Well, one of my hobbies is building cars - about 18 months ago, I finished my latest one, and I've had a hankering to make one myself. So, I designed a new body for the existing chassis (this, for those of you who don't know the regulations means it doesn't need to be re-tested as a new car). I approached the manufacturer of the kit with the designs, and he was (and still is) interested in making it.

However, he wasn't convinced that we could take my design and get it carved out of foam (ready for the mould to be taken) - certainly not without £20K+ spent on doing it.

I persuaded him to have a go, so I set about designing a machine that could do it.

The machine would need to be a 5-axis CNC machine in order to get in most of the nooks and crannies, although two of the axes could be manual.

The initial design was for a 5x2x2m machine, with the cutting head suspended - I agreed with him that I'd build it in his workshop (I don't have such a space available to me); I'd fund the electronics and such, and he'd fund the mechanics (it didn't end up that way).

When we started, it was scaled down to be a 2.5x2x1.8m machine, since getting a 5m length of some kind of threaded bar was too expensive - we'd do a third of the car at a time.

About a week and a half into the build, we decided that we'd cut blocks of foam 1200x600x100mm and stack them to form the body, but as we had it mostly built, we'd use the existing frame. This also meant a 2.5 axis machine was required (some of the more intricate bits would need to be done by hand).

Unfortunately, while accuracy was good enough (the nearest mm is fine; I was getting conceptually better than 0.01mm), speed wasn't (it would take something like 700 hours to do a whole car). Increasing the speed was possible (and I did spend some time doing it), but then the size of it was causing problems with vibrations, and accuracy went out the window.

So I did a quick bit of research (well, looking at YouTube videos :) ) and found a design that was ideal for the size we're now doing. So, now we're happy in what we need to achive, I'm more-or-less ready to start.

In summary, the broad design was right for what we had originally aimed to do, but we chose inadequate steel sizes - and when we went to the smaller size cutting, it was just too big (there was also a requirement for it to be movable - although I'm trying to get him to relax that :) ).

I have to say that it was a very good learning exercise - I'd not done anything like that before (except for a "scanner" I made at school some 20 years ago - that had a resolution of a Lego brick).

ETA: I have seen yours, Smiler, and the new design is fairly similar to that, although the bed was going to be closer to the X rails. It might change :)