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Thread: AC and DC Servo projects with Kaflop+Kanalog

  1. #1

    Default AC and DC Servo projects with Kaflop+Kanalog

    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.

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    So many projects, so little time...


  2. #2
    Community Moderator Al_The_Man's Avatar
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    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.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Registered TomKerekes's Avatar
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    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

    TK
    http://dynomotion.com


  4. #4

    Default encoder advice?

    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.

    So many projects, so little time...


  5. #5
    Community Moderator Al_The_Man's Avatar
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    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.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  6. #6

    Default US Digital Encoders

    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

    So many projects, so little time...


  7. #7
    Community Moderator Al_The_Man's Avatar
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    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.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  8. #8
    Community Moderator Al_The_Man's Avatar
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    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.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  9. #9

    Default US Digital encoder help

    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

    So many projects, so little time...


  10. #10
    Community Moderator Al_The_Man's Avatar
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    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.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  11. #11

    Default

    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.

    So many projects, so little time...


  12. #12
    Community Moderator Al_The_Man's Avatar
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    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.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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