injection mould weld line causes and improvement measures
Data: 2020-01-06 15:35 Browse Times :
Due to poor exhaust residual gas generated during the injection injection mould cavity is compressed , not only products, but also lead to weld burn marks appear. When the melt filling gas is pushed into the confluence of the site is easy to melt between two strands streams generated sandwich , ultimately impede stream integration, not only to promote but also reduce weld lines generated at the weld line strength . PS plastic parts in the full exhaust at the weld line strength is 36.5MPa, but not only 17.5MPa exhaust . Vent or using a vacuum injection mould fully air-entraining eliminate all help reduce weld marks. In addition , the creation of a cold slug can melt the cold slug site striker confluence ( commonly known as junk sales ) in parts of the weld marks appear . Improve the melt temperature at the end of the confluence of plastic parts , not only can reduce the generation of weld lines , and can enhance the strength at the weld line .
Design c. temperature regulation system
The lower injection mould temperature is not conducive to more fully fused melt . injection mould design , if the cooling water from the confluence of the melt too close , then melt the seams to reduce the viscosity due to temperature rise can not be fused , will produce significant weld marks. Cooling system designed properly, can also cause injection mould temperature distribution difference is too large , resulting in the plastic melt during filling , different results in different parts of the cavity fill rate due to temperature , causing weld marks . Therefore, a reasonable temperature control system design , injection mould temperature will fluctuate evenly distributed , reducing the generation of weld lines .
Now realize the thermal shock injection injection mould temperature control regulation system , the injection mould cavity surface temperature can quickly convert the injection injection mould process according to the needs of each stage . This thermal shock injection mould temperature control system , due to their common advantage is that the surface can be formed rapidly , uniformly cool , and can rapidly heated to near or equal to the melting temperature of the raw material , thus forming a good product quality, easy to produce weld marks, injection mould defects such as flow marks . Another advantage of the magnetic effect of a rapid heating of the battery circle injection mould surface , then use the water cooled injection mould to injection mould temperature control method can improve the quality of plastic parts , to avoid the generation of weld lines .
d. cavity, the design of the surface roughness of the core
Surface roughness cavity, core filling flow will also affect the speed of the plastic melt . The surface roughness is too large, the melt flow rate slows down , the condensation layer of injection mould wall thickening , the material flow cross-section is reduced , the flow resistance is increased , the melt temperature difference between the expansion of branch weld strength. When machining injection mould cavity surface roughness if inconsistent, also due to the different speeds resulting melt filling weld line formation.
e. die structural improvements in other areas
One can eliminate the hole injection injection mould structure has the appearance of weld line of products , the specific method is injection injection mould products, just fill in the cavity is completed , the use of inlay cavity softer core of molten material to be cut , get products holes. This method can be used for various types of surface holes of plastic products , the weld line can be completely eliminated at the holes , thereby improving product quality. There is also a special injection mechanism , the actual production, moving, set the template is not locked when ( gap 2mm) for injection injection mould, injection amount is needed in the secondary injection mould 70 % -80% of the injection volume . As the injection mould is not completely closed when there is no diversion effect of the core , it will not form a weld line , it is possible to completely eliminate the generation of weld lines .