What are the common defects of Plastic Products?
A: The common defects of plastic products are as follows:
Inadequate plastic products: Due to insufficient feeding, poor filling of the material, excessive inflation, poor exhaust, etc., the filling cavity is not fully filled, and the plastic product has incomplete or incomplete cavity filling.
Unstable dimensions: Mainly due to poor mold strength, poor accuracy, instability of the injection molding machine, and unstable forming conditions, the dimensional changes of plastic products are not stable.
Bubbles: Due to over-inflation or poor exhaust in the melt, residual gases in the plastic product are present, and the volume is smaller or clusters of holes (note that it should be distinguished from vacuum bubbles).
Pits (dents) or vacuum bubbles: Due to poor packing pressure, uneven cooling of plastic products, uneven wall thickness, and plastic shrinkage.
Excessive flash: Due to poor mold closing, excessive clearance, plastic fluidity is too good, and too much material is added to make the plastic product have thin wings along the edge.
Poor welding: Due to the fact that the material temperature drops when the melt is shunted and merged, and the resin is incompatible with the admixture, when the melt is shunted and merged, the welding is poor, and a fine seam line is apparently formed along the surface or inside of the plastic product.
Surface Ripple: As the melt does not fill the cavity along the surface of the mold, it flows into the semi-cured state along the surface of the cavity or there is a phenomenon of stagnation.
Silver stripe markings: Due to moisture or aeration in the material, and too much volatiles, the shearing effect of the melt is too large, the adhesion of the molten material to the surface of the mold is poor, or rapid cooling or miscellaneous materials or decomposition and deterioration, and plastic The surface of the product appears silvery-white needle-like stripes or mica-like makeup marks (water marks) along the material flow direction.
Warpage, deformation: The internal stress caused by the residual stress, shear stress, cooling stress, and uneven shrinkage during molding; poor mold release, insufficient cooling, insufficient strength of plastic products, mold deformation, etc., cause shape distortion of plastic products. Warpage is uneven from the type of hole, uneven wall thickness and other phenomena.
Cracks: Due to excessive stress in plastic products, poor mold release, uneven cooling, poor plastic properties, poor design of plastic products, and other ills (such as deformation), the surface of plastic products and feed inlets are additionally subject to fine cracks, or Cracking or cracking under load and solvent.
Black spots, black bars: Due to the decomposition of plastic products or flammable volatiles in the material, the air is decomposed and burned under high temperature and high pressure, and the combustion material is injected into the cavity with the melt, and black spots, black streaks, or plastic spots appear on the surface of the plastic products. The surface of the product is a charred burn.
Uneven color or discoloration: Due to poor distribution of pigments or fillers, discoloration of plastics or pigments on the surface of plastic products is not uniform. The reason for the uneven color varies with the appearance of the phenomenon. In the vicinity of the feed inlet, the distribution of pigments is mainly uneven. For example, when the color of the entire plastic product is uneven, the heat stability of the plastic is poor, and when the color of the welded portion is uneven, the pigment is related to the nature of the pigment.
Plastic products are fragile: Due to poor plastics, obvious directionality, large internal stress and poor structure of plastic products, the strength of plastic products is reduced, and brittle and brittle (especially along the material flow direction is easier to crack).
De-molding failure: Due to the strong filling effect and poor mold release performance, the plastic products are difficult to demold or the plastic products are deformed or broken after demolding, or the residual direction of plastic products does not meet the design requirements.
Mica flecks layered and peeled: Due to mixing with different materials or low mold temperature, the shearing effect is too large when the melt flows along the surface of the mold, so that the material sheet is exfoliated and the physical properties are reduced. Gate mold: Due to mechanical resistance in the sprue bushing, cooling is insufficient or the lever fails, making the gate stick in the sprue bushing.
Cold block, deadlock: Due to cold material or poor plasticization, there is material that is not fully plasticized, so that the plastic product has a hard block plastic.
Poor transparency: Due to poor contact between the molten material and the mold surface, there are small cavities on the surface of the plastic product causing light scattering or plastic decomposition, foreign matter impurities, or the mold surface is not bright, so that the transparency of the transparent plastic is poor or uneven.
Impurities, foreign bodies: Due to imperfections in plastics, impurities in plastic products are foreign objects. Surface luster: Due to poor mold roughness, melt and mold surface is not close, material temperature and mold temperature, etc., so that the plastic surface is not shiny, there are scars, the surface was milky or black and other phenomena.
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