How should the extrusion blow molding process for HDPE barrels be controlled?

How should the extrusion blow molding process for HDPE barrels be controlled?


① The extruded blow-molded HDPE barrels are shown as in the figure. The HDPE used for extrusion blow-molding should have a melt flow rate (MFR) of 0.25 to 0.35 g/10 minutes. If the MFR is too small, the processing will be difficult; if it is too large, the molded part may sag. Generally, hollow-grade resins are selected.
② The barrel temperature of the extrusion mold should be controlled at 150 to 210℃. While ensuring that the molded part of the extrusion blow-molding is smooth, the processing temperature should be as low as possible.
③ To ensure that the molded part adheres closely to the mold cavity wall and obtains the desired shape, the blow-molding pressure is generally controlled between 0.5 and 0.65 MPa. For containers with large volume and thin barrel walls, or resins with a lower MFR, the blow-molding pressure should be higher; conversely, the blow-molding pressure should be lower.
④ The blow-up ratio of HDPE barrels is generally between 1.5 and 3.0. For larger containers and those with thinner barrel walls, a smaller blow-up ratio should be selected; conversely, a larger blow-up ratio should be chosen. 
⑤ The temperature of the blow molding mold is 20℃, and the blow molding pressure is 0.6 MPa.
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