Custom injection moulding process

custom injection molding
Custom injection moulding  is a process of shaping plastic by melting it and injecting it into a predesigned mold. The process was first designed in the 1930s and was originally based on metal die casting designs. It offers many advantages to alternative manufacturing methods, including minimal losses from scrap (since scrap pieces can be melted and recycled), and minimal finishing requirements. This process differs from metal die casting in that molten metals can simply be poured; plastic resins must be injected with force.

The china custom injection moulding process uses large injection molding machines, which advance the resins through six major processes to produce everything from computer parts to plastic Halloween spiders. Although this machine is a complex piece of equipment, custom injection moulding will consists of two basic elements: the injection unit and the clamping unit. The process starts with a mold, which is clamped under pressure to accommodate the injection and cooling process. Then, pelletized resins are fed into the machine, followed by the appropriate colorants. The resins then fall into an injection barrel, where they are heated to a melting point, and then injected into the mold through either a screw or ramming device.Then comes the dwelling phase, in which the molten plastics are contained within the mold, and hydraulic or mechanical pressure is applied to make sure all of the cavities within the mold are filled. The plastics are then allowed to cool within the mold, which is then opened by separating the two halves of the mold. In the final step, the plastic part is ejected from the mold with ejecting pins. The completed part may contain extraneous bits called runners, which are trimmed off and recycled. The entire process is cyclical, with cycle times ranging from between ten and 100 seconds, depending on the required cooling time.

Custom injection moulding process requires some complex calculations. Every different type of resin has a shrinkage value that must be factored in, and the injection molds must compensate for it. If this value is not precisely determined, the final product will be incorrectly sized or may contain flaws. Typically, this is compensated for by first filling the mold with resin, holding it under pressure, and then adding more resin to compensate for contraction. Other complications may include burned parts resulting from the melt temperature being set too high, warpage resulting from an uneven surface temperature, or incomplete filling due to a too slow of an injection stroke.

China custom injection moulding can be surprisingly expensive, sometimes upward of $100,000 US Dollars (USD). If the desired part quantity is great enough, however, the mold cost becomes relatively insignificant, and the resulting plastic parts are very reasonably priced. Some molds are made with more than one cavity; these multicavity molds cost more than their single cavity counterparts, but due to increased production efficiency, the cost per part is minimized.

China custom injection moulding method can be used with a variety of plastic resins. The most popular resins for this type of molding include polypropylene (PP), polyethylene (PE), and ABS. Each has its own set of advantages and disadvantages, and they are chosen based on the desired characteristics of the final part.


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When the side wall of the plastic molding products with a hole recess boss, plastic injection molding products not directly emerge from the injection molds forming holes, grooves and bosses molded parts must be made of the activities, known as core activities. Completion of the activity type out and reset mechanism called pumping institutions.

(A) China mold company -Classification of core-pulling mechanism

  1. China mold motor core pulling , rely on the action of the inspection injection mold, core-pulling machine with the active core, the core extraction. Core pulling motor with large ejection force, labor intensity, high productivity and easy to operate, widely used in production. Their transmission mechanism can be divided into the following categories: bevel pillar core oblique block core pulling, rack and pinion core pulling.
  2. Manual pumping core mold, relying on human to extract core activities either directly or through pass parts. The disadvantage is that production, labor-intensive, and restricted, it is difficult to get a large core pulling force, the advantage of the mold structure is simple, easy to manufacture, manufacturing mold cycle is short, suitable for the trial and small batch production of plastic products. Characteristics of plastic parts limitations, can not use the motor core pulling, you must manually pumping the core. Manual core pulling their transmission mechanism can be divided into the following categories: a screw mechanism core pulling, rack and pinion core pulling activities insert core, core-pulling.
  3. Hydraulic pumping the core of the core activities, relying on the hydraulic cylinder, and its advantages can be replaced according to the size of the ejection force and the length of the core-pulling distance the core hydraulics, to get a larger ejection force and longer pulling distance , due to the use of high-pressure liquid as the driving force transfer smooth. The disadvantage is that the operation process, but also the whole set of hydraulic core pulling device, therefore, its use is limited in scope, it seldom used.

(B) China mold company — core-pulling distance and the calculation of the ejection force

Core from the plastic molding monk pumped without prejudice to the plastic products prolapse of the monk, that core pulls in the direction of the distance, called core-pulling distance. Pulling distance should be equal to the molding hole depth plus 2-3 mm.

A. Pulling distance calculation as shown in Figure 3-102.

Calculated as follows:

To S = Htgθ (3-26)


S —— pulling distance (MM)

The H —— oblique guide posts required to complete the core pulling stroke (MM)

theta —– oblique angle of inclination of the guide post, and generally 15 · 20 ·

the calculation of the ejection force plastic products in the cooling package tight core, resulting in the force of the package tight, To the core extracted must overcome the resistance of the friction caused by the package tight force, this force is called the ejection force at the beginning of core pulling the moment required release force.

Affect the ejection force of many factors, broadly summarized as follows;

  • Core forming part of the surface area and cross-sectional geometry: a core molding part of the area is large, wrap-tightening force, the mold clamping force; product shape of the cross-sectional area of the core, including the tightening force is small, and also its releasing; core cross-sectional shape is rectangular or curved, package shipping force, the release force is also large.
  • The plastic shrinkage, coefficient of friction and rigidity: The plastic shrinkage, large clamping force on the core package, the release force is also large; good surface lubricity performance plastics, the release force is small; soft plastic, hard plastic required ejection force small.
  • The wall thickness of the plastic products: inclusive area of the same size plastic products, thin-walled plastic products shrinkage, the ejection force is also small shrinkage; captured wall plastic products, mold release force.
  • Plastic products the same side at the same time the number of core-pulling: When plastic products have more than two hole slot on the same side of the pumping mechanism pulls into plastic products have more than two of the same side of the hole slot, the use of sampling World institutions at the same time pulls, due to the contraction of plastic products Pitch, the ejection force.
  • The active core molding surface roughness: the active core molding surface of the contact surface of the plastic article Pulling relative friction against the release force, have a great impact, therefore, the injection molder surface should be smaller roughness (usually Rα0.4um), processing of grain to the requirements and pulls in the same direction.
  • China mold company process; injection pressure, dwell time, cooling time for the ejection force. When the injection size, dwell time is short, the ejection force. Long cooling time, condensing contraction of plastic products is substantially complete, the package tight force, ejection force.

Under the influence of various factors, the ejection force computing power formula is as follows:

F = Lhp (u * cosα-sinα)

Wherein F —- ejection force (N)

The L — core activities are cross-sectional shape of the plastic products package tight perimeter (MM)

H — forming part of the depth (MM)

P — unit area packet clamping force, and generally … 12Pa;

u — friction slope (°)

Aircraft machines injection molded parts

injection moled parts

Aircraft machines component

CN-MOULDING as few china plastic injection molding company, that have capacity make new mould and invest new plastic injection molded parts for our customer,
We combine design, engineering and manufacturing in east of china, shanghai city.

With engineering and tool making operations in shanghia, China—a global capability that cuts lead times and allows for competitive baseline pricing.

The article describle about new injection molded parts used for Aircraft machines

and it use for aerial photo and video for production, film, movie.

It is our honor can make such high precision plastic injection molded parts through china mold maker what about Aircraft machines.

it is a vehicle that sustains itself in and propels itself through the air; an airplane, helicopter, glider, or the like. A spherical flying machine that can take off and land just about anywhere, roll along walls and hover like a helicopter was .

Injection Molding Company

Aircraft plastic part-made by CNMOULDING

Cnmoulding is owned and China business company specializes in aircraft windshield, window manufacturing, glass fiber fairing and plastic exterior and interior manufacturers, we have many years of production experience, production of all kinds of plastic accessories, remember this is China, a few factory specializing in the production of various types of related accessories CNMOULDING was the mark.