First CNC router build - motor and driver help

Hi all,

i am just about to start to build my own CNC router and i am looking to make it to cut 8ft x 4ft aluminium composite panels (not that hard to cut)

i am making the machine from aluminium extrusion and its going to have 3 axis using 25mm x 3mm pitch threaded bar for all 3...which i allready have all machined to the right size.

i am going to use one 25mm threaded leadscrew in the middle for the x axis.

i have the full idea for the machine but the only thing i have not yet purchased is the stepper motors and the controller/drivers to run the machine....can anyone suggest what motors would be best for this size of machine anbd the size of leadscrews i am using?

does anyone know of a complete kit i could buy that would be suitable for this?
i am not really bothered about the machine being really fast or anything just want it the cut/engrave the soft aluminium panels without any problems. (maybe using mach3 software)

i have heard allot about the nema 23 and 34 motors but not sure if these would be suitable ...can anyone help? or does anyone know where i can buy the full kit?

thanks very much,

Gaz

You're going to struggle to get good feedrates with only 3mm pitch screws especially on the X axis where whipping is likely to be a problem over that length. You'll need good, probably one angular contact pair, bearings at both ends of the screw unless you tension the screw, or rotate the nut instead of the screw. I did the latter on my 1.7m X axis, 20mm diameter screws.

I also think you will have to put wires under the gantry (like on the old drawing drawing boards) to stop it racking. It would be better and easier to just use 2 screws though.

Difficult to say about motors without knowing more (mass of gantry, desired feedrates etc), but as a rough guide 3nm nema 23 for Z and Y, and something bigger (34 size) for X iff you've only got one screw.

You say not fast, but do you really want to have to wait a few minutes for the gantry to traverse the length of the bed? That may well be the case if the whipping on the X axis screws is bad.

thanks for the replys....

i think you might be right i might have to go with 2 leadscrews on the x axis but this will not be a problem to add another if the one down the middles does not do the job i will just machine another leadscrew and move them to each side of the machine.

i am going to get all the structure together first and then buy the motors last but its looking good so far i have some good ideas for the machine and i will take some pictures to show you guys how i have made it and the finished machine....maybe it could help others to build there machines....looks really proffesional out of the aluminium extrusions :) really happy so far. will keep you posted once i get all the pictures.

thanks,
Gaz