Hello folks,
I am a newcomer in the DIY CNC arena. I have so far successfully tried the following setup:
Arduino UNO compatible (AZ-Delivery)
CNC Shield 3, powered with 12VDC, 10A
2 x Pololu 4988
2 x NEMA 17 steppers 42SHDB4036Z
GRBL 1.1f
UGS 2.0
and it all works. My goal is to have a rather large CNC router, in which the workpiece is moved on the XY plane, and the tool goes up and down on Z. Due to the size of the working set, the X and Y trolleys have to be split in two, each driven by a motor of its own, for a total of 2+2 motors (X + Y) plus the Z motor. It goes beyond the capability of the vanilla CNC shield (4 channels). My first idea was to double the sandwich of the shields, having two shields "in parallel" one on top of the other, but 1) CNC shields don't seem to be easily stackable 2) return signals (such as endpoint switches eg) have to be managed properly.
The second possibility I can find on Pololu doc is driving the stepper motors in series, on the very same channel from one A4988 ( X and Y). This seem reasonable, since the steppers are driven by current. The workaround I can expect is to raise the MOT power to 24 VDC (still within the limit of A4988), and to cut and paste the wires to the motors.
In this way, I would use one single CNC shield, and only three A4988 drivers on top of it.
Before trying, here I am to ask for some guru's response. Am I missing something?
A better solution might be to have one driver per motor and common up the step and direction connections. Getting the motors mechanically synchronised initially could be challenging but provided neither feedscrew binds and causes its motor to lose steps it should be OK.
the goal is a simple XY platform moving underneath a single tool. But as the platform is going to be wide and deep, I think to give it two trolleys for each axis, each driven by a motor of is own
does it make problem? are motors too weak or belts too short?
i trying to imagine. Could you take a photo of your CNC and add in the picture what you want to change?
Kolaha,
thank you for your interest.
The issue is not in power, is in balancing. I am planning to operate on workpieces not small, for example boards, and my choice has been to keep the tool steady, moving the workpiece. Generality of tool is important.
If the workpiece were small, I could place it on a platform (I call it trolley) .
But it may be wider, it may fall aside, when operating on the edges. So, I am thinking about double trolleys on X, and double trolleys on Y, on top of them. To have an idea of what a pair of trolleys is, here's a photo, with my work in progress.
To see a "0.9" version of a single trolley, two Axis prototype, there's a second picture here below.
Sorry for not having more material.
if i understand correct you want simple widened work area. for this you need nothing more as longer rails(maybe 3-4 parallel) and maybe belts instead of threaded bolts.
if some axis need 2 motors you can use second CNC shield and connect it with wires, 1:1, here
Unfortunately, I need double drive in both axis, that is why the Protoneer CNC Shield is not enough. And my working area is not only wide, but requesting to hold the piece on its perimeter, not in the center. I understand that it could be clear with a photo, I'll surely send one asap. Thanks
In sketch 1, you can see the horizontal rails, carrying two trolleys each. Caveat: only the first in each rail is driven by the leadscrew, the second is freerunning.
In sketch 2, two vertical platforms are laid on the trolleys, and hold the vertical rails, along with the vertical motors and leadscrews
In sketch 3, the vertical trolleys roll up and down, and on top of them will be anchored the actual workpiece.
Next draft, will be the output of a CAD! I swear
Problem: new users can not upload attachments....
Interesting clue. Actually, the pression of the tool (drill, milling, whatsoever) works if it's top-down, if it were bottom-up the carriages would pop out of the rails.
