Retro-fitting old machine with new gear

[timewarnings]

Here's my first post, so i can include links in the next post (cnczone rule i guess).

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[timewarnings]

This doesn't happen very often (i don't think), but I thought this would be the place to find info. Thanks in advance for advice.

RUN DOWN: Some friends salvaged an old Vytech CNC from a burned down sign shop. Everything works fine, kind of. You can manually jog it to and fro, but you can't plug it into a computer. The dedicated computer was some how lost in the chaos and Vytech no longer makes these machines or distributes back logged drivers, or pci slot cards, etc. A serial cable was the only interface to be found (not even sure its a legit serial interface. could just be the plug with all pins reassigned or something), and obviously requires special drivers that are now lost in the pages of history. I thought i could just hack the stepper cables and fit them into a new board...only to find that this thing uses huge 7amp servo motors which i had never really seen before.

seems like it might be impossible to recover the electronics. This site:

here

is telling me that servos can't compete with steppers, except in huge industrial applications...so i'm guessing this is just an old machine using antiquated technology. There are still companies selling interfaces for servos..........

so my question is this:

Should I try to find new servo driving electronics so I can plug this thing into a computer? ...stick with the old fangled way and maybe blow a lot of money on complicated inferior stuff no one else is really using...hoping that it's some how better and easier than scrapping a totally functional (yet antique) system...

Or should I just buy THIS and retro fit these NEMA34s in where the servos used to be....then calibrate the aftermath????..and have a nice updated system with tons of online community support and what not....assuming the whole thing works.

what potential problems could i encounter with the retrofitting if i go that route?

could the ABL systems be different, or incompatible for some reason?...obviously the motor dimensions would have to fit in the allotted spaces...these 960oz motors are also 7amps, so i'm guessing they're as powerful as the old servos.

THANKs in advance, CNCzone folks! Any help is appreciated.

[Al_The_Man]

is telling me that servos can't compete with steppers, except in huge industrial applications...so i'm guessing this is just an old machine using antiquated technology. There are still companies selling interfaces for servos..........

IMO, That statement in and of itself is rubbish, unless they are referring strictly to the cost factor?
My personal usage and preference is servo's regardless of the application.
If you have servo's in place there is every likelihood you can find an applicable driver, if necessary, depending on what control you settle on?
Al.

[timewarnings]

IMO, That statement in and of itself is rubbish, unless they are referring strictly to the cost factor?
My personal usage and preference is servo's regardless of the application.
If you have servo's in place there is every likelihood you can find an applicable driver, if necessary, depending on what control you settle on?
Al.

Yeah, I was a little suspicious. They said this was the no BS run down and that their competitors were liars, but at the same time they're defiantly trying to sell you a product thus siding clearly with their product.

Al, what driver brand would you recommend, since you have experience with them?

[wcarrothers1]

Not ashamed to say it. But all my builds have been done with servos. I have 2 reasons for not using steppers. Well maybe 3.. 1 is I could not stand the noise if I used steppers. Second, I could not stand the "chance" I would miss a step and have the machine lie to me for the rest of the day (my step dad owned a fab shop with many cnc's and his first big machine was a stepper machine and still to this day mentions how it " might or might not" end up lieing about where it was over the course of a job..

I would not build a stepper machine unless it was a very small engraver. Not saying people who have are wrong. But just saying to me the exter expence of servos over the long run is small. Considering for example my first machine was built in 2006 spread that expence over 6 years and compair that to it never missing a step in that time. That is enough payment for me.

b.

[timewarnings]

Also HERE are some other folks on CNCZone that are having trouble with VyTeks and the AMC3 controllers. Seems like this is the last of a dying breed. Al, any recommendations on new controllers? How does the software work? Mach is only for stepper motors right?

[Al_The_Man]

Mach also works with servo's, if you have the motors and encoders there are a few drives that will work with Mach, depending on the motor size and encoder resolution.
Al

[RCaffin]

This site: ... is telling me that servos can't compete with steppers, except in huge industrial applications...

Let's take a close look at what they are saying.

> Positioning errors don't occur, since stepper motors know in advance where they are going and when to stop.
Ah - so? Actually, they don't. They just do what the driver tells them to do, up to the point where they lose pulses. Then you have NO feedback, while with modern servos you gat a fault signal.

> Sufficiently powerful stepper motors for a given application do not lose steps.
True, but where do you find a 5 kW stepper?

> If a servo motor encounters the same obstacle, it will sit there and fight itself until it
> breaks a gear tooth or burns up.
Crap. Most intelligent servo controllers will fault when the following error gets more than a defined amount. And you can also put in thermal/magnetic breakers on the power input. (Mine has both.)

Suspect, very suspect. Caveat emptor.

Cheers

[timewarnings]

It sounds like everyone loves servos here. So, any recommendations for a good controller?

Something like THIS?

I've never wired up a servo system...but they have 9pins I think....so figure out where each one goes....and beyond that just match up specs between control and motors?

IE: my motors say 7amp, and the linked controller has a 20amp peak, and 12 continuous....so it wouldn't be sufficient for moving all 3 axis at once...probably.

any way, google isn't the best at turning up results for this type of search. So again: any recommendations on tried, true, trusted brands that make a good servo controller??????

This whole process seems like a can of worms. Am I right? Like, are the feedback mechanisms pretty standardized over the course of the 15 years since these motors were made?...this involves hacking serial cables, and matching up wiring diagrams, and hoping all the necessarily inputs and outputs align (i mean from a layman perspective).

[Al_The_Man]

If you go with something like Mach, you will need the original machine drawings and replace the drives for Larken/Granite etc depending on what voltage they run at?
DC brushed motors were commonly used with a DC tach feedback to the drive, now the tach is not used.
Al.

[Enk1du]

It sounds like everyone loves servos here.

I don't know about a specific "love" for servos, but what everyone does love is saving money and you've got servos so why not use them?

[RCaffin]

are the feedback mechanisms pretty standardized over the course of the 15 years since these motors were made?

Pretty much so. A lot of servo amps these days emulate a stepper, but at much higher power.

Inputs are:
Raw DC power for motor
Step and Dir logic signals
A, B and possibly I back from optical encoder (typically HP or whatever they are called today)
Disable logic signal (used with eStop)

Outpts are:
Power to motor
Fault signal to eStop/CPU

Cheers

[Al_The_Man]

Like, are the feedback mechanisms pretty standardized over the course of the 15 years since these motors were made?...this involves hacking serial cables, and matching up wiring diagrams, and hoping all the necessarily inputs and outputs align (i mean from a layman perspective).

When updating an older system fitted with DC brushed motors, generally everything is the same except if using Mach etc, the drive/control would be step/dir instead of analogue as already mentioned, and if the motors are fitted with tach, these are no longer used and can be disconnected.
Although if only 15yrs old, they may not exist.
Al.