New Build Log ... 2440 X 1220 X 300

[JAZZCNC]

First let me say for a first machine this will be challenge so don't go rushing into it without carefully researching and drawing up a detailed design.

Forget driving gantry from centre and really forget using ballscrews for the long axis unless your prepared to get into rotating ballnuts etc. Rack & pinion is the way to go for the long axis. Using R&P brings it's own challenges but they are much easier and cheaper to solve than ballscrews and mostly just means choosing the correct motors and ratio's.

Profile is fine and easy to work with but it's very expensive compared to steel. For a machine this size then you'll want minimum 80x80x5 steel.
Build it in such a manner that you don't really have gantry sides, make the sides of the machine high and sit the gantry directly on the bearings. There are several builds here that use this setup so just look around the build threads.
Hi-win style profiled linear rails are what you need so forget round rails and they easily handle the debris, infact much better than round rail does.


Regards a 4th Axis then if your wanting to use like a Lathe then forget using a stepper motor.! They just don't spin fast enough or have enough torque.
Even if you want just a rotary axis for 3D work then I'd look at using a Rotary Axis converted with a Stepper motor.? Reason being is the Resolution. Steppers connected to pulleys don't give enough ratio so the resolution is low and for better or more detailed work then much higher ratios are preffered.

Make the Axis rails longer than the bed and put the 4th axis on the end has messing around with removing portions of the bed will soon become a pain. Also if the 4th axis is below the bed this means the Z axis is over extended giving much greater chance of flex and poor finish. Having the 4th axis on the end higher up makes much stronger giving better finish quality.
Another reason for the top rails extending past the end other than 4th axis is that you can machine the edges or ends of panels or cut dovetails etc this is very useful in many ways.

Like I say this will be a very big challenge for a first machine but it is do-able but not if you rush into it so go carefull, be patient and ask questions.

Oh and forget Kress spindles they are toys. Like eddy recommends 2.2Kw or larger is the way to go.