X Axis; 2 ball screws, 2 steppers or belt drive from 1

[wkevinm]

Hi I am in the process of finalizing design of my 1st CNC Router: Z-300mm, Y-700mm, X- 900mm.

My current design has 2 stepper motors driving 2 ball screws on the X Axis, the linear rails/guides and bearings have all been ordered. All of the Extruded aluminum has been ordered as well.

Before I commit to buying the Stepper motors, drivers, and the like I am uncertain if it would be best to use 2 Stepper motors and a 4 Axis board or 1 Stepper motor driving both of the ball screws via a belt arrangement.

Does anyone have experience with either? any recommendations.

picture of current design attached:

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[peteeng]

Hi Kevin - It would surprise me if the cost of the belt/pulleys etc would be less then just a second motor. Then there is the logistics of where the belt goes taking up space. Plus the belt will add compliance to your system. So I'd go the two motor route. I'd also put a leg or bend or make thicker your motor mount plates on the long axis. They look a bit thin in the image and will deflect under the screw loads. Peter

[wkevinm]

Thanks Peter,

I had a similar thought on the X axis bearing supports, they are at 1/4" now I will beef up to 3/8 or 1/2".

Kevin

[nlancaster]

I would also go two steppers, and add some sort of 90degree plate to the stepper drives, even 3/8 or 1/2 could flex messing with your accuracy.

[peteeng]

Hi Kevin - Don't be shy no such thing as too stiff. And cost on a flat part vs material is small 1/2" or bends. Peter

[wkevinm]

lancaster and petereng

Thanks for the advice. I will add some metal to increase stiffness as you have suggested. I never gave the ball-screw support as much focus as your advice is recommending. When I stop to think of it, it makes sense that all the force placed on the machine comes through the various ball screw supports in some fashion.

My next major purchase will be the stepper motors (Nema 23) and drivers, power supply and the like. Assembly will not likely start until January, this is when I expect components to start arriving.

[wizard]

Hi I am in the process of finalizing design of my 1st CNC Router: Z-300mm, Y-700mm, X- 900mm.

I’m assuming moving gantry here. A moving table design would be a different consideration.

My current design has 2 stepper motors driving 2 ball screws on the X Axis, the linear rails/guides and bearings have all been ordered. All of the Extruded aluminum has been ordered as well.

This is usual and for the most part good practice. That doesn’t mean other geometries can’t be made to work.

Before I commit to buying the Stepper motors, drivers, and the like I am uncertain if it would be best to use 2 Stepper motors and a 4 Axis board or 1 Stepper motor driving both of the ball screws via a belt arrangement.

.
A single stepper solution can be made to work. How well depends upon many factors so it becomes a bit of an engineering challenge. In many ways a dual stepper motor solution is easier to implement.

Does anyone have experience with either? any recommendations.

picture of current design attached:

Most of my experience with dual lead screws operating in parallel off a single motor (servo) is on injection mold machines. In the case of these machines it can work well but you need to realize much engineering goes into the solution. Also the spread between lead screws isn’t as large as seen on many routers.

I can’t say a single motor solution will not work, but as the distance between lead screws increases it becomes a far bigger challenge.