Postional referencing

Could someone give me a quick explanation about the differences in 'dog-type', dogless, stopper, and non-stopper reference configurations. From the parameters my machine is 'non-stopper dogless' and I'm not sure what this means. (Doing a search online for 'dog-type' or 'dog servo' brings up everything that has NOTHING to do with machining.)

Which is better?

Thx.

Bones288 said:

Could someone give me a quick explanation about the differences in 'dog-type', dogless, stopper, and non-stopper reference configurations. From the parameters my machine is 'non-stopper dogless' and I'm not sure what this means. (Doing a search online for 'dog-type' or 'dog servo' brings up everything that has NOTHING to do with machining.)

Which is better?

Thx.

Click to expand...

What exactly causes a 090 P/S alarm?!

^^^ This might help (a bit).[From Pm forum.].

I'm guessing a "Dog" in this case is an inverted specially profiled mini ramp (that can be bolted or adjusted to a particular position (at the factory when they build the machine)) that triggers a fixed micro switch. As used for homing.

from post #5 in cited thread …

"The Feeler is setup with 2 dogs and 2 switches per axis. One dog activates the limit and causes an E-stop. The other switch causes the machine to slow down after hitting the first ramp on the other dog, then when it eases off the back ramp the machine looks for the index encoder pulse. "

Then a discussion about absolute encoders ensues etc.

Proximity switch dog | WordReference Forums

^^^ This one in Spanish was kinda funny too...

I agree this is a difficult one to google lol...

"what to do about dog acceleration and deceleration " (agility training for dogs.).

Assuming you are talking about a Fanuc or Mitsubishi control......

Bones288 said:

Could someone give me a quick explanation about the differences in 'dog-type', dogless, stopper, and non-stopper reference configurations.

Click to expand...

Dog type can be used with incremental or absolute encoders, but typically is only found on machines with incremental encoders. There is a reference position deceleration limit switch and a ramped block (the dog) that actuates the switch. A simplified explanation...The machine travels until the switch is opened and then closed again and the index mark on the encoder is read.


Dogless is only used with absolute encoders and does away with the reference position limit switch and a ramped block (the dog). The reference point can be set by parameters or by positioning the axis close to the reference position and then moving the axis until the index mark is read while a reference setting parameter is enabled. The encoder positions are retained by backup battery power while the machine is off. Axis movement while the power is off is tracked and the control's position counters are updated when power is applied.

I've never seen a stopper type reference used with a Fanuc or Mitsu control, but they do offer that ability. It would be used with incremental encoders primarily, but could be applied to absolute encoders. A stopper reference drives the axis at low speed in a torque limited mode against a hard stop. The axis then reverses direction until the encoder index mark is read.

Bones288 said:

From the parameters my machine is 'non-stopper dogless' and I'm not sure what this means.

Click to expand...

It means it has absolute encoders and no reference limit switches. There usually will be some method determined by the machine builder to establish the machine reference point. Keep the backup batteries in good shape. Lots of folks ignore that then spend some amount of time diddling around trying to properly re-establish the reference point after the batteries die and the position is lost.

Bones288 said:

Which is better?

Click to expand...

Would not really want to say one method is better than another, they are just different ways to use different hardware and machine builder preference.

Mits controller, you're correct. I'm attempting to revive a CV500a and have everything verified EXCEPT turning on the spindle and tool changes.
(Just a minor thing, right?)

I'm having some issues with the ATC's '2nd Zero' position and the spindle over traveling past machine zero (0,0,0) and rams into the mechanical stops on the Z+.

I'm sure it's something on the user end (or some jinxed parameter).

Also, I took your advice ahead of time and bought a stack of batteries for the servos. Now I just need a few for the actual memory.

Thanks again.

One of the top 3 crashes I've been witness to was due to stopper type referencing, avoid if at all possible.

Tonytn36 said:

One of the top 3 crashes I've been witness to was due to stopper type referencing, avoid if at all possible.

Click to expand...

Yeah, it doesn't take a lot of imagination to see how that could go badly wrong..

gregormarwick said:

Yeah, it doesn't take a lot of imagination to see how that could go badly wrong..

Click to expand...

It was on an engine block decking / facing machine. 36" diameter cutters, probably 400+hp spindles (big motors on that joker) and 3" twin ball screws. The cutters and block came out in chunks, the ball screws were snapped in two, the machine frame was bent beyond repair. They swapped out the whole section of the block line - under warranty - ouch!. I remember the tech screaming at his design guys "trying to save pennies!" They didn't want the expense of running wire and reference switches or (at the time) much more expensive absolute encoders. It was a loud boom!

I was really surprised to find that lots of robotics and positioners used in the semiconductor manufacturing process used stopper type referencing. Lots of times the robot or positioner would be jogged up to a reference fixture until the axes torqued out. The software then set the position to zero and things were off to run. No backing up to an encoder index mark or anything.

The machine tool industry while usually better is not always good. When I went to Fadal for new dealer tech training session, I was amazed to see their reference method (1960s tech) and the lack of limit switches. Despite that they were telling us techs that they were "on the leading edge of machine tool technology". Half of us in the class nearly choked try to withhold the outright laughter we wanted to let out.

@OP,

Is your machine equipped with the MSC802M? If so I have a fair amount of experience with those.