Recalque na injeção de material plástico

Summary

In this video, the speaker dives into the essential role of recalque (backpressure) in the injection molding process, highlighting its significance in ensuring proper cavity filling and preventing defects like warping. The discussion covers the timing and control needed for recalque to optimize pressure and prevent material backflow. Through a real-life anecdote, the speaker demonstrates how improper recalque settings led to defects, underscoring the importance of understanding and managing this phase. The video offers valuable insights for professionals seeking to improve their injection molding processes for higher-quality plastic parts.

Takeaways

• 😀 Understanding the function of recalque (pressurization) is essential for solving problems in plastic injection molding.
• 😀 Recalque starts after the mold cavity is filled to around 95%, helping to prevent defects and ensuring dimensional accuracy.
• 😀 The pressure applied during recalque should be 30-60% of the injection pressure, crucial for finalizing the part's formation without over-pressurizing.
• 😀 Correct recalque timing is vital; it should occur only when the material has cooled sufficiently in the entry point of the mold.
• 😀 Adjusting the recalque pressure and timing according to the material’s cooling time can prevent sink marks and other surface issues.
• 😀 The concept of the 'colchão' (cushion) plays a critical role in ensuring recalque is effective; without it, recalque cannot function properly.
• 😀 Changing the recalque pressure too late or incorrectly can lead to defective parts, such as material leaking or improper cavity filling.
• 😀 Knowledge of recalque and its proper application is crucial for ensuring the consistency and quality of molded parts.
• 😀 The pressure for recalque should always be lower than the injection pressure to avoid pushing material out of the mold improperly.
• 😀 Real-world experience, like adjusting recalque settings during molding, helps avoid defects and teaches valuable lessons about timing and pressure management.

Q & A

What is recalque in the injection molding process?

Recalque refers to the packing pressure applied during injection molding to prevent material from retracting after the mold is filled. It helps compensate for material shrinkage and ensures the part maintains its dimensional accuracy.

At what point in the injection molding cycle should recalque pressure be applied?

Recalque pressure should be applied once the mold is 95% filled, marking the transition from filling to packing the material in the mold.

Why is recalque pressure important in injection molding?

Recalque pressure is critical because it prevents defects such as shrinkage, voids, and warping in the molded part by compensating for material contraction and ensuring that the mold is completely filled.

What is the typical range for recalque pressure during injection molding?

Recalque pressure is typically set between 30% to 60% of the injection pressure, depending on the material and mold characteristics.

What is meant by 'colchão' in the context of recalque?

The 'colchão' refers to the material cushion formed in the mold when it is nearly filled. Recalque pressure is applied once the colchão reaches 95% of the cavity's full capacity, helping to ensure complete filling and compensate for shrinkage.

How does recalque affect the quality of the molded part?

Recalque ensures that the molded part is filled correctly and retains its shape and dimensions by preventing material from retracting and compensating for shrinkage. This leads to a higher-quality, defect-free part.

What could happen if recalque pressure is applied too late or too early?

If recalque pressure is applied too early, there may be excessive pressure in the mold, leading to internal stresses and defects in the part. If applied too late, it can result in incomplete filling and shrinkage, causing voids or sink marks.

What is the role of the time factor in recalque pressure?

The time factor is crucial because recalque pressure should only be maintained long enough for the material to cool at the entry point of the mold. Prolonged recalque can lead to defects, while insufficient recalque can cause incomplete part filling.

How does the pressure of recalque compare to injection pressure?

Recalque pressure should always be lower than the injection pressure. If recalque pressure exceeds the injection pressure, it can cause material to leak or flow improperly, leading to defects like overfilling or excess material in the mold.

Can recalque pressure affect both the mechanical and visual quality of the part?

Yes, recalque pressure directly influences both the mechanical strength and the visual appearance of the part. Correct recalque ensures proper filling and prevents defects that could affect the part's functionality and aesthetics.