This gantry will bend and twist like crazy. Aluminum is out of question if gantry not reinforced. Irving told you also about the rack and pinion and aluminum.

The difference between mediocre machine and a good one is not $$$ but the amount of time you do a proper research and later make right decisions.

Better read some build logs here and things will begin to clear. Or you will regret later. I don't see how rack and pinion will be much cheaper than ball screw at the current China prices. And the rotating nut assembly is not so much different than the RP assembly money wise.


No offence but most of all - Z300mm, seriously? On a first machine, big machine and making decisions about motors without making a detailed drawing not having clear idea about what material you will like to cut mainly.

So why don't you just take a breath, read the forums, make your drawings, show them here, discuss them, correct them, etc. Start from the bed structure, gantry, Z, rails etc.