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  1. #13
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    Default Re: 5-axis for machining metals

    Hi I Do Alu Milling with an heiz 400T (now Even with toolchanger ) i Do molds with it my learnings if you stay small and Slow you can use a Router but this is really Slow we Talk of 9 to 20 machining hours of a piece. I now have the need to mill Steel (i designed an toolchanger ) so i have now a novakon like machine but build in europe i right now about to do an trunnion Setup which ill Post in that Forum so if you explains more your Kind of pieces i my be able to help or give hint s ..

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    Default Re: 5-axis for machining metals

    Hi guyz,

    After some turbulent months, I am back on track to start designing the machine.

    I have done some research, and turns out 5 axis is a ***** to build up, specially for Iron and steel.

    So basically I would go and build up a CNC router, and then add 4th and 5th axis.

    What I have been breaking my mind, is the motors I would use for this machine.

    Leadshine easy servos (closed loop steppers with digital drivers) are my favorites.

    I would put this 86HS80-EC-1000 motor and its matchin driver HBS86H.

    Idea is to put this 3 motors on each axis of the machine, and then add 4th axis, with this motor (or even 12 Nm motor) with direct ratio on rotary axis.

    I was also thinking the 1:2 or 1:3 reduction via double steel wire reinforced belts.

    What I am considering is this Leadshine sets, but I dont know how they perform, and would they be suitable for such application.

    Link to motors and drivers.
    damencnc.com - Closed-loop Stepper Systems

    @Tkamsker

    I am really interested in the help you are willing to provide. Also, building your own ATC is amazing. I am currently designing the machine, so I can add ATC at some point.

    Help needed.

    Thanks

    Last edited by lopata; 01-04-2016 at 06:21 PM.


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    Default Re: 5-axis for machining metals

    Quote Originally Posted by lopata View Post
    Hi guyz,

    After some turbulent months, I am back on track to start designing the machine.

    I have done some research, and turns out 5 axis is a ***** to build up, specially for Iron and steel.

    So basically I would go and build up a CNC router, and then add 4th and 5th axis.

    What I have been breaking my mind, is the motors I would use for this machine.

    Leadshine easy servos (closed loop steppers with digital drivers) are my favorites.

    I would put this 86HS80-EC-1000 motor and its matchin driver HBS86H.

    Idea is to put this 3 motors on each axis of the machine, and then add 4th axis, with this motor (or even 12 Nm motor) with direct ratio on rotary axis.

    I was also thinking the 1:2 or 1:3 reduction via double steel wire reinforced belts.

    What I am considering is this Leadshine sets, but I dont know how they perform, and would they be suitable for such application.

    Link to motors and drivers.
    damencnc.com - Closed-loop Stepper Systems

    Help needed.

    Thanks
    Like many have said here before, I would design the mechanics of the system before the electrical system (including motors). Mechanical designs tend to evolve over time, and if you have already constrained your motors then you might end up spending more money if you need something different.

    That being said, I would not gear reduce anything if you can avoid it - especially with steppers. Steppers perform best at low RPMs and continue to fall throughout the range. You may or may not need this because of what you intend on machining, but it is something to consider. You will probably not need a greater resolution either, microstep at 4000 steps/rev or similar and you'll have more than enough resolution.

    Those steppers look like good options and leadshine makes good products. There's a note in the torque curve that says "if higher torque at higher speeds is required, you can change the holding torque percentage to 100% [from 40% that the curve is rated at]" They will require some playing around with software, but they should be fairly straightforward.

    Hope that helps a little.



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    Default Re: 5-axis for machining metals

    Thanks Iron man

    I was considering direct drive, and forgot the basics of the stepper drive.

    All 3 axes will be with 8Nm motors, and 4th axis will probably go with 12 Nm steppers.

    Problem which is occuring is the design of the 5th axis, as this motors are Nema 34, and quite large. Feels like I have to design it from the end, and Z axis will be redesigned.



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    Default Re: 5-axis for machining metals

    Quote Originally Posted by lopata View Post
    Thanks Iron man

    I was considering direct drive, and forgot the basics of the stepper drive.

    All 3 axes will be with 8Nm motors, and 4th axis will probably go with 12 Nm steppers.

    Problem which is occuring is the design of the 5th axis, as this motors are Nema 34, and quite large. Feels like I have to design it from the end, and Z axis will be redesigned.
    The 4th axis typically won't need as much power as the other axes. If you know a feed rate that you'll be cutting a material at, and the dimensions of the stock, you can do a ballpark calculation of the RPM required for the 4th axis, then figure out motor RPM (through any belts/reducers/gears). I am sure it will be low, which again, is perfect for a smaller stepper motor. I imagine a nema 23 would be sufficient for most setups, but again without the hardware it's tough to say.

    What's nice about the closed loop steppers is that you don't really care if you are way oversized. You won't hit resonance points and lose torque like in an old school stepper setup.

    Check these guys out
    http://www.tormach.com/product_rotaryproducts.html



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    Default Re: 5-axis for machining metals

    Further to my first advice;

    1. Forget the 12 Nm steppers and direct drive.
    Technically Very Bad Idea.
    You want 100x more angular resolution AT THE LOW END, 10x more accuracy, and 10x or more top speed and 3-10x more acceleration.

    I have an existing belt drive, C axis, on the lathe now.
    Its about 100x better than the proposed solution, and its barely adequate.

    Fwiw..
    I am using a 2.5 kW brushless ac servo motor, of 2.5 kW power.
    With 1:3 belt drive, using good industrial components, 10x more rigid (HTD 8 mm profile and 30 mm wide) and 10x more tension (50-80 kg tension on belts) than typical hobby builds.
    The belts have zero backlash.

    I have 90 Nm torque (30 Nm peak x 3), and 30.000 steps/rev, and it is, like I said, barely adequate for indexing in metal.
    So, the 12 Nm stepper, will only have 400 steps/rev accuracy, and less than 6Nm (half step) torque, for holding position.
    It will be about 15-20 times less torque than needed.

    Simply wont work, for indexing apps, in metal.

    If you use a small servo (stepper) to drive a low-backlash rotary table, then it will work fine.
    The reason is that worm-gear drives cannot be backdriven, but steppers are like springs, and yield easily (upto 1-full-step) near a full step or 1.8 degrees or 1/200 of a rotation.

    Your motors are immaterial, at this point.
    They are also cheap, and easily replaced, later on.

    My suggestion:
    Forget the motors,
    Focus on mechanical drives.

    My suggestion:
    Use some low backlash planetaries for 300€ or so each.
    A stepper will drive these, easily.

    I may even go to the planetaries(likely) or harmonic drives, myself.

    The smaller the stepper (2-3 N, nema 23) the faster it will run, and the faster it will accelerate.
    A big stepper (12 Nm) will typically run at 300-500 rpm max.
    A small one, 2.5 Nm, 600-1000 rpm at 48-68 V DC.

    The same size servo will run 3000 rpm, and deliver 3x-5x more torque at the top end.

    You real torque on steppers depends on the max speed you run at, and is usually about 1/3-1/6 the nameplate.
    Thus, a 3Nm stepper => 0.3 Nm stepper (to 1 Nm, depending).



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    Default Re: 5-axis for machining metals

    Quote Originally Posted by hanermo View Post
    I have 90 Nm torque (30 Nm peak x 3), and 30.000 steps/rev, and it is, like I said, barely adequate for indexing in metal.
    So, the 12 Nm stepper, will only have 400 steps/rev accuracy, and less than 6Nm (half step) torque, for holding position.
    It will be about 15-20 times less torque than needed.

    If you use a small servo (stepper) to drive a low-backlash rotary table, then it will work fine.
    The reason is that worm-gear drives cannot be backdriven, but steppers are like springs, and yield easily (upto 1-full-step) near a full step or 1.8 degrees or 1/200 of a rotation.
    You bring up a good point about the mechanical system - a worm drive is superior for the application for the reasons you stated.

    I have to disagree with what you're saying about the stepper motors though. 400 steps/rev accuracy? No, the stepper motors are essentially servo motors with a 1000 line encoder - after quadrature that's 4000 counts/motor revolution - that's 0.09° resolution. Accuracy is a function of the drive system and tolerance on the encoder. They will have 12Nm holding torque, not 6Nm. Holding torque is always higher in a stepper motor than dynamic torque and typically what the motor is rated for.

    Quote Originally Posted by hanermo View Post
    The smaller the stepper (2-3 N, nema 23) the faster it will run, and the faster it will accelerate.
    A big stepper (12 Nm) will typically run at 300-500 rpm max.
    A small one, 2.5 Nm, 600-1000 rpm at 48-68 V DC.

    The same size servo will run 3000 rpm, and deliver 3x-5x more torque at the top end.

    You real torque on steppers depends on the max speed you run at, and is usually about 1/3-1/6 the nameplate.
    Thus, a 3Nm stepper => 0.3 Nm stepper (to 1 Nm, depending).
    Hanermo, the motors linked provided the torque curves over the operating range. What you said may apply to the junk high inductance chinese stepper motors, but these will reach 1000RPM (at least the 8.0Nm one will).

    Schneider/IMS made a Nema42 sized stepper that will run up to 3000RPM
    http://motion.schneider-electric.com...s/MDM42_AC.pdf

    Some small stepper motors can hit 6000RPM.

    Your real torque depends on the torque curve, not a thumb calculation of the nameplate - that's only something you assume when you are dealing with steppers that have no listed specifications.



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    Default Re: 5-axis for machining metals

    Quote Originally Posted by hanermo View Post
    I may even go to the planetaries(likely) or harmonic drives, myself.
    The Nabtesco Vigo drives and Harmonic Drive reducers look awesome for a rotary table application, and could probably even be driven by a fairly small nema23 motor. I worked on an instrument where we used a Nabtesco reducer and it was a high performer, we ran it open loop as well and never lost steps with some aggressive accelerations. There's over 10,000 of these instruments in the field and these items NEVER break. I have almost been tempted to buy one or two on Ebay when I see them at a good price.



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    Default Re: 5-axis for machining metals

    Thank you guys for your thoughts.

    As I am buying an extra motor and driver, I will be tempted to try a direct connection to 4th axis, instead of Tormach solution. Al thou they do look pretty plug and play solution.

    What I am considering is the motion controller.

    What I used before, on my 1st machine, is a simple breakout board, and Mach3 as a motion controler, but now I am looking for a standalone connection.

    This is something I am lurking about, so maybe you can help out.

    CSMIO/IP-M 4 axis motion controller 4 axis Ethernet Motion Controller (STEP/DIR)

    SMC6480 Leadshine 4 axis motion controller Leadshine Technology Co., Ltd.

    6 Axis Ethernet SmoothStepper Motion Control Board with Terminals for Mach3, Mach4 : is in the loop, but I dont know much about it, and I believe that above solution should work better. (Remark: My opinion is based on apsolutly nothing)

    Budget is to go up to 250-300 Euros/USD for a quality ethernet motion controler, used with Mach3/4 or standalone motion controler with screen and commands.

    Idea is to build a quality machine, with quality components, which will be later upgraded with ISEL 2.2 KWh ATC spindle.



  10. #22
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    Default Re: 5-axis for machining metals

    hi iopata i work on an trunnion setup i have already the worm drive at home but first i do the frankenstein version using an manual 4 th axis and konvert it to cnc one which carries then the trunnion using the roundino as 5 th axis i will then measure the "errors" in the system and see how far theory and real world are sepereate this frankenstein system you can easily connect to any dir step driven system so if you are interested i ll do extea video for you


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    Default Re: 5-axis for machining metals

    Hello Tkamsker,

    I would love if you could a video, as I need all the info I could get.
    I will do my Frankestein, and see how it goes from there.
    Tormah solution is really an option, if the direct mount fails.



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    Default Re: 5-axis for machining metals

    Hello Guys

    I a bit baffled with the design.

    Thing that bother me is the design itself, and rigidity of the system.

    I am designing a cnc mill something similar to Gabriels (aka Katran), and now I am wondered by the rigidity of that machine.
    5-axis for machining metals-large-jpg
    5-axis for machining metals-large-jpg

    My main concern is the rigidity of the Z axis, for cutting iron and steel. As I would be doing some light pressure mold production, and I want the machine to be rigid enough, but on the other hand, to be simple in design.
    Linear guides will be between 25 mm and 35 mm, so there should be a major stiffness in the machine.
    I know that for proper pressure modling cutting, there should be weight and stiffness in the machine, but I would go with conservative cutting, and upgrade my machines/knowledge from there.

    Another option is to build the Fixed gantry for the Z-axis, and put the sliding table beneath it. A big gantry bridge would be built, and it should be more than enough.
    Also, I have read somewhere, that single ballscrew table is a bad design, and that there should be 2 motors per axis for the better stiffness.
    My doubt in that claim is that with 25 mm ballscrew, and 25 linear guides, there should not be a problem with the width of the table of 400 mm.

    Correct me if I am wrong please.

    @Tkamsker any news about the video?



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