Šta je princip, karakteristike, primjena i proces brizganja strojem za brizganje?

Danas ćemo razgovarati o principu, karakteristike, primjena i proces brizganja po mašina za brizganje.

1. Princip od brizganje. Dodajte plastiku u granulama ili prahu u rezervoar mašine za ubrizgavanje. Plastika se zagrijava i topi u mašini za ubrizgavanje kako bi održala protok, a zatim ubrizgan u zatvoreni kalup pod određenim pritiskom. Nakon hlađenja i oblikovanja, topi se Plastika se stvrdnjava i postaje potrebni plastični dio. To

2. Karakteristike brizganja
Injekciono prešanje ima kratak proizvodni ciklus i visoku produktivnost. Injekciono prešanje može proizvesti plastične dijelove složenih oblika, visoke zahtjeve za veličinom i raznim umetcima, što je teško postići drugim metodama oblikovanja plastike; drugo, brizganje je u procesu proizvodnje Lako je realizovati automatizaciju, kao što je injekcija, demolding, uklanjanje kapija i druge operacije mogu se automatizirati, pa je injekcijsko prešanje široko korišteno.

2.1 Prednosti:
Ciklus oblikovanja je kratak, efikasnost proizvodnje je visoka, i lako je realizovati automatizaciju. Može formirati složene oblike, tačne dimenzije, plastični dijelovi sa metalnim ili nemetalnim umetcima, stabilan kvalitet proizvoda, i širok spektar primjene.

2.2 Nedostaci:
Cijena opreme za brizganje je relativno visoka; struktura kalupa za injektiranje je složena; troškovi proizvodnje su visoki, proizvodni ciklus je dug, i nije pogodan za proizvodnju jednodijelnih i maloserijskih plastičnih dijelova.
3. Primjena Osim nekoliko termoplasta (fluoroplastika), gotovo svi termoplasti mogu se koristiti za proizvodnju plastičnih dijelova brizganjem. Injekciono prešanje se ne koristi samo za oblikovanje termoplasta, ali se također uspješno koristi za oblikovanje termoreaktivne plastike. Trenutno, njeni oblikovani proizvodi čine 20-30% svih aktuelnih plastičnih proizvoda. Kako bi se dodatno proširio opseg brizganih plastičnih dijelova, neke posebne tehnologije ubrizgavanja razvijene su posebno za oblikovanje plastičnih dijelova sa posebnim svojstvima ili posebnim strukturalnim zahtjevima. Kao što je precizno ubrizgavanje visoko preciznih plastičnih dijelova, višebojno brizganje kompozitnih plastičnih dijelova u boji, sendvič brizganje sendvič plastičnih dijelova sastavljenih od različitih materijala iznutra i izvana, i brizganje kompresije optički prozirnih plastičnih dijelova. To

4. Proces brizganja

4.1 Priprema prije oblikovanja

Inspekcija izgleda sirovine i mjerenje performansi procesa: uključujući inspekciju plastične boje, veličina i ujednačenost čestica, fluidnost (indeks topljenja, viskozitet), termička stabilnost i brzina skupljanja. To

Predgrijavanje i sušenje plastike: uklonite prekomjernu vlagu i isparljive tvari u materijalu kako biste spriječili defekte ili degradaciju na površini plastičnog dijela nakon oblikovanja, što će uticati na izgled i unutrašnji kvalitet plastičnog dela. Metoda sušenja materijala: male serije proizvodnje, korištenjem sušenja u pećnici; masovna proizvodnja, korištenjem sušenja ključanjem ili sušenja u vakuumu.
Čišćenje bačvi: Cijev se mora očistiti prilikom mijenjanja proizvoda, mijenjanje materijala i boja. To

Ubacite predgrijavanje: smanjiti temperaturnu razliku između materijala i umetka, smanjiti napon skupljanja plastike oko umetka, i osigurati kvalitetu plastike. To

Izbor sredstva za odvajanje: Uobičajena sredstva za otpuštanje uključuju cink stearat, tečni parafin i silikonsko ulje. To

4.2 Proces ubrizgavanja

Hranjenje: Dodajte plastiku u granulama ili prahu u rezervoar mašine za ubrizgavanje. To

Plasticizacija: Kroz grijanje uređaja za grijanje mašine za injektiranje, plastična sirovina u vijku se topi i postaje plastična talina dobre plastičnosti. To

Punjenje kalupa: Plastificirana plastična talina se gura klipom ili zavrtnjem mašine za ubrizgavanje da uđe i ispuni šupljinu kalupa kroz mlaznicu i sistem za izlivanje kalupa pri određenom pritisku i brzini. To

Održavanje pritiska i hranjenje: nakon što talina ispuni šupljinu, ispod klipa ili zavrtnja mašine za ubrizgavanje, talina i dalje održava pritisak za punjenje, tako da talina u buretu nastavi da ulazi u šupljinu kako bi nadopunila plastiku u šupljini. Skupljanje je potrebno i može spriječiti da talina teče natrag.
Za hlađenje nakon što se kapija zamrzne: Nakon nekog vremena, rastopljena plastika u šupljini se učvršćuje u čvrstu supstancu kako bi se osiguralo da plastični dio ima dovoljnu krutost kada se izvadi iz kalupa i da ne uzrokuje savijanje ili deformaciju. To

Demoulding: Plastični dio se hladi na određenu temperaturu, a mehanizam za izbacivanje gura plastični dio iz kalupa. To

4.3 Naknadna obrada plastičnih dijelova

Razlozi i efekti naknadne obrade:
Zbog neravnomjerne plastifikacije ili neravnomjerne kristalizacije, orijentacija i hlađenje plastike u šupljini; ili zbog utjecaja metalnih umetaka ili nepravilne sekundarne obrade plastičnih dijelova, neka unutrašnja naprezanja neizbežno postoje u plastičnim delovima , Rezultat je deformacija ili pucanje plastičnih dijelova tokom upotrebe, pa treba da pokušamo da ih eliminišemo. To

Tretman žarenjem: proces toplinske obrade u kojem se plastični dijelovi stavljaju u tekući medij za zagrijavanje konstantne temperature (kao što je topla voda, vrelo ulje, tečni parafin, itd.) ili pećnica sa cirkulacijom vrućeg zraka na određeno vrijeme, a zatim se polako ohladi na sobnu temperaturu.
a) Temperatura: 10°~15° viša od radne temperature ili 10°~20° niža od temperature izobličenja toplote.
b) Vrijeme: Generalno, može se izračunati na oko pola sata po milimetru ovisno o vrsti plastike i debljini plastičnog dijela. To
c) Funkcija: Uklonite unutrašnje naprezanje plastičnog dijela, stabilizirati veličinu plastičnog dijela, povećati kristalnost, stabiliziraju kristalnu strukturu, čime se poboljšava njegov modul elastičnosti i tvrdoća. Tretman za kondicioniranje vlage: metoda naknadne obrade koja stavlja tek izvađene plastične dijelove u medij za grijanje (kao što je kipuća voda, rastvor kalijum acetata) za ubrzavanje ravnoteže apsorpcije vlage. (Uglavnom se koristi za plastiku koja je visoko higroskopna i lako oksidira, kao što je PA)

a) Temperatura: 100~121℃ (gornja granica se uzima kada je temperatura toplotne distorzije visoka, a donja granica se uzima obrnuto).
b) Vrijeme: Vrijeme držanja je povezano s debljinom plastičnog dijela, obično 2~9h. To
c) Svrha: Uklonite rezidualni stres; make the product reach moisture absorption balance as soon as possible to prevent dimensional changes during use. To

5. Process parameters of injection molding

5.1 Temperatura

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. To

Plastic characteristics: heat-sensitive plastics such as polyoxymethylene, polyvinyl fluoride, itd. 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. To

The temperature distribution of the barrel generally follows the principle of high front and low back, to je, 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. To

b) Temperatura mlaznice

Generalno, 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. To

c) Temperatura kalupa

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. To

5.2 Pressure

(1) Plasticizing pressure (povratni pritisak): refers to the pressure of the melt on the top of the screw when the screw retreats when the screw injection machine is used. To

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. To

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
To
(2) Pritisak ubrizgavanja: refers to the pressure exerted by the plunger or the top of the screw on the plastic melt. To

Funkcija: 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. To

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. U normalnim okolnostima: 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. To

5.3 Vrijeme

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, veličina, 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. Stoga, 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. To

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. To

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.