Plastic hollow containers, with their lightweight, low cost, and high safety, are widely used in the beverage, pharmaceutical, cosmetic, food, and chemical industries, attracting many manufacturers to choose plastic containers to replace traditional glass containers.
The principle of blow molding is that thermoplastic resin is extruded or injection molded into a tubular plastic preform, which, while hot (or heated to a softened state), is placed in a split mold. After the mold is closed, compressed air is immediately introduced into the preform, causing it to inflate and adhere tightly to the inner wall of the mold. After cooling and demolding, various hollow products are obtained.
Common Problems in Blow Molding
The working pressure of compressed air used in blow molding is relatively high, generally reaching 3.0 MPa. Under this pressure, gaseous water and oil contaminants in the compressed air tend to accumulate into liquid contaminants. This applies to both oil-free compressors and oil-injected screw compressors. The following are defects in blow-molded products caused by various factors related to compressed air:
1. Insufficient compressed air pressure causes an orange-peel texture on the surface of the blow-molded product, or unclear outlines or graphics. Insufficient pressure can also result in the blow-molded product not meeting volume requirements.
2. Impurities in the compressed air cause pitting on the surface of the blow-molded product.
3. Excessive compressed air pressure causes the mold to break during molding.
4. Water and oil contaminants in the compressed air cause dirt and grime on the product.
Therefore, selecting appropriate compressed air post-treatment equipment is crucial.
Compressed air post-treatment equipment generally includes dust removal equipment, water removal equipment, and oil removal equipment. Corresponding purification facilities are configured for gases used in different applications.