I remember distinctly my initial knowledge about creating a die which had been meant to die casting china in to a deep, contoured shape. Not knowing much about aluminum, I assumed that it needs to be extremely formable-after all, they are beverage cans from using it, don’t they?
My first thoughts were, “This could be a cake walk. I’ll bet this stuff stretches a mile. Yep, it needs to stretch a good deal because it’s really soft.”
This thought process was obviously a testimony to my ignorance regarding aluminum.
I feel I lost a big section of my hair working to make that job work. I have to have spent weeks fighting splits and wrinkles. It wasn’t long before I got to the conclusion that drawing and stretching aluminum were not as simple as I had thought.
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Given that I am a little bit wiser with respect to the formability of aluminum and aluminum alloys, I understand that my problem really was not the fault in the aluminum, but alternatively the fact that during the die tryout stages, I was thinking like steel rather than aluminum. Until then, all of the things that I will have performed to correct the situation using a die which was forming steel, I have done with the aluminum. Needless to say, I failed.
The reality is that aluminum is not really steel. It doesn’t behave like steel, it doesn’t flow like steel, and it certainly doesn’t stretch like steel. So performs this make aluminum challenging to form? No, not if you feel like aluminum.
Aluminum is not necessarily a bad metal; it’s merely a different metal. Like any metal, they have positives and negatives, and the secret is to understand the material’s behavior before designing a part or creating the procedure and die that happen to be to generate it.
In case you are comparing aluminum to deep-drawing steel, generally you will find that aluminum lacks nearby the elongation ability of steel. As an illustration, typical deep-drawing steel has elongation somewhere around 45 percent, while a 3003-O temper, meaning “dead soft,” aluminum will have elongation near 30 percent.
Generally and dependant upon the alloy, aluminum has poor stretch distribution characteristics in comparison to deep-drawing steel. It is known as a material that strains locally, which means that many of the stretch that happens when the metal is put through a stretching operation will take place in a compact, localized area.
However, keep in mind that the forming punch geometry has a greater impact on exactly how the metal stretches compared to metal itself. Stamped parts to be made out of aluminum has to be designed to ensure the part shape forces the metal to distribute stretch more evenly.
Aluminum ironing process
Figure 2Generally speaking, aluminum is a superb material when ironing can be used. During ironing, the metal is squeezed down a vertical wall to enhance the surface area while reducing the metal’s thickness. Ironing will be the basic process employed to make beverage cans.
Parts requiring a great deal of stretch in a small area with small male radii are doomed for failure if designed of aluminum, especially if the final geometry is going to be made in a single forming operation. On the other hand, large, liberal radii and flowing, gentle geometries are best-designed for aluminum.
First, don’t confuse drawability with stretchability. Drawability is the metal’s power to flow plastically when subjected to tension, while stretchability is definitely the increase of surface as the result of tension.
Dependant upon the type, aluminum can draw very well (see Figure 1). It features a good strength-to-weight ratio and is also well-designed for the deep-drawing process, along with multiple draw reductions. The reductions percentages are extremely much like those often used when drawing deep-drawing steel.
Although aluminum is soft, it may still be abrasive. While it fails to rust conventionally, it forms a white powdery substance called aluminum oxide, that is utilized to create 10dexppky wheels. Which means the same abrasive that you have been utilizing to grind your tool steel die sections could be present around the aluminum sheet surface.
You may prevent this poor interface by using high-pressure barrier lubricants, which keep your aluminum from touching the tool steel sections during forming and cutting.
In most cases, aluminum is a great material when ironing works extremely well. During ironing, the metal is squeezed down a vertical wall to boost the surface area while reducing the metal’s thickness. It increases the metal sheet’s surface area by squeezing the metal rather than exposing it to tension. Ironing will be the basic process used to make beverage cans (seeFigure 2).
When aluminum is ironed, it almost compressively flows such as a hot liquid across the wall of your die cavity and punch, plus it shines to some mirrorlike surface finish.
Aluminum has more springback than soft draw-quality steel. However, the volume of springback that happens could be controlled by designing the stamped product with respect to the springback value.