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Common problems and treatment methods of ultrasonic welding

First ,The strength can not meet the standard

First of all, we must understand that the strength of the 

ultrasonic welding machine

can never reach the one-piece molding, can only be close to the strength of the one-piece molding, and its welding strength must rely on the cooperation of a variety of factors, what are these combinations?

Plastic material: The result of ABS welding with the material is definitely stronger than the strength of ABS and PC welding each other, because the melting point of the two different materials is not the same, and the strength of the welding cannot be the same.What if ABS is fused with PP and PE? If the ultrasonic wave instantaneously emits 150 degrees of thermal energy, although the ABS material has melted,PVC, PP, and PE are only softened. We continue to heat up to more than 270 degrees, at this time PVC, PP, PE has reached the ultrasonic welding temperature, but abs material has been resolved to another molecular structure.

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conclusion:

1. The stronger the welding strength of the plastic material with the same melting point.

2. The larger the melting point gap of the plastic material, the smaller the welding strength.

3, the higher the density of the plastic material (hard) will be higher than the welding strength of the lower density (high toughness).

Second,Scars or cracks may occur on the surface of the product

During ultrasonic welding, it is common for product surfaces to be scarred, fractured or cracked at the junction.

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Because in ultrasonic operations, two situations will occur:

1. High thermal energy directly contact the surface of plastic products.

2. Vibration conduction. Therefore, when ultrasonic vibration acts on plastic products, the surface of the product is prone to burns, and plastic columns or holes with thin wall thickness within 1m/m are also very easy to produce rupture, which is an unavoidable phenomenon of ultrasonic operation.

On the other hand, due to the lack of ultrasonic output energy (extension table and HORN upper mode), it is necessary to use a long time to weld when the vibration friction energy is converted into thermal energy to accumulate thermal energy to make up for the lack of output power. This kind of welding method is not the vibration friction thermal energy achieved in an instant, but the heat energy needs to be accumulated by the welding time. Even if the melting point of the plastic product reaches the welding effect, this will cause the heat energy to stay on the surface of the product for too long, and the accumulated temperature and pressure will also cause the product to burn, break or rupture. At this time, the power output (number of segments), welding time, dynamic pressure and other coordination factors must be considered to overcome the lack of such operations.

Workaround:

1. Reduce pressure;

2. Reduce the delay time (early vibration);

3. Reduce welding time;

4. Reference media overwriting (such as PE bags);

5. Mold fixture surface treatment (hardening or chrome plating);

6. Reduce the number of machine segments or reduce the upper die expansion ratio;

7. Products that are easy to crack or break, the fixture should be made into a buffer, such as soft resin or cover cork, etc. (this refers to not affecting the welding strength);

8. Easy to break products at right angles with Rangles.