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Author Topic: Machine Retrofit Servo Zero Point  (Read 1767 times)

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Machine Retrofit Servo Zero Point
« on: December 06, 2016, 11:34:40 PM »
So I'm retrofitting a Mori SL1 CNC Lathe. I'm changing out everything and use some AC Servos and Drives. My question is, as i've been told, that on the original machine once you set the home function for each axis - which is it goes to it's limit switch and backs off - it then finds the the correct position on the servo's encoder to be exactly at the same point when you start the machine each time. It was explained to me that there is a home position on the encoder or something to this affect.

How would I program that in Mach 3. Basically what I want is to home the machine when I turn it on everyday and have it be accurate. To me, on a lathe, backing off after touching off of a limit switch is not accurate enough.

Thanks.
Re: Machine Retrofit Servo Zero Point
« Reply #1 on: December 07, 2016, 06:08:40 AM »
Use a motion controller or drives that has encoder based homing.
It hits the home switch and then backs off until it sees the index pulse of the encoder. Very accurate. The DSPMC/ip has this as an option. I am not sure if any other boards do this but I would assume that some of them do. You can also do this in your servo drives but would have to rewrite the homing routine in Mach.


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.
Re: Machine Retrofit Servo Zero Point
« Reply #2 on: December 07, 2016, 12:41:27 PM »
Ah, cool. Nice unit. Pricey though. I'll see if the smoothstepper can do that.
Re: Machine Retrofit Servo Zero Point
« Reply #3 on: December 07, 2016, 04:33:56 PM »
Look into the possibility of the drives doing it internally. I think Hood has some drives setup that way and he just altered the homing script to accommodate it.

The vital system stuff is a little pricey but worth every penny. I have three of them and a Hiconn.

What kind of drives are you using?

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.
Re: Machine Retrofit Servo Zero Point
« Reply #5 on: December 08, 2016, 05:07:18 AM »
They "look" nice and I like that they don't use any tough to find connectors but I have no experiance using them and without the manual to see if they have a built in homing routine I don't know if they will do what you want. Price is very reasonable.

Take a look at the clearpath servo as well. https://www.teknic.com/products/clearpath-brushless-dc-servo-motors/

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.
Re: Machine Retrofit Servo Zero Point
« Reply #6 on: December 08, 2016, 10:25:48 AM »
Thanks for the help, I appreciate it.

I've lost interest in the smoothstepper, a little behind the times from what I've been reading. The Pokey stuff seems interesting and updated frequently. Arturo from CNC4PC suggested them and says they will do the index pulse homing and do threading based on the servo's own encoder on z, not sure how that works if I'm not using an encoder on the spindle or maybe he assumed I was and this was just a way to improve timing. PLUS the Pokeys has it's own proprietary PLC built in that I can use to program the tool changer. Not ladder logic though, which sucks.

Also from smoothstepper forum they said those servos would work. I want to stay with AC so I don't have to have a separate power supply, if that's required, never worked with servo's before assume a DC one would need a PS.
Re: Machine Retrofit Servo Zero Point
« Reply #7 on: December 08, 2016, 04:31:19 PM »
Some dc drives take ac input.

Mach4 now has a PMC that uses ladder logic!!!!!!

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.
Re: Machine Retrofit Servo Zero Point
« Reply #8 on: December 08, 2016, 04:47:12 PM »
lol all these options are hurting my brain!!

I thought Mach4 wasn't quite there yet with the lathe part?
Re: Machine Retrofit Servo Zero Point
« Reply #9 on: December 08, 2016, 08:44:58 PM »
I don't know how well it is working with lathe but I will be setting mine up as soon as I finish a few other things.

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.