Flash
Common flash edges are located on the parting surface, the molding surface of the core pulling slider, and the surface of the ejection mechanism. It is preferred to adjust the mold testing process conditions, such as whether the amount of injection material is too large, whether the injection pressure is too large, or whether the mold locking force is insufficient (use a dial indicator to measure whether the mold is expanding). In addition to mold testing process factors, the main causes are poor machining accuracy or fitting accuracy of mold parts, small arcs at the junction of the parting surface and the mold cavity, and other reasons. Corresponding measures can be taken to solve these problems. For example, if the parting surface has a flash, it is necessary to grind and match each collision surface to reduce the gap between the parting surfaces; Another example is that there are small arcs at the junction of the parting surface and the mold cavity, such as only within 0.03-0.06mm, and within the wall thickness tolerance range, the small arcs on the parting surface can be ground off a bit (this will reduce the thickness of the product).
Eject white prints and even penetrate the workpiece.
The reason for whitening is that the ejection force exceeds the elastic limit of the plastic. First, check whether the release angle is too small, even if it is a negative angle (undercut). Secondly, check whether the polishing of the relevant parts of the core meets the required surface roughness. It is also necessary to check whether the fitting of the parts is too loose, or the wall thickness of the part is too thin, or the strength is insufficient in the mold design. The main reason is that mold temperature cannot be ignored. Generally, mold temperature exceeding 40 ℃ is often the main factor for top whitening of plastic parts. Mold deformation during injection molding is also a possible cause. Before checking the deformation of the mold, it is also necessary to adjust the mold testing process conditions to reduce the injection pressure to a small enough level. Excessive injection pressure is also one of the reasons for producing white marks.
Weld mark
Weld marks are formed when molten plastic resin passes through obstacles during mold filling, or when the cold material fronts of the two gate streams meet, resulting in poor welding. Weld marks can usually be solved by increasing the material temperature, mold temperature, and other methods to improve the fluidity of the molten material or improve the injection rate. When certain parts of the product require no welding, the gate position should be changed, or the size of some gates and cavities should be changed, that is, the location where the material streams meet should be changed to transfer the welding trace to a low photosensitive area and a stress insensitive area. Adding vent holes or opening "trash pins" at the weld line can also reduce the weld line.
Shrinkage marks
Cooling shrinkage marks of plastic can be seen in certain parts of the product, especially at the surface where the product intersects with the ribs. This is due to the thickness of the material here, and the surrounding area condenses earlier than this area. When condensing there, it is no longer possible to obtain molten material supplement from the surrounding area. The improved method is to reduce the thickness of the reinforcement during product design. Generally, the thickness of the reinforcement should be below the wall thickness dimension at the intersection, and the depth should not exceed 3 times the wall thickness at the intersection. Or use a gas assisted injection method to increase the gas flow path. The second is to increase the injection pressure, appropriately reduce the material temperature, and increase the pressure retaining pressure during injection molding. The best method is to use gas assistance.
Filamentous scar
The silver filiform scars on the surface of the workpiece are commonly referred to as silver filiform scars. The main reason for this is that there is water mixed in the molten material or mold, which can be solved by drying the material and mold first. Some scars may also be caused by excessive material temperature or excessive time spent by molten material in the barrel, as well as decomposition gas from the melt during injection. They can be solved by reducing the material temperature and minimizing the time spent by molten material in the barrel, or by appropriately controlling the injection speed.
Scorch
The performance is that some parts of the product are burnt, which is mainly caused by poor mold exhaust, excessive material flow speed, and other reasons. Therefore, corresponding countermeasures should be taken to solve the problem.
The surface of the workpiece is not bright (before surface melting)
During mold testing, process parameters such as injection rate, material temperature, and mold temperature can be adjusted accordingly. The mold can be further polished and trimmed with additional exhaust gas.
Workpiece warpage
This is caused by uneven cooling and molding strain of the workpiece. It can be solved by increasing injection pressure, reducing mold temperature, and increasing melt temperature during mold testing. If it still cannot be resolved, the mold should be repaired. It can be solved by changing the gate position, gate form (better than a straight gate with a fan shape), cooling runner position, and cooling temperature uniformity. Fixtures are also used to fix and reshape products that have just come out of the mold to solve warpage.
Insufficient injection
Some parts of the test piece are defective. It is mainly caused by insufficient injection volume, poor exhaust, low injection pressure, low material temperature, and low injection rate. It can be solved by adjusting process parameters item by item during mold testing.
If it is still difficult to solve, the mold should be repaired. During mold repair, it is necessary to consider whether the mold flow path is smooth, whether the exhaust is smooth, whether the wall thickness of the product is too thin, and whether the cold material hole is too small, and then take corresponding countermeasures to solve the problem.
Dahetian is a leading brand manufacturer of water chillers and mold thermostats in Dongguan, specializing in the research and development of industrial water chillers, freezers, water-cooled water chillers, air-cooled water chillers, screw chillers, mold thermostats, mold temperature control equipment, and other series of products. Tel: 0769-83660871/1362318867 http://www.owadajx.com         http://www.owadajx.cn