Higher billet temperatures and faster extrusion speeds means metal flow becomes more fluid. The metal flow usually tends to fill the larger voids in the die face and resists trying to fill constricted areas. The shapes dimensions and tolerances are compromised using this method and often the profile is unsuccessful.
The extrusion ratio is the ratio of the area of the work billets cross section Ao to that of the extrusion's cross section Af. There is a general rule that if an alloy has higher mechanical properties the extrusion rate needs to be lower. The extrusion ratio will be a clear indication to the amount of mechanical working that will occur as the shape is being extruded. If the extrusion ratio of a profile section is low, then parts of the shape will have less mechanical work performed on it, especially the shapes largest mass of metal.
When the extrusion ratio is higher, greater pressure will be needed to force the metal through the smaller opening in the die, this means that intense mechanical working will occur. Maximum pressure will be needed for hard alloys that require the lowest billet temperature.
This results in poor surface characteristics. The weight per metre will determine the size of the press you will need to extrude your profile but again this all depends on a number of considerations;. Regardless of your requirements, there is a wide range of operations that can be performed on aluminum profiles to create the perfect fit for your project.
Aluminum extrusion is a process for creating parts with specific cross-sectional profiles by pushing heated alloy material through a die. Shapes created can be solid, hollow, and semi-hollow; and they can be simple or they can be complex.
The process of extrusion is an interesting one, resulting in foot long profiles that can then be heat treated, finished, and fabricated to customer specifications. Aluminum extrusions can be designed to fit a wide range of products used in various industries. But product designers often have difficulty achieving optimal extrusion profile design and reducing manufacturing costs.
In this guide, we provide 11 tips to help you optimize your designs for the extrusion process. Reduce manufacturing costs, maximize quality, and improve production speeds.
Home Blog. What is Aluminum Extrusion? Table of Contents. What Kinds of Shapes Can be Extruded? There are three main categories of extruded shapes: Solid , with no enclosed voids or openings i. Hollow , with one or more voids i. Semi-hollow , with a partially enclosed void i. First, a round-shaped die is machined from H13 steel. Or, if one is already available, it is pulled from a warehouse like the one you see here. Next, a solid, cylindrical block of aluminum alloy, called a billet, is cut from a longer log of alloy material.
It is preheated in an oven, like this one, to between degrees celsius. Once the billet has been preheated, it is transferred mechanically to the extrusion press. Before it is loaded onto the press, a lubricant or release agent is applied to it. Now, the malleable billet is loaded into the extrusion press, where the hydraulic ram applies up to 15, tons of pressure to it. Another result of excessive extrusion temperatures and speeds is tearing of metal at thin edges or sharp corners.
This results from the metal's decrease in tensile strength at excessively high-generated temperatures. At such speeds and temperatures, contact between the metal and the die bearing surfaces is likely to be incomplete and uneven, and any tendency toward waves and twists in the shape is intensified. As a rule, an alloy's higher mechanical properties means a lower extrusion rate.
Greater friction between the billet and the liner wall results in a longer time required to start the billet extruding. The extrusion ratio of a shape is a clear indication of the amount of mechanical working that will occur as the shape is extruded. When the extrusion ratio of a section is low, portions of the shape involving the largest mass of metal will have little mechanical work performed on it.
This is particularly true on approximately the first ten feet of extruded metal. Its metallurgical structure will approach the as-cast coarse grain condition. This structure is mechanically weak and shapes with an extrusion ratio of less than may not be guaranteed as to mechanical properties. As might be expected, the situation is opposite when the extrusion ratio is high. Greater pressure is required to force metal through the smaller openings in the die and extreme mechanical working will occur.
Normally acceptable extrusion ratios for hard alloys are limited to and for soft alloys, it is The normal extrusion ratio range for hard alloys is from to , and for soft alloys is to These limits should not be considered absolute since the actual shape of the extrusion can affect results.
The higher the extrusion ratio, the harder the part is to extrude which is the result of the increased resistance to metal flow. Hard alloys require maximum pressure for extrusion and are even more difficult because of their poor surface characteristics which demand the lowest possible billet temperature. Difficulty factor is also used to determine a part's extrusion performance. Weight per foot is of primary importance because of the consideration for profitable press operation.
As might seem obvious, a lighter section normally requires a smaller press to extrude it. However, other factors may demand a press of greater capacity such as a large, thin wall hollow shape. Though it has low weight per foot it may take more press tonnage to extrude it. The same reasoning applies to the factor as with the extrusion ratio. A higher factor makes the part more difficult to extrude consequently affecting press production.
The tongue ratio also plays an important role in determining a part's extrusion performance. The tongue ratio of an extrusion is determined as follows: square the smallest opening to the void, calculate the total area of the shape, and then divide the opening squared by the area.. The higher the ratio, the more difficult the part will be to extrude. In order to help us understand your needs and requirements and service you better, the following is a check list of things to consider when submitting items to an extruder for quoting or new business:.
Aluminum Extrusion Process. After a billet reaches the desired temperature, it is transferred to the loader where a thin film of smut or lubricant is added to the billet and to the ram.
The smut acts as a parting agent lubricant which keeps the two parts from sticking together. The billet is transferred to the cradle. The ram applies pressure to the dummy block which, in turn, pushes the billet until it is inside the container.
A large part of the finished cost is due to monopoly factors. Then the die design cost and the die life.
Then add the cut and trim, delivery, annealing, tempering, warehousing etc. Even if the aluminum was free, you can see how these add up on their own, as these videos show. There are a few standard extrusions that are made by many people — these are cheaper as monopoly factors are less of a factor, and being standard sizes, each die makes very large volumes of product.
Monopoly factor??? Not hardly. I am employed as a controls engineer for one of the larger extruding companies and the field is quite competitive. We deal in the larger items, like the extrusions used for storefronts, hospitals, office buildings, etc. Scrap is a large component of the cost. Shipping, manual labor costs, anodizing, all add to the cost of the product.
Extrusion, while a science, also has some black magic involved in the die designs. It is a fascinating business, and designing and maintaining the electrical controls is really …ok…fun! I had a ton of these made nearly 10 years ago. So disappointing when you spend so much and you order them to the exact length only to get them in the mail and stand them up on end side by side and they point in all different directions.
These are cut on the fly, just as wood is. The result is imperfect. It IS a damned shame, but that is an assembly line type, constantly moving process for you. Extrusions are cheap. Minimum order size is the smallest billet which is about lbs. These are all almost universally made from H13 tool steel- which is massively more expensive than aluminum. I know this because I used to recently make them. The main cost is these though is in the skilled machine time and subsequent finishing and polishing operations needed to make them.
There is no way you get dies of any kind made cheap- unless you go to China- in which case you will almost certainly be paying twice- the second time for Americans or otherwise to fix the terrible shoddy work of Chinese die shops in this particular field.
Cost follows that. Sarcastic intent not indicated. You watched that video, and the only inputs you noticed where the aluminum and the extrusion die? Respectfully a profitable business may not be in your future. Sarcasm on my part intended. This process is also used to put the PVC sheathing onto electrical wiring, the wires are pulled through the dies as the PVC is squirted out to form the sheathing around it.
I have visited two of our cable suppliers. Multiconductor cables and twisted pairs are fun to watch being made.
Every fiberglass ladder starts with a Pultrusion, produced by fiberglass rovings , mat and resin pulled through a precise heated die, curing in the process. Extrusion of aluminum is a pushing process. Pultrusion is a pulling process.
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