Extrusion molds are basic tools that ensure the formation of aluminum profiles and have the correct shape, size, and accuracy. Aluminum profile manufacturers also account for a large proportion of the production cost of aluminum profiles. A few thousand yuan extrusion mold usually can only produce a few tons of profiles, which requires repair. If it is a complex profile, such as a hollow profile, its lifespan is less, so how to improve its lifespan? Below, we will share some methods for repairing profile defects caused by hollow profile extrusion molds.

1. The reason for the concave arched surface of the hollow aluminum profile wall is that the working strip of the mold core is lower than the working strip of the lower mold hole, and the effective length of the working strip of the mold core is too short.

Correction method: Place a spacer ring between the mold core and the lower mold, so that the working belt of the mold core is at the same height as the sizing belt of the lower mold hole under stress. At the same time, reduce the same thickness at the outlet of the lower mold.

2. The reason for the protrusion of the aluminum profile wall is that the mold has been used for a long time, and the aluminum profile features severe wear on the working strip of the mold core, resulting in grooves and increased friction resistance. The slow metal flow causes the protrusion of the hollow profile wall.

Correction method: If the wall thickness tolerance of the profile allows, the surface of the working strip of the mold core can be filed or polished to reduce friction resistance; If the wear of the working strip of the mold core is severe and the wall thickness of the profile has reached the upper deviation, the mold can be preheated to around 300 ℃, the mold core shape can be repaired, and then filed to the required size and polished before use; If the mold core working belt is not worn out, simply file the obstruction on the outer side and the retention on the inner side of the mold core working belt.

2、 There are seam corners or poor welding

Hollow profiles are extruded using a planar split flow combination die, and the metal undergoes the process of split flow and welding, so there are welding lines in the hollow profile. If the metal welding is not good and gaps appear, it is a defect.

There are two reasons for the occurrence of gaps: 1. The diversion hole or welding chamber is narrow, the metal supply is insufficient, the metal does not form sufficient hydrostatic pressure in the welding chamber, and the product is not welded properly and flows out of the mold hole, resulting in welding gaps in the product; 2. Excessive lubrication and poor lubrication cause poor welding of hollow profiles. The former can be solved by grinding or milling to expand the area of the diversion hole and welding chamber, increase the metal flow, and enable the metal to form sufficient hydrostatic pressure in the welding chamber. The latter can be solved by using the non lubricated extrusion aluminum profile process.

3、 Bending and twisting

Cause of occurrence:

1. The working belt of the mold core and lower mold hole is not properly matched, causing uneven metal flow velocity in various parts of the profile;

2. The size and position of the diversion holes in the symmetrical hollow aluminum profile mold are processed asymmetrically, resulting in uneven metal supply and uneven metal flow velocity;

3. The processing of the diversion hole is irregular or there are obstacles on the mold core that hinder metal flow.

Correction method for aluminum profiles:

1. Grind the outlet area of the mold core or diversion hole using appropriate methods, and if necessary, expand these diversion holes appropriately to ensure a balanced supply of materials.

2. Remove obstacles by polishing.

4、 Profile surface stripes

Stripes appear on the outer surface of aluminum extruded profiles, which are more pronounced after anodizing. This defect is often found in areas with large wall thickness differences of profiles, welding areas of metal under the diversion bridge, and on the back with forks and threaded holes on the inside.

Cause of occurrence

1. The forks and threaded holes on the inner side of the aluminum profile cause surface stripes due to insufficient or excessive metal supply;

2. Stripes on the surface of the profile caused by the welding area under the diversion bridge of the extrusion mold;

3. There is a problem with the design of aluminum profile cross-sectional drawings. Due to the large wall thickness difference of the aluminum profile, stripe like color differences occur at the location of sudden changes in the length of the working strip after anodizing;

4. Due to insufficient cooling capacity of the machine, black striped areas are formed after anodization;

5. The poor quality of the casting billet itself affects the color difference of the stripes after anodizing of the extruded material.

Correction method:

1. Firstly, check the design drawings to see if there are any significant differences in profile wall thickness, branches, and threaded holes;

2. The diversion bridge should be designed on the non decorative surface of the profile. While ensuring the strength of the mold, the welding chamber should be as large as possible to allow the metal to form sufficient hydrostatic pressure;

3. A large diameter pipe or a large size hollow profile mold can be equipped with an upper welding chamber on the male mold;

4. The method for repairing the stripes at the forks or threaded holes on the inner side of the profile is to polish the working strip of the mold holes in these areas, polish them smooth, or modify or reduce the connection transition radius of these areas;

5. Sometimes the stripes are formed by the material itself of the casting billet, requiring a uniform heating temperature and thorough homogenization annealing of the casting billet;

6. After the extrusion material is released from the mold hole, its grain size depends on the temperature entering the quenching zone and the cooling rate of the quenching zone. If the cooling temperature is too low and the cooling speed is uneven, it will cause excessive grain size or uneven grain size, and the color difference will become more obvious after anodizing. It is required that the operator adjust the air pressure and cooling water pressure of the cooling system in a timely manner.