Plastic Injection


Plastic Injection

Plastic Injection
Injection molding is a molding method that obtains a resin product by melting raw material plastic pellets with heat, injecting into a mold, and then cooling and solidifying.
Among various molding technologies, it has the highest precision and can be used for a wide range of tasks from minute ones to equipment covers. As mass production is achieved in a short time, it can be applied to everything around us. It is made as a product by injection molding.

Product use
Machine parts (gears, cases, covers, etc.), automobile parts (resin parts inside and outside the car), home appliances (outer and inner parts of general household appliances), PC-related/electronic devices (connectors, housings, etc.), medical devices. It is used in a wide variety of products, including physics and chemistry analysis equipment, food manufacturing equipment, toys, and beauty equipment.

From prototype to mass production

We support production from more than 1000 pieces. If it is less than that, we support by prototyping before mass production. For example, we may make 100 prototypes and then start full-scale mass production. Our strength is that we can handle everything from trial production to mass production. Please feel free to contact us as we can handle a large variety of small lots.
Injection molding gives product designers and engineers the incentive to think “outside the box.” Advances in technology lead to design and product innovations that were previously considered impractical, and greater reliance on injection molder partnerships resulting in OEMs converting forward-thinking concepts to finished products.
Collaboration is the key to creative solutions. Injection molders that are willing to truly partner with an OEM to understand the dynamics, parameters, and end-use of a project are better positioned to help product engineers make informed choices — especially when those insights are paired with a breadth of specialization in sophisticated modeling programs and methodologies such as Design for Manufacturability (DfM). Working together toward the best possible design, mold, and process helps OEMs take stronger, longer-lasting, and less expensive products to market faster. When you partner with Viet Chuan, the job doesn’t begin and end with manufacturing the part. Our services cover the full life cycle of the product, from plastics design through assembly and packaging.
Marks — sink and burn — are cratering in thicker parts of the component and brown surface discolorations, respectively. Sink marks indicate shrinkage within the inner portions of the component while burn marks represent materials degradation.

General causes: Sink marks can happen because of insufficient cooling and curing, incorrect cavity pressure, or excessive gate temperatures. Burn marks are caused by excessive heating of materials or injection speeds that are too fast.

For sink marks, injection molders will lower mold temperatures, increase holding pressure, or adjust holding times for more cooling and curing.
For burn marks, injection molders will reduce injection speeds or mold and melt temperatures, and optimize degassing/gas venting.
Warping results from uneven shrinkage across the various parts of the mold.

General causes: Cooling is non-uniform, and the materials are stressed. Parts often twist, bend, or are otherwise deformed when the internal stresses are released.

Solutions: Injection molders prevent warping by
Monitoring and adjusting cooling times to minimize residual stresses in the part,
Designing the mold with one wall thickness to ensure molten plastic flows in only one direction,
Selecting plastics with low susceptibility to shrinking and deformation, which means typically staying away from semi-crystalline materials.
By offering so many value-added capabilities under one roof, we help our customers control product development costs, shorten their supply chains, improve product and process quality, and get to the market faster.
Automotive components can be susceptible to rework, rejection, and budget-breaking increases in the total cost of production if the parts used contain molding defects. Often these defects evidence themselves during end product review — when it could be too late for a remedy.

Preventing this costly scenario is paramount because the quality and accuracy of plastic automotive components can affect vehicle safety and reliability. Product engineers can greatly influence outcomes when they know what to look for and partner with an experienced complex injection molder who can help prevent or remediate common molding defects, like:

Short Shot Molding results from molten plastic not properly filling the mold cavity and leaving some sections with no plastic. The end product is, or quickly becomes, faulty because of this inconsistency.

General causes: There are several possibilities including incorrect shot calibration or plasticizing capacities, early solidification of a plastic that is too viscous, or trapped air caused by poor degassing or gas venting.

Solutions: Injection molders approach the solution based on the cause:

Fill rate or hesitation problems can be remedied by raising the injection pressure, speed, or temperature.
Flow restrictions may be fixed by clearing frozen flow channels or through mold redesign.
Inadequate venting is resolved by adding air vents near the end of the affected channels.
Lines — flow and weld — are consequences of how molten plastic travels through a mold. Flow lines are streaks, patterns or lines that show the physical path of the plastic prior to, and as it was, cooling. Weld lines show where plastics meet each other from separate parts of the mold.

General causes: Flow lines result from varying molten plastic flow speeds and directional changes within mold contours, when wall thicknesses change or injection speeds that are too low for consistent solidification. Weld lines occur when two or more flow fronts bond inadequately because of partial solidification of the molten plastic.


For flow lines, injection molders will optimize injection speeds and pressure, adjust locations where wall thicknesses and flow directions or speed abruptly change, or locate gates within the component’s thinner walls.
For weld lines, injection molders will raise molten plastic temperatures, increase injection speeds, rethink the design to make it a single source flow or switch to a plastic with less viscosity or a low melting temperature.