一. 基本理念:Basic opinion:



1. 什么是最佳的流动状态:

What is the best flow state:


流体流动状态应该是喷泉状的,最佳的流动状态是流体前端的流动速度在型腔内处处相等。由于流动方向上截面积的不同,在其变化的位置应进行注射速度的调节 (注意:机床上所能设定的注射速度是指螺杆的前进速度)。

The flow state should be like fountain, and the best is that the speed of the front melt is the same everywhere in the cavities. For different areas in the direction that is vertical with the flow way, we must adjust the injection speed.


2. 什么是最佳的压力,温度分布状态:

What is the best pressure and temperature state:


最佳的压力和温度分布状态是压力和温度分布在型腔内部处处相等,并且随着熔体地逐步冷却而下降并使最终产品的内应力为零。

The best pressure and temperature state should be like this that the pressure and temperature everywhere in cavities are the same, and make the force of the part inside be zero finally as the melt solidified. 


实际压力分布状况是浇口附近最大并随着距离的增加而降低。 (记住:螺杆头处的熔体和流动着的熔体前端存在压力差是使熔体发生流动的根本原因)

The actual pressure around the gate is the highest and as the distance goes it’s getting lower and lower。


所以,综合来讲,参数设定的一般准则:

(1) 尽量选用高的注射速度(螺杆前进速度)

(2) 尽量选用高的料筒温度

(3) 尽量选用高的模具温度

So the general principles when setting parameters are:

(1) As fast injection speed as possible (Screw forward speed)

(2) As high cylinder temperature as possible

(3) As high mold temperature as possible


二. 基本概念:Basic conception:


1. 收缩:Shrinkage:

(1)收缩的原因:.a.热胀冷缩;

.b.熔体结晶;

.c.分子取向;对于未增强型材料,其熔体在流动方向上的收缩总是大于垂直方向;对于增强型材料,正好相反

. d.状态变化

The reasons of shrinkage: a. Chang from hot to cold;

b. Crystallization ;c. Molecule orientation;

d. Form changing


(2)收缩的阶段:

The stages of shrinkage:


它包括三个阶段:

a.从注射开始到保压结束;

b.从冷却时 间开始到脱模前;

c.脱模后

It contains three stages: 

a. From injection stage to end of holding stage;

b. From cooling stage to demold stage;

c. After demold.


(3)变形:

Deformation

变形的根本原因时收缩的不均匀。造成收缩不均匀的原因有:

The root cause of deformation is inhomogeneous shrinkage. The causes of inhomogeneous shrinkage are as follows:


a. 冷却(即温度分布)不均匀

Inhomogeneous cooling


b. 壁厚不均匀

Different wall thickness


c. 压力分布不均匀

Not average location of pressure location


d. 分子取向

Molecule orientation


e. 脱模受力不均

Inhomogeneous forces when demolding


2. 结晶

Crystallization:


(1)什么是结晶:

What is crystallization:


简单的说,结晶就是指分子的有序排列

In a short word, it means to make the molecule in order.


(2)结晶的影响因素:

Factors affecting crystallization:


结晶的影响因素:冷却速度。冷却速度越快,结晶程度越低。

The cooling speed affects the crystallization. The faster cooling speed the

more crystallization


(3)结晶对产品性能的影响:

How does crystallization affect the parts:

结晶度越高:密度越高

收缩越大

光洁度越好

强度越高

韧性变差

The more crystallization: The higher density

The more shrinkage

The better surface

The stronger of the parts


3. 粘度:

(1)什么是粘度:

What is viscosity:


粘度是流体本身的一种性能,它的大小是流体流动性能的一种衡量。数值越大,流体的流动性能越差。

Viscosity is a character of the flowing material. Its value is used to measure the flowing character. The bigger value it is, the worse flowing character it is.


(2)粘度的影响因素:

What affect the viscosity:


a.温度

Temperature


b.剪切速度

Shear rate


c.压力

Pressure

速度和压力的敏感程度是不同的,并且在不同的注射速度下哪一个起主导作用也是不同的


4. 止回阀:

Non-return valve:


a. 止回阀的功能是什么:

Function of non-return valve:

在注射,保压时防止熔体倒流,从而给予熔体我们所需的压力和速度。

To prevent the melt flowing back when injection and packing.


b. 怎么判断止回阀或料筒损坏

How to recognize the non-return valve is broken:


(3)注射速度太快:易出现焦斑,飞边,内部气泡或造成熔体喷射

Too fast injection speed: burns, flash, air bubble inside or melt jet.

注射速度太慢:易出现流动痕, 熔接痕,并且造成表面粗糙,无光泽 Too slow injection speed: Flow line; weld line, or bad surface.


* 注射速度和注射时间设定的一般原则:

General principles when setting injection speed or injection time:


2. 转压点: Switch point:

(1)怎么确定转压点: How to set switch point:

一般来说,转压点是指在零保压压力的情况下把产品打到95%满时, 由注射到保压的切换点。

Normally the switch is the changing point of screw from injection phase to holding phase, when the parts are 95% of their volume. 


对于薄壁产品(如:扎带):一般打到产品的98%

To the thin wall thickness parts (Example: Cable strap): Up to 98% of their volume.


对于非平衡流道:一般为70%-80%,应视具体情况而定。并建议采 用慢-快-慢多级注射。

To non-balance runners: Normally it’s up to 70% to 80%. It should be


determined by the reality. We suggest using step injection speed (Slow-

Fast- Slow).


(2)转压点太高:产品充模不足,熔接痕,凹陷,尺寸偏小等 Too high switch point: empty part, weld line, sink mark, and small dimension


转压点太低:飞边,脱模困难,尺寸偏大等

Too low switch: flash, difficult to demold, big dimension. 


3. 保压压力:

Holding pressure:


(1)怎么确定保压压力:

How to set the holding pressure: 


优化的保压压力一般为最低保压压力和最高保压压力的中间值。 

The optimized holding pressure is in the middle of the maximum and minimum normally.


最低保压压力:在准确的转压点基础上,给予一定的保压压力,当产品刚出现充模不足时的保压压力。

Minimum holding pressure: based on the correct switch point, the pressure when the parts start to be empty .


最高保压压力:在准确的转压点基础上,给予一定的保压压力,当产

品刚出 现毛刺时的保压压力。

Minimum holding pressure: based on the correct switch point, the pressure when the parts start to have flash.


(2)一般来说: Normally:

PA保压压力=50% 注射压力

POM保压压力= 80% 注射压力;

PP/PE 保压压力=30-50% 注射压力

PA Holding pressure = 50% Injection pressure

POM Holding pressure = 80% Injection pressure;

PP / PE Holding pressure = 30-50% injection pressure


4. 保压时间: Holding time:

(1)怎么确定保压时间: How to set holding time:

保压时间的确定以浇口冷凝为依据。通过产品称重来确定。

Holding time is determined by the solidification time of the gate. We decide it according to the weight. 


(2)保压时间太长: 影响周期

Too long holding time: Waste time

保压时间太短:重量不足,产品内部空洞,尺寸偏小

Too short holding time: Not enough weight, empty inside, small dimension

*

5. 螺杆转速

Rotation Speed:

预塑的目标是:获得均一稳定的熔体


(1)怎么确定螺杆转速:

How to set the rotation speed:

作为原则,螺杆转速的确定必须使螺杆的预塑时间,回吸时间与射台 的回退时间之和略短于冷却时间。

As a rule, the rotation speed is determined by that the total dosing time, retract of screw and retract of injection unit must be a little bit shorter than the cooling time.


(2)螺杆转速太快:塑化不均(从而造成产品冷料,充模不足和断裂 等),材料分解(从而造成焦斑,色差,断裂等) 

Too fast rotation speed: Inhomogeneous melt (which cause empty parts, broken), material decomposed (which cause burns, different color, broken etc) 


螺杆转速太慢:影响周期

Too slow rotation speed: Waste time.


6. 冷却时间: Cooling time:


作为原则,冷却时间的设定应越短越好,以产品不变形,不粘模,无过深的顶出痕为基本要求。并且:螺杆转速: PA<1.0m/s; POM < 0.7 m/s; 

As a rule, the cooling is the shorter the better based on the parts are not deformed, not sticky and without too deep impressed by ejectors.


* 推荐的脱模温度如下:

Suggested demolding temperature is as follows:


7. 背压:

Backpressure:

(1)什么是背压:

What is backpressure:


背压是指螺杆预塑时,液压缸阻止螺杆后退的力,其大小等于螺杆前 端熔体对螺杆的反作用力。

Backpressure is the hydraulic force preventing the screw going back as

dosing, the value is equal to the force that the melt in front of the cylinder to the screw.


(2)怎么确定背压:

Ho to set the backpressure:

背压的确定取决于不同材料的性能,通常由材料供应商提供。 

一般来说:PA: 20-80 Bar ; POM : 50-100 Bar ; PP/PE : 50-200 Bar 

The backpressure is determined by the material character and its value is offered by the supplier.

Normally: PA: 20-80 Bar; POM: 50-100 Bar; PP/PE: 50-200 Bar

20%时: 喷嘴下料口 When one-shot quantity is less than 20% of maximum :

b. 一次注射量在20%-70%之间时:喷嘴下料口

c. 一次注射量大于70%时:喷嘴下料口


(2)熔体温度太高:材料分解(从而造成产品气泡,色差,焦斑,断裂 等)

Too high melt temperature: Material decomposed (Which cause air bubble, different color, burns, broken etc.)


熔体温度太低:材料塑化不均,熔体内含冷料(从而造成充模不足, 冷料,产品断裂等)

Too low melt temperature: Inhomogeneous melt with cold material inside (Which cause empty parts, broken parts etc.)


11. 模具温度:

Mold temperature:

(1)为什么需要模温:

Why the mold temperature is needed:

无论模具温度高低,它的作用始终是为了在稳定生产过程中使模具维

持一定的温度,起冷却作用的。 


a. 一次注射量小于总料量的

真正重要的模温是指模具型腔的温度,而不是模温机上显示的温度。

通常,在稳定生产过程中型腔温度会达到一个稳定的动态平衡,并高于

显示温度10度左右(对于大模具在生产之前必须使模具充分加热,尤其是薄壁,且流长比 很大的产品模具)

Whatever the mold temperature is high or low, its function is to keep the cavity temperature on the same level. It is for cooling.

For the big mold, it must be heated enough before start production .


(2)模具温度会影响什么

What the mold temperature affect:

会影响熔体的流动性和冷却速度。

Affect the melt flow rate and the cooling speed.


因为影响流动性,从而影响产品外观(表面质量,毛刺)和注塑压

力;

For affecting the flow rate, the mold temperature affects the appearance of

the parts and the injection pressure.


因为影响冷却速度,从而影响产品结晶度,进而影响产品收缩率和机

械强度性能.

For affecting cooling speed, the mold temperature affects the crystallized rate and then affects the shrinkage and the mechanical strength.


(3)模温高:流动性好;结晶度高;收缩率大(从而造成尺寸偏小);变 形;需要更长的冷却时间

High mold temperature: good flow character; high-crystallized rate; big shrinkage (Which cause small dimension); need more cooling time


模温低:流动性差(从而造成流动纹,熔接痕);结晶度低;收缩率

小(从而造成尺寸偏大)

Low mold temperature: bad flow character; high-crystallized rate; small shrinkage (Which cause big dimension)



三. 常见产品缺陷及其原因:Normal defects and the reason:



(1)流涎:.

Material escaping from nozzle:


a. 材料烘干不彻底或材料受潮

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