New build.Stell frame cnc 1500X1000.Ball screw and gearing calculations

[JAZZCNC]

Hi Vagelis,

Don't worry to much about what the Spec's say regards critical speed it's mostly a guide.
I can tell you from experience that you will easily run 1.5mtr length 20mm screws @ 1500rpm with out any problems provided they are aligned and use correct end bearings.

Regards the speeds and feeds then this is mostly determined by the Strength of machine, Material, cutter quality and spindle being used.
For the stronger DIY machine using 2.2Kw spindle then you'll probably cut woods and at around 6-8mtr/min, plastics maybe slightly less depending on plastic type and cutter used.
For aluminium then you'll be much much slower rarely above 1500mm/min with 800-1200mm most common.

Rapid speeds only really matter if you have a large table area and plan to do lots of drilling or point-to-point work, other than that then they are mostly just for showing off.!!
When doing 3D work then you'll want higher accelerations rather than high velocity.

My suggestion is go 2:1 and if you find it too fast then it's easy to change a pulley. Remember you set the Speed of the machine in motor tuning and just because it can run at 1500rpm doesn't mean you have to go that fast.
My machine which uses 1.5Mtr 5mm pitch 20mm screws geared 1:2 can reach 11 Mtr/min (screw spinning at 2200rpm.!!) using steppers but I Don't have it tuned that high because I don't need rapid speeds. So I sacrifice speed in favour of better acceleration and higher torque, also often on smaller work having high acceleration over high velocity is actually quicker due to amount of short movements.

Either 2:1 or 3:1 will work fine for your needs but I'm sure 2:1 will give you a better balance.