[Myk Bates]

I am starting two new projects. One is a large CNC router with AC servos the other is a Bridgeport Interact Series 1 with DC servos. Both will use KFLOP+Kanalog. I have done one other Bridgeport conversion with the original steppers and Geckos. That used Mach 3 for control. I didnt like the open loop. Too many position errors, slow, and flaky on cold days below 30 F.

Ill start with the Bridgeport because I have some photos to help figure out what things are. I am using AMC 30A20AC drives. I figure starting here will help me undrestand the KFLOP when I go to do the other project which also uses AMC drives. I was told these SEM servo's on the Bridgeport have Heidenhein"Tachometers." I opened one up to see and to me it looks like an encoder but I cant find any info on it.

My question is what is it and how does it communicate with Kanalog? I don't want to burn things up doing what I think is right. Magic smoke is not my friend.

Any help would be great. Everyone here has been alot of help in the past.

[Al_The_Man]

I believe they are the incandescent type and use a 11µa quadrature sinewave output, so unless you convert to RS420 differential, they may not be suitable for Dynomotion?
You will however be able to get rid of the 6.5v/1krpm DC tach's, I just remove the brushes to avoid any problems in the future.
As you can see by the encoder disc, they are pretty coarse resolution, but they make up for it in the sine mode by using the arctangent function to increase the res.
It may be better to source some through shaft TTL encoders?
I usually run the A-M-C drives in the torque mode and AMC have an app note on setting the pots for this mode also.
Al.

[TomKerekes]

Hi Myk,

I think your best bet would be to just replace those with standard digital optical encoders with differential output.

Unless there is a module to convert the output to digital quadrature with reasonable resolution already in the machine someplace.

Potentially if you could locate sine/cosine analog signals you could feed those into Kanalog ADCs and use our Resolver Input mode to do the arctangent calculations. But this would be fairly complicated and may not give great results due to distortion and such.

Regards

[Myk Bates]

Wow... that's a ton of information. Thanks. I get lost in all the terminology. I guess that shows my newness and how much I don't know. Thanks for the info. Since new encoders seem to be the way to go can either of you give me advice on what I should look at or where? I have heard of US Digital and CNC4PC has one but it says that it is capacitive (and I think I saw the same one on digikey). Automation Direct even has some. I should mention that in the end (and this is a process) I would like to have an accurate machine that is able to do 3d profiling (albeit a a bridgeports pace) and rigid tapping which will involve an encoder on the spindal.

Considering the capabilities of the machine is a cheapie just fine or will I gain performance or precision with better quality/price?

Seeing how my level of understanding is a gnats eybrow above nill I'm basically looking for keywords when I search. Are digital, optical, diferential output and quadrature what I need to be looking for?

The shaft below the threads is just under 10mm.

Thanks for the help.

[Al_The_Man]

I would suggest either US digital, Toyo or Renco for a through hole encoder, I tend to use a minimum 1k to 2kp/rev, differential (TTL/RS420) output, the resolution is increased by x4 in the controller.
Confirm first they are through hole and not shaft encoders.
Al.

[Myk Bates]

Thanks Al. I am looking at US Digital encoders. When you say "I tend to use a minimum 1k to 2kp/rev" are you referring to what they call cycles per rev (CPR)? I’m looking at their product # E3-2000-394-IE-H-D-B which has a 2000 CPR. Their E5 only goes up to 1250 CPR and ends up being more expensive.

Do I need to have indexing? They give that option but I don’t know what they are referring to. Maybe that would be for spindle orientation?

Thanks

[Al_The_Man]

Index or reference pulse is a one pulse/turn output that is usually used on servo's for accurate home position, typically you would have a home limit switch where the axis would rapid to, after which the servo would back off the limit in slow speed and when the marker was seen by the control, this would be registered as the home or zero position.
Spindle orientation is another application.
2kp/rev would be PPR.
Al.

[Al_The_Man]

Unfortunately US digital are the only encoder supplier that lists CPR and PPR which make s it very confusing.
The CPR is the counts after the X4 multiplication by the controller.
The basic counts rev (before x4) is usually the only one specified by almost every other encoder manuf. as they would be unaware as to whether the pulses were going to be used X1, X2 or X4 by the controller.
Al.

[Myk Bates]

I see. In other words I need to divide their CPR # by 4 and end up with 1000 or 2000. That will give me the 1k or 2k per rev you mentioned.

Easy enough
Thanks

[Al_The_Man]

Unfortunately their glossary page leaves a lot to be desired, I find a lot of ambiguous descriptions, as well as wrong terminology and definitions.
US Digital | Support » Glossary
Al.

[Myk Bates]

I was just looking at the specs and noticed that CPR was the PPR divided by 4. Sounds like CPR is one full rotation and PPR refers to pulses generated by the disk on each revolution which happens to be 4X.

[Al_The_Man]

This is the basics.
A quadrature encoder produces two pulses 90° apart (hence quadrature).
The pulse count of a single pulse is the pulses/rev #.
When the controlling device receives the two square upped pulses, it has the option of using the basic pulse/rev (x1) or use two pulse edges (x2), or all four for X4.
A differential encoder also provides a complement of the two basic pulses for noise free transmission.
Al.

[TomKerekes]

Hi Myk,

One "line: on the encoder disk generates one square-wave full cycle of the A and B signals. When the A and B signals go through one complete cycle there are 4 separate edge transitions which are counted by the encoder input as "encoder counts". A square wave cycle is sometimes referred to as a "pulse". So:

N lines per rev = N cycles per rev = N pulses per rev = 4N encoder counts per rev

I'm always amazed that encoder manufacturers often don't spell out what they are referring to. But most often they spec the lines per rev.

HTH
Regards
TK

[Al_The_Man]

In all the encoder manuf. I have dealt with, which have been quite a few over the years, I have never seen one, apart from USdigital to specify the count in the X4 number.
BTW the 4 edge transitions are counted in the subsequent electronics, not in the encoder.
Of course, the other very misapplied descriptive term is the word 'Quadrature' to indicate x4.
Al.

[Myk Bates]

Well this is all good schooling. I would have used Renco (I have those on my other servos for the router project) but they have apparently been bought out buy heidenhein and while I was able to find specs I was not able to find a place to buy them. A search for Toyo kept turning up Koyo so I struck out there too.

US Digital on the other hand has a nice looking site that is easy to find. Unfortunatly they are not clear as to what they are counting. Al's referance to their glossery of terms showed CPR is

"Cycles Per Revolution. The number of full quadrature cycles per full shaft revolution (360 mechanical degrees)."

so the quadrature cycle is the four edge transitions on the wave you were refering to. Basically 200 is 50 slots in the disk.

but then it says " A 200 CPR encoder can provide 200, 400 or 800 positions per revolution depending on whether x1, x2 or x4 quadrature decoding is done." So I looked at their definition for a cycle which says

"One complete four-state quadrature cycle." (up one side across the top and down the other... i think) " One quadrature cycle is generated by one line and one window, called a line pair on the encoder disk.
Each cycle is divided into 360 electrical degrees (°e) and can be decoded ( by Kflop) into 1, 2, or 4 counts, referred to as x1, x2, or x4 resolution multiplication" Which then led me to Resolution (Their term) which says

"The number of full quadrature cycles" (Slots in the disk times 4)"per full shaft revolution (360 mechanical degrees). Note that each cycle can provide 1, 2, or 4 counts, called x1, x2, or x4 decoding or multiplication, depending on how it is decoded."
So then I had to look up decoding which says:

"The quadrature signal produced by incremental encoders has 4 state changes per quadrature cycle. A 500 CPR encoder has 500 cycles (2000 quadrature states) per revolution. x1 decoding means that the external electronics counts only state per quadrature cycle, so there will be 500 counts per revolution. x2 counts two states per quadrature cycle (1000 counts per revolution). x4 counts every quadrature state (2000 counts per revolution)."

Al's right. They are confusing. I think that what I now understand is that if I buy a 1000 CPR encoder that means 500 Slots in the round disk which means 1000 cycles which the KFLOP will multiply by 4...

No thats not right either because US Digital states

" A 500 CPR encoder has 500 cycles (2000 quadrature states)"

Which would lead me to believe that 500 CPR means 500 Slots in the round disk producing 2000 cycles (not to be confused with CPR which means cycles per revolution)

Sorry for the long post. I'm just trying to get my head around this and make sure I buy the right encoder.

I think Ill order a 1000 CPR and give it a shot. I cant see a reason it would not work.( but then that isnt saying much)

[Al_The_Man]

Email them and clarify it?
Al.

[Myk Bates]

I called US Digital technical support today and was told that CPR and PPR were basically the same. I asked the same question a few different ways and got the same answer. I was also told that a 1000 CPR meant 1000 “windows” or slots in the disk. That is what I thought I understood at one point. Then I asked if CPR and PPR were the same why does the E3 encoder say it is capable of 64 to 2500 cycles per revolution (CPR) but it is also capable of 256 to 10,000 pulses per revolution (PPR) which is four times what the CPR is. I was then directed to the page on the EM1 which reads the disk and told to look at the part on timing. According to the drawing and definition one cycle is one slot which is one quadrature pulse that has four states (quadrature).
Based on that I will order a 2000 CPR encoder (which should have 2000 slots in the disk) unless KFLOP will not be able to use that for some reason that I do not yet understand.
Let me know what you guys think
Thanks again for all the help.

[Myk Bates]

I ordered a E3 2000 Line (Window, Slot CPR, something) encoder yesterday and received confirmation today that it was shipped out today. I'll see what I can learn from it before I order more.

[Al_The_Man]

Maximum encoder resolution is usually limited by the encoder input frequency capability, so this would be dependent on your encoder resolution and the maximum rpm of the motor.
Al.

[Myk Bates]

While waiting for my encoder to show up I went ahead and hooked up the KFLOP+Kanalog to my laptop. I got the drivers installed and verified that there was communication. I then went on a hunt for information on how to wire up the Kanalog, AMC drive, servo, and encoder. I found a lot of info on KFLOP but not about Kanalog. Fish4Fun did a great job and actually got me interested in trying out KFLOP on his project. But his project is different and so I continue the hunt. I am new to all this and want to make sure that I don’t wire things wrong. The power to the servo is simple. The connection from Kanalog to the Drive and Encoder is not. From what I can tell I will be using the Analog inputs and outputs to connect to the drive. But I don’t know which ones or how to set them up to talk to each other. There is info on connecting with a snap amp but I am not using that. Any info here or a point in the right direction would be a lot of help.

Thanks