in terms of the resin to be used</B> 按使用树脂定义的射出重量<p></p></FONT></P>
<P><FONT face="Arial Unicode MS">If the article to be moulded is made of a resin different than PS, then the shot weight in the specification could not be used immediately, but must be calculated as follows: <p></p></FONT></P>
<P><FONT face="Arial Unicode MS">如果模塑的材料非PS，说明中射出重量不能直接使用，须做如下转换：<p></p></FONT></P><PRE><FONT size=2><FONT face="Arial Unicode MS">Shot weight in terms of a resin = c * b/1.05<p></p></FONT></FONT></PRE><PRE><FONT face="Arial Unicode MS" size=2>where b = S.G. of the resin,</FONT></PRE><PRE 17.25pt"><FONT size=2><FONT face="Arial Unicode MS">c = shot weight in terms of PS (S.G. = 1.05)<p></p></FONT></FONT></PRE><PRE><FONT size=2><FONT face="Arial Unicode MS">射出重量＝C*b/1.05<p></p></FONT></FONT></PRE><PRE><FONT size=2><FONT face="Arial Unicode MS">其中 b＝使用树脂的S.G.，c＝按PS计算的射出重量<p></p></FONT></FONT></PRE>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">Table 2 lists the S.G. of some common resins. <p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">表2列出一些常用树脂的比重<p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">Example 1: POM has an S.G. of 1.42. It is to be moulded in a PIMM with a shot weight of 8 oz (in PS). This machine has a shot weight of<BR>8 * 1.42 / 1.05 = 10.8 oz of POM. <p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">例1：POM比重为1.42，注塑机的射出重量为8oz(PS),这台设备POM的射出重量为8 * 1.42 / 1.05 = 10.8 oz<p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">Example 2: PP has an S.G. of 0.86. It is to be moulded in a PIMM with a shot weight of 8 oz (in PS). This machine has a shot weight of<BR>8 * 0.86 / 1.05 = 6.6 oz of PP. An 8 oz. (in PS) PIMM would not have provided the capacity needed by 8 oz. of PP. <p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">例2：PP比重为0.86，注塑机的射出重量为8oz(PS),这台设备POM的射出重量为8 * 0.86 / 1.05 = 6.6 oz，所以8oz(PS)的注塑机不能满足8oz的PP的需求。<p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS"><B>2.1.4 Selecting a machine with sufficient shot weight</B> 选择足量的注塑机<p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">Shot weight should not be equal to the combined weight of the article (or articles for a multicavity mould) plus runners that could be injection moulded. The latter is set at 85% of the shot weight for articles with low requirement, e.g. figurines; 75% of shot weight for articles with high requirement, e.g. crystal parts. The discrepancy is due the much higher injection pressure when there is a mould. High requirement moulding uses high injection pressure. </FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">Example 3: Figurines made of UPVC (S.G. 1.38) with a combined weight of figurine plus runners of 4 oz. are to be moulded. What size of machine is sufficient? </FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">Shot weight in terms of PS = 4 * 1.05/1.38 = 3.04 oz. Using the 85% guide line, the machine shot weight needed = 3.04/0.85 =3.58 oz. <p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">射出重量不等于制品与流道重量的总和，后者的设定，对低要求的制品，为射出重量的85%，对要求高的制品，为射出重量的75%，其差别在于模内较高的注射压力，高要求的模塑需要较高的射出压力。<p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">例3：UPVC比重1.38，制成的制品总重4oz。多大注塑机是足够的？<p></p></FONT></P>
<P 0in 0in 0pt"><FONT face="Arial Unicode MS">以PS计算的射出重量=4 * 1.05/1.38 = 3.04 oz.以85%为准则，要求的注塑机射出重量＝3.04/0.85 =3.58 oz<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman"><B>2.1.5 Selecting a machine which is not too big</B> </FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">An injection moulding machine of a specified shot weight can be used to mould article(s) including the runners weighing from 35% to 85% of the shot weight. The lower limit comes from bending on the platens, barrel resident time of the resin and electric power consumption per kg of processed material. <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">指定重量的注塑机可以模塑制品的范围是其射出重量的35%~85%，下限源于模板的弯曲，料筒的滞留时间和每公斤材料消耗的电能。<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">A small article using a small mould puts undue bending on the mould platens, causing them to deflect (which affects product quality), and to break in the extreme. <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">小的模具至于不合适的模板会引起变形，甚至会断裂。<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">If a big machine is used to mould small articles, the melt in the barrel could degrade due to unduly long residence time. Barrel residence time could be estimated as follows. <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">若用大机模塑小制品，材料会因长的滞留时间而引起降解。料筒滞留时间可从如下估计：<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Barrel residence time =<BR>(weight of melt in barrel * cycle time) / (actual shot weight) <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Weight of melt in the barrel is estimated to be the weight in two times the injection volume. <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">料筒滞留时间＝(料筒中熔体重量*周期)/(实际射出重量)<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">料筒中熔体重量估计为射出容积的2倍。<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Moulding small parts with a big machine is inefficient in energy usage per kg of material processed, also known as specific power consumption. <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">大的机器成型小的产品其实是能量的浪费。<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Example 4: The same figurine in example 3 is to be moulded in a big machine. What is the biggest machine that could be used? </FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Using the 35% rule, the biggest machine that could be used has a shot weight = 3.04/0.35 = 8.7 oz. <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">例4：同例3中的产品，要用大的机器成型，最大可用多少？<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">按35%的原则，可用最大注塑机的射出重量：3.04/0.35 = 8.7 oz.<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Example 5: What is the residence time of UPVC (S.G. 1.38) in a machine with screw diameter of 55 mm, injection stroke of 250 mm, shot weight (PS) of 567 g, and a cycle time of 10 s moulding shots weighing 260 g? </FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Volume of melt in the barrel is estimated to be two times the injection volume = 2 * 3.1416 * 5.5 * 5.5 * 25 / 4 = 1188 cm3 </FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Barrel residence time = 1188 * 1.38 * 10 / 260 = 63 s <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">例5：注塑机螺杆直径55mm，注射行程250mm，PS射出重量是567g，原材料为UPVC（SG为1.38），周期10s，模塑制品重量260g.求其滞留时间？<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">料筒中熔体体积估计为2倍的射出体积＝2 * 3.1416 * 5.5 * 5.5 * 25 / 4 = 1188 cm3 ，料筒滞留时间＝1188 * 1.38 * 10 / 260 = 63 s。<p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">Having multicavities per mould to increase the articles' weight and to increase the mould size are solutions to using bigger machines. Alternatively, lowering the barrel temperature would help avoid degradation due to long residence time. <p></p></FONT></P>
<P 0cm 0cm 0pt"><FONT face="Times New Roman">对大的注塑机，可使用多模腔或大模腔提高制品总重，或降低料筒的温度。</FONT><p></p></P>
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