Configurate Slave Axis

I too am looking for a solution to drive this two steppers on a gantry axis configuration. I would have thought this would be common enough to have a solution implemented already (having been away from EMC for about 10 years). One configuration of the machine parts I have has two steppers and two home switches. So there is no built in code to home and check both switches for skew, missed step accumulation and fix it automatically? Slaving two drives together off common outputs is not going to cut it. Please tell me I am not going to have to write code before I can use EMC.

Hi

I do not have 2 motors on one axis..... But i read that problem quite often. Here a hack I'd do it.

Use two configs.
In the first you have only the two axis (x/y) you want to home. U use this only in case you fear to be none square!
With normal g code run both slowly into home=end switch. G1 Fslow Xbig Ybig. Until one of the switches produce the expected error.
Then retract both axis parallel a bit out of switch. Than hit home button.
Home first x than y . Slowly in short distance so you do not bent too much.

After that you use the normal configuration with one home switch and parallel end switches..
See no reason to square again if you only want to find home position.

My 5 cents.
Mike

Take a look at...
linuxcnc.org/docs/html/man/man9/gantrykins.9.html

Rick G

Thanks for the reply's. I remember now, the kinematics and HAL stuff was being written when I last checked in. I see I have some reading to do to understand how to edit the kins scripts. gentrivkins and the other one are a good place to start. Thanks for the leg up.

Mark

mwe wrote:

Thanks for the reply's. I remember now, the kinematics and HAL stuff was being written when I last checked in. I see I have some reading to do to understand how to edit the kins scripts. gentrivkins and the other one are a good place to start. Thanks for the leg up.

Mark

I started a post here www.linuxcnc.org/index.php/english/forum...with-x-axis-2-joints and from what little I understand that there is no solution as yet (for me anyway with no programming knowledge) to get this sorted.

I have reluctantly had to go to Mach3 for my router. But I wait in hope a solution will come along.

I still would like to thank the people on here that are trying to sort the problem out.

Happy New Year to one and all. ..Clive

andypugh wrote:

Clive wrote:

I started a post here www.linuxcnc.org/index.php/english/forum...with-x-axis-2-joints and from what little I understand that there is no solution as yet (for me anyway with no programming knowledge) to get this sorted.

What does Mach3 do about homing "slaved" axes? Do you know what the sequence of events during the homing step?

This is what I found :-




Re: Homing Problem - Slave Axis

« Reply #1 on: January 30, 2009, 09:04:52 PM »

---

Hi, Joepardy

Try this in your "Ref All Home" Button's, I had similar Issues with a X, A, dual Axis system awhile back.

DoButton( 24 ) 'Z Home Axis
RefCombination( 9 ) 'X + A Home
DoButton( 23 ) 'Y Home Axis

Hear's some info to review from some Post's.

"Art wrote....> Common problem. When you home , the slaving is disabled till the home is
> done. This is done to auto-square the gantry of such a system, thats why
> the
> lack of slaving when you stop the homing.. The solution is to make the
> homing go in the correct order. This is done by modifying the Homing
> button.. If you open the 1024.set file in the screen designer and double
> click the "Ref All-Home" button, you will see the code is
>
> DoButton( 24 )
> DoButton( 23 )
> DoButton( 22 )
> DoButton( 25 )
>
> This basically calls the Z, then X then Y and A homes. This needs to be
> changed to ..
>
> DoButton( 24 ) ' this homes the Z
> DoButton( 23) ' this homes the Y
> RefCombination( 9 ) ' this will home the X and A at the same time.
>
> RefCombination accepts a number where X = 1 , Y = 2, Z = 4, A = 8, you
> simply add the values of the axis
> you wish to home, so X + A = 9..
>
> The squaring will be automatic and can be adjusted by your settings for
> the home position of the switches..
> Thanks,
> Art
> www.artofcnc.ca

Art also wrote this... and I found the complete "Refcombination" listing here....

"Art wrote.... The home switches, (which may be set to the same input as the limit
switches), are used only for homing. The axis will move to the switch, then
slowly move off.

The program by default does one at a time, because thats the most usual
combination. YOu CAN move any combination at once by editing the RefAll
buttons script. There is a command called RefCombination( n ) which will ref
any combination of the axi s. N is calcuated by adding the following
numbers..

X - 1
Y - 2
Z - 4
A - 8
B - 16
C - 32

Ref X and Y together would be RefCombination( 3 )

What I think is happening is (in my case) X and B are slaved and when homing both drive towards the home switches and then back off independently and set. the two joints are then locked as one for the general running of the machine.

You can adjust each switch to get the correct squaring or set the program to come off each switch by an amount that would square the gantry.

I understand that it is not ideal (its works with SS and my prologic controller board from the lan port.) I am not a fan of Mach3 but needs must

Thanks Andy for taking an interest. ..Clive

andypugh wrote:

Clive wrote:

The program by default does one at a time, because thats the most usual
combination. YOu CAN move any combination at once by editing the RefAll
buttons script.

You realise that this is _more_ programming than doing exactly the same thing in LinuxCNC?

The point is that such a sequence might make the squaring temporarily worse mid-sequence, which is why I didn't push it as the solution.

Andy I am not sure what you mean as altering the button script is a simple process, and both X and B motors run together and they appear to back of the home switches together. I think you can alter the adjustment in software the amount of backing off each does to square the gantry for the home position.

So if the switches are in the true square positions I don't follow that it will make the gantry rack too much.

Are you saying that this could be done in Linuxcnc and if so would you have the time to point me to the correct way to do it?

I have just realised that I have hijacked this post or is it the same topic. ..Clive