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Author Topic: Auto tuning slaved axis with Delta Servo Drives  (Read 6784 times)

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Auto tuning slaved axis with Delta Servo Drives
« on: May 21, 2013, 03:51:39 PM »
Hi Guys!

And the battle to tame this CNC goes on…. I have got the tool change working well but now that I am doing real cutting I have noticed the movement was far from ok.

Any sharp changes in direction cause overrun, poorly cut parts and wasted material. Moves around non arc curves (splines made up of lots of short lines) cause shuddering of the gantry. I also can not get smooth movement from a g1 to g2/g3 without a slight pause as if it has turned of cv mode. A true circile would pause on each line of code. The only solution has been to reduce my feeds right down.

I have tried every cv distance/angle setting with slight improvement but not enough so assuming my servo drives may be the issue. I have worked out how to auto tune the Y and Z axis and seeing better results but as I have two servos on the X axis (A is slaved to the X inside Mach3) and unsure how to auto tune both at the same time.

I found a few posts that suggested setting BOTH drives up from a “virtual master” and using a 1:1 gearing  but could not work out for the life of me how to do that with my drives.

Could some of the masters cast a few pointers my way as I would love to get my router running smoothly!

THANKS!
Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #1 on: May 21, 2013, 04:19:10 PM »
I could not upload the pdf for the 750w delta servo motors and ASDA-AB drives. The link below is from their website.

http://www.delta.com.tw/product/em/motion/motion_servo/download/manual/ASDA-B2_M_EN_20120131.pdf

Offline Hood

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Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #2 on: May 21, 2013, 05:17:10 PM »
Ok on page 58 it tells you about the command options. You would need to set it up as the option I have highlighted in screenshot below. You would then feed the encoder outputs from the master drive into that drive at the pins indicated.
Hood
Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #3 on: May 21, 2013, 06:32:33 PM »
I think I follow along but will attach two images as I am not 100% sure of the wiring.

I am assuming I need to wire the position pulse outputs from the master drive to the Highspeed Position Pulse Input of the slave as in the image "cnc servo slave from outputs"

My gut feeling tells me the above is correct or did you mean wire it as in the image "cnc servo slave direct from encoder"

will there be any issues with have one motor follow the other (lag causing one to fight the other as they are mechanically connected) ? In a robotic forum I found some info on they suggest "slaving" both motors to one drive.
Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #4 on: May 21, 2013, 06:40:17 PM »
Slaved from the master drive outputs


Encoder direct to slaves

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Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #5 on: May 22, 2013, 02:55:43 AM »
I am not sure which way would be best, I would think connecting two motors to a single drive would be problematic as you could only have one motors encoder feeding back, also  you would be tuning the drive to the two motors rather than a single.
Having said that slaving a drive and motor to the master drive and motor may also cause problems lke you say.
I think what you would likely need to do is slave one drive/motor and do an auto tune on the master then enter the values that are in the master to the slave then tune again. Might have to do that a few times.
Auto tuning may only get you close, all depends on the drive, for example I feel the auto tune in my AB drives is not great and I usually manual fine tune after. The Telemecanique drives however have very good autotune and so far have not had the need to manuallty tune.

Regarding the wiring diags, it is the first one you would use, however you would not have the step/dir signals connected to the slave at this point, only would you do that if you went with Mach controlling it as a slave rather than having it slaved to the other drive.

Hood
Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #6 on: May 22, 2013, 03:07:52 AM »
Thanks heaps for that info hood!

I was only planning on slaving them so I can auto tune to give me a ball park to start manually tuning as this is my first servo system. It is very new to me so I was hoping the autotune would at least get me close to speed up the overall process.

Have you tried the software that comes with the delta drives? I cannot work out how to get a smooth output on the built in oscilloscope. Have you had any luck?

Do you use the Pcurve settings to get less jerk in your system?
Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #7 on: May 22, 2013, 09:04:30 AM »
Hi Jestah,
Make sure that you either put a G64 in your initialization string or at the begining of your G-code. Mach3 has a nasty habit of turning it off regardless of how you have it set on the general config page.

I would also ask what version of Mach3 are you running? .066 has been problematic for some people, myself included.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

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Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #8 on: May 22, 2013, 02:40:29 PM »
No afraid not, have only ever used UltraWare, UltraMaster for Allen Bradley/Gidding and Lewis  drives and PowerSuite for the Telemecanique drives.

Hood
Re: Auto tuning slaved axis with Delta Servo Drives
« Reply #9 on: May 22, 2013, 07:39:27 PM »
Hi Jestah,
Make sure that you either put a G64 in your initialization string or at the begining of your G-code. Mach3 has a nasty habit of turning it off regardless of how you have it set on the general config page.

I would also ask what version of Mach3 are you running? .066 has been problematic for some people, myself included.

Mike

I will make sure to add G64 into my header and I think I am going to try going back a few versions of mach3 as I have had LOTS of bugs the past few weeks. (Soft limit warnings that are suggesting a G53 Z0 move is above my Zmax limit, sometimes not running the startup macro I have in the initialization string and homing often fails causing one the sides of my gantry to rack until the servo errors out )

If I could get my sticky fingers on a real oscilloscope could someone talk me through how to hook it up to tune my servos. I have found lots of info to tune geckos but not much on AC drives

Been a bit busy to do the wiring of the drives today but going to make time to give it a shot tomorrow! Thanks everyone for all the help!