What Is a Feed Ratio?

The inlet is also called the gate. It is the narrow opening between the runner and the cavity, and it is also the shortest part. Its role causes the molten plastic to accelerate when it enters the cavity, which is conducive to filling the cavity quickly. The plastic in the mouth is condensed first to close the cavity to prevent the molten plastic from flowing backwards and to prevent the cavity pressure from falling too fast, so that shrinkage holes or depressions are created in the product, which facilitates the separation of the cast condensate from the product after molding.

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The 3D solid of the inlet is shown in Figure 1. According to the structural characteristics of the part,

Condition before the feed port renovation

The feed inlet seal of the cylindrical mixer is shown in Figure 11.

Figure 11/12/13 (3 photos)

Mutually sealed structure. The positive bell mouth is fixed on the barrel by M14 bolts, which can rotate with the barrel; the reverse bell mouth is welded to the feeding funnel, which is a non-rotatable part. There is a 50mm gap between the front and back bell mouths to ensure that during normal operation of the mixer, there will be no friction or collision between the two parts of the front and back bell mouths that are running relatively. The problems with this sealing structure are: Because the center of the cylinder of the mixer changes with the load and the wear of the driving tires, the front and back bell mouths are not concentric, and the gap is difficult to reach the same. Sliding friction occurs in some parts, eventually leading to the cutting of the edge portion of the positive bell mouth. The upper part of the positive and negative bell mouths are scoured by materials, causing severe wear and short service life. A large amount of dust leaks from the gap between the two bell mouths, which seriously pollutes the environment.

Improvement measures at the inlet

(1) First improvement

The original sealing device was completely removed, and an inner labyrinth seal as shown in FIG. 12 was used. The dimensions of the end of the feed funnel and the inlet of the mixer are as shown in the figure. A 1760mm circular plate is cut with a 10mm thick A3 steel plate, and then a 1150 × 970mm square hole is cut in the center of the circular plate, which is cut into two symmetrical pieces and welded to the end of the discharge opening of the feeding funnel. It is required that the circular plate is substantially parallel to the end surface of the cylinder. Then, the processed cylinder with an inner diameter of 1760mm, a width of 150mm, and a thickness of 4mm was cut into sections, and welded to the outside of the circular plate, and the gap with the inner end surface of the cylinder was maintained at 50mm. The inner labyrinth seal greatly reduces the amount of leakage and dust, but there is also the inconvenience of replacing the cylinder. The distance that the cylinder can rise when the tire is changed and the coupling is restricted. The arc seal plate and the cylinder stop The gap is large and the sealing effect is not ideal.

(2) The second improvement

The arc sealing plate in the inner labyrinth sealing structure was cut, and the diameter of the 1760mm circular plate welded to the end of the discharge opening of the feed funnel was reduced to 1654mm; 16 round holes of 14mm were cut uniformly at the stop of the cylinder. Then use a waste transportation tape to cut a length of 5250mm and a width of 230mm of sealing rubber. After punching in the sealing rubber, fix it with M12 bolts at the stop, and make a soft connection seal as shown in Figure 13. This sealing method effectively reduces the contact gap. The gap between the 1654mm circular plate and the rubber is only 5mm, which greatly improves the sealing effect, and the rubber has a long service life and is easy to replace. This improvement completely solves the problem of material leakage, and the dust leakage is greatly reduced, but there is still a certain amount of dust.

Dust control at the inlet

In order to solve the problem of dust at the inlet, an appropriate amount of water was added to the part to reduce dust (the insufficient part of the water required for mixing and granulation was supplemented by a flow meter), but the addition of water caused sticky material and blockage on the inner wall of the funnel, which affected The material flow is stable, resulting in production fluctuations. To this end, we made two further improvements.

(1) Improvement One

An 860mm × 950mm hanging vibration plate is installed at the dropping point on the inner wall of the feeding funnel of the mixer, one end of which is hinged to the funnel wall and can rotate around the hinge support. Two vibrators are installed at the corresponding parts on the outside of the funnel, and the vibrator is started, and the high-frequency micro-swing will be generated when the vibrating plate is suspended, which will shake down the bonded materials and make the material flow smooth and stable. After the improvement, the use effect is good, but the vibrator is easy to burn out, the vibration plate is severely worn, and the vibration noise is large. It also increases the daily repair, repair work and maintenance costs.

(2) Improvement 2

Remove the vibrator and the hanging vibration plate, and design and make a 860mm × 950mm industrial ceramic lining plate, install the lining plate at the blanking point on the inner wall of the funnel, and paste the cast stone lining on the rest of the funnel. The area remains smooth and flat. Because ceramic liners and cast stone liners are non-stick, resistant to abrasion, and have a long service life, especially industrial ceramic liners also have a certain impact resistance, while cast stone liners are inexpensive and can be solved well. It solves the problem of sticking and blocking the material, so that the dust at the inlet of the mixer is solved. ^[2]