Mach3 Retrofit to 1989 CNC Lathe

[Al_The_Man]

I don't know why they would have a tach, they are not really used now, and if you did need tach operation, the Hall sensors would do it as a digital tach.
It looks like they have the latest type of encoder that also has commutation tracks on it that simulate the old hall effect devices once used.
Re-reading the description it points to the motors being 3 phase synchronous rather than BLDC? The former generally uses a different commutation method than BLDC.
??
Al.

[TomKerekes]

Hi jim_cliff11,

Yes I believe all you said is correct. The drive uses those 120 degree signals to do the 3 phase commutation. They are sort of like a low resolution absolute encoder.

The Drive + Motor + rotor position encoder + tachometer allows the motor to be brushless commutated and move at a commanded velocity in a controlled manner.

KFLOP+Kanalog then closes the Lead Screw Position Loop by reading the Lead Screw Encoder Position, comparing to the desired destination, and commanding the drive's velocity to move to correct any error.

HTH
Regards

[jim_cliff11]

Al, the lathe is an old school unit built in 1989 with 3 phase AC servo motors.

Thanks Tom.

I was concerned about creating two loops if the drives used the rotor position encoders on the motors to compare actual to commanded movement. As these RPD encoders are only used for 3 phase commutation I don't think I need to worry about this, and as such all I need to do is apply an analog signal to the drives from Kanalog.

I will replace the encoders on the axis with differential encoders suited for Kanalog, I was thinking:

Incremental encoder with shaft - CNCdrive - webshop
or
ENI-1024 magnetic kit encoder - CNCdrive - webshop

Would these do the job?

I did find a page on the Dynomotion site with detailed requirements on encoders, but for the life of me I cant find it now!

Update, just seen the Kflop only supports single-ended encoders, is this the same for Kanalog Tom? Can you suggest a suitable rotary encoder compatible with Kanalog?

Thanks

[jim_cliff11]

Second update:

Tom, found the page I was after. It was in the FAQ if anyone else needs it:
Dynomotion Motion Control Boards for CNC Manufacturing and Robotics Applications


Kanalog does accept differential encoder inputs, whereas Kflop on its own is single-ended.

I've settled on the following from CNCDrive:

Differential signal with index
Incremental encoder
1024 counts per rev.
http://cncdrive.com/downloads/ENI_10...der_manual.pdf

I used 3 of these encoders on my bridgeport mill conversion and they have performed flawlessly.

Couple of questions:

1. Am I right in thinking these will work with Kanalog?
2. For the spindle encoder I will be using the index channel, which counts 1 complete rev? I need this for single point threading? Correct?

Thanks

[TomKerekes]

Hi jim_cliff11,

Am I right in thinking these will work with Kanalog?

Yes they seem to have differential outputs and should work with Kanalog's differential inputs.

For the spindle encoder I will be using the index channel, which counts 1 complete rev? I need this for single point threading? Correct?

The Index channel is optional. The AB channels are sufficient and superior to track Spindle angle and perform multi-pass single-point Threading. The Index channel can be used if for some reason an absolute spindle orientation is required. Basically to "home" the spindle. For example if a tool change requires the spindle to be at a specific orientation. Or you need to cut one or more passes of a Thread, power down, then power back up and cut additional passes. Since you have the inputs available you might as well connect them whether you use them or not.

HTH
Regards

[jim_cliff11]

Thanks for the reply Tom,

This morning I took the current encoders off the lathe.

X is a Sopelem Ri620-26 2500ppr
Z is the same
B (spindle) is a Sopelem Ri640-13 1024

Can’t find any data sheets for these units as they are dyed.

Looking at the following now as they have a standard 6mm shaft.
http://shop.cncdrive.com/index.php?productID=767

The ppr count is considerably lower than the original encoders. But if I’m counting both channels leading and trailing edges this would give a cpr of 2000. These are also single ended encoders but cncdrive do a differential line driver which converts to differential. Are there any disadvantages in using a diff line drive over an actual differential encoder? Can the cpr still be multiplied by 4?

[Al_The_Man]

With a single ended, the count can still be X4, the advantage with a line driver/differential is they are more immune to noise pick up issues in long runs or noisy environment.
I use the same IC as the ENI-1024 uses to convert where necessary.
Al.

[jim_cliff11]

Yeah thought so.

To be honest I'm going to have to make adapter couplings and mounts to fit the new encoders whatever I go for so I'll probably just stick with the ENI-1024. There proven and cheap, yet reliable and robust with a reasonable ppr. Having said that the CPR is 1024 maximum. Given the axis encoders I've removed are 2500ppr, i may be sacrificing a substantial amount of accuracy going with the ENI-1024?

Do you make your own encoders then Al?

[Al_The_Man]

Usually 1024 is considered the lowest you want to go, gives you 4096/rev with x4.
No, I just have had to fit RS485 line drivers where the encoder already supplied was single ended, and it was in a very noisy environment.
Al.

[Al_The_Man]

Re-reading the manual, the way it is worded, it would appear the pulses are already x4, which if so would make the native resolution as 256p/rev.
And if so, a bit of smoke and mirrors has been used.
Al.

[jim_cliff11]

Re-reading the manual, the way it is worded, it would appear the pulses are already x4, which if so would make the native resolution as 256p/rev.
And if so, a bit of smoke and mirrors has been used.
Al.

Yeah that’s the way I interpreted it to Al.
The single ended encoder they sell is 500ppr which should give me 2000cpr. These is more reasonable.

Does anyone have any information regarding the Sopelem encoders I have? I’m guessing they’ll be an older analog type, rather than the digital Kanalog needs. Is there a way to test them?

[Al_The_Man]

I have never seen or heard of them, is there any more info on the unit themselves?
If you can identify the power leads, a 'scope or even a meter may be able to identify the others.
Al.

[TomKerekes]

Hi jim_cliff11,

If the originals state 2500ppr then they were most likely 10000 quadrature counts/rev.

As a general rule the system resolution should be at least 10X better than the precision you want to achieve.

What lead screw pitch do you have? Any gearing or belt reduction? What precision do you require?

See:

Dynomotion

Regards

[jim_cliff11]

Not sure on the lead screw pitch at the moment to be honest Tom. Something I really need to check though! Both axis do have belt reduction, again I need to check this out.

Turns out the Z axis wasn't a Sopelem, but a Litton encoder. I've been able to find a datasheet for this and have the following information:

Litton
G58LSLDBI
2500-521-05

G58 Incremental rotary encoder
6mm shaft
RS422 Line driver output circuit
A&B channels - Differential
2500 Line Count
5vdc supply

From the datasheet (attached) it even looks digital.
I'm not to sure what the RS422 line driver means, or the 2500 line count (2500 quadrature counts/rev)?
Could this potentially be compatible with Kanalog?

[Al_The_Man]

The RS422 is the differential line driver in order to transmit the inverse of the A & B (4) signals. Similar to the one used on the ENI-1024
2500 means that the final resolution would be 10k line count.
Al.

[jim_cliff11]

Just hooked the encoders up to the oscilloscope and got the confirmation I need; they are digital and output a quadrature square wave form.
Both channels are offset from one another and their inverted counter-parts are the same.

5vdc in from a regulated supply.

Can't see why these wont work with Kanalog, so I'll give them a try.

[Al_The_Man]

They are also higher quality encoder.
Al.

[TomKerekes]

Hi jim_cliff11,

They should work with Kanalog.

Regards

[jim_cliff11]

Hi all,

Just wiring the lot up now and have a few questions:

1. Does Kanalog recieve it's power from the Kflop board JR1 power supply? I'm using a standard PC power supply which will put 5v and 12v in.
2. I'll be running my diff encoders to JP1. There is pins for each quadrature channel A0+, A0-, B0+, B0- etc. But where from Kanalog do I take my 5v encoder supply from? I'm guessing in terms of earthing the encoder I can just use any earthing pin on Kanalog?

Thanks,
Jim

[TomKerekes]

Hi Jim,

Does Kanalog recieve it's power from the Kflop board JR1 power supply?

Yes

I'm using a standard PC power supply which will put 5v and 12v in.

PC Power supplies are usually not a good choice as they usually have an undesirable Earth GND connection. They are also over powered and the 12V is not used.

I'll be running my diff encoders to JP1. There is pins for each quadrature channel A0+, A0-, B0+, B0- etc. But where from Kanalog do I take my 5v encoder supply from?

You might use the +5V and GND terminals on Kanalog

I'm guessing in terms of earthing the encoder I can just use any earthing pin on Kanalog?

I assume you mean DC GND. Which should usually be kept isolated from Earth Ground.

Regards