100x100x3mmm tubes works best IMO as most simple the build and could be cut at home using Rage or normal saw. And yes, if you could find sth like 80x120mm even better. The ideal for the gantry is 200x80, but as no such 2x 100x100 or similar will be alright.

Better do the Z with the rails on the front plate and they to slide, not the bearings. makes a stronger Z. I would concentrate on the Z mainly and do the machine around it. As the machine is as strong as its weakest link, the Z is the weak spot most of the times.


Abot the feeds and the speeds:



Most of the time on a home diy machine there is no tool change, to save time, tools or babysitting the job. No toolchange= slower machining speeds. I would say that most of the machines do not need to move faster than 5000mm/min in real life.
For example normally my rapids are 1500mm/min and normally i machine wood at 1500mm/min

But there are cases where i have to make a production run. Say 300 pieces of something. And then i push the machine properly. Say if slow it will do the job for 12 min, when i push it it will do the job for 4 min. And that matters as it could save me a day or two. At these cases i am in the 7-8k mm min.

My machine can do 20k min.when servos at 3k rpm and even faster as my servos are 6k rpm rated , that is at 3k mm /sec acceleration. I have machined at 16k mm/min and while it makes me smile to see my baby move like a bullet shot from a gun that 250kg gantry, it starts to feel and look really Dangerous. The ball screws start to heat up, so i have to grease everything perfectly before hand. The biggest problem is cause wood starts to chip sometimes as its not perfect material like the plastic or similar. So at the end of the day my philosophy is : Less time i spend on the machine=The better , hence the slower speeds give me perfect finish and i spend less time on the machine. Now if i had ATC i would have pushed jobs using roughing bits, normal and then finishing passes, but as its not the case, i am happy..

So, nope. You don't need a fast machine . You need a precise machine that is free of vibrations and gives you perfect finish.