John's Alu Profile build

[Evengravy]

More progress made over the weekend. I didn't quite get to the table top pouring but have the majority of the prep done. I also received the ballscrew to motor mounts (finally) so was able to install and test those. No issues so far, noise is greatly reduced and I have it running up to 6 meters/min currently. Beyond that I get stalling but may be able to tweak it a little more later.

Next step in the table build was to build a mould for the concrete top which will be cast soon. I'm awaiting some more super plasticiser but that should be here soon. Calculating the approx weight it will be in the order of 400KG when cast, so my first concern was bracing the open section well.



I chose to use studding which was left over from the building of the workshop in which this machine resides. I made up three sets of braces one for each side and a beefier version for the middle section. I chose to do this with the consideration that it needs to be knocked out from underneath later: I want it to be solid but also removable after the fact. There were some additional braces between these sections that isn't shown here.

On top of this some 11mm ply was set and sealed with silicone between joints. I chose to have the ply a little lower than flush with the walls, this might be difficult to see in the photographs but the idea is that the concrete pour will step down 10mm (vertical) over the end of the block walls before meeting the ply on the inner side of the blocks, creating a key of sorts. I thought this would add some additional strength.



Toward the front I added some 34mm (I think) plastic conduit so I can cleanly route a few wires from left to right (front left Y motor and home/limit switch). This is cut to be a tight push fit against the ply walls, which are fixed to the walls with masonry nails and a 600Kg ratchet strap is added for additional support from bowing. I also ran some lengths of string through the conduit/pipe and fed these through the ply walls at each end such that I can easily pull my wiring through post casting later.



All the wooden surfaces that will be removed were given a couple of coats of beeswax to function as a release agent to aid removal post concrete pour.



Lastly, high tensile steel rebar was added in an overlapping cross pattern. I chose to tack weld these together with the ARC welder and prop them up towards centre (ish) with some rock that can stay in situ as I cast.



I've got a few little gaps here and there to fill with silicone but as soon as the plasticiser arrives I should be good to go on the casting of the top section. I roped my brother in law to help out, likely it will be Saturday next when I get started on that bit.