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Special molding machine for LCP

Release time: 2017-07-05
Viewed: 64

Liquid Crystal polymer is developed in the early 80 s a new type of high performance engineering plastics, Name: Liquid Crystal Polyester, LCP for short.

LCP has been widely used in chemical industry, electronic newsletter, military machinery, aerospace, automotive and other fields, LCP excellent comprehensive performance is more and more attention by the governments, its products have introduced various applications in the field of high technology, known as super engineering plastics.

The characteristics of the LCP

Liquid crystal polymer resin for beige, commonly has a white opaque solid powder.

Density is 1.4 ~ 1.7 g/cm3.

LCP series features include: have the autofrettage effect;

Small linear expansion coefficient;

Good heat resistance;

The flame retardant;

Low melt viscosity, good fluidity, forming shrink, good chemical resistance, wear resistance and antifriction sex are excellent.

The application range of the LCP

LCP has been used in the microwave container, can be high and low temperature resistance.

LCP can do printed circuit boards, satellite electronic components, the jet engine parts;

Used in electronic electrical and automobile mechanical parts or components;

Can also be used for medical treatment.

Summary of LCP material special injection molding machine selection

Bei LCP material must choose special injection molding machine, and pay attention to the following:

(1) must choose LCP material special injection molding machine.

(2) screw/feed tube need to use better abrasion resistance materials.

Screw compression ratio, the length to diameter ratio and the teeth have special requirements.

(3) the screw head can use to prevent the reverse flow structure.

(4) need more precise temperature control system.

Wikipedia correlation mouth temperature has a special machine

PID SCR temperature precision of temperature control system, the feed tube PID + SSR difference + / - 5 ℃ temperature, nozzle section PID SCR precision electric heating temperature control system + / - 1 ℃ (see chart).

(5) the nozzle part need special design.

(6) charging and injection system response to acute.

(7) injection tube capacity to pay attention to with products weight, not too much or too little.

 


The molding technology of the LCP

(1) cylinder temperature.

Usually nitrogen-treated barrel temperature, nozzle temperature, suitable for resin temperature as shown in table 1.

Table 1

E4000 series

Resin dry conditions

The temperature

Around 140 ℃

time

4 ~ 24 hours

Feed tube temperature (℃)

The back of the

330 ~ 350

In the middle

350 ~ 370

The front of the

370 ~ 390

nozzle

370 ~ 390

Suitable for resin temperature (℃)

380

Mold temperature (℃)

40 ~ 160

Injection pressure (MPa)

120 ~ 160

The holding pressure (MPa)

40 ~ 60

Screw back pressure (MPa)

0 ~ 5

Injection speed

In the high speed

Screw revolution (RPM)

100 ~ 150

It is important to note that LCP material residue in feed tube retention time is too long or too much easier to make LCP material, product surface will have bubbles, general feed tube melt over 3 seconds and then open mold, residual guarantee within 5 mm.

However, if the downtime forming again, requires the waste injection will feed tube.

(2) the proportion of back pressure to make more accurate and more stable feeding.

(3) the speed of the screw is generally 100 ~ 150 RPM.

If it is containing glass fiber or carbon fiber material, in order to prevent the glass fiber is broken, should reduce speed accordingly.

In addition, the back pressure is as low as possible, the products can be used to back pressure, small back pressure can be 0.

(4) high sensitivity injection system and the automatic V - P injection pressure, holding pressure P (V) conversion function to make products stable precision. The necessary conditions (such as the product is very precise), advice at gate cavity pressure sensors, the V - P switch is closer to reality.

(5) the injection pressure depends on the material, products shape, mold design, gate and runner, etc.

But after the LCP its melt viscosity is very low, so the injection pressure is lower than the general resin.

LCP cure time is faster, so high-speed injection is one of the important requirements of injection moulding machine, special dobbin products, products more xiaoyue thin more trouble, the injection speed should be higher than the requirements of the injection pressure.

Flat beer products the holding time is not too long, otherwise easy to cause warping deformation and stress.

(6) the molding cycle depends on the size of the products, shape, thickness, die structure and forming conditions.

LCP material has good liquidity, so the filling time is shorter, and crystal shape faster so molding cycle is shorter.

LCP special mould process

LCP products mold design is critical, mold should be adopted into the gate of the ordinary open mouth, and do not use hot mouth, otherwise the products blister easily, namely high temperature can cause the product far.

On general mold temperature about 140 ℃, the (former) mould temperature should be higher than (after) mode, because of the high temperature melt glue (former) mould good liquidity is not easy to cause cold glue, model (after) under low temperature products easy crystallization forming, under the (former) (back) on the mold temperature is not more than 15 ℃.

In die temperature selection, to shorten the molding cycle, prevent front and deformation, should choose to lower mould temperature;

If require high dimensional stability of products, reduce joint production, and the problem of insufficient filling should choose higher mold temperatures.

The LCP material handling process

LCP material before use should be dry, the temperature about 145 ℃ or so, time is about 4 ~ 24 hours after the dehumidification of LCP material residual moisture content should be under 0.02%, dew point in a - 35 ℃.

The requirement to the peripheral devices

Drying of material aspects: it is recommended to use vacuum dehumidification drying machine, don't use the general drying machine.

For vacuum dehumidification drying machine can take out the moisture in LCP material, while the general drying machine can't take out the moisture in material completely, the quality of the more difficult to meet the requirements of products.

 

The die temperature machine, mould temperature control: recommended, followed by the electric heating rod.

Generally use hot oil mold temperature is the most stable, because of the hot oil can cycle was widespread in the mold, the mold temperature is uniform.

Heat and hot water faster, stability is the worst.


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