热流道平衡balancing

Balancing

平衡

The effect of hot runners on improving injection mold balancing

热流道对模具提高注射平衡的影响

When more than one gate is required within a system, the question of balance is raised. When

running multicavity molds, it

’

s important that all the gates perform identically. This is especially

true when molding highly toleranced and thin wall components. If the gates do not all behave

in the same manner, the mold is said to be unbalanced. Serious imbalance can result in some

cavities being over packed and sticking in the mold, while other cavities remain under packed

and retain poor dimensional stability.

当系统需要一个以上的澆口，

平衡的问题就突顯。

当运行多腔 模具，

所有澆口相同的表現很重要。

尤其是，

< br>当成型薄壁零件和高精度零件。

如果浇口并不都以同样的方式表现，

模具被称为不平衡。

严重的不平衡会导致一些腔过度饱压和贴在模腔，

而其他仍在饱压和保持尺寸稳定性差。

In recent years, the construction of higher cavity tools and demand for better quality parts has

put an increased emphasis on mold fill balancing. Since the majority of these tools incorporate

hot runners, at times the hot runner has been falsely accused of being the direct cause for the

imbalanced filling of cavities. A poorly constructed hot runner system can cause imbalance.

However, a well-built hot runner system, monitored by a top-quality temperature controller, can

be a valuable tool to assist the processor in fine-tuning the seven key issues that can lead to

mold fill balance. These eight key phenomena that contribute to mold fill balance are.

近年来，

高等腔模具和质量更好的产品的需求已经加强了对模具填充平衡。

由于这些模具的大 多

数将热流道，

在时代的热流道已被错误地指控为不平衡填充空 腔的直接原因。

一个简陋的热流道

系统可以引起不平衡。然而， 建立良好的热流道系统，一个高品质的温度控制器，可以协助处理

进行微调的八个关键问 题，可能导致一个有价值的模具，填充平衡。

这八个关键的现象，有助于模具填充平衡。

1. venting uniformity

1,

排氣均匀性

2. uniform wall sections

2,

均匀的壁部分

3. uniform mold temperatures

3,

统一的模具温度

4. effects of shear on melt viscosity

4,

剪切对熔体粘度的影响

5. uniform heat profile

5,

均匀的热分布

6. naturally balanced manifold design

6,

自然平衡流道设计

7. injection profile and velocities

7,

注塑曲線和速度

8. proper temperature control

8,

适当的温度控制

1. venting uniformity

1,

排氣均匀性

Non-uniform venting is the number one cause of mold fill inbalance. A common misperception

is that venting is acceptable so long as there is no evidence of burning on a part. However,

poor venting can lead to significant backpressure in the cavity and the end result is poor fill

balance.

非均匀排氣是模具填充平衡不平衡的头号原因。

一个普遍的误解是，排氣是可接受的只要没有

证据燃烧了成品。然而，不良的 排气会导致在腔中显着的背压，最终的结果是差勁的充填平衡。

The volume of air in the cavity needs to be displaced by the molten plastic. In the example of a

syringe barrel, the size of the syringe orifice will determine how fast the plunger can move

forward and how much pressure is required to push the plunger. If a mold exhibits poor venting,

it will require more pressure and time to displace the air in the cavity in order for the plastic to

fill the volume.

在型腔中的空气的体积，

需要被熔融塑料替換。

在注射筒为例，

注射器的孔的大小将决定活塞可

以前进的速度和需要多少压力推动活塞。

如果一个模具排气表现不良，

它将使塑料来取代填充体

积腔的空气需要更多的压力和时间。

Ironically, the depth and size of vents is often determined by how easy the resin flashes and

not by how quickly the cavity fills. By having insufficient venting, the cavity backpressure

makes it more difficult to fill. If all the cavities exhibit the same level of venting, poor or

acceptable, fill balance is not impacted. If the vent-ing characteristics across the cavities vary,

then the mold fill will be imbalanced.

具有讽刺意味的 是，排气口的深度和大小往往是树脂毛刺来确定而不是如何迅速腔填充来确定。

通过不足 的排气，使得它更难填。如果所有的模腔排气表现出相同差的水平，

或可接受的，充填< /p>

平衡不受影响。如果排气性在不同的情況，充填会失去平衡。

The best way to check for vent uniformity from cavity to cavity is to do a pressure leak-down

test. By fabricating a fixture specific to your mold cavity or core, you can check venting at the

parting line. The fixture needs to be machined flat and cover the cavity parting line. This fixture

also requires a pressure gauge and valve shut off. Clamp the fixture to the parting surface.

Apply air pressure, then close the valve and measure the time required for the air to leak out

through the vents. Do this for every cavity on the tool. This won

’

t tell you if you have a general

venting problem, however it will tell you if your venting is consistent from cavity to cavity.

检查排气均匀性的最好办法是做一个压力泄漏测 试。

制备了特定的型芯夹具，

您可以检查在分型

线的排气。

夹具需要加工的平盖的分型线。

此装置还需 要一个压力表和阀门关闭。

夹紧夹具分模

面。将空气压力，然后 关闭阀和测量空气排出通风口所需要的时间。在模具每腔做这个测量。

这

不会告诉你如果你有一个通用的排气问题，但是它会告诉你，如果你是每腔一致的排气

< br>

2. uniform wall sections

2,

均匀的壁部分

Uniform wall sections are not only critical for dimensional stability of the part, but also affect

how fast the cavity fills.

均匀的壁厚不仅是成品尺寸稳定性的关键，也是影响模腔的填充速度。< /p>

An unbalanced fill can be directly attributed to dissimilar wall sections from cavity to cavity.

Even very small differences in steel dimensions can yield a large change in part volume.

Clearly, a high cavity mold with different part volumes across the cavities will not fill in a

balanced fashion.

一个不平衡的填充可以直接归因于不同的壁厚。

甚至在钢的尺寸很小的差异充填可能产生大的变

化。显然，在高腔模具呈現不同的產 品，表示充填不是一个平衡的方式。

The following chart is based on a small part (test strip) measuring 1.00

”

x 2.00

”

x .080

”

.

Applying the same logic to the gate diameter, we can see an almost 7% change in gate

diameter, however the flow volume or cross sectional area changes 14%. As you can see,

very subtle changes in wall sections and gate diameters can have a severe effect on cavity

balancing.

下面的图表是基于一小 產品（试纸）测量

1“×2“×080”。

< br>应用相同的逻辑製造的澆口直径，我们可以看到在浇口直径近

7%

的变化，但流量或横截面面积

的变化，

14%