There are several manufacturers out there which make rackmount enclosures which use a extrusion down both sides to hold the entire case together. The top, bottom, front and rear of the case are standard sheet metal pieces. Growing the case in any dimension (other than thickness which is set by the extrusion) is just a matter of cutting the extrusion and the sheet metal to the correct length - something that anyone with a way to cut metal in a precision manner can do. No bending necessary.
For a product I'm developing I'd love to be able to use this style of enclosure manufacturing to both save shipping costs (since the extrusions and other panels can be shipped flat), and also to provide flexibility in customization, since getting flat sheets of metal cut to a drawing (including holes) is a lot easier than finding a manufacturer who can build rackmount enclosures. I'd like to be able to buy just the extrusions and source my own 'flat stock'.
Unfortunately, I haven't been able to find a source for these extrusions which will sell them to me without the entire enclosure to go with (with one exception, but they were really pricey) - which eliminates a lot of the benefit of the extrusion as a simple construction material which I can then add my own flat stock to.
Does anyone have an idea where to source these extrusions in a relatively high volume - I'd expect to use something on the order of 150 linear feet (~45 linear meters) of extrusion per month if things go like I would expect them to.
Some sample pictures/diagrams to better show what I'm talking about:
http://www.protocase.com/images/products/images/ext_alum_image_14.jpghttp://www.frontpanelexpress.com/fileadmin/user_upload/Downloads/Handbuecher_Datenblaetter/PDFs/Manual-2008.pdf