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注塑机知识

送你一本注塑工艺手册~~中英文对照【外资注塑人必看】

发布时间:2016-11-28 14:37:00 点击:
工艺注塑手册 Injection process handbook
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
The material is not dried enough or it is wet.


b. 预塑速度 (螺杆转速) 太快
Dosing speed is too fast.


c. 喷嘴温度太高
The nozzle temperature is too high.


d. 不好的回料 (粉状)
Too much powder in regrinds.


e. 回吸量不够
Not enough retract


f. 喷嘴接触力不足
Not enough force between the nozzle and the mold bush.


g. 喷嘴与模具浇口套尺寸不匹配
The dimension of the nozzle and the mold bush is not correct.


h. 喷嘴接触表面脏 (造成表面不平)
Dirty interface of the nozzle


(2)预塑不稳:
Plastification unstable:


a. 回料比不合理或不稳定
Regrind rate is unreasonable or unstable


b. 背压太低
Back pressure is too low


c. 长料杆架桥
Long regrind


d. 材料受潮
Wet material


e. 下料处温度不合理(太高)
Unreasonable cylinder temperature around the hopper (Too high)


(3)飞边
Flashes


a. 参数设置不准确 (转压点太低,保压太高,射速太快,温度
太高)
Wrong setting parameters (Too low switch point, too high
holding pressure, too fast injection speed, too high temperature
etc)


b. 模具脏
Mold is dirty


c. 锁模力不足
Locking force is not enough


d. 模具问题(损坏)
Mold is injured


e. 设备问题(压力不稳)
Machine problems (Unstable pressure)


f. 喷嘴温度过低
Too low nozzle temperature


g. 塑化不均(长料杆,螺杆转速过快,背压太低等)造成冷料
Inhomogeneous melt


h. 回吸太小造成止回阀关闭不稳定
Too little retract to cause the non-return valve closing unstably


(4)充模不足
Incomplete:


a. 参数设置不准确 (转压点太高,保压太低,射速太慢,温度 太低)
Wrong setting parameters (Too low switch point, too high
holding pressure, too fast injection speed, too high temperature
etc)


b. 模具脏
Mold is dirty


c. 喷嘴温度过低, 结构不合理
Low temperature in the tip of nozzle, and wrong structure 


d. 止回阀或料筒损坏
Non-return valve or cylinder is broken


e. 浇口, 流道尺寸太小
Too small gate, runners


f. 不干净的回料 (含杂料)
Other material in the regrind


g. 材料受潮
Wet material


h.设备问题(压力不足)
Machine problem (Not enough pressure)


I. 射台没对准
The nozzle is not in the centre of the runner.


h. 回吸太小造成止回阀关闭不稳定
Too little retract to cause the non-return valve closing unstably


(5)不时充模不足:
Sometimes Incomplete:


a. 射速太低(特别是PA, POM)
Injection speed is too low (Especially for POM)


b. 对大产品,熔体温度不够
Melt temperature is too low


c. 塑化不均(背压太低,转速太快)
Not homogeneous melt (Back pressure is too low, rotation speed
is too fast)


d. 喷嘴温度不够
Nozzle temperature is too low


e. 止回阀或料筒损坏
Non-return valve or cylinder is broken


f. 杂质
Other materials inside

g. 模具脏
Mold is dirty

h. 材料烘干不彻底或材料受潮
Material is wet

I. 射台没对准
The nozzle is not in the centre of the runner.

h. 回吸太小造成止回阀关闭不稳定
Too little retract to cause the non-return valve closing unstably

(6)焦斑
c. 产品顶出不均
Part is ejected not balance

d. 冷却时间不够
Not enough cooling time
e. 射速太低
Too low injection speed

f. 压力太大造成粘模
Too high pressure to cause sticky on cavities


g. 塑化不均造成内应力
Not homogeneous melt to cause force inside


h. 模具温度分布不均
Mold temperature not uniform


(9)尺寸不稳
Dimension not stable


a. 参数控制不稳 (模温, 料温,保压太低或太高, 冷却时间)
Parameter control not is precise (mold temperature, melt temperature, cooling time)


b. 回料比不合理或不稳定
Regrind rate is unreasonable or unstable


c. 止回阀或料筒损坏
Non-return valve or cylinder is broken


d. 回吸太小造成止回阀关闭不稳定
Too little retract to cause the non-return valve closing unstably


(10)重量不稳定
Unstable weight


a. 参数设置不准确 (模温, 料温,保压太低或太高, 冷却时间,保
压时间不够)
Not correct setting parameter (mold temperature, melt temperature, cooling time)


b. 喷嘴温度太低
Nozzle temperature is too low


c. 保压时间太短
Holding time is too low


d. 止回阀或料筒损坏
Non-return valve or cylinder is broken


e. 回料比不稳定
Unstable regrind rate


f. 回吸太小造成止回阀关闭不稳定
Too little retract to cause the non-return valve closing unstably


(11)产品易断裂
Easily broken parts


a. 熔体温度太高或太低
Melt temperature is too high or too low


b. 材料湿
Wet material


c. 射速太低或太高
Injection speed is too low or too fast


d. 模具温度太高或太低
Mold temperature is not reasonable
 
e. 熔接痕
Welding line

f. 杂质
Other materials inside

g. 塑化不均(背压太低,转速太快,回料长料杆)
Not homogeneous melt (Back pressure is too low, rotation speed is
too fast, long sprue)

h. 模具锐边
Mold sharp place

i. 不稳定回料比
Unstable regrind rate

(12)熔接痕:
Welding line:

a. 射速太慢
Too low injection speed

b. 熔体温度太低
Too low melt temperature

c. 模具温度太低
Too low mold temperature

d. 排气不畅
Bad vent

d. 色母;塑化不均
Pigment; inhomogeneous melt

e.模具,产品设计不合理
Design of mold or parts not reasonable

(13)表皮分层:
Delamination:

a. 材料潮湿
Wet material

b. 杂料
Mixed material

c.色母有问题
Pigment problem

d.射速太快
Too fast injection speed

四.当产品出现问题时:When there is a problem:

(1)你必须搞清楚问题:
You must be sure the problem:

a.问题是什么
What is the problem?

b.什么时候发生的
When does the problem happen?

c.发生在哪一部位,哪一个型腔
Where is the problem and which cavity? 

d.每模都发生还是偶尔有
How often does it happen? Sometimes or always.

(2)你必须思考可能的原因有哪些
You must think what are the possible reasons

(3)你必须确认材料是否有问题
You must be sure the material has problem or not:

a.材料干燥吗
The material is dry or not

b.原材料质量好吗
The quality of raw material is good or not

c.回料质量好吗(是否无长料杆,无其他杂料,无
污物,无太多粉尘等)
The quality of regrind is good or not (Any long sprue, mixed material, dirty things, too much powder, etc.)

d.回料比添加合理吗,过程控制准确吗
The regrind ratio is reasonable and stable or not,

(3)你必须确认模具是否有问题
You must be sure the mold has problem or not:

a.水路,气路连接正确吗
Are the water pipes and air pipes connected
correctly?

b.型腔内部清洁吗
Are the cavities clean?

c.模具型腔有损坏吗
Is there any injury in cavities?

(4)你必须确认机床是否有问题:
You must be sure the machine has problem or not;

a.机床止回阀坏吗
Is the non-return valve broken?

b.料筒磨损了吗
Is the cylinder broken?

c.注塑时实际压力能达到吗
Is the actual pressure from machine enough?

* 通常,在稳定生产24小时以上而没有任何问题出现的话,我们认为该生产工 艺参数是稳定并合理的。所以一般来说,在稳定生产过程中出现的问题不应是工 艺参数问题,应主要查找其他方面。
Normally if the production is running for more than 24 hours without any
problems, we will think the parameters are stable and reasonable. So when you have problems in a mass production, it should not be the parameters’ problem and we need to try to check down the others.


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