First design - Few questions

[JAZZCNC]

Is it worth the hassle and expense designing & building one from scratch, or just go with an item as per the link?
Unless I can get a clear performance advanage seems not...
Looking to machine woods and Aluminium, on a 1200x800x100 machine.

Yes it very much is worth the hassle of building one has the Z axis is THE most important area of the machine as it's taking all the cutting forces so if it flexs the results show in finish quality. Doesn't matter how good or well built rest of machine is if Z axis flexs the results will be poor and inaccurate.!!

Regards the linked Z axis then it's Terrible design that as everything you don't want in a Z axis, namely Unsupported rails with not enough bearing support and overhanging front plate. (completely useless for machining aluminium with.!!)
Also the aluminium plate looks like standard hot rolled plate that hasn't even been surfaced flat and true. So any chance of accurecy is none existant as 99% of rolled plate isn't flat.!
For accurate and true Z axis you need surfaces machined flat and parallel or use Machine ground cast tooling plate which is what I use. It's surfaces are ground flat and parallel to each other also being cast plate it's very stable and doesn't distort when machined.