Why do plastic pallets have welded seams?

Views:0     Author:Site Editor     Publish Time: 2020-11-06      Origin:Site

Why do plastic pallets have welded seams?

When the plastic pallet is produced, it is necessary to melt the polyethylene raw material first, and then enter the injection molding machine for injection molding in this state. When the plastic pallet meets the hole of the insert in the cavity of the mold, it will produce areas where the flow rate is not continuous, and the area where the flow of the mold material used to supplement is interrupted. When they meet in multiple strands, they cannot be fully melted. A linear weld seam appears. In addition, welded joints will also appear during gate injection molding, and the strength of the welded joints is poor. The main reasons are as follows:

Processing aspects: The injection molding machine has slow injection pressure and speed, and the barrel temperature and mold temperature are too low, which causes the molten material entering the mold to cool down prematurely and weld seams. When the injection pressure and speed are too high, jetting will occur and weld seams will appear. The speed should be increased and the back pressure should be increased to decrease the viscosity of the plastic pallet and increase the density. Plastic pallets should be dried well, and recycled materials should be used less. If the amount of release agent is too much or the quality is not good, weld seams will appear. Reduce the clamping force and facilitate exhaust.

For plastic pallet molds: there are too many gates in the same cavity, so the gates should be reduced or set symmetrically, or set as close to the welding seam as possible. If the welding seam is not well exhausted, an exhaust system should be installed. If the runner is too large, the size of the gating system is improper, and the gate is opened to avoid the flow of melt around the insert hole, or use the insert as little as possible. If the wall thickness changes too much or the wall thickness is too thin, the wall thickness of the part should be made uniform. If necessary, a fusion well should be opened at the weld joint to make the weld joint separate from the workpiece.

For plastic pallets: Lubricants and stabilizers should be appropriately added to plastic pallets with poor fluidity or heat sensitivity. Plastic pallets contain a lot of impurities. If necessary, replace with good quality plastic pallets.


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