Hi Tribbles,

The first one is never right :)

Since I started mine, I have replaced the unsupported rails on the X with 25mm HIWIN rails and the entire Z axis is now steel. I was getting slight tramlines in really dense materials which I could only put down to the rails and the flex in the PVC. I bolstered the PVC with Ally angle down the sides but it didn't really reduce the flex much so I had to go nuclear and replace the lot with steel. Solid as a rock now :)

I have approx 200mm of height on the Zaxis simply because I want to add a fourth axis sometime soon but I could have got away with much lower, indeed the Z axis plate which carries the whole Z axis, I have made adjustable so I can raise it for the 4th axis and lower it when I need to get really close to the table, takes ten minutes to change over.

I'd really love to see your first machine though, it's fascinating to see how people have got around problems and even if it didn't work for you, ther might be something in there that could be the spark of an idea for someone else.

Re: the long screws for the 5m axis, did you not consider rack and pinion for this? it would have given you the speed and maintained a good degree of accuracy, certainly the same as you achieved using screws. On a machine that size I think I'd have gone for R&P on at least the X & Y but until I see this monster (hint, hint), who can say what we would have done.

Anyway, thanks for the detailed reply, I like people who dream large :)

Jeff.