Design av sprutformens avgasspår

Injektionsform ska utformas av avgasspår och är ett verktyg för att producera plastprodukter; Det är också ett verktyg för att ge plastprodukter en komplett struktur och exakta dimensioner. Injektionsmålning är en bearbetningsmetod som används i massproduktionen av vissa komplexformade delar. Speciellt, Den hänvisar till högtrycksinjektionen av plasten som smälts genom värme i mögelhålan med formsprutningsmaskinen, och den gjutna produkten erhålls efter kylning och stelning.

Mögelkomposition

Även om formens struktur kan variera mycket på grund av plastens variation och prestanda, Plastprodukternas form och struktur, och typen av injektionsmaskin, grundstrukturen är densamma. Formen består huvudsakligen av ett hällsystem, ett temperaturkontrollsystem, bildar delar och strukturella delar.

Bland dem, the pouring system and molded parts are the parts that are in direct contact with the plastic and change with the plastic and the product. They are the most complex and the most variable parts in the plastic mold, requiring the highest processing finish and precision.

The injection mold is composed of a movable mold and a fixed mold. Den rörliga formen är installerad på den rörliga mallen för formsprutningsmaskinen, och den fasta formen är installerad på den fasta mallen för formsprutningsmaskinen.

Under formsprutning, the movable mold and the fixed mold are closed to form a pouring system and a cavity. När formen öppnas, the movable mold and the fixed mold are separated to take out the plastic products. In order to reduce the heavy workload of mold design and manufacturing, most of the injection molds use standard mold bases.

exhaust vent

It is a trough-shaped air outlet opened in the mold to discharge the original gas and the gas brought in by the molten material. When the melt is injected into the cavity, the air originally stored in the cavity and the gas brought in by the melt must be discharged out of the mold through the exhaust port at the end of the material flow, otherwise the product will have pores, poor connection.

Dissatisfaction with the filling of the mold, and even the accumulated air will burn the product due to the high temperature generated by the compression. Under normala omständigheter, the vent can be located either at the end of the melt flow in the cavity or on the parting surface of the mold. The latter is a shallow groove with a depth of 0.03-0. 2mm and a width of 1.5-6mm on one side of the cavity.

During injection, there will not be a lot of molten material in the vent hole, because the molten material will cool and solidify at the place and block the channel. The opening position of the exhaust port should not be facing the operator to prevent accidental spraying of molten material and hurting people. Dessutom, the matching gap between the ejector rod and the ejector hole, the matching gap between the ejector block and the stripper plate and the core can also be used for exhaust.

1. The role of the exhaust slot

The function of the exhaust groove mainly has two points: one is to remove the air in the mold cavity when the molten material is injected; the other is to remove various gases generated during the heating process of the material. The thinner the product, ju längre bort från grinden, Öppningen av avgasspåret är särskilt viktigt.

Dessutom, för små delar eller precisionsdelar, Öppningen av ventilationsspåret bör också vara uppmärksam på, Eftersom det inte bara kan undvika ytförbränningar och otillräcklig injektionsvolym, men eliminera också olika defekter av produkten och minska mögelföroreningar. Till

Så, Hur kan avgaserna från forma hålighet betraktas som tillräcklig? Generellt, Om smälten injiceras vid den högsta injektionshastigheten, Men inga fokalfläckar finns kvar på produkten, Det kan övervägas att avgaserna i kaviteten är tillräckligt.

2. Avgemetod

Det finns många sätt att uttömma mögelhålan, Men varje metod måste garanteras: the size of the exhaust slot should be designed to prevent the material from overflowing into the slot while the exhaust slot is exhausted; för det andra, it should prevent clogging. Därför, when measuring from the inner surface of the cavity to the outer edge of the cavity, the height of the venting groove above 6-12mm should be about 0.25-0.4mm.

Dessutom, too many exhaust grooves are harmful. Because if the clamping pressure acting on the parting surface of the mold cavity without opening the vent groove is very large, it is easy to cause cold flow or cracking of the mold cavity material, which is very dangerous.

In addition to venting the mold cavity on the parting surface, it can also achieve the purpose of venting by arranging an venting groove at the end of the material flow of the pouring system and leaving a gap around the ejector rod, because the venting groove If the selection of the depth, width and position of the opening is not appropriate, the flash burr produced will affect the appearance and accuracy of the product. Därför, the size of the above gap is limited to prevent flash around the ejector rod.

Special attention should be paid here: when parts such as gears are exhausted, even the smallest flash may be undesirable. For this type of parts, it is best to use the following methods to exhaust:

(1) Completely remove the gas in the flow channel;

(2) Shot peening the mating surface of the parting surface with 200# silicon carbide abrasive. Dessutom, the opening of the exhaust groove at the end of the material flow of the pouring system mainly refers to the exhaust groove at the end of the runner. Its width should be equal to the width of the runner, and the height varies depending on the material.

3. Design method Based on many years of experience in injection mold design and product testing, this article briefly introduces the design of several exhaust grooves. For product molds with complex geometric shapes, it is best to determine the opening of the vent slot after several mold trials. The biggest disadvantage of the overall structure in the mold structure design is poor exhaust
4. There are several ways to vent the core of the integral cavity: (1) Use the groove or insert installation part of the cavity; (2) Use the side insert seam; (3) Partially make it into a spiral shape; ( 4) Install a slotted slat core and open a craft hole in the longitudinal position;

(5) When the exhaust is extremely difficult, adopt the mosaic structure, etc.; if the dead corners of some molds are not easy to open the venting groove, first of all, the mold should be appropriately changed to the mosaic processing without affecting the appearance and accuracy of the product. , It is not only good for processing the exhaust groove, but sometimes it can also improve the original processing difficulty and facilitate maintenance.

4. Exhaust slot design when thermosetting plastics are molded. Exhaust of thermosetting materials is more important than thermoplastic materials. För det första, the runners in front of the gate should be exhausted. The width of the exhaust slot should be equal to the width of the runner, and the height should be 0.12mm. All sides of the mögelhålrumshould be exhausted. The exhaust slots should be 25mm apart, 6.5mm wide, and 0.075-0.16mm high, depending on the fluidity of the material. Softer materials should take lower values.
5. The ejector rod should be enlarged as much as possible, and in most cases, 3-4 flat surfaces with a height of 0.05mm should be ground on the cylindrical surface of the ejector rod, and the direction of the wear marks should be along the length of the ejector rod. Grinding should be carried out with a fine-grained grinding wheel. The end face of the ejector rod should be ground with a chamfer of 0.12mm, so that if there is a flash formed, it will adhere to the workpiece.

Conclusion Properly setting up the exhaust groove can greatly reduce the injection pressure, injection time, holding time and clamping pressure, and make the molding of plastic parts easy, thereby improving production efficiency, reducing production costs, and reducing machine energy. Consumption.

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