Siyini isimiso, izici, isicelo kanye nenqubo yokubumba umjovo ngomshini wokubumba umjovo?

Namuhla ake sikhulume ngomgomo, izici, application and process of injection molding by umjovo udini umshini.

1. The principle of umjovo udini. Faka ipulasitiki eyimbudumbudu noma eyimpuphu ku-hopper yomshini womjovo. Ipulasitiki iyashisisa futhi inyibilikiswe emshinini womjovo ukuze iqhubeke igeleza, and then injected into a closed mold under a certain pressure. After cooling and shaping, it melts The plastic is solidified to become the required plastic part. Ku

2. Characteristics of injection molding
Injection molding has a short production cycle and high productivity. Injection molding can produce plastic parts with complex shapes, high size requirements and various inserts, which is difficult to achieve by other plastic molding methods; secondly, injection molding is in the production process It is easy to realize automation, such as injection, demolding, gate removal and other operations can be automated, so injection molding has been widely used.

2.1 Advantages:
The molding cycle is short, the production efficiency is high, and it is easy to realize automation. Ingenza izimo eziyinkimbinkimbi, izilinganiso ezinembile, izingxenye zepulasitiki ezinezinsimbi noma ezingezona ezensimbi, izinga lomkhiqizo ozinzile, kanye nobubanzi bohlelo lokusebenza.

2.2 Ukubi:
Intengo yemishini yokubumba umjovo iphakeme kakhulu; ukwakheka kwesikhunta sokujova kuyinkimbinkimbi; izindleko zokukhiqiza ziphezulu, umjikelezo wokukhiqiza mude, futhi ayifanele ukukhiqizwa kwezingxenye zepulasitiki eziyingxenye eyodwa kanye nenqwaba encane.
3. Isicelo Ngaphandle kwama-thermoplastics ambalwa (i-fluoroplastics), cishe wonke ama-thermoplastics angasetshenziswa ukukhiqiza izingxenye zepulasitiki ngokubumba umjovo. Ukubunjwa komjovo akusetshenziselwa ukubunjwa kwe-thermoplastics kuphela, kodwa futhi isetshenziswe ngempumelelo ekubunjweni kwepulasitiki ye-thermoset. Okwamanje, I-akhawunti yemikhiqizo yayo ebunjiwe 20-30% yayo yonke imikhiqizo yepulasitiki yamanje. Ukuze kuqhutshekwe wandise ububanzi umjovo olubunjiwe izingxenye plastic, ubuchwepheshe obukhethekile bomjovo senziwe ngokukhethekile ukubumba izingxenye zepulasitiki ezinezakhiwo ezikhethekile noma izidingo ezikhethekile zesakhiwo.. Njengomjovo onembayo wezingxenye zepulasitiki ezinembe kakhulu, umjovo wemibala eminingi wezingxenye zepulasitiki ezinemibala ehlanganisiwe, isangweji umjovo wezingxenye zepulasitiki zesangweji ezakhiwe ngezinto ezahlukahlukene ngaphakathi nangaphandle, kanye nokubunjwa kokucindezelwa komjovo kwezingxenye zepulasitiki ezibonisa ngale. Ku

4. Inqubo yokubumba umjovo

4.1 Ukulungiselela ngaphambi kokubumba

Ukuhlolwa kokubukeka kwempahla eluhlaza kanye nokulinganisa ukusebenza kwenqubo: kuhlanganise nokuhlolwa kombala wepulasitiki, usayizi wezinhlayiyana nokufana, uketshezi (ncibilikisa index, i-viscosity), ukuzinza okushisayo kanye nezinga lokuncipha. Ku

Ukushisa kwepulasitiki nokomisa: susa umswakama owedlulele kanye nokuguquguquka kwezinto ukuvimbela amaphutha noma ukuwohloka ebusweni bengxenye yepulasitiki ngemuva kokubunjwa, okuzothinta ukubukeka kanye nekhwalithi yangaphakathi yengxenye yepulasitiki. Indlela yokomisa impahla: ukukhiqizwa kweqoqo elincane, usebenzisa i-oven drying; ukukhiqizwa ngobuningi, usebenzisa ukomisa abilayo noma ukomisa nge-vacuum.
Ukuhlanza imigqomo: Umgqomo udinga ukuhlanzwa lapho ushintsha imikhiqizo, ukushintsha izinto kanye nemibala. Ku

Faka preheating: nciphisa umehluko wezinga lokushisa phakathi kwezinto ezibonakalayo kanye nokufakwayo, nciphisa ukucindezelwa kokuncipha kwepulasitiki ezungeze okufakiwe, futhi uqinisekise ikhwalithi yepulasitiki. Ku

Ukukhethwa kwe-ejenti yokukhulula: Ama-ejenti okukhululwa asetshenziswa ngokuvamile afaka i-zinc stearate, upharafini owuketshezi namafutha abicah. Ku

4.2 Inqubo yomjovo

Ukondla: Faka ipulasitiki eyimbudumbudu noma eyimpuphu ku-hopper yomshini womjovo. Ku

I-Plasticization: Ngokushisisa idivayisi yokushisa yomshini womjovo, impahla eluhlaza yepulasitiki kusikulufu iyancibilika futhi iba yipulasitiki encibilika enepulasitiki enhle. Ku

Ukugcwaliswa kwesikhunta: I-plasticized melt encibilika iphushwa i-plunger noma isikulufu somshini womjovo ukuze ingene futhi igcwalise imbobo yesikhunta nge-nozzle kanye nohlelo lokuthulula lwesikhunta ngengcindezi ethile nangesivinini.. Ku

Ukugcina ingcindezi kanye nokudla: ngemva kokuba ukuncibilika kugcwalise umgodi, ngaphansi kwe-plunger noma isikulufu somshini womjovo, incibilika isagcina ingcindezi yokondla, ukuze ukuncibilika emgqonyeni kuqhubeke nokungena emgodini ukuze kugcwalise ipulasitiki emgodini Ukuncipha kuyadingeka futhi kungavimbela ukuncibilika ukuthi kubuyele emuva..
Ukupholisa ngemva kokuba isango liqandisiwe: Ngemva kwesikhathi esithile, ipulasitiki encibilikisiwe emgodini iqiniswa ibe into eqinile ukuze kuqinisekiswe ukuthi ingxenye yepulasitiki inokuqina okwanele lapho idilizwa futhi ingabangeli i-warpage noma ukuguqulwa.. Ku

Ukubhidliza: Ingxenye yepulasitiki ipholiswe ezingeni lokushisa elithile, futhi indlela yokukhipha iphusha ingxenye yepulasitiki ngaphandle kwesikhunta. Ku

4.3 Ngemuva kokucubungula izingxenye zepulasitiki

Izizathu kanye nemiphumela yokucubungula ngemuva kokucubungula:
Ngenxa ye-plasticization engalingani noma i-crystallization engalingani, ukuma nokupholisa kwepulasitiki emgodini; noma ngenxa yethonya lokufakwa kwensimbi noma ukucubungula okungalungile kwesibili kwezingxenye zepulasitiki, ezinye izingcindezi zangaphakathi zikhona nakanjani ezingxenyeni zepulasitiki , Okuholela ekuguquguqukeni noma ekuqhekekeni kwezingxenye zepulasitiki ngesikhathi sokusetshenziswa, ngakho kufanele sizame ukuwaqeda. Ku

Ukwelashwa kwe-anealing: inqubo yokwelapha ukushisa lapho izingxenye zepulasitiki zibekwe endaweni yokushisa eqhubekayo yokushisa okuphakathi kwamanzi (njengamanzi ashisayo, amafutha ashisayo, upharafini owuketshezi, njll.) noma kuhhavini wokuhambisa umoya oshisayo isikhathi esithile, bese ipholiswa kancane ilingane negumbi lokushisa.
a) Izinga lokushisa: 10°~15° ngaphezu kwezinga lokushisa lokusebenza noma ngo-10°~20° ngaphansi kwezinga lokushisa lokuphazamisa ukushisa.
b) Isikhathi: Ngokuvamile, ingabalwa cishe isigamu sehora ngemilimitha ngayinye ehlobene nohlobo lwepulasitiki kanye nobukhulu bengxenye yepulasitiki. Ku
c) Umsebenzi: Susa ukucindezeleka kwangaphakathi kwengxenye yepulasitiki, uzinzise usayizi wengxenye yepulasitiki, ukwandisa ubucwebe, uzinzise isakhiwo sekristalu, ngaleyo ndlela ithuthukise imodulus yayo enwebekayo nobulukhuni.Ukwelashwa kwesimo sokuswakama: 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) Izinga lokushisa: 100~121℃ (the upper limit is taken when the heat distortion temperature is high, and the lower limit is taken vice versa).
b) Isikhathi: The holding time is related to the thickness of the plastic part, usually 2~9h. Ku
c) Okuhlosiwe: Eliminate residual stress; make the product reach moisture absorption balance as soon as possible to prevent dimensional changes during use. Ku

5. Process parameters of injection molding

5.1 Izinga lokushisa

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. Ku

Plastic characteristics: heat-sensitive plastics such as polyoxymethylene, polyvinyl fluoride, njll. 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. Ku

The temperature distribution of the barrel generally follows the principle of high front and low back, leyo, 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. Ku

b) Izinga lokushisa le-Nozzle

Ngokuvamile, 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. Ku

c) Izinga lokushisa lesikhunta

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. Ku

5.2 Pressure

(1) Plasticizing pressure (ingcindezi emuva): refers to the pressure of the melt on the top of the screw when the screw retreats when the screw injection machine is used. Ku

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. Ku

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
Ku
(2) Ingcindezi yomjovo: refers to the pressure exerted by the plunger or the top of the screw on the plastic melt. Ku

Umsebenzi: 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. Ku

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. Ngaphansi kwezimo ezijwayelekile: 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. Ku

5.3 Isikhathi

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, ubungako, 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. Ngakho-ke, 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. Ku

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. Ku

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.