They say you only learn by making mistakes. Well I learned that for a structure to be stiff it has to be braced against twisting as well as bending. Wasting a whole weekend certainly hammers the point home!
My second attempt was smaller, much sturdier and a lot easier to make. I completed it in two evenings as opposed to two days and with no injuries! I made all the pieces out of 18 mm MDF sheet whereas the first attempt was a mixture of 18 mm, 12 mm and 8mm. All the pieces were rectangles so I got them cut at B&Q where I bought the wood. I used two 1200 mm by 600 mm sheets and all the cuts were free. Here is the kit of parts I came home with.
I used 12 mm beading and PVA glue again to make the joints, but this time I used more screws and no nails.
Here is the finished woodwork. No detectable movement no matter how hard I push on it.
And here it is with the axes installed. The x-axis is wired to its controller and a power supply. This is a small 24V 100W switcher made by Sanken Power Systems. I chose this from the random selection of PSUs I have collected because my z-axis stepper is 24V and the XY controller can run from anything between 24 and 60V. I don't know if I will need a 12V rail yet, I am hoping to get away without it.
Wiring and electronics next.