Bubble or peeling: the convex bubble appear on the surface of the product. It is commonly in the head or tail. The complete one is called bubble and the broken one is called peeling.
The reasons of foaming and peeling from Surface of extrusion product:
1. Poor wear tolerance of extrusion cylinder and squeeze pad, improper suit size of extrusion cylinder and squeeze pad. The diameter difference of gasket exceeds the allowable value;
2. Extrusion cylinder and squeeze pad are very dirty with sticky oil, water, graphite, etc.;
3. Lubricating oil contains water;
4. Too much shovel on the surface of ingot or it is too deep. There are pores, water or trachoma on the surface of ingot;
5. The cylinder is not clean when replace the alloy;
6. Extrusion tube temperature and squeeze ingot temperature is too high;
7. Ingot temperature and size exceed the allowed negative deviation;
8. Non-drum-shaped filling caused by the long length of cast ingot, filling too fast and uneven temperature of the ingot which result in incomplete exhaust of cylinder;
9.The design of die hole is unreasonable, or cut the residual material properly lead to leak of the residual material from shunt hole and diversion hole. The gas enter the surface when it is extruded.
The elimination method:
1. Reasonable design the suit size of the extrusion cylinder and squeeze pad. Check the tool size regularly to ensure compliance with the requirements. Repair it in time when the extrusion tube appears belly. And squeeze pad can not be out of tolerance;
2. To keep clean, smooth and dry of tools and ingot surface;
3. Replace the alloy and thoroughly cleaning tube;
4. Often check the equipment to prevent the high temperature and fast speed;
5. Strict implementation of the process regulation and the system;
6. Reasonable design and produce tooling. Diversion holes and diffluence holes designed to 1 degree of ~ 3 degrees slope;
7. Strict operation, proper cutting of residual material and complete exhaust.