[brandercreative]

Hi All,

Have just started ordering parts for my new CNC build

all the extrusion is 80x120mm. I will be using ballscrews on all axis aswell as supported linear rails.

looking at 2x1300mm Ballscrews for Y-axis and 1x 2500mm Ballscrew for X-axis.

the next problem i have is selecting the appropriate stepper motors. Going to go for Nema 23 but dont no how much torque is needed to drive the screws.

I have been told that the ballscrews have a Pitch of 2505 and 2005 is 5mm.
5mm movement per turn.

Appreciate any help on selecting the correct steppers.

Ben

[pippin88]

I'd look at 10mm pitch screws. 5mm pitch is going to be quite slow over that distance as steppers max rpm is fairly low.

What stepper drivers are you looking at? The max voltage of the driver will be important in picking the optimum stepper. Gecko drive has done good literature on their site.

[brandercreative]

I'd look at 10mm pitch screws. 5mm pitch is going to be quite slow over that distance as steppers max rpm is fairly low.

What stepper drivers are you looking at? The max voltage of the driver will be important in picking the optimum stepper. Gecko drive has done good literature on their site.

Thanks for your input pippin. I guess the only thing im worried about is losing resolution by moving to the 10mm pitch screws. Thoughts on this?

I have had a quick look at gecko and will do some more reading soon. Kind of looking for some direction with the stepper motors to suit the type/length/speed of ballscrew.

Cheers

[brandercreative]

So at the moment im looking at the G540 Controller accompanied with on of these two steppers i have found-

High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Automation Technology Inc

387 Oz-in NEMA 23 Stepper Motor (Dual Shaft) [SM-03] - US$49.90 : Homann Designs!, The preferred CNC Component Supplier

is this appropriate for the setup?

[pippin88]

The Homann designs 387ozin steppers are a great match for the g540 with 48v power supply. This setup is usually sufficient for most machines, but I've only worked with machines half the size you are planning. Homann designs are great to deal with, highly recommended.

Some people move up to Nema 34 steppers with higher voltage drivers and power supply for these big machines

Curious that you are planning 2 screws on y axis, one on x. Which axis is going to be your gantry? The most common way would be x axis with 2 screws (one on each end of gantry to prevent racing) with y axis being the gantry with only one screw needed.

[brandercreative]

The Homann designs 387ozin steppers are a great match for the g540 with 48v power supply. This setup is usually sufficient for most machines, but I've only worked with machines half the size you are planning. Homann designs are great to deal with, highly recommended.

Some people move up to Nema 34 steppers with higher voltage drivers and power supply for these big machines

Curious that you are planning 2 screws on y axis, one on x. Which axis is going to be your gantry? The most common way would be x axis with 2 screws (one on each end of gantry to prevent racing) with y axis being the gantry with only one screw needed.

whoops had the axis names around the wrong way. 2x1300mm ballscrews on the x axis and 1x2500mm on the y. Y Axis is the gantry.

I went this way to try and eliminate racking etc which would be more prone with having 2 long ballscrews, 1300mm is much more acceptable.

Will get in touch with homman, they are only a short drive from me too.

[pippin88]

The problem with the long axis being the gantry is sag / deflection. You need a much much bigger beam (put some numbers in an online deflection calculator) which increases cost, weight and decreases speed (all other things being equal).

The length of screw won't effect racking - if you are driving both sides of the gantry racking should be eliminated. Length of screw affects screw whip, which occurs at high speed. Screw whip can be reduced by bigger screws. I suggested 10mm pitch as it will require half the rpm for the same linear speed. Lots of people use rack and pinion for long axes top avoid these problems (but not 100% without own problems)

[brandercreative]

interesting... im calculating using 50-100 pounds as the force and the deflection is huge (0.4") what would be a more acceptable deflection figure? Thinking i may need to revise design to have the shorter gantry

[CDF]

interesting... im calculating using 50-100 pounds as the force and the deflection is huge (0.4") what would be a more acceptable deflection figure? Thinking i may need to revise design to have the shorter gantry

What calculator are you using?

[brandercreative]

What calculator are you using?

Beam Deflection Calculator - Hollow Rectangular Beams Calculation - Mechanical Engineering Calculators Online