Thread: Dual driving x axis setup

Hi Mike
Go Config Menu then Slave Axis.
Screen attached shows X axis slaved to A.
I set the same motor setting to each axis but Mach should be good enough to work it out if they vary.

Hi Mike,
You most likely will have to run the A motor backwards so first time you jog do it gently so the gantry doesn't do the splits.

thanks Rod,

I thought i could connect one side up and float the other side (ie not connect the block to the gantry side) for the first run. This would allow me to check the direction of travel of the connection block from the linear nut.

I was just looking at your Tubot photos online and noticed that you had an adjustment link from the screw nut plate to the gantry side. Did you need this fine adjustment to provide proper alignment between both sides of the gantry? I have noticed on my unit (still slightly out of square) that the left side hits just before the right side. I can try to take most of this out when i go over the unit and start to square it all up 100%, but should I incorporate some fine adjustment into the system just in case?

Originally Posted by seafurymike

I thought i could connect one side up and float the other side (ie not connect the block to the gantry side) for the first run. This would allow me to check the direction of travel of the connection block from the linear nut.

Good thinking


I was just looking at your Tubot photos online and noticed that you had an adjustment link from the screw nut plate to the gantry side. Did you need this fine adjustment to provide proper alignment between both sides of the gantry? I have noticed on my unit (still slightly out of square) that the left side hits just before the right side. I can try to take most of this out when i go over the unit and start to square it all up 100%, but should I incorporate some fine adjustment into the system just in case?

The brackets are there for fine tuning allignment of the screw to the gantry sides so the screw doesn't bind.
To allign the gantry sides if you are using ballscrews you can turn one screw slightly. If you are using belts then loosen a pulley, allign, then tighten the pulley back up.

.

Ok, so i should look at adding the fine adjustment in so i can do the fine tuning too. I have added a couple of pictures showing the current setup. The screw will be covered up by a plate all the way along which i hope will keep all the crud off of it.

One photo shows the steel adaptor plates I made up, which now need to have a thread added in the side for the adjustment screw. I can use a lock nut and put a fixed block on the gantry to give me the fixing position for the bolt. More maching, yipee. Been having lots of fun lately making those adapter blocks.

Hi Mike,
Nice work.
Square rails and extrusion should make it a strong machine. I enjoy the machining side of a build too.

During normal operation the slave just follows the master and the steps per, velocity and acceleration of the master is used. The tuning settings for the slave are ignored.

The gotcha is, when you home with dual home switches, Mach decouples the slaved axis and then uses the slaves tuning settings for that side.

This is when you will suddenly come unstuck if settings differ.

Greg

So is it typical to run dual home switches for the X Axis? I would have thought that at some stage I would "slam the gantry" against the end stop to ensure alignment. From here on cant i just home to one switch and assume both sides are aligned?

I think i'm trying to get my head around how I would run/operate the machine over a period of time

/M

Originally Posted by Greolt

During normal operation the slave just follows the master and the steps per, velocity and acceleration of the master is used. The tuning settings for the slave are ignored.

The gotcha is, when you home with dual home switches, Mach decouples the slaved axis and then uses the slaves tuning settings for that side.

This is when you will suddenly come unstuck if settings differ.

Greg

I have dual axis on my machine with both axis having the same tunings, but i have yet to see Mach do this individual setting of the A and X axis. It just seems to do the A axis and forgets all about X.

Hi Bob,
If you have a smoothstepper I am not surprised. I have not been able to get a repeatable homing on X/A with the smoothstepper.
Just a check have you set general config to "Home slave with master" - see attached.

Hi Rod

No smoothstepper yet. Not enough money yet.

Yes, I do have a tick to home them together. I just went downstairs and then unticked the box; turned off the power to the steppers and then purposely misaligned them; tried to get Mach to home both axis. This still failed, so I reticked the box and tried again - still no Mach realignment of both axis.

In the end, I had to turn the A and X axis back of, hand align them and then let Mach do its own thing - but it still only does the one axis.

Originally Posted by seafurymike

So is it typical to run dual home switches for the X Axis? I would have thought that at some stage I would "slam the gantry" against the end stop to ensure alignment. From here on cant i just home to one switch and assume both sides are aligned?

Hi Mike

This is Rod's way of making sure that both axis are aligned to the end of their travel. (See his previous posts)

Yes, you cam make that assumption, but is it warranted? How do you KNOW that you haven't lost steps in one of the axis?

Mike/Bob
Yeah slamming the gantry is fun.

I think some of the readers took me seriously when I said this so to make it perfectly clear I really don't recommend doing this.

Lets call it "Auto Gantry Squaring" for want of a better name.

For this to work you need separate home switches on each side of the gantry, each with their own input pin.

Lets say we have B axis slaved to X axis. (keep A for your rotary axis)

When we issue a "DoOEMButton (1022)" command (ref X), as we do when referencing, this is what happens;

X and B move simultaneously toward the home switch. Hits X axis home switch and moves off the switch.

Then X remains still while B moves towards its home switch and then moves off the switch. This movement should be no more than a mm or so, depending on your switch setup.

That's how mine works. I find it reassuring to see that little dance.

Alternatively, we can use the "RefCombination(17)" command (ref X and B)

This will home both sides of the axis simultaneously. No little dance but still "Squares the Gantry". Still needs separate home switches.

Setting "Home Slave with Master Axis" disables "Auto Gantry Squaring" altogether and homes the axis as if it only had one home switch.

Note that all of the above is when using the LPT.

SmoothStepper does homing internally. And it seems every new firmware version has the homing method changed. This is why I don't use a SS on my router.

Greg