Rigid Square-Tube All-Metal Frame for DIY Projects (3D Printer, Metal Frame Furniture, etc)

thingiverse

Update 30/03/2016: I added this design to Sketchfab for easier 3D viewing at https://skfb.ly/MB6I. Because suitable aluminum profiles are hard to find in my area and, given that even in Western Europe there are still many places where T-slot/V-slot ALU extrusions can't be found, I considered using the next best thing - ALU/Steel square tubes available in any hardware store. After searching online, I found all connectors were plastic, 3D printed or bought from the same hardware store as the tubes (which is still some kind of plastic - ABS maybe) and didn't like that. I wanted an all-metal sturdy frame capable of holding tools or vibrations (a 3D printer) or just its own weight (furniture: cabinets, etc). I also wanted a solution that can be easily scaled up without changing the layout of existing patterns, whatever partition one would like to create. My solution involves two types of tubes (two patterns of holes that is): 1. Tubes with 4 holes at each end, two+two for receiving the two threaded legs of U-bolts. 2. Tubes with only one hole at each end, a hole that will receive the bolt that the U-Bolt will lock to when fastened. The hardware involved is as follows: steel/alu tubes, two lengths (L1,L2); long U-Bolts that can fit inside the tube, flush with its face and length that would allow it to span the square dimension and the distance from the hole to the edge of the profile. I used an U-bolt that had M4 threads and a curvature diameter where I could fit almost perfectly an M5 bolt's threaded cylinder. I also need nuts for the U-Bolts (M4 in my design), M5 bolts + Nuts for the U-bolt's stopper, and M5 Hex Couplers of a length that would clamp the U-Bolt to the tube's face. This can be either a cut-to-length Hex Coupler or a similar length stack of Washers and/or Nuts. Note: The need for the hex coupler is dictated by the fact that without it the tube is free to move on the bolt's direction. This might not be a practical issue once the U-Bolts are fastened with locknuts but just to be on the safe side and to accommodate the higher precision needed by machinery like a 3D printer for example. This setup doesn't allow any tube to rotate around its axis or translate along any of his edges. It should be like a single piece of metal carved out from a block. I have uploaded both an STL to exemplify (with a nice exploded view of one of the planes) and the RSDOC file I used to build the CAD of the design - you can download and use for free the DesignSpark Mechanical to visualize that one or modify or play with it as you please. Please let me know if you know of or have an even simpler solution that can be scaled to as many partitions as one needs, keeping the number of individual parts as low as possible.