Re: Problem keeping my gantry square, using a dual drive slaved set-up with Geck

Hi, Petre:

Have you tryed changing the gecko's around X and A to see if the
problem goes to the other side of your gantry.

The blue connectors will unplug form the gecko's if you have enough
wire to swap them around.

In setup if the X and A axis has the same stepper's, same ratio of
reduction like 5:1. You should have the same value in X and A setup.

You say that when you, Home it's goes out of track

You say you dont have limit / home switch'es, Is it setup properly in
config. port's & pin's, Input's.

Hope this help's, Chip

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "apples0_17" <apalais@...> wrote:
>
> Problem keeping my gantry square, using a dual drive slaved set-up
> with Gecko's.
>
> Hi all,
>
> I have been out in the shed for the last few days trying to get the
> gantry square and also set the correct steps per unit. This is what
> I have been doing.
>
> Although this is for a plasma cutting table, I can not find any way
> of working out the steps per unit in the SheetCam .set screen for
> mach3. So what I have been doing is going into the mill, Mach3
> screen, which is called 1024, I think. Once in there I can go into
> the settings page and enter which axis to check/set-up etc.
>
> Once I have done this I just transfer the number from the mill
> screen motor tuning page back into the SheetCam plasma screen motor
> tuning page.
>
> So far so good,
>
> Now what is happening is that I will get the gantry set up square.
> I will reference the xyz, then zero the xyz. (Note: I do not have
> limit or home switches on the table yet.) Then I will open up the
> set steps per unit box in the setting page and I will select the x
> axis to calibrate. I enter a value of 3000mm, the machine will run
> up to the 3000mm mark, it might be out a bit say 2997mm. Then I
> enter the 2997mm into the box that asks me how far it travelled. It
> then say's it will set this number as the steps per unit. As this
> is a dual drive set up I have been opening up the motor tuning page
> and making the slaved axis A, the same number as the X axis.
>
> So now when I go back and home the gantry is not square. It is only
> clamped together at the moment so I can see that it has moved out of
> square. And not just a little bit but I'm talking 3-4 inches.
>
> The only things that I can think of that would be causing this are:
>
> I am using 2 gecko's. One for each motor. For the current set
> resistors, I need to use 270,000ohms. One gecko has the correct
> resistor, but the other Gecko has a bunch of resistors twisted
> together to make a value that is close to the 270K mark. I did
> measure it with a meter when I first made it up and it was not
> exactly 270K. I only had one 270K resistor at the time so that's
> why I made a McGyver one up. I have just left the home made
> resistor there.
>
> Now I am thinking that if one has the correct resistor value of 270K
> and the other has say 250K. Will this effect the synchronisation of
> the two motors that are slaved together in Mach? I guess that one
> motor will be getting say 6amps and the other might be getting 5.5
> amps, or what ever it might be.
>
> Will this make one motor move slower than the other motor and
> causing it to go out of square? I'm pretty sure that it will effect
> the motors acceleration as the other motor has 0.5amps more power
> that the other.
>
> I have even made my acceleration figures really low so that they do
> not miss steps, but this does not do anything. The only other think
> that I can think of is that the one motor on the one side has more
> resistance to drive than the other motor.
>
> On the plus side, It looks like that If I can fix this problem I
> will be able to get my machine square, set the steps per unit and
> then I should be able to move anywhere on the table within 1.0-0.5
> of a mm. Pretty cool!
>
> So any ideas with this problem of mine?
>
> Cheers,
>
> Peter
> Australia
>