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Thread: Cast Bench Top CNC Build

  1. #21
    Member mactec54's Avatar
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    Default Re: Cast Bench Top CNC Build

    Quote Originally Posted by RCaffin View Post
    Hi Mactec

    I am curious. I looked up the Teknic web site for the ClearPath motors, and was a bit confused. It seemed as though they were telling me what they wanted to say, but I could not get answers to my questions.

    It may be of course that I was expecting something different from what they offer. I was looking for details like angular resolution (I did find it, but the spec was obscure) and how to connect a ClearPath DC motor to a Gecko servo driver for a CNC. I imagine that the stuff might be fine if you want to automate a production line, but I could not see how to hook it up to, say, Mach3 or Mach4.

    Help?

    Cheers
    Roger
    You can use any software you want to use, they have there own built in drive, so no other drive is needed, this is the part most fall for, you are correct automation would be there ideal use

    They have more than one Encoder resolution option, the cost goes up with each step up, even there highest resolution is no where near what you want it to be for CNC machines, the magic number for encoders is the minimum of 14Bit so any number above this is Ideal for CNC machines and of cause the pole count of the servo motor there Pole count is ( 3 ) the normal Ac servo motor is ( 10 ) Pole to ( 12 ) Pole

    Mactec54


  2. #22
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    Default Re: Cast Bench Top CNC Build

    KiwiEngineer, sounds like I need to hook you up with my Kiwi mate Andrew Beck. He has done a lot of big retrofits and sells some machine tooling on his web site which I've forgotten the URL of. He can set you up with some well priced servos and no doubt help you get them going.. I'll see if I can dig him up for you.

    But be warned, he'll probably talk you into using Linuxcnc because thats what he uses and he's just been appointed the Mesa Electronics distributor in our region. They make a whole range of amazing CNC controller boards for Linuxcnc.

    Rod Webster
    www.vmn.com.au


  3. #23
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    Default Re: Cast Bench Top CNC Build

    So Andrew has been in contact. He's in Taranaki. He said he's bringing some servos in shortly so could share the shipping with you. If you send me a PM I'll share his email address with you.

    Rod Webster
    www.vmn.com.au


  4. #24
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    Default Re: Cast Bench Top CNC Build

    It will be good to have a Mesa distributor in our part of the world



  5. #25
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    Default Re: Cast Bench Top CNC Build

    Quote Originally Posted by pippin88 View Post
    It will be good to have a Mesa distributor in our part of the world
    Agreed, I offered to be a 3PL here in .AU as we ship stuff all over the country every day..

    Rod Webster
    www.vmn.com.au


  6. #26
    Member mactec54's Avatar
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    Default Re: Cast Bench Top CNC Build

    Quote Originally Posted by rodw View Post
    So Andrew has been in contact. He's in Taranaki. He said he's bringing some servos in shortly so could share the shipping with you. If you send me a PM I'll share his email address with you.
    You would have to know what servos he is using / importing not all Servos and Drives are created equal

    Mactec54


  7. #27

    Default Re: Cast Bench Top CNC Build

    Hi Rod, Ive actually already brought some Nema 24 stepper motors for this build, long with a Gecko 540 and UCCNC. Plan is to keep it pretty low cost on the motor side until i feel the need to upgrade to servo motors in future if i need to do so. I dont plan to be doing any crazy high speed cutting. But would be great to get a contact here for future builds or improvements.

    Is it bad i havnt heard of Mesa Electronics till now?



  8. #28

    Default Re: Cast Bench Top CNC Build

    Quote Originally Posted by mactec54 View Post
    You would have to know what servos he is using / importing not all Servos and Drives are created equal
    Hi Mactec, Have you had much experience with IONI? I know a few people that use these in robotic project and love them. https://granitedevices.com/ionicube-...-drive-boards/



  9. #29
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    Default Re: Cast Bench Top CNC Build

    Quote Originally Posted by KiwiEngineer View Post
    Hi Mactec, Have you had much experience with IONI? I know a few people that use these in robotic project and love them. https://granitedevices.com/ionicube-...-drive-boards/
    No have not used them myself, and would never have a need for them, Know some that have and where not happy with how the run there motors, there drives are for when you have a servo motor and no drive, this is where there Drives can be used in some cases, Normally when you buy a Servo motor you get the matching servo drive, so this is not something the normal machine builder would buy

    There Drives seem to work best with Dc servo motors they did not perform vey well with Ac servos which is what almost everyone uses

    There control looks interesting but without more spec's, it's just another control

    Mactec54


  10. #30
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    Default Re: Cast Bench Top CNC Build

    Hello KiwiEngineer,

    I saw this post and thought I’d take a moment to provide some clarity regarding ClearPath motors for CNC machine designs. Disclosure: I’m an engineer at Teknic.

    There are a number of topics that can cause confusion and challenges when designing a machine. I will mention just a few of these topics.

    First, contrary to some opinions expressed here, the reality is that ClearPath motors are used successfully on thousands of OEM CNC machines annually (as well as on hundreds of DIY machines). The ClearPath SD series of motors have been used with many different CNC controllers including Masso (headquartered in Australia) and Centroid’s Acorn (which you mentioned earlier). There are many helpful integration videos for both controllers with the ClearPath SD series, as well as integration videos for Mach4 breakout boards.

    Second, I should also mention that contrary to the statement that the ClearPath motors have 3 poles, the ClearPath motors have 8 poles. Through extensive testing and multiple design phases, we found that 8 poles provided superior performance with our rotor and stator design.

    Lastly, I want to discuss picking the appropriate encoder density to meet your performance objectives. Below is an excerpt of a response that was published several years ago that discusses encoder density in detail. The post is somewhat lengthy, but I hope it provides some clarity regarding this topic.

    If you have any other questions regarding ClearPath integrated servo motors or motion control, feel free to call Teknic as 585-784-7454 or send us a contact request at:

    https://www.teknic.com/contact/

    Best regards,
    Tom T. – Teknic Servo Systems Engineer

    ************************************************** **********************************
    Encoder resolution
    ClearPath servo motors (less than 1 hp) have a 12,800 count per rev optical encoder. This provides a repeatability of 0.028 degrees. (ClearPath motors of 1 hp or more have a 64,000 count per rev optical encoder which provides 0.006 degrees of repeatability.)

    For technical reasons beyond the scope of this post, we limit the command resolution to 2x the encoder resolution. Command resolution is the smallest increment that the motor can be commanded to move, i.e., 0.056 degrees for the smaller motors (with repeatability of 2x better than that). This means, for example, that if you have a fractional hp ClearPath motor connected to a 5 turn per inch ballscrew, you can command moves as small as 0.00003 inches.

    This command resolution is well beyond the capability of most mechanical systems, and is sufficient for almost all CNC applications. (With some ClearPath models you can save about 15% by opting for a lower command resolution—but still get the same 12,800 count/rev encoder resolution—and you would still achieve 0.0002 inches of linear resolution in the above ballscrew example.)

    During ClearPath’s development, we looked at using a 16-bit magnetic encoder because it was actually much cheaper than the optical encoders we were looking at (and the one we ultimately chose), but we decided against it for several reasons. The native resolution of these magnetic encoders is actually very low; in other words, they must significantly interpolate the magnetic signal to get their stated resolution.

    For example, it’s not uncommon for a magnetic encoder to use a 2-pole magnet, which means it natively generates only one sinewave per revolution. The motor position is estimated based on the output amplitude of the hall-effect sensors that measure the magnetic field strength of the magnet as it rotates.

    You can imagine the difficulty of accurately dividing one sinewave into 65,536 parts (16 bits) in the face of errors such as run-out, noise, offset, short- and long-term drift, sensor hysteresis, non-linearities, temperature effects, etc. Even though we could have compensated in firmware for some of these errors, the ultimate accuracy of the encoder would have been only about 0.1 degree (1 part in 3,600). Because of the extreme interpolation, the accuracy of magnetic encoders is nowhere close to their stated resolution (the accuracy is typically 15-20x worse than the resolution). This situation is even more pronounced with a 20-bit magnetic encoder.

    These magnetic encoders also have a serial output rather than a direct high-speed output right from the sensor. This means that the servo algorithm has to wait for position updates (typically about 100 microseconds) rather than getting continuous feedback. This delay in the position (and velocity) update means that the servo is always using somewhat stale position and velocity data (e.g., at 3,000 RPM, you would have a positional change of 327 counts before the servo knows anything has changed). As you can imagine, accurate and timely encoder data is crucially important to the quality of servo performance.

    Considering these disadvantages, we decided that the cost savings of using a magnetic encoder were not worth the performance degradation. And the resolution of the optical encoder is more than sufficient.



  11. #31

    Default Re: Cast Bench Top CNC Build

    Howdy yall,

    So i havnt given up on this build. I just need to decide on the gantry and z axis design. I have a few in mind that i will share and hopefully start the ball rolling again.

    However i made a purchase i may regret...But i think its perfect for me to learn a little more and so i have the capability to machine some of the part of my own instead of out sourcing. A GL-45 or a RF-45 clone.

    This mill has definitely seen a few hours of work in its life haha. Mainly aluminium thankfully, so the guide ways look fine. The plan is to convert to CNC. I will probably make a new thread for this once i get a little deeper into the project. For now i need a little help choosing the motors for this.

    I see lots of people use closed loop steppers for these builds. Are they really necessary?

    I was planning on using some Nema 34 1000oz for the X and Y axis and 1700oz for z axis. with some sort of counterweight.

    I would prefer to buy from https://www.omc-stepperonline.com/cl...er-kit/page/2/ as they are cheap and easy to deal with. Does anyone have any other site with better motors?

    From what people are saying its best to find stepper motors with under 5mH inductance, if im not doing any crazy fast feeds does this affect me? Also how reliable and safe are these cheap power supplies they provide in the kits?

    Sorry for soo many questions haha.

    Attached Thumbnails Attached Thumbnails Cast Bench Top CNC Build-216748726_180988357378979_42831617253512354_n-1-jpg  


  12. #32
    Member peteeng's Avatar
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    Default Re: Cast Bench Top CNC Build

    Kia Ora across the ditch - I think you will find Nema23 will do what you want. Depends on your screw pitch. 5mm is common for a mill and it will provide 100's of kgf to cut with. With SOL I have found that buying the individual parts are cheaper then their kits. Their power supplies are very good. I have bought cheaper PS from other vendors and they are not as good as holding the smoke in as SOL's (SOL PS's I haven't killed yet others not so lucky) . Plus SOL come with mounts which is really useful!! Peter

    closed loop steppers are not necessary. For the extra cost I think they give a bit more torque at higher speed but that's about it. Put the extra $$$ into other things in the machine or jump to servos...



  13. #33
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    Default Re: Cast Bench Top CNC Build

    It is not the motors you need to worry about; it is the leadscrews. You will have to use ball screws, and you will have to use a reduction between the motor and the ball screw. Forget gearboxes: they are expensive and have backlash. Go for GT2 toothed belts and pulley, with medium tension in the belts. You can get real GT2 from American vendors or pseudo-GT2 from ebay/China. The difference between them is mainly in the mind.

    I have no idea how much slop there will be in the dovetails, so you will have to be very careful there. Normally one uses linear bearings for this.

    With enough reduction and a fine pitch on the ball screw it probably won't matter whether you use steppers or servos. It won't be super fast, but it cannot be that with dovetails anyhow. On the other hand, you will NOT need huge power on the axis motors. All this business about 1 kW axis servos is (imho) just marketing hype. I monitor the actual current going into each of my servos, and I rarely see more than a few hundred milliamps at 50+ V. OK, linear bearings take less power, but still....

    Cheers
    Roger



  14. #34

    Default Re: Cast Bench Top CNC Build

    Hi Peter and Roger,

    Yes the plan is to use a 2005 ball screw with double nut. But from some of the builds ive been following, using beefy motors and direct driving with a low backlash coupling looks like a cleaner way.

    Sadly im a sucker for clean and tidy. I would try avoid having a belt and pulley system if i can.(More guards to make)

    The gibs on the ways actually seem very good. I gave them a good clean and there seems to be no slop once adjusted . I plan to upgrade the lubing system for the guide ways to help the motion of the dovetails.

    One day i will do servos. But for now i think some steppers wiill do me well.

    Rohan



  15. #35
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    Default Re: Cast Bench Top CNC Build

    Guards ... huh?
    My motors are inside other stuff so they don't need guards - convenient for me.

    Cast Bench Top CNC Build-7331-jpg
    Personally, I find the use of GT2 belts to be really clean and tidy. The motor can be folded back and placed where convenient. I don't have to worry about the direct coupling with any backlash as GT2 belts don't have backlash. I am resolving 0.8 microns with this system.

    Cheers
    Roger



  16. #36

    Default Re: Cast Bench Top CNC Build

    Hi Roger,

    I understand with some builds you can get away with hiding belts. But with a mill-drill type conversion they become very hard to do so. My friend did a belt version and made guards to cover the belts so no swarf chewed up the belts. But somehow the little ****s always found there way in.

    I personally use timing belts at work all the time and i have no problem using them.

    Rohan

    Attached Thumbnails Attached Thumbnails Cast Bench Top CNC Build-p1011009-1-jpg  


  17. #37
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    Default Re: Cast Bench Top CNC Build

    Yeah, swarf . . .
    I agree.

    Cheers
    Roger



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