Mfundo yake ndi chiyani, makhalidwe, kugwiritsa ntchito ndi njira yopangira jekeseni pogwiritsa ntchito makina opangira jekeseni?

Lero tikambirane mfundoyi, makhalidwe, ntchito ndi ndondomeko jekeseni akamaumba ndi makina jekeseni akamaumba.

1. Mfundo ya jekeseni akamaumba. Onjezani pulasitiki granular kapena ufa mu hopper ya makina jakisoni. Pulasitiki imatenthedwa ndikusungunuka mu makina ojambulira kuti isapitirire, ndiyeno jekeseni mu nkhungu yotsekedwa pansi pa kukakamizidwa kwina. Pambuyo kuzirala ndi kupanga, imasungunuka Pulasitiki imalimba kuti ikhale gawo lapulasitiki lofunikira. Kuti

2. Makhalidwe wa jekeseni akamaumba
Jekeseni akamaumba ali yochepa kupanga mkombero ndi mkulu zokolola. Kumangirira jekeseni kumatha kupanga mbali zapulasitiki zokhala ndi mawonekedwe ovuta, zofunikira zazikulu ndi zoyika zosiyanasiyana, zomwe zimakhala zovuta kuzikwaniritsa ndi njira zina zopangira pulasitiki; chachiwiri, jakisoni akamaumba ali m'kati kupanga Ndikosavuta kuzindikira makina, monga jekeseni, kugwetsa, kuchotsa zipata ndi ntchito zina zitha kukhala zokha, kotero kuumba jekeseni kwagwiritsidwa ntchito kwambiri.

2.1 Ubwino wake:
Kuzungulira kozungulira ndi kwaufupi, kupanga bwino ndikwambiri, ndipo ndikosavuta kuzindikira makina. Ikhoza kupanga mawonekedwe ovuta, miyeso yolondola, zigawo zapulasitiki zokhala ndi zitsulo kapena zopanda zitsulo, khola mankhwala khalidwe, ndi osiyanasiyana ntchito.

2.2 Zoipa:
Mtengo wa zida zopangira jekeseni ndi wokwera kwambiri; kapangidwe ka jekeseni nkhungu ndizovuta; mtengo wopangira ndi wokwera, nthawi yopanga ndi yayitali, ndipo siyoyenera kupanga magawo apulasitiki amodzi ndi ang'onoang'ono.
3. Kugwiritsa Ntchito Kupatula ma thermoplastics ochepa (fluoropeslastics), pafupifupi thermoplastics onse angagwiritsidwe ntchito kupanga mbali pulasitiki ndi jekeseni akamaumba. Kumangira jekeseni sikumagwiritsidwa ntchito popanga thermoplastics, komanso wakhala bwino ntchito akamaumba mapulasitiki thermoset. Pakadali pano, zinthu zake zowumbidwa zimawerengera 20-30% pazinthu zonse zapulasitiki zamakono. Pofuna kukulitsa kukula kwa jekeseni wopangidwa ndi pulasitiki, matekinoloje ena apadera a jakisoni apangidwa makamaka kuti azitha kuumba zida zapulasitiki zokhala ndi zinthu zapadera kapena zofunikira zapadera.. Monga jekeseni mwatsatanetsatane wa zigawo zapulasitiki zolondola kwambiri, jakisoni wamitundu yambiri wamitundu yambiri yamapulasitiki, jekeseni masangweji a masangweji pulasitiki zigawo zopangidwa ndi zipangizo zosiyanasiyana mkati ndi kunja, ndi jekeseni psinjika akamaumba optically mandala pulasitiki. Kuti

4. jekeseni akamaumba ndondomeko

4.1 Kukonzekera musanayambe kuumba

Kuyang'anira mawonekedwe azinthu zopangira ndikuyesa kuyeza magwiridwe antchito: kuphatikizapo kuyendera mtundu wa pulasitiki, kukula kwa tinthu ndi kufanana, madzimadzi (Melt Index, mamasukidwe akayendedwe), kukhazikika kwamafuta ndi kuchuluka kwa kuchepa. Kuti

Pulasitiki preheating ndi kuyanika: chotsani chinyezi chambiri komanso kugwedezeka kwa zinthuzo kuti mupewe zolakwika kapena kuwonongeka pagawo la pulasitiki mutatha kuumba., zomwe zidzakhudza maonekedwe ndi khalidwe lamkati la gawo la pulasitiki. Njira yowumitsa zinthu: kupanga magulu ang'onoang'ono, pogwiritsa ntchito kuyanika uvuni; kupanga zochuluka, pogwiritsa ntchito kuyanika kowiritsa kapena kuyanika vacuum.
Kuyeretsa migolo: Mgolo uyenera kutsukidwa posintha zinthu, kusintha zipangizo ndi mitundu. Kuti

Ikani preheating: kuchepetsa kusiyana kwa kutentha pakati pa zinthu ndi kuikapo, kuchepetsa kupsinjika kwa shrinkage ya pulasitiki mozungulira choyikapo, ndikuwonetsetsa kuti pulasitikiyo ndi yabwino. Kuti

Kusankhidwa kwa wothandizira: Zomwe zimagwiritsidwa ntchito nthawi zambiri zimaphatikizapo zinc stearate, mafuta a parafini ndi silicone. Kuti

4.2 Njira jakisoni

Kudyetsa: Onjezani pulasitiki granular kapena ufa mu hopper ya makina jakisoni. Kuti

Plasticization: Kupyolera mu Kutentha kwa chipangizo chotenthetsera cha makina a jakisoni, pulasitiki zopangira mu wononga amasungunuka ndi kukhala pulasitiki kusungunuka ndi pulasitiki wabwino. Kuti

Kudzaza nkhungu: Pulasitiki yosungunuka yapulasitiki imakankhidwa ndi plunger kapena screw ya makina a jakisoni kuti alowe ndikudzaza nkhungu kudzera mumphuno ndi ndondomeko yothira nkhungu pa kuthamanga kwina ndi kuthamanga.. Kuti

Kusamalira ndi kudyetsa nkhawa: pambuyo kusungunula kudzaza patsekeke, pansi pa plunger kapena screw ya makina a jakisoni, kusungunuka kumasungabe kukakamiza kwa chakudya, kotero kuti kusungunula mu mbiya kumapitilira kulowa m'bowo kuti awonjezere pulasitiki m'bowo Shrinkage ikufunika ndipo ingalepheretse kusungunuka kubwereranso..
Kuziziritsa chipata chitatha atazizira: Patapita nthawi, pulasitiki yosungunuka yomwe ili m'kati mwake imakhazikika kukhala yolimba kuti iwonetsetse kuti gawo la pulasitiki limakhala lolimba mokwanira pamene likuphwanyidwa ndipo silimayambitsa nkhondo kapena kusintha.. Kuti

Demoulding: Mbali ya pulasitiki imakhazikika pa kutentha kwina, ndipo makina otulutsa amakankhira mbali ya pulasitiki kunja kwa nkhungu. Kuti

4.3 Pambuyo pokonza magawo apulasitiki

Zifukwa ndi zotsatira za pambuyo pokonza:
Chifukwa cha pulasitiki yosagwirizana kapena crystallization yosiyana, kulunjika ndi kuziziritsa kwa pulasitiki mu patsekeke; kapena chifukwa cha chikoka cha amaika zitsulo kapena zosayenera yachiwiri processing zigawo pulasitiki, zovuta zina zamkati zimakhalapo m'zigawo zapulasitiki , Zomwe zimapangitsa kuti pakhale kusintha kapena kung'ambika kwa zigawo zapulasitiki panthawi yogwiritsira ntchito, choncho tiyenera kuyesetsa kuwathetsa. Kuti

Annealing chithandizo: njira yochizira kutentha momwe zigawo zapulasitiki zimayikidwa mumlengalenga wotentha wokhazikika wamadzimadzi (monga madzi otentha, mafuta otentha, parafini wamadzimadzi, etc.) kapena kutentha kwa mpweya wotentha uvuni kwa kanthawi, ndiyeno pang'onopang'ono utakhazikika kutentha kwa chipinda.
a) Kutentha: 10° ~ 15 ° apamwamba kuposa kutentha kwa ntchito kapena 10 ° ~ 20 ° kutsika kuposa kutentha kosokoneza kutentha.
b) Nthawi: Nthawi zambiri, ikhoza kuwerengedwa pafupifupi theka la ola pa millimeter yokhudzana ndi mtundu wa pulasitiki ndi makulidwe a gawo la pulasitiki. Kuti
c) Ntchito: Chotsani kupsinjika kwamkati kwa gawo la pulasitiki, khazikitsani kukula kwa gawo la pulasitiki, kuwonjezera crystallinity, khazikitsani mawonekedwe a crystalline, potero kuwongolera zotanuka modulus ndi hardness.Humidity wokonza mankhwala: a post-treatment method that puts the newly demolded plastic parts into a heating medium (such as boiling water, potassium acetate solution) to speed up the moisture absorption balance. (Mainly used for plastics that are highly hygroscopic and easily oxidized, such as PA)

a) Kutentha: 100~121℃ (the upper limit is taken when the heat distortion temperature is high, and the lower limit is taken vice versa).
b) Nthawi: The holding time is related to the thickness of the plastic part, usually 2~9h. Kuti
c) Cholinga: Eliminate residual stress; make the product reach moisture absorption balance as soon as possible to prevent dimensional changes during use. Kuti

5. Process parameters of injection molding

5.1 Kutentha

a) Barrel temperature

The barrel temperature should be between the viscous flow temperature (or melting point) and the thermal decomposition temperature. The temperature of the plunger barrel is 10-20°C higher than the temperature of the screw barrel. Kuti

Plastic characteristics: heat-sensitive plastics such as polyoxymethylene, polyvinyl fluoride, etc.. must strictly control the maximum temperature of the barrel and the residence time in the barrel; the thermoplastic plastic with glass fiber should increase the barrel temperature due to poor fluidity. In order to prevent the melt from being hardened early in the barrel, the temperature of the barrel tends to take a small value.
Plastic parts and mold structure: For thin-walled parts, the barrel temperature is higher than thick-walled parts; for parts with complex shapes or with inserts, the barrel temperature should also be higher. Kuti

The temperature distribution of the barrel generally follows the principle of high front and low back, ndiye, the temperature of the rear section of the barrel (feeding port) is the lowest and the nozzle temperature is the highest.

For the screw injection machine, in order to prevent thermal degradation of the plastic due to the shear friction heat between the screw and the melt, the melt and the melt, and the melt and the barrel, the temperature of the front section of the barrel can be slightly lower than the middle section. To judge whether the temperature of the barrel is appropriate, the air injection method can be used to observe or directly observe the quality of the plastic parts.

During air injection, if the material flow is uniform, smooth, bubble-free, and uniform in color, the material temperature is appropriate; if the material flow is rough, silver wire or discoloration, it means that the material temperature is inappropriate. Kuti

b) Nozzle kutentha

Nthawi zambiri, it is slightly lower than the maximum temperature of the barrel to prevent the molten material from drooling at the nozzle. But it should not be too low, otherwise the melt will have premature solidification at the nozzle and block the nozzle, or premature solidification will be injected into the mold cavity and affect the quality of the plastic parts. Kuti

c) Kutentha kwa nkhungu

The mold temperature is determined by the characteristics of the plastic, the size and structure of the plastic part, performance requirements and other process conditions. Mold temperature ↑, fluidity ↑, density and crystallinity ↑, shrinkage rate and productivity ↓.
The mold temperature is usually controlled by a constant temperature cooling medium; there is also a way to maintain a certain temperature by injecting the molten material into the mold to achieve a balance between natural heating and natural heat dissipation; in special cases, resistance wires and resistance heating rods can also be used to maintain a certain temperature. The mold is heated to keep the mold at a constant temperature. But no matter what, for the plastic melt, it is a cooling process. Kuti

5.2 Pressure

(1) Plasticizing pressure (chitseko chambiri): refers to the pressure of the melt on the top of the screw when the screw retreats when the screw injection machine is used. Kuti

The plasticizing pressure increases, the temperature of the melt and its uniformity are improved, the color materials are mixed uniformly, and the gas in the melt is discharged. But the plasticization rate is reduced, and the molding cycle is prolonged. Kuti

In general operation, under the premise of ensuring the quality of plastic parts, the plasticizing pressure should be as low as possible, generally about 6MPa, and usually rarely more than 20MPa
Kuti
(2) Kuthamanga kwa jekeseni: refers to the pressure exerted by the plunger or the top of the screw on the plastic melt. Kuti

Ntchito: Overcome the flow resistance of the melt flow during the filling process during injection, so that the melt has a certain filling rate; when the pressure is maintained, the melt is compacted and prevented from flowing backward. Kuti

Size: It depends on the type of injection machine, the type of plastic, the mold structure, the mold temperature, the wall thickness of the plastic part, and the structure and size of the pouring system. Under normal circumstances: injection pressure of high-viscosity plastic> low-viscosity plastic; high injection pressure for thin-walled, large-area, and complex-shaped plastic parts; simple mold structure, larger gate size, and lower injection pressure; plunger injection machine Injection pressure> screw injection machine; the barrel temperature and mold temperature are high, and the injection pressure is low. Kuti

5.3 Nthawi

The time required to complete an injection molding process is called the injection molding cycle.

6. Formulation of plastic molding process regulations According to the use requirements of plastic parts and the process characteristics of plastics, the correct molding method is selected, the molding process and molding process conditions are determined, and the selection of plastic molds and molding equipment are rationally designed to ensure the smooth molding process Carrying out this series of work for the plastic parts to meet the requirements is usually called the formulation of the process specifications for the plastic parts.
It is a guiding technical document in plastic molding production and an important basis for organizing production. It runs through all stages of the production process and must be strictly implemented.6.1 Analysis of plastic parts

The shape and structure of the plastic part determine the structure of the mold, and it has a great influence on whether the plastic part can be formed smoothly and the quality after forming.

In order to ensure the quality of plastic parts, usually the following points need to be paid attention to:

6.1.1 Analysis of plastics

(1) Analysis of the performance of plastics
(2) Analysis of plastic process performance

6.1.2 Analysis of the structure, dimensions, tolerances, and technical standards of plastic parts

(1) Does the structure of the plastic part meet the requirements of molding processability?
(2) Dimensions, tolerances and technical standards of plastic parts

6.2 Determination of the molding method and process flow of plastic parts

According to the characteristics of the plastic, the requirements of the plastic parts, and the structure, kukula, production batch, use conditions and molding equipment of the plastic parts, a series of feasible molding programs are proposed. Through the comparative analysis of each plan, the best molding method of plastic parts is determined according to the actual production conditions on site. After the molding method of plastic parts is determined, the process flow should be determined.
6.3 Determination of molding process conditions

Appropriate process conditions should be selected for qualified plastic parts formed by various molding methods. There are many factors that affect the plastic molding process, and there are many process conditions that need to be controlled, and the relationship between the process conditions is very close. Chifukwa chake, a comprehensive analysis must be made according to the characteristics and actual conditions of the plastic, and the more reasonable process conditions must be selected initially, and then tested During the molding process, the process conditions are gradually revised according to the actual situation of the molding of the plastic parts and the inspection results of the plastic parts. Kuti

6.4 Selection of equipment and tools

When the molding method is determined, the appropriate molding equipment must be selected, and the relevant process and installation parameters of the equipment and mold must be checked. Different molding methods use different molding equipment. In addition to the molding equipment, other processes also need to select the corresponding equipment, and indicate the specifications and technical parameters of the equipment used in accordance with the process. Kuti

6.5 Formulation of process documents

The preparation of process documents is to summarize the content and parameters of the above process regulations and determine them in the form of appropriate process documents as the basis for production preparation and production process. Plastic parts process card is the most important process document in production.