Hi,I am fairly new to design and have been doing technical drawing for only a few months. We have an item, that supports up to about 800KG of weight, as a C shaped channel. We are currently making this out of 3mm Mild Steel. Due to a new design, we are changing this design to avoid welding and painting the above part. This means we will be making the part from Galv sheet.I would like to make the part from Aluminium because 1) There will be no rust, 2) I think it will look better than Galv sheet but I need to keep the cost down.We use 3mm mild at the moment, because it is easier to weld than 2mm, not for strength really.Therefore, my question is, in everybody's opinion, would it be OK to make it from 2mm Aluminium, or is this likly to end in disaster?FYI, the part is 1600mm long, then on each long side there are presses of up 250mm, down 80mm and down 20mm. The weight is supported at 4 points on the 80mm flanges.What a question for my first go Answers! TIA
Aluminum is not as strong as steel, so you would need a thicker piece. Also you need to select the aluminum alloy to match the application, there are many different alloys. And Al is more expensive than steel, so you have to look at your cost budget. Galvanized will not rust, so your only reason is looks? Not a decision for you to make, but for the customer.
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Aluminium is expensive as far as I know. I would do the costing on the aluminium first. Also aluminium is a little weaker so you'll need a thicker sheet. I would go with galvanised.
Aluminium needs to be 50% thicker than steel for the same strength.
That is actually a complicated question that may need serious engineering. First of all, pure aluminum is rather soft and flexible and you may need to consider an aluminum alloy, perhaps an alloy used in aircraft structures to resists loads. The nature of the load (concentrated or distributed) may affect how the channel tends to bend and the strength needed to resist bending. C channels many tend to bend, shear, twist or buckle and could also fail where loads are applied or at end connections. Likely, mechanical engineers would make a freebody diagram of the channel and study its loading and physical restraints to calculate the strengths needed. Then it is likely a safety factor (10%, 50%, etc. extra strength) would be required depending upon the consequences of failure. If public safety is at issue, calculations should be performed (or checked) by a licensed professional engineer. Because channels (usually) can not be custom made at rolling mills (unless there is a huge order) the next larger available channel in the correct alluminum alloy may be required. Often insurance and product liability demand a correct solution. If the existing mild steel flange works, it (or an assembly drawing) could be presented to show the necessary configuration and help identify possible interferences if channel dimensions must change. Depending upon environment (wet, dry etc.) mixing metal parts may raise corosion concerns. For example, drainage from copper flashings on roofs tends to corode aluminum gutters. Aluminum alloy will likely be more expensive than mild steel and titanium would be stronger and lighter than aluminum (and is now being used in aircrafts) but would be even more expensive. Channel cost may be more important in a large production run than in a one of a kind structure.
