Profile Joints – Part 2
Working with Alusic t-slot aluminium extrusions, I get to build all manner of different things on a regular basis. Most of the time the standard connection is the ‘go to’ joint to use. Occasionally, I come across a situation where the simple standard connection just doesn’t cut it. So, today I’m introducing you to just a few of the other many different t-slot aluminium connection methods. In doing so, I’ll be using some of the items found in the Fixing Accessories section of the Alusic catalogue.
Late 2016 I was putting together a batch of custom designed workbenches when the customer announced that they wanted an LED light panel mounted above the main work surface of each workbench. No problem, I thought. Just tell me exactly what height these lights need to be, and, send me a certified drawing for them.
I needed the certified drawing to work out panel frame dimensions and support structure. A few days later, one of the light panels arrived at the front counter in lieu of a certified drawing. Much better option! This would help ensure the panel support frame would fit exactly. I was also informed that the panel height was to be 1200mm above, and centred over, the bench work surface.
We quickly deduced that adding a pair of uprights at the back of each workbench to hold the light panel mounting frame would be more than adequate to hold the static load. I decided on a cantilever design held together using standard connections.
That was all fine until it was let slip that some of the workbenches would be indirectly attached to pieces of equipment that would put some not insignificant vibrations into the workbenches a number of times per day. I soon realised that the simple jointed cantilever design would, in the long term, likely not cope with the dynamic loads caused by vibrating machinery. Of particular concern was the mass of the light panel, in it’s frame, swinging on the end of 1200+mm uprights.
So, a quick design review later. It was decided to use fixing angles (084.305.033) for the main joints and make braces for the uprights using some joint angles (084.305.011).
The fixing angles made the joints stronger and more rigid than they would have been otherwise. Using joint angles to make braces for the uprights stiffened the structure enough to almost completely eliminate oscillations that would be generated by the vibrating machinery. Thinking about it now, just the braces would probably have been adequate to keep oscillations, and hence joint loads, down enough for the original simple joint design to cope. Oh well … I think there is a saying in the engineering world that has something to do with “belts and braces”.
A few months after that, the same customer said they wanted some more workbenches (different design of course) also with the LED light panels. This time though, they wanted to be able to adjust the braces up or down a little for operator head clearance.
At first that seemed a bit complex, not to mention costly. A stock of different length braces to be removed and replaced by maintenance personnel as and when required. I could see there would be no way to guarantee that adequate length braces would not all soon be replaced by under size braces, or even removed completely. Not a viable option.
Then the Alusic catalogue came to the rescue. Instead of using a joint angle at the end of each brace and making different size braces it was decided to use a screw swivel joint (084.311.010) at the end of each brace. That would ensure every LED panel support would be adequately braced as well as have a degree of adjustment using just a hex key.
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