Production process and classification of injection mold

Time:2020-09-24 10:11:40 / Popularity: / Source:

1 Production process of injection mold

injection mold 
Mold is a model, products are made according to this model, but how is mold produced? Most of mold professionals can't answer it. Mold has played an irreplaceable role in our lives. Most of our daily necessities cannot be separated from molds, such as computers, telephones, fax machines, keyboards, cups, and other plastic products. What’s more, outer covers such as cars and motorcycle engines are also made with molds. More than 20,000 kinds of molds will be used for a car, so role of molds in modern life is irreplaceable. As long as it is mass-produced, it cannot be separated from mold, at least in last 50 years.
So how is mold made?
Following is an introduction to mold production process:
1) ESI (Earlier Supplier Evolvement): This stage is mainly a technical discussion between customer and supplier on product design and mold development. Main purpose is to allow supplier to clearly understand design intent and accuracy requirements of the product designer, and also allow product designer to better understand capabilities of mold manufacturer and product process, so as to make a more reasonable design.
2) Quotation: Including price of mold, life of mold, turnover process, number of tons required by machine, and delivery time of mold(A more detailed quotation should include product size weight, mold size weight and other information.)
3) Purchase Order: Customer orders, deposits issued, and supplier orders accepted.
4) Production Planning and Schedule Arrangement: At this stage, we need to respond to customer for specific date when mold is finished.
5) Mold design (Design): Pro / Engineer, UG, Solidworks, AutoCAD, CATIA, etc.
6) Material procurement 
7) Machining: Processes involved are roughly turning, milling, heat treatment, grinding, CNC, electric spark (EDM), wire cutting (WEDM), JIG GRINGING , engraving, toss, etc.
8) Mold Assembly
9) Trial Run
10) Sample Evaluation Report (SER)
11) SAM Approval

2 Classification of injection mold

mold manufacturer 

(1) Single-part injection mold

When mold is opened, movable mold and fixed mold are separated, so that plastic part is taken out. It is the simplest and most basic form of injection mold. It can be designed as a single cavity injection mold or a multi-cavity injection mold as required. It is the most widely used injection mold.

(2) Double parting surface injection mold

Double parting surface injection mold has two parting surfaces. Compared with single parting surface injection mold, double parting surface injection mold adds a partially movable intermediate plate (also called movable gate plate) in fixed mold part. It is equipped with gates, runners, other parts and components required for fixed mold), so it is also called a three-plate (moving mold plate, intermediate plate, fixed mold plate) injection mold;
It is often used for single-cavity or multi-cavity injection molds with pin gate feeding. When mold is opened, intermediate plate is separated from fixed mold plate at a fixed distance on guide post of fixed mold so as to remove condensate of gating system between two mold plates. Double parting surface injection mold has a complicated structure, high manufacturing cost, and difficult parts processing. It is generally not used for molding of large or extra large plastic products.

(3) Injection mold with lateral parting and core pulling mechanism

When plastic part has side holes or undercuts, it is necessary to use a core or a slider that can move sideways. After injection molding, movable mold is first moved down a certain distance, and then slanted section of bent pin fixed on fixed mold plate forces slider to move outward, and at the same time, push rod of demolding mechanism pushes pusher plate to demould plastic part from core.

(4) Injection mold with movable molded parts

Due to some special structures of plastic parts, injection molds are required to be provided with movable molding parts, such as movable convex molds, movable concave molds, movable inserts, movable threaded cores or rings, etc. When mold is demoulded, it can be removed from mold together with plastic part and then separated from plastic part.

(5) Automatic thread unloading injection mold

For plastic parts with threads, when automatic demolding is required, a rotatable threaded core or ring can be set on mold, using mold opening action or otating mechanism of injection molding machine, or a special transmission device to drive threaded core or threaded ring to rotate. Thereby, plastic part is released.

(6) Runnerless injection mold

Runnerless injection mold refers to method of adiabatic heating of runner to keep plastic between nozzle and cavity of injection molding machine in a molten state, so that there is no condensate in gating system when plastic part is removed once mold is opened. The former is called adiabatic runner injection mold, and the latter is called hot runner injection mold.

(7) Right-angle injection mold

Right-angle injection molds are only suitable for angle injection molding machines. Unlike other injection molds, feeding direction of this type of mold during molding is perpendicular to opening and closing direction. Its main runner is set on both sides of moving and fixed mold parting surfaces, and its cross-sectional area is usually constant. This is different from other injection molds. At the end of main runner, in order to prevent wear and deformation of injection molding machine nozzle and inlet end of main runner, a replaceable runner insert can be provided.

(8) Injection mold of demolding mechanism on fixed mold

In most injection molds, ejection device is installed on the side of movable mold, which is conducive to work of ejection device in opening and closing mold system of injection molding machine. In actual production, because some plastic parts are limited by shape, it is better to leave plastic part on the side of fixed mold. In order to make plastic part come out of mold, a demolding mechanism must be set on the fixed mold .

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