Was about to get a toy- then I did some research...

[Juranovich]

Those motors sound a little weak to me. You should use the motor calculation sheet to determine what you need. Mines a similar size, and I use 2x2010 X screws (2x4nm low-inductance nema23 steppers) and a 1610 Y screw (3.1nm).

I'm at that stage where I think I've figured out the basic mechanics of a CNC, but I now start to realize all the intricacies of the fine details. So thanks for pointing me in the right direction. I suspect I'll go for 1610 on X and Y to avoid whip and keep the 1605 on Z for precision. As I decide on the final gantry design (and the associated weight) I'll get back to the motor calc to figure out the steppers needed. Just one question though, if I have two steppers driving the long axis, should I input half the total weight of the gantry in the calculator?

Also, you don't happen to have any comments on the frame?

[AndyUK]

If I have two steppers driving the long axis, should I input half the total weight of the gantry in the calculator?

Good question. It's a topic worth discussing. My personal view is that you should double the screw inertia (you have two screws to spin), but also double the motor torque (two motors, after all!)

Also, you don't happen to have any comments on the frame?

Keep posting and I'll comment when you've posted some pictures of your design :) I'm quite a fan of extruded aluminium profiles, it makes the whole thing a lot easier - my gantry went together in hours, my steel and epoxy X axis took weeks. I don't think you can 'overbuild' though...

[Juranovich]

Good question. It's a topic worth discussing. My personal view is that you should double the screw inertia (you have two screws to spin), but also double the motor torque (two motors, after all!)

That sounds much more logical than my suggestion as the weight is naturally not disappearing anywhere... I'm now lacking a homer simpson "duh" emoji for my question! :)