For the initial portion of the design process, I start my designs with the runner or subrunners that feed the gate(s). First, I need to know the type of material being used and the flow length of the material from where it loses its heat source. In all cases, this location is either the nozzle of the molding machine, a hot tip gate if using a hot runner system, or the orifice in a heated sprue bushing. 

在設(shè)計過程的初始階段，我的設(shè)計從流道或喂料給澆口的分流道開始,。首先,，我要知道塑料的類型以及從塑料離開熱源開始計算的流長。此一熱源或為成型機(jī)的噴嘴,，或為熱流道系統(tǒng)的熱嘴灌口,，或為熱主流道的出口。

Amorphous materials such as polystyrene, SAN, acrylic, ABS, or polycarbonate need bigger runners—based on the wall thickness of the part—than crystalline resins. Crystalline resins include polyethylene, polypropylene, acetal, nylon, and PBT polyester. 

不定形材料如聚苯乙烯,、苯乙烯/丙烯腈共聚物,、聚甲基丙烯酸甲酯(亞克力)、丙烯腈/丁二烯/苯乙烯(ABS)或聚碳酸酯等比結(jié)晶性材料需要較大的流道 – 流道尺寸基于產(chǎn)品壁厚,。結(jié)晶性樹脂包括聚乙烯,、聚丙烯、縮醛,、尼龍和聚對苯二甲酸丁二酯(PBT),。

I also need to know the wall thickness of the part we are going to mold before I can get started. For this exercise we will use a nominal wall of .100 inch and ABS as the material. 

我還需要知道成型產(chǎn)品的壁厚才能進(jìn)行流道尺寸訂定,。且以名義壁厚0.1吋(2.54mm)和塑料ABS做個練習(xí)。

Next, I need to know how many cavities are involved. For this exercise we will calculate the runner sizing for a 16-cavity mold. Each runner level up from the runner that feeds the gate needs to be larger in diameter by .025 to .050 inch. I most often use .025 inch as my incremental number but have used .040 inch when working with metric-based customers. With metric sizing calculations I can make the runner level jumps in multiples of .040 inch and end up with runner sizing of 3, 4, or 5 mm in my final calculations. This metric approach just seems easier to me and I suspect I am drifting towards using millimeter or .040-inch jumps in all of my runner calculations. 

其次,，我要知道模腔數(shù)目,。在此練習(xí)，我們要為一模16腔的流道估算尺寸,。從喂料給澆口的流道溯源而上,，每上一級流道，其直徑增大0.025吋到0.050吋(0.6mm到1.3mm),。我最常用的增量是0.025吋(0.6mm),，但是，當(dāng)客戶采用mm公制時,，我就采用0.040吋(1.0mm)作為增量,。流道尺寸以mm計時，我會使得流道升級為0.040吋(1.0mm)的倍數(shù)而最終獲得3,、4或5mm等整數(shù)流道尺寸,。這種公制作法似乎較為容易，我可能會逐漸更多的采用0.040吋(1.0mm)作為估算流道升級的增量,。

C. Hsu：增量未計及流道長度和下游塑料總重(或總體積),，此為美中不足之處。

A few years ago I attended a seminar where the instructor suggested runner level jumps of .050 inch each. While I find these jumps of .050 inch to work quite well, I prefer to use .025 inch jumps between levels. This increment allows me to size a runner that meets my needs without exceeding an acceptable regrind level (usually less than 25 percent). 

幾年前,，我參加一場研討會,，講師建議流道升級的增量為0.050吋(1.3mm)。雖然,，此一增量0.050吋(1.3mm)滿好的,，我仍然較喜采用0.025吋(0.6mm)作為增量，此一增量0.025吋(0.6mm)可以滿足需求,，還可減少回料的使用,，以免超過一般可以接受的回料重量比25%。

For the .100-inch wall thickness, referring to Table 1 indicates that for ABS material I need a diameter of .225 inch for the subrunner that feeds the gate (fourth-level runner). The basic rule for this calculation is that the runner diameter must be 1.5 times the thickest section of the part. I have found that if this rule is not followed, sinks and voids don’t pack out. 

當(dāng)壁厚是0.1吋(2.54mm)而塑料是ABS時,，參看表1得知喂料給澆口的四級流道的直徑應(yīng)為0.225吋(5.72mm),。此一估算基于：流道直徑必須是產(chǎn)品最大壁厚的1.5倍。我發(fā)現(xiàn)此一規(guī)律若不遵循,，保壓就無法消除縮痕和縮孔,。

Notice that amorphous materials require a larger diameter than the rule calls for. Amorphous materials are more shear sensitive than crystalline materials, so I bump up my sizes 30 to 50 percent when calculating runners for amorphous materials. 

請注意：不定形材料需要比上述規(guī)則訂定的直徑還要大些。不定形材料較之結(jié)晶性材料,，對剪切的敏感度高，所以我會將估算出的不定形材料的流道尺寸加大30到50%,。

C. Hsu：不定形材料的PS,、SAN,、acrylic和ABS的許容剪切速率(1041/s)分別為4.0、3.8,、2.1和1.2,；結(jié)晶性材料的LDPE、HDPE,、PP和PA的許容剪切速率(1041/s)分別為4.0,、6.5、2.4和1.0 (C-MOLD Reference Manual, 32-11-92),。就此看來,，不定形材料對剪切的敏感度不一定比結(jié)晶性材料高。

Now that I have the calculation for the subrunner that feeds the gate, I apply the appropriate diameter from the chart for each of the runner levels heading towards the sprue. The next runner level, number three, is .025 inch larger than runner four, or .250 inch in diameter. Next up is runner two, which is .275 inch, and the main runner is .300 inch. With the runners sized, we now move on to the sprue bushing and nozzle orifice. As we move from the main runner to the sprue O-diameter (small end of the sprue), we double our jump number so we can fit the nozzle orifice size between that of the sprue O-diameter and the main runner diameter. This means we jump .050 inch from the main runner size of .300 inch to a sprue O-diameter of .350 inch. Then we size the nozzle orifice .025 inch smaller than the sprue O-diameter, making the nozzle orifice .325 inch. 

現(xiàn)在已經(jīng)算出喂料給澆口的分流道直徑,，可以從表一找出溯流而上直到主流道的各級流道的合適直徑,。上一級(三級)流道直徑較之四級流道大0.025吋(0.6mm)，也就是0.250吋(6.35mm),。 再上一級(二級)流道直徑是0.275吋(6.99mm)以及一級分流道(main runner)直徑是0.300吋(7.62mm),。各級流道尺寸訂定后，可以訂主流道襯套和噴嘴口徑的尺寸了,。從一級分流道移到主流道的O-直徑(主流道小端直徑)時,，我們將增量加倍使得噴嘴口徑可以在主流道O-直徑和一級分流道直徑之間。 這意味著：0.050吋(1.3mm)的增量加到一級分流道直徑0.300吋(7.62mm)后,，主流道O-直徑應(yīng)為0.350吋(8.89mm),。于是，我們訂噴嘴口徑較之主流道O-直徑小0.025吋(0.6mm)而成為0.325吋(8.26mm),。

Nozzle, Runner Shapes

噴嘴和流道的形狀

With sizing completed, it’s time to consider the type of nozzle that will work best with the material being run. Amorphous materials such as ABS require a full taper nozzle on the molding machine as they do not like or need shear points. Nozzles other than a full taper design cause shear points in the material’s flow path.

尺寸訂定完畢,，是時候考慮噴嘴的類型以優(yōu)化材料的加工。不定形材料如ABS者需要裝一全錐形噴嘴(full taper nozzle)在成型機(jī)上,，因為ABS不喜或不要剪切點,。非全錐形噴嘴造成塑料流路的剪切點。

Shear splay, dark streaks, and other cosmetic defects often seen on molded parts can be traced back to using the wrong style of nozzle. It is also why molding technicians are forced to use higher barrel melt temperatures in their process setups, and we all know that higher barrel melt temperatures can cause longer cycles.

成型品外觀上常見的剪切水花,、暗線條和其他外觀缺陷往往可以歸咎于錯誤形式噴嘴的使用,。這就是為什么成型技工不得不提高料溫試圖消除前述禍患，但是這么做,，周期時間勢必拖長,。

C. Hsu：提高料溫固然可以降低黏度、剪切應(yīng)力,、摩擦生熱和熔膠升溫,，但是提高料溫本身就是熔膠升溫，熔膠升溫到塑料當(dāng)中低分子成分的氣化點時，瓦斯氣和水花(水花是氣痕)就產(chǎn)生了,，熔膠升溫到塑料的燃點時,，暗線條就產(chǎn)生了 --- 提高料溫一刀兩刃，得失難言,，不若擴(kuò)大噴嘴口徑,。

Next, we need to be sure that the runner design is appropriate for the type of gate being used. Figure 1 shows the relationships of flow channels when using different runner designs. 

接下來，我們要確認(rèn)流道設(shè)計對我們采用的澆口類型是適配的,。圖1示出不同的流道設(shè)計被采用時,，流路之間的好壞關(guān)系。

Figure 1. Full-round runners are the best design for any gate, but half-round or trapezoidal runners can be used with subgates.

圖1. 對任何澆口來說,，全圓流道是最好的設(shè)計,，但是半圓或梯形流道也適用于潛伏式澆口。

A full-round runner of the correct diameter is always a good design choice for any type of gate but an absolute requirement for an edge gate. The edge gate also needs to come off the center of the full-round runner and pass through an abrupt transition as it goes through the gate. An edge gate that comes off the side of a full-round runner is considered a high-shear gate and can cause blush on the surface of the part just inside the gate. 

對任何類型的澆口來說,，正確直徑的全圓流道都是最好的設(shè)計,，對邊緣澆口而言，更是絕對的選擇,。邊緣澆口必須出自全圓流道的中心-塑流會經(jīng)歷突然的轉(zhuǎn)變,。邊緣澆口出自全圓流道的邊緣會成為高剪切澆口而在其下游的產(chǎn)品表面生出霧斑。

While full-round runners work well for edge gates, they also work for subgates and three-plate runners where the runners transition into individual drops. 

全圓流道可以很好的與邊緣澆口同工,，與潛伏式澆口和三板模流道(自此延伸出次主流道)也可合作愉快,。

Half-round or trapezoidal runners should only be used with subgates. You can also use a trapezoidal runner design for feeding the drops in a three-plate runner design. Be careful when designing trapezoidal runners since the depth, not the width, of the runner should be used for the flow calculation. 

半圓或梯形流道只應(yīng)用于潛伏式澆口。梯形流道可以用來喂料給三板模的次主流道(drops),。要注意的是：設(shè)計梯形流道時,，流動計算(flow calculation)出的尺寸是深度，而非寬度,。

How to Size a Runner

如何訂定流道尺寸

1. What type of material is being run?

   用甚么類型的塑料加工?

   Amorphous materials require runner diameters 30 to 50 percent greater than semicrystalline materials.

   不定形材料需要的直徑比結(jié)晶性材料需要者大30到50%,。

2. What’s the wall thickness?

   壁厚多少?

   The runner diameter should be 1.5 times the part’s thickest section.

   流道直徑應(yīng)為產(chǎn)品最大壁厚的1.5倍。

3.  How many cavities?

   一模幾腔?

   Use runner size increments of .025 inch.  Start with the smallest diameter at the runner feeding the gate and finish with the sprue O-diameter (the largest dimension).

   從喂料給澆口的流道的最小直徑開始,，上溯到最大直徑的主流道O-直徑,，

   流道直徑的逐級增量采用0.025吋(0.6mm)。

C. Hsu：當(dāng)單位是mm時,，采用0.040吋(1.0mm)作為增量,。

更多徐昌煜老師案例解析，可觀看《注塑成型問題診治》系列線上課程,。

-End-

作者：徐昌煜

編輯：阿瑪小K