Haochen 20 years of focus on multimode cavities and small spacing hot runner

1. Briefly describe the working status of check valves during plasticization, injection, and pressure maintaining processes;

Plasticization: On;

Injection molding: closed;

Pressure maintaining: closed;

2. Briefly describe the relationship between injection speed and injection pressure, as well as the relationship between holding speed and holding pressure;

The relationship between injection pressure and injection speed is as follows:

In the injection molding process parameters, the speed and pressure are dominant, and there is no direct relationship between the two.

In production, such as setting an injection speed of 100mm/s, when the actual injection pressure is less than the set pressure value, the screw will inject at a speed of 100mm/s
Plastic speed molding. When the actual injection pressure exceeds the set pressure value, the screw cannot reach an injection speed of 100mm/s. Actual injection pressure
The relationship with injection speed is that the faster the speed, the greater the actual pressure value. The higher the injection speed, the greater the pressure you are required to set. Very fast
Slow time also requires high set pressure. That is to say, the point with the lowest injection pressure generally does not occur at the fastest or slowest speed.

3. If there are focal spots on the product, how do you usually solve them;

Clean the mold surface;

Find the location of the focal spot and reduce the injection speed;

? Reduce mold temperature;

Reduce clamping force;

? Reduce material temperature;

Mold surface stickers to increase mold exhaust are generally not recommended;

4. Briefly describe the impact of mold temperature on product deformation?

In terms of molds, the main factors that affect the deformation of plastic parts include the pouring system, cooling system, and ejection system.

For the control of mold temperature, the temperature difference between the moving mold and the fixed mold, between the mold core and the mold wall, and between the mold wall and the insert should be determined based on the structural characteristics of the product,
So as to control the different cooling and contraction rates of various parts of the product.

After demolding, the product tends to bend in the direction of traction towards the higher temperature side to offset the orientation shrinkage difference and avoid the product changing according to the orientation pattern
Shape. For products with completely identical product shapes, the mold temperature should be kept consistent to ensure balanced cooling of all parts of the product.

What are the possible reasons for a product that is not fully filled and has flash during production?

There is a gap between the movable and fixed mold core and the broken surface;

Poor mold exhaust;

Insufficient machine locking force;

There are foreign objects on the mold surface;

Why is the process of retreating after plasticization necessary? How to optimize?

The size of the rebound can directly affect product quality issues. If it is too large, it can easily cause silver threads on the surface of the product, while if it is too small, the product may have unstable residue
Fixed, unstable product quality, mold runner overflow, nozzle threading, etc. The general experience value should not be less than 5mm.

How to optimize: Based on empirical values, fine tune the defects of the product in actual production until no overflow occurs and qualified products are produced
Stop.

What is the impact of back pressure on the product? How is the setting of back pressure generally carried out?

High back pressure:

The molten material pressure at the front end of the material barrel is too high, the material temperature is high, the viscosity decreases, and it is easy to fill, but it will increase the product contour flash;

Long storage time and prolonged heating of the melt in the material barrel cause thermal decomposition, resulting in poor color difference on the surface of the product;

Slow screw retreat, long material storage time, long forming cycle, affecting production efficiency;

Due to high melting pressure, molds with cold flow channels (not affected by needle valves) are prone to salivation, which can cause cold material blockage in the flow channels during injection molding
Or cold material spots appear on the surface of the product;

The mechanical wear of the screw and material barrel is large, which affects the service life;

Low back pressure:

The screw retreats quickly, the density of the melt flowing into the front end of the barrel is small, air is trapped, and the surface of the product is silver wire;

Poor plasticization, unstable material quantity, and significant changes in product weight and size;

Poor phenomena such as surface shrinkage, cold material lines, and uneven gloss of the product;

Bubbles are prone to appear inside the product;

Low melt temperature, high viscosity, poor melt fluidity, etc;

Setting of back pressure: The principle is from small to large (specific values can be referred to by the material supplier and the structural characteristics of the product)

8. What should you do when you find that the remaining material quantity is unstable?

1. Check if the screw three piece set is intact;
2. Check whether the injection pressure is stable and whether the inside of the nozzle is clean;

3. Check if there is material leakage from the nozzle;

4. Whether the screw temperature and mold temperature are stable within the allowable deviation value;

5. Is the loosening value of the screw set too small, causing cold material;

9. How to quickly find a reasonable locking force?

Calculation method: mold locking force=projected area of all products (including flow channels) X mold cavity pressure;

Practical method: First, set a locking force, and set an empirical value (not too small) based on the product size and machine tonnage. When the product has no

When there are burrs, gradually reduce the locking force until the product has burrs, and take the pressure value of the previous (non burrs) with burrs.