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Thread: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

  1. #21
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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Thank you very much for your response. I've bought AC servos, 2x0.75kW for X and Y and 1kW for Z axis. They are going to be mounted directly. I'll keep you posted how it goes, but according to your writing, my decision wasn't bad.

    Best regards,
    Jure



  2. #22
    Activation process men8ifr's Avatar
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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by hackish View Post

    Micro-steps should be called micro-guesses. Most of the drivers are toys,

    A proper AC servo ... stop within a fraction of a degree. .
    This would seem to disagree - is it wrong?

    https://www.orientalmotor.com/steppe...er-motors.html

    The author seems to make/sell servo's and steppers so I can't see any real reason for bias..

    This is the only 'real' data i've seen on accuracy though I have worked out:

    hybrid steppers with a 1000 line encoder mean the encoder has a 0.36degree accuracy.

    A 2 phase stepper with 16 microsteps is microstepping (target value!) 0.11degrees - so as far as I know the encoder will miss the first 2 or 3 'missed' microsteps though perhaps software can make much better use of the encoder?

    Of course if you ran at 256 microstepping (target microstep 0.007deg) the encoder could miss 50 microsteps..



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    got a link to the spindle/driver you are using?



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by men8ifr View Post
    This would seem to disagree - is it wrong?

    https://www.orientalmotor.com/steppe...er-motors.html

    The author seems to make/sell servo's and steppers so I can't see any real reason for bias..

    This is the only 'real' data i've seen on accuracy though I have worked out:

    hybrid steppers with a 1000 line encoder mean the encoder has a 0.36degree accuracy.

    A 2 phase stepper with 16 microsteps is microstepping (target value!) 0.11degrees - so as far as I know the encoder will miss the first 2 or 3 'missed' microsteps though perhaps software can make much better use of the encoder?

    Of course if you ran at 256 microstepping (target microstep 0.007deg) the encoder could miss 50 microsteps..
    That opinion is limited to higher cost hybrid units with high resolution encoders and drivers. The reality is that it represents the upper 1% of stepper motors, and steppers still suffer from significant torque falloff as RPM goes up. The micro-stepping size thing affects open loop motors and many of the hybrids with lower number of PPR encoders. I've certainly seen a number of hybrid steppers that will lose the occasional step here and there, and then fault out when running longer programs. The servos I'm running are 2500 pulses per rev if that gives an idea of what is typical.

    I've got a set of 400w servos and they're quite a bit of overkill for a benchtop mill. They would have been sufficient for my old bridgeport. The 0.75kw units quoted here are going to be a lot of overkill.



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Do the servo's have (and control to) 2500 pulses/rev or 1/2500 rev degrees = (0.14 degrees) ? i.e if I move a servo 0.14deg it will detect this (encoder is 2500 lines?) and move back?



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by men8ifr View Post
    Do the servo's have (and control to) 2500 pulses/rev or 1/2500 rev degrees = (0.14 degrees) ? i.e if I move a servo 0.14deg it will detect this (encoder is 2500 lines?) and move back?
    As far as testing I did a number of years ago, yes on the servos I run.

    I did some testing on a few hybrid servos to help someone diagnose a system that was losing steps and the answer was no. We attached an arm (about 24" long) and tried to measure the fractional turns but couldn't get a consistent result. Every 15 degrees or so it seemed to snap into a consistent point but otherwise it was your best guess where it would go. You could push the arm back and forth and it would bounce around and land practically anywhere. On my servo it would actively hold on that spot until you forced it and the driver would immediately give you a servo position fault.



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by men8ifr View Post
    This would seem to disagree - is it wrong?

    https://www.orientalmotor.com/steppe...er-motors.html
    It does have the caveat "with no load," and it's referring to their 5-phase stepper motors, which have 2.5x as many steps per rev as a standard 2-phase. It doesn't say, (but I bet it depends on) being at a full or half-step as well. Steppers aren't quite linear in between half-steps. Also, the 'with no load' caveat is a big one. At full load, just before skipping a step, the motor will be a full step off (1.8 deg for normal steppers, not sure about 5-phase their steps are smaller, but may actually be off multiple steps at full load.) Of course you should never be pushing a stepper that hard (or you will be losing steps,) but .5 deg is much more likely than .05 deg.



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by blackie9900 View Post
    got a link to the spindle/driver you are using?
    Sorry it took me a while to anser, here is a link to the DMM Servo I bought

    https://store.dmm-tech.com/products/...ac-servo-motor

    Here are all parts, Servo, driver, motor and encoder cables


    Item Part Number Part Description Notes Unit Price Quantity Total
    1 DYN4-T01A2-00 DYN4 AC Servo Drive - T01 Frame

    1.3~1.8kW servo motor pair 267.00 1 267.00
    2 120-DST-A6HK1 130mm Frame, 1.8kW, Keyed Shaft, 200V Class 378.00 1 378.00
    3 CAEN-HH3-TSP 3m Encoder Cable - 130mm Frame Servo Motor 35.00 1 35.00
    4 CAMP-HH3-SSP 3m Motor Cable - 130mm Frame Servo Motor 36.00 1 36.00



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Update: I received my PM-30MV last week. It took 4 months since I ordered it.

    Here is a link to the my first ever YouTube video on un-packing and walk-around. I will be posting a ton of Videos on YouTube for this build:





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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    So are you happy with your choice (size) of machine? Did you get an accuracy report with it?

    Why are you replacing the spindle motor? What can you do with a servo drive there you could not do simply controlling the spindle speed?

    Keep posting updates, very interested in this as I will be converting a similar sized machine though probably from a different factory in China so no idea how the build quality will compare.

    I would be interested in a test for me if you could, place a dial indicator on a shaft (like top part of a drill chuck) in the spindle in the X direction and standing in front of the machine push the chuck left and right, do you get deflection? How much? Then repeat for Y. On my current mill I got 0.04mm in both directions, I adjusted the Gibs and preload on the spindle and got it down to 0.02mm but I'm hoping this PM30 sized machine is a lot stiffer/better a lot comes down to the machining of the dovetails and surprisingly while my spindle was not loose, adding more preload stiffened it up quite a bit. I can post a video on YouTube how to do this if it's a bit confusing?



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by men8ifr View Post
    So are you happy with your choice (size) of machine? Did you get an accuracy report with it?

    Why are you replacing the spindle motor? What can you do with a servo drive there you could not do simply controlling the spindle speed?

    Keep posting updates, very interested in this as I will be converting a similar sized machine though probably from a different factory in China so no idea how the build quality will compare.

    I would be interested in a test for me if you could, place a dial indicator on a shaft (like top part of a drill chuck) in the spindle in the X direction and standing in front of the machine push the chuck left and right, do you get deflection? How much? Then repeat for Y. On my current mill I got 0.04mm in both directions, I adjusted the Gibs and preload on the spindle and got it down to 0.02mm but I'm hoping this PM30 sized machine is a lot stiffer/better a lot comes down to the machining of the dovetails and surprisingly while my spindle was not loose, adding more preload stiffened it up quite a bit. I can post a video on YouTube how to do this if it's a bit confusing?
    Since I am new to milling, I have ordered mostly Chinesium tools and acessories such as end mills tool holders etc.. based on finish quality, appearance and initial fit and finsh, and comparing them to my other Chinesium purchases, the PM30 is very solid and I am super happy. It feels heavy and solid, the finish quality on machined surfaces look and feel really good.

    The one very disappointing part was documentation. No quality or accuracy report. The manual seem to be for a different machine and even has subtitles with "lathe" in them. I will be calling PM about this.

    As for Servo spindle, I have a longer objective to add a fourth axis and have the machine totally software controlled. Besides rigid tapping, Acorn will manage spindle speed variation when needed. I initially was going the VFD route, but I could not find a VFD that has single phase in / single phase out 220 AC. I decided to go the route of servo spindle. It will become handy if/when I decide to replace the spindle for much higher rpm's.

    This a hobby for now. So building a cnc machine without prior experience is the challenge and objective. I have no idea what I will be machining early on. I hope to become good at this by the time I retire and start some sort of a small business. I have a southbend 9 on which I did a total tear down and rebuild. It is almost done too. To finsh answering your question about the servo spindle, it is not about what I want to do now, but rather what the machine is capable of years down the road, when I retire.

    As for you final question, the head is removed already. I will clamp it to the x table, extend the spindle and measure selection as you mentioned. As soon as I can.

    Sent from my SM-N910V using Tapatalk



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Quote Originally Posted by cnc-geek View Post
    Since I am new to milling, I have ordered mostly Chinesium tools and acessories such as end mills tool holders etc.. based on finish quality, appearance and initial fit and finsh, and comparing them to my other Chinesium purchases, the PM30 is very solid and I am super happy. It feels heavy and solid, the finish quality on machined surfaces look and feel really good.

    The one very disappointing part was documentation. No quality or accuracy report. The manual seem to be for a different machine and even has subtitles with "lathe" in them. I will be calling PM about this.

    As for Servo spindle, I have a longer objective to add a fourth axis and have the machine totally software controlled. Besides rigid tapping, Acorn will manage spindle speed variation when needed. I initially was going the VFD route, but I could not find a VFD that has single phase in / single phase out 220 AC. I decided to go the route of servo spindle. It will become handy if/when I decide to replace the spindle for much higher rpm's.

    This a hobby for now. So building a cnc machine without prior experience is the challenge and objective. I have no idea what I will be

    Sent from my SM-N910V using Tapatalk

    Same with my AMAT25LV I just got.
    Documentation that came is for a WMD25VB and the specs are a bit different to the ones published on the sales site.
    Looked at the PM25 manual online and the part numbers were identical lol.

    Weren't going to un-crate it for about a month but will have to just to make sure the advertised specs that made me buy it in the first place are/can be reached.

    As for tooling I will say this:
    Chinesium end mills are good enough however I found the Chinese ebay special collet holders and chucks are not!
    My advice is not to cheap out on the ER holders/collets etc.
    One of my MT3 Chinese holders had a run-out of 0.12mm!? My more expensive one can be as low as 0.004mm (BIG difference)

    Never even looked at the cheap ones when I changed to R8.

    I still use the Chinese throw away end mills but wouldn't touch the collet chucks/holders ever again.
    The 50mm face mill + arbor types have been fine.


    Be glad when I get the SeigX2 back up & running, can't wait to start tearing this new one to bits



  13. #33
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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Fwiw ..
    the OP did the right thing buying real servos.

    Here is how it works.

    The best steppers with the best motion control engine at 68 V DC accelerate to about 1000 rpm, for about 50% of their rated torque.
    On nema 23 sizes.
    Most steppers deliver maybe 20%-25% torque at 800 rpm.
    They take about 0.1 - 0.2 secs to get to 800 rpm.

    So a Nema 23 3Nm stepper delivers about 0.6 Nm at 800 rpm and must be used at 0.6 Nm and 800 rpm, minus some margin.

    A bigger Nema 34 stepper has more inertia and inductance, and accelerates slower.
    A 6 Nm stepper might get 6-800 rpm, 1-1.2 Nm, with luck.
    And go to 600 rpm in about 0.3 secs.

    Now, let us look at real servos, in Nema 34 size first and 23 next.

    I use 220V AC servos, 10.000 count, on my industrial lathe.
    3Nm cont, 10 Nm peak.
    No-load, the servo will go to 3000 rpm in about 20 ms or less.
    0.02 secs.

    During that acceleration, it will use 10 Nm, vs about 1.2 Nm for the Nema 34 stepper.
    About 8-9x more.

    It accelerates to 3000 rpm / 0.02 secs vs 600 rpm / 0.3 secs = 45 times faster.
    The nema 34 servo at 10.000 counts, has a led that displays in real time the error.
    It will use 10 Nm peak torque to catch up to any positional error.
    From rest, a 1/10.000 count movement will use 10 Nm.

    A single command to move 1/10.000 revs will always be obeyed and will always work, or fault, or show the error in the led display.
    In practice all movements end always end up with zero errors.
    The servo is vastly more powerful than the motion-control train stiction and mechanical errors and always position to zero error at endpoints.

    In motion, the error may be 300-600 counts spindle and 20-300 on x/z depending on load and speed.
    Increasing the tuning, I could get it down to 30-50 counts or less.
    So far I have not done so, because the movements are extremely violent.

    Reality:
    So, a 10.000 count ac servo will always move 1/10.000 counts with 100% reliability.

    This does not mean the linear axis moves.
    Screws wind, mounts have poor bearings, yokes bend.
    Gibs and slides have stiction.
    It is just a question of how much.

    ---
    In use, the errors on x, z, are about 0-1-2 counts, no more, when entering a typical cut.
    This is about 0-1 micron in accuracy.
    Mostly x and z are zero difference, and the spindle might change 1-2 counts, over 30.000 counts/rev.

    My spindle is a c axis.
    HTD 8-30 mm timing belt, Good for 20 Hp plus.
    It can index in 1/30.000 rev increments.
    90 Nm peak torque.
    The spindle speed never varies when entering std cuts. It maintains whatever pid error it had.

    I have stalled it about 6 times, using about 8 kW of cutting power.



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    I just posted my YouTube Video detailing my Fusion 360 3D model





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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Interesting. Are you hoping to use the brake on the spindle for doing tool changes?



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    The brake is on the Z-axis Servo motor. Hopefully I did not mis-state things.



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    Quote Originally Posted by cnc-geek View Post
    The brake is on the Z-axis Servo motor. Hopefully I did not mis-state things.
    I probably just misread it. I think I understand that you are going to use the z brake to stop it from freewheeling down once the machine is off.



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    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Looking forward to seeing you do this! I'm in the early stages of planning for a similar machine with similar servos including the spindle.

    Will you look at putting linear rails on this? My plan is to run with the guideways for a while then upgrade to square rails on all axis.


    did you draw up your model or download it from somewhere? It looks pretty detailed.

    Thanks for documenting it all, I'll be following closely



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    Default

    Acorn plus servo pm30? Dream build i would say, linear rail would match ac servo nice, dc servo just keep it dovetail.



  20. #40

    Default Re: New Build/PM30-MV Mill/Acorn/DMM DYN4-.75KW X/Y/Z SERVO/1.8KW DMM SERVO SPINDLE

    Is there a reason that you went with brakes for the Z axis instead of gas spring? I'm planning a similar build and brakes just seems to be not necessary.



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