the mold surface roughness is a very important technical parameter in mold making, because the surface finish of the molding area directly affects the surface roughness of the plastic part. A range of polishing tools is used to meet a different surface finish requirement. The society of plastics industry classifies mold surface finishes into 12 grades in 4 categories:
A—mirror image, it is typically polished with diamond paste, it’s surface finish Ra is 0—0.0001mm, applicable for plastic parts whose surface should have high luster. In general, mirror image is further classified into A1, A2, and A3.
B—smooth, it is usually polished with sand paper. It’s surface finish is between 0.0001—0.0002mm, applicable for plastic parts with a typical surface requirement. This category can be further classified into B1, B2, and B3.
C—Semi-smooth.it is polished with whetstone. It’s surface finish is between 0.0002—0.0008mm, applicable for plastic parts without a specific surface finish requirement. This category is also further classified into C1, C2, and C3.
D—General. Sand blasting is commonly used. This category is also further classified into D1, D2, and D3.
I agree with you
Injection molding is one of the most commonly applied processing methods for plastic components. Heat transfer coefficient (HTC), which describes the heat conducting ability of the interface between a polymer and cavity wall, significantly influences the temperature distribution of a polymer and mold during plastic component injection molding. This study focuses on HTC under diverse processing situations. On the basis of the heat conducting principle, a theoretical model for calculating the average HTC within an injection cycle was presented. Experimental injection studies were also performed to acquire necessary temperature data. The heat quantity and HTC across the interface between a polymer and cavity wall was on the basis of the results of the experimental injection studies. The factors influencing the HTC were analyzed on the basis of the factor weight during injection molding cycle. Finally, the surface roughness of plastic components obtained from disparate processing situations was measured and compared with the surface roughness of inserts. The surface roughness results are in good agreement with the HTC value and can be used to interpret the cause of variation. The results of this study will be beneficial for understanding the heat transfer process comprehensively, predicting the temperature field, arranging the cooling system, and offering precise HTC for numerical simulation.
To check the roughness changes of treated surface, we used a surface profiler, which is a non-touch roughness profiler. The following 4 specimens were measured.
– Treated surface
• solid surface
• micro-cellular foamed plastic surface
– Untreated surface
• solid surface
• micro-cellular foamed plastic surface
As the machine injects material into the mold, it must be able to get into every nook and cranny of the cavity. However, different surface finishes can change how the material flows, potentially preventing it from filling, resulting in insufficient filling pressures or material freezing prematurely.
When surgeons are doing delicate work, they need to be able to hold their tools properly, and the tool should also feel comfortable in their hand. so the surface of product in the mold is different as well
Certain materials will not release with inconsistent or flawed surface finishes. For example, silicone, thermoplastics and metal injection molding commonly require high-quality surface finishes for proper ejection from the mold cavity.
Some molds need to be textured. For example, if operators are making a mold of a medical part—like an endoscope, which a surgeon needs to hold with gloves—they will need to develop a uniform texture for gripping. Medical utensils often need to have a highly tactile capability.
Aesthetics also can play a huge role in surface finish decisions, as the the mold’s surface finish could dramatically change the final part’s application.
For example, silicon requires a mirror finish to work properly, as sometimes the finished piece cannot be touched and residue and oil from machinists’ hands cause issues.
The ratio of flow area of the rougher half with the total flow area of the molded part is used to evaluate the significance of surface roughness effect. The experimental results revealed that mold surface roughness does resist the cavity filling of polymer melt in micro injection molding. For the limited range of injection rate investigated, it is not significant on the surface roughness effects. The increase of mold temperature will decrease surface roughness effects. The change of melt temperature within the range allowed by the process is insignificant for surface roughness effects.