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Views: 0 Author: Site Editor Publish Time: 2022-04-30 Origin: Site
An important indicator of aluminum extrusion profiles is the wall thickness. Doors and windows in the 60 series have nominal wall thickness of 1.4mm. The actual measured wall thickness is often different from the nominal wall thickness of the profile, for example 1.4mm measured value is 1.42mm. So why is there a bias? The following is an introduction.
The standard of construction aluminum extrusion profiles is GB/T5237.1-2017. The national standard stipulates that the wall thickness of profiles is divided into three groups.
In practical production, group one is commonly known as wing wall thickness, and group two and three are collectively known as cavity wall thickness (cavity wall thickness, including horizontal and vertical ). Wall thickness deviation is divided into general precision, high precision and ultra high precision. The higher the grade, the smaller the deviation value of wall thickness. The deviation of profile wall thickness is ±0.09mm, and the maximum and minimum deviation is 0.18mm. For example 1.4mm, the wall thickness of 1.31mm to 1.49mm is in the tolerance.
The manufacturing material of die mostly is die steel H13 (4Cr5MoSiV1) with good comprehensive mechanical properties. Mold processing process: blanking → lathe → marking → rough milling → drilling → rough grinding shunt hole → heat treatment → plane grinding → fine milling → wire cutting → electric spark → upper and lower mold fine grinding → polishing → assembly.
The gap of the mold hole is the passage of aluminum through the mold, which forms a certain shape after it passes through the hole. This path is known as the work belt of the mold. The work belt is flat and smooth, the surface of the extruded profile will also be smooth. The gap width of the die hole determines the profile wall thickness. The smaller the gap, the thinner the wall will be.
Through the die hole molding process, aluminum is extruded at high temperatures and high pressure. In the production of metal aluminum by machines, friction will occur on the surface of the work belt, which will result in the material's surface being not smooth, rough, grainy, etc. So the mold machine unloads the mold by passing it through an aluminum block, maintains and polishes the mold.
The process of polishing involves using tools such as sandpaper and a file to remove the wear marks on a work belt in order to make the surface smooth and traceless. The polishing operation reduces the thickness of the working belt, grinding some of it off. As a result, the gap between the die hole and the working belt increases slightly. Prior to working on the extrusion machine, the mold should always be polished. The wall thickness of the aluminum profile will be slightly thicker when the mold is on the machine per time.
Nitriding the die will increase the surface hardness of the working belt and reduce the wear of aluminum on it. After the nitriding treatment is completed, a layer of nitride will be applied to the working belt of the die, improving the hardness of the die and reducing wear.
There is processing deviation in mold processing, and the wall thickness of extruded profile is deviated from the theoretical wall thickness, which is generally controlled within the range of 0.05mm. The extrusion speed also has an effect on the wall thickness of the profile, and the difference between the fast speed and the slow wall thickness is about 0.02mm.
According to GB/T5237.1 standard, profile wing wall wall thickness of high precision is ±0.13mm (deviation range 0.26mm), ultra high precision is ±0.09mm (deviation range 0.18mm). Mold from the initial machine wall thickness to more than the standard wall thickness, the wall thickness interval size is the service life of the mold. If the interval is small, the service life of the mold is low, the number of profiles produced by the mold is small, and the production cost of the manufacturer is high.
A reasonable wall thickness control standard for profiles should be conducted from the design, the processing, and the extrusion process. Additionally, the thickness deviation range for mold walls is 0.2mm, which is very high precision, which can be implemented by most manufacturers. There are some manufacturers like MetalPlus that can control within 0.15mm, raising the cost will not be too much. The manufacturer will encounter a cost challenge if the wall thickness deviation is within 0.10mm (±0.05mm).
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