Thread: one lead screw or two
just rebuilding my router properly. aluminium extrusion in a u shape with 3/4" joining the top for the y axis. i have assembled the x rails on to a steel frame and connected the extrusion to the x axis slides, but if hold on to one of the sides i can move the other side a fem mm by hand, obviously not good! i was going to drive the x axis with just one ballscrew mounted to the bottom of the "u" but should i mount two one to each side of the miiddle of the "u". if i do this , how do i drive both motors. can i just use one driver board or do i need two? help needed before i machine motor mounts and screw supports next week. thanks all
In my CNC router I have 2 screws (M16x1.5) on X and 2 screws on Y axis.
X axis has 2 motors and two belts - so each leadscrew has separate motor and belt - one driver
Y axis has 2 motors and one common belt for both leadscrews and motors - one driver
the danger on separate motors like my X axis is when one of them stall and second motor doesn't, then it twists the axis (what happened to me once).
Since I rebuilt Y axis as described above I never had any problems with it.
The only thing i would improve is to designate one controller to one motor only, but like always the problem is the funds :) .
I can't assure you that is the proper arrangement but it works fine for me and I think results speak by themselves.
Forgot to mention motors are connected parallel to the driver and I would never go for one lead screw even in the centre of axis
I would always use two motors for the X axis. Most controller pcbs should give you the option of using one of the outputs for a slave x axis. Using two drives for the x axis will increase accuracy of your machine and should allow you to drive the x axis faster than with a single drive.
Definitely go for two - it's clearly the most stable option. You haven't stated how wide your gantry is though, if it's really small and light cuts you might get away with it.
You should only use one stepper motor per driver, not two on one driver. It might be ok...as long as the motors are identical, but what if one stalls? Another way to do it is to link the two ballscrews with a timing belt and just use one motor.
It is normally done with two motors connected to two drivers connected to separate outputs on the parallel port. Mach3 will, using limit switches, control both so that both drivers receive the same signal whilst the machine is running, and when homing it can move them individually to square up the gantry. The manual for Mach3 explains it - look up slave axis.
Yet another method is to use wires to link the two sides of the gantry mechanically. Think of how it's done for the ruler on a drawing board...
might just get an extra motor and ballscrew then
Same lines I'm thinking along. Means dedicating an extra axis, though, and I'd like to have the option of retro-fitting a rotary axis (sometime) later - so a 5-axis system, then? It'll need a 5-axis break-out board, to start with. (How do you add more axes? Does it need another com/lpt/usb port; EMC supports up to 9 axes, apparently... ) and a separate driver for each motor. And that's it??
'xcuse me chipping in, hope it's okay...
...cheers, Eric."Just because Innovation is not universally accepted is not, in itself, proof of Superiority of Convention"
Robert van der Plas
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