It requires the production of plastics injection molding mac

It requires the production of plastics injection molding machine should pay attention to the

The proportion of injection speed control has been widely used in the injection molding machine manufacturer. Although computer-controlled injection speed control system segment already exists, but the relevant information is limited, the advantages of this machine's settings rarely get to play. This article will explain the advantages of application of multi-stage injection speed, and an overview of its use in eliminating short shots, air traps, shrinkage defects and other products.

The close relationship between injection speed and product quality makes it a key parameter for injection molding. By determining the filling speed segment beginning, middle, end, and to achieve a smooth transition to another set point set point, we can guarantee the stability of the surface speed of the melt to produce the desired molecular orientation and asked the smallest internal stress. At this rate we recommend the following subparagraph principles: 1) the speed of the fluid surface should be constant. 2) should be used to prevent rapid injection plastic injection plastic melt during freezing. 3) injection speed setting should be taken into account in the critical region (such as the flow path) quickly filled at the same time slow down the inlet position. 4) injection speed should be guaranteed immediately after stopping to fill the mold cavity to prevent over-filling, flash and residual stresses.

Set speed segmented basis must take into account the geometry of the mold, the other flow restriction and instability. Speed setting injection molding processes and materials must have a more clear understanding of knowledge, otherwise it will be difficult to control the quality of products. Since the melt flow rate difficult to measure directly, by measuring the forward speed of the screw, or calculate the indirect cavity pressure (to determine non-return valve is not leaking).

Material properties are very important, because the polymer may be degraded due to the different stresses, molding temperatures can result in increased degradation of the vigorous oxidation and chemical structure, but the shear-induced degradation becomes small, since the high temperature reduces the viscosity of the material, reducing shear stress. Undoubtedly, the multi-stage injection speed of molding such as PC, POM, UPVC and other heat-sensitive materials and their deployment material helpful.

Die geometry is the determining factor: thin-walled require maximum injection speed; thick-walled parts need to slow - fast - slow speed profile in order to avoid defects; in order to ensure the quality standard parts, injection speed should be set to ensure that a melt flow rate of strikers constant. The melt flow rate is very important because it will affect the molecular orientation and the surface state of the part; when the melt front reaches the cross-regional structures should slow down; for complex mold radial diffusion, should ensure that the amount of melt through balanced increase; long flow paths must be filled quickly in order to reduce the cooling melt striker, but injection of high-viscosity material, such as a PC case is an exception, because the speed is too fast will be cold material into the cavity through the inlet.

Adjust injection speed can help to eliminate defects due to the flow in the inlet position appears to slow down caused. When the melt flow through the nozzle and the inlet channel to reach the surface of the melt striker may have cooled and solidified, or due to a sudden narrowing of the flow path of the melt caused by stagnation until build up enough pressure to push through the melt outlet, which will appear peaks through the inlet pressure. High pressure will cause such damage to the material and the inlet flow marks and surface defects such as burning, this situation can overcome these deficiencies through the inlet just before the deceleration method. This reduction can be prevented inlet bit excessive shear, then the rate of fire increased to its original value. Because the precise control of slowing the rate of fire in the inlet position is very difficult, so in the last paragraph of deceleration flow path is a better solution.

We can control the last paragraph of the injection speed to avoid or reduce such as flash, burned, trapped gas and other defects. Filling the last paragraph of deceleration can be prevented overfill the cavity to avoid burrs and reduce the residual stress. Due to poor mold flow path or exhaust end filling problems caused by trapped gas, it can also reduce exhaust velocity, especially the last paragraph of the exhaust velocity of injection to be addressed.

Short shot due to the speed at the inlet is too slow or partial solidification of the melt flow disruption caused by the causes. Just when local flow through the inlet or hinder accelerate injection speed can solve this problem.

Flow marks, inlet charred, molecular cracking, delamination, flaking, etc. occur on heat-sensitive material defect is caused by excessive shear caused when the inlet.

Injection speed depends on the smooth parts, glass fiber filled materials are particularly sensitive, especially nylon. Dark spots (wave pattern) is due to flow instability caused by changes in viscosity caused. Distorted flow can cause wavy or uneven mist, depending on what kind of defect generation what extent the flow instability.

When the melt through inlet speed injection results in a high shear, heat-sensitive plastics will scorch, this charred material will pass through the cavity to reach the flow front, showing the surface of the part.

To prevent radio lines, injection speed must be set to ensure the rapid and slow filling flow path through the inlet region. Find out the speed conversion point is the essence of the problem. If too early, excessive increase in filling time, if too late, too much inertia will lead to the exit flow patterns appear. The lower melt viscosity, the higher the cylinder temperature of the emitting pattern appears this trend is more obvious. Due to the small inlet requires high-speed high-pressure injection, it is also an important factor leading flow defects.

Shrunk by more effective pressure transmission, smaller pressure drop can be improved. Low mold temperature and screw speed is too slow advance significantly shortens the length of flow must be compensated by a high rate of fire. High-speed flow will reduce heat loss and heat generation due to high shear frictional heat will cause the melt temperature, the outer parts of thickening speed slows down. Cavity Cross bits must have sufficient thickness to avoid too much pressure drop, otherwise there will be shrunk.

In short, most of the injection molding defects can be resolved by adjusting the injection speed, so adjust the injection molding process is a reasonable set of skills injection speed and Segmentation