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Precision injection molding is a popular method used for manufacturing automobile parts. While the process is quite efficient and productive, some precautions are required. One primary concern is the formation of a flash. Flash refers to unwanted excess material (typically a thin plastic layer) that is formed at the interface between the mold’s two halves. It is considered a defect because it leads to compromised plastic molded part quality and dimensional inaccuracies. Dealing with flash requires extra resources and time, so it’s best to avoid its occurrence in the first place. Fortunately, there are ways to achieve that.
Common Reasons Why the Flash Occurs
The flash in precision injection molding of car parts occurs due to the following common reasons:
1. Mold
Mold-related problems are the top causes of flash occurrence in precision injection molding. These problems include the following:
- Rough Mold Surface: If the mold surface is rough, it causes excess material flow, which sticks to the plastic molded part and leads to flash formation.
- Over-Wear Sliders of Cores and Cavities: Over-wear sliders of cavities and cores lead to misalignment and excess movement of the mold halves, resulting in the formation of a flash.
- Asymmetrical Design: Asymmetrical design leads to uneven material flow, which increases the risk of flash during precision injection molding.
- Lack of Air Exhaust Holes: Lack of air exhaust holes in the mold leads to trapped air inside that makes the material flow in unwanted directions, causing many issues, including flash formation.
2. Material
The type of material used in precision injection molding is important. No matter what material you use, make sure it has high viscosity. Otherwise, you can expect the following:
- High Fluidity: High fluidity of the material will result in the molten liquid flowing out of the mold shape and creating distortions, ultimately forming a flash.
For complex parts, using low viscosity and high fluidity is fine.
3. Molding Operation
Molding operation-related negligence can contribute to flash formation. The top reasons include the following:
- High Injecting Pressure: High injecting pressure leads to increased and excessive flow of the molten material, causing flash formation.
- High Temperature Of The Melted Material: High temperature lowers the viscosity of the melted material, creating excessive flow and leading to flash formation.
- Uneven Injecting Pressure: Uneven injection pressure can cause the melted material to flow unevenly and leads to flash formation.
- Too-Much Injection: Too-much injection or over-filling creates leakages and increases the risk of flash.
How to Shorten the Injection Molding Time
There are ways to shorten the precision injection molding time and minimize the risk of flash formation. Here are the top 6 recommendations:
1. Regularly Maintain the Mold
Proper maintenance of the mold helps ensures that you get reliable and consistent results and avoid any mold issues.
2. Balance The Mold
Balancing the mold can help ensure even material flow, hence reducing the risk of flash formation and leading to shorter molding times.
3. Set Air Exhaust Holes
Blocked air vents, or lack of them, are one of the common causes of flash formation and increased precision injection molding time. For the best results, set air exhaust holes with an average depth of 0.03mm and width of 3mm to prevent trapped air in the mold.
4. Choose Materials with Low Viscosity and High Fluidity
For complex parts and high-precision plastic injection molding, it is recommended that you choose materials with low viscosity and high fluidity to allow them to easily flow through the mold and provide desired results.
5. Decrease The Injecting Pressure
The injecting pressure directly affects the temperature and viscosity of the melted material. Reducing it is recommended to avoid flash formation problems.
6. Increase The Clamp Pressure
For the best results, the clamping pressure must be precise. If it is too low, it can cause flash formation. Increasing it ensures proper mold alignment and shortens the molding time.
Choose a Reliable Plastic Injection Molding Service for the Best Results
The above-listed are some recommendations to prevent flash formation in precision injection molding of car parts. If this all seems too much, you can always hire the services of a professional injection molding service provider to ensure everything goes right and your project is completed on time. The seasoned brand HordRT is a trusted name in this industry. It offers reliable plastic injection molding services that help achieve consistent results.
The benefits of choosing a reputed provider like HordRT include professional service, fast production time, the use of high-quality plastic parts, a variety of material and finish options, competitive pricing, and more. HordRT’s production facility and commitment to quality ensure optimal prototyping results and minimize the risk of issues like flash formation. Contact HordRT to learn about its rapid plastic injection molding service in detail.
