Technical Problem 8 from Fiberglass Compression Molding--Sink Marks

Technical Problem 8 from Fiberglass Compression Molding--Sink Marks

Description:The depressed deformation on the surface,ribs,raised part and/or the back side(shiny or dark).
Condition:uneven shrinkage during molding.Solution:
1).use low or no shrinkage resin in formulation for sheet molding compound(SMC).2).Increase the temperature of Cavity or Core and to bring the temperature difference between Cavity and Core to 5--6℃.
3).increase the pressure and shorten the length of glass fiber.4).improve the mold design,change the feed position.
5).narrow the gap between core and cavity of fiberglass mold.

Analysis of reasons for Warpage of Plastic Injection Molding Products-2

1)Design of the gating system,the gate location, form and number of gates of the injection mold will affect the filling state of the plastic raw material in the mold cavity and then result in deformation of the plastic part. The longer the flow distance, the greater the internal stress caused by the flow and the filling between the frozen layer and the central flow layer.Conversely, the shorter the flow distance, the shorter the flow time from the gate to the flow end of the plastic injection parts, and the freezing during filling.The thickness of the layer is reduced, the internal stress is lowered, and the warpage deformation is also greatly reduced.
For a large flat plastic part, if only one center gate or one side gate is used, since the shrinkage rate in the diameter direction is larger than the shrinkage ratio in the circumferential direction, the molded plastic part will be distorted.Point gates or film gates can effectively prevent warpage. When molding by spot casting, the position and the number of gates have a great influence on the degree of deformation of the plastic part due to the anisotropy of shrinkage of the plastic. 
Since 30% glass fiber reinforced PA6 is used, a large injection molded part with a weight of 4.95 kg is obtained, so that a plurality of reinforcing ribs are provided along the flow direction of the surrounding wall, so that a sufficient balance can be obtained for each gate. In addition, the use of multiple gates can also shorten the flow ratio (L/t) of the plastic, thereby making the density of the material in the cavity more uniform and shrinking more uniform. At the same time, the entire plastic part can be filled with a small injection pressure. The smaller injection pressure can reduce the molecular orientation tendency of the plastic and reduce the internal stress, thereby reducing the deformation of the plastic part.

Technical Problem 8 from Fiberglass Compression Molding- Surface Ripple

Technical Problem 8 from Fiberglass Compression Molding- Surface Ripple

Description:Ripple on the long,vertical and thin surface of fiberglass parts,which is at right angles to the direction of flowing.Also due to other adverse flow conditions (wall thickness difference) may result in Irregular surface ripple. 

Condition:Complex design of the product prevents uniform material flowing.

Solution:In most cases it cannot be completely eliminated, but can be improved in the following ways: Increase pressure, change the feeding position,to use low shrinkage or no shrinkage resin.