【徐昌煜老师】流道尺寸订定(一)

昵称35953524 2024-07-19 发布于江苏

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流道尺寸订定(一)

徐昌煜

先进成型技术学会创会理事

2024年6月16日

关键词(keywords)

流道尺寸订定(runners sizing)、流长(flow length)、不定形材料(amorphous material)、结晶性树脂(resin)、增量(increment)、四级流道(fourth-level runner)、许容剪切速率(allowable shear rate)、一级分流道(main runner)、注道O-直径(sprue O-diameter)、全锥形喷嘴(full taper nozzle)、剪切点(shear point)、气化点(gasification point)、燃点(burning point)、全圆流道(full-round runner)、潜伏式浇口(subgate)、边缘浇口(edge gate)、雾斑(blush)

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兹翻译美国Bob Hatch先生在Injection Molding Magazine(IMM，注射成型杂志) 2003年2月期刊上发表的一篇文章《Sizing runners(订定流道尺寸) 》并附上我的批注或点评(一般为粗斜体，C. Hsu是我的代号)与大家分享：

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.

在设计过程的初始阶段，我的设计从流道或喂料给浇口的分流道开始。首先，我要知道塑料的类型以及从塑料离开热源开始计算的流长。此一热源或为成型机的喷嘴，或为热流道系统的热嘴灌口，或为热主流道的出口。

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(亚克力)、丙烯腈/丁二烯/苯乙烯(ABS)或聚碳酸酯等比结晶性材料需要较大的流道 – 流道尺寸基于产品壁厚。结晶性树脂包括聚乙烯、聚丙烯、缩醛、尼龙和聚对苯二甲酸丁二酯(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.

我还需要知道成型产品的壁厚才能进行流道尺寸订定。且以名义壁厚0.1吋(2.54mm)和塑料ABS做个练习。

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，我要知道模腔数目。在此练习，我们要为一模16腔的流道估算尺寸。从喂料给浇口的流道溯源而上，每上一级流道，其直径增大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，当客户采用mm公制时，我就采用0.040吋(1.0mm)作为增量。流道尺寸以mm计时，我会使得流道升级为0.040吋(1.0mm)的倍数而最终获得3、4或5mm等整数流道尺寸。这种公制作法似乎较为容易，我可能会逐渐更多的采用0.040吋(1.0mm)作为估算流道升级的增量。

C. Hsu：增量未计及流道长度和下游塑料总重(或总体积)，此为美中不足之处。

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).

几年前，我参加一场研讨会，讲师建议流道升级的增量为0.050吋(1.3mm)。虽然，此一增量0.050吋(1.3mm)满好的，我仍然较喜采用0.025吋(0.6mm)作为增量，此一增量0.025吋(0.6mm)可以满足需求，还可减少回料的使用，以免超过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.

当壁厚是0.1吋(2.54mm)而塑料是ABS时，参看表1得知喂料给浇口的四级流道的直径应为0.225吋(5.72mm)。此一估算基于：流道直径必须是产品最大壁厚的1.5倍。我发现此一规律若不遵循，保压就无法消除缩痕和缩孔。

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.

请注意：不定形材料需要比上述规则订定的直径还要大些。不定形材料较之结晶性材料，对剪切的敏感度高，所以我会将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的许容剪切速率(1041/s)分别为4.0、3.8、2.1和1.2；结晶性材料的LDPE、HDPE、PP和PA的许容剪切速率(1041/s)分别为4.0、6.5、2.4和1.0 (C-MOLD Reference Manual, 32-11-92)。就此看来，不定形材料对剪切的敏感度不一定比结晶性材料高。

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.

现在已经算出喂料给浇口的分流道直径，可以从表一找出溯流而上直到主流道的各级流道的合适直径。上一级(三级)流道直径较之四级流道大0.025吋(0.6mm)，也就是0.250吋(6.35mm)。再上一级(二级)流道直径是0.275吋(6.99mm)以及一级分流道(main runner)直径是0.300吋(7.62mm)。各级流道尺寸订定后，可以订主流道衬套和喷嘴口径的尺寸了。从一级分流道移到主流道的O-直径(主流道小端直径)时，我们将增量加倍使得喷嘴口径可以在主流道O-直径和一级分流道直径之间。这意味着：0.050吋(1.3mm)的增量加到一级分流道直径0.300吋(7.62mm)后，主流道O-直径应为0.350吋(8.89mm)。于是，我们订喷嘴口径较之主流道O-直径小0.025吋(0.6mm)而成为0.325吋(8.26mm)。

Nozzle, Runner Shapes

喷嘴和流道的形状

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.

尺寸订定完毕，是时候考虑喷嘴的类型以优化材料的加工。不定形材料如ABS者需要装一全锥形喷嘴(full taper nozzle)在成型机上，因为ABS不喜或不要剪切点。非全锥形喷嘴造成塑料流路的剪切点。

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.

成型品外观上常见的剪切水花、暗线条和其他外观缺陷往往可以归咎于错误形式喷嘴的使用。这就是为什么成型技工不得不提高料温试图消除前述祸患，但是这么做，周期时间势必拖长。

C. Hsu：提高料温固然可以降低黏度、剪切应力、摩擦生热和熔胶升温，但是提高料温本身就是熔胶升温，熔胶升温到塑料当中低分子成分的气化点时，瓦斯气和水花(水花是气痕)就产生了，熔胶升温到塑料的燃点时，暗线条就产生了 --- 提高料温一刀两刃，得失难言，不若扩大喷嘴口径。

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.

接下来，我们要确认流道设计对我们采用的浇口类型是适配的。图1示出不同的流道设计被采用时，流路之间的好坏关系。

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

图1. 对任何浇口来说，全圆流道是最好的设计，但是半圆或梯形流道也适用于潜伏式浇口。

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.

对任何类型的浇口来说，正确直径的全圆流道都是最好的设计，对边缘浇口而言，更是绝对的选择。边缘浇口必须出自全圆流道的中心-塑流会经历突然的转变。边缘浇口出自全圆流道的边缘会成为高剪切浇口而在其下游的产品表面生出雾斑。

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.

全圆流道可以很好的与边缘浇口同工，与潜伏式浇口和三板模流道(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.

半圆或梯形流道只应用于潜伏式浇口。梯形流道可以用来喂料给三板模的次主流道(drops)。要注意的是：设计梯形流道时，流动计算(flow calculation)出的尺寸是深度，而非宽度。

总结：

How to Size a Runner

如何订定流道尺寸

What type of material is being run?
用甚么类型的塑料加工?
Amorphous materials require runner diameters 30 to 50 percent greater than semicrystalline materials.
不定形材料需要的直径比结晶性材料需要者大30到50%。
What’s the wall thickness?
壁厚多少?
The runner diameter should be 1.5 times the part’s thickest section.
流道直径应为产品最大壁厚的1.5倍。
How many cavities?
一模几腔?
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).
从喂料给浇口的流道的最小直径开始，上溯到最大直径的主流道O-直径，
流道直径的逐级增量采用0.025吋(0.6mm)。