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  1. #37
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    Default Re: Stepper Options

    Quote Originally Posted by 109jb View Post
    All I ever said is that I don't regard encoders on steppers as totally useless as was stated by another user.

    A rotary encoder can be bought for about $15, and LinuxCNC can read them through a $6, or surplus parallel port card. If you are like me and play around with 3D printers you can print up some simple mounts and for about $50 you can have a system that can detect lost steps and stop the machine. If a step is never lost then the machine never faults. In my opinion the peace of mind, and the education of doing it is worth the $50. It is also a lot cheaper to do this than to change to a closed loop stepper or servo system. If you disagree then fine, don't add encoders to your steppers
    LinuxCNC reading quadrature encoder signals with a parallel port might be a little slow. It's probably reliable to about 25khz pulses, only good for low resolution encoders. Better yet would be one of the Mesa FPGA cards. The FPGA can be programmed with quadrature counters with digital filtering. I've done that with Xilinx FPGA's.

    Microchip has some micro controllers that have built in quadrature decoders. Really easy to use. Good for several MHz counting. I don't think Atmel has mcu that has built in quadrature but the last time I looked was a couple years ago. You would have to do the counting with hardware interrupts which is good for about 200khz on a atmega328

    I have C code and Verilog fpga quadrature code if you need them.



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    Default Re: Stepper Options

    So I spent a few minutes on this

    https://motion.schneider-electric.co...-control-ip20/

    Above is the part # data sheet from the first EBay add I posted a link to. The same data sheet I posted earlier. So this is for "MDI1" It says for

    Control Type = Programmable Motion Control
    # of I/O = 4 I/O points, programmable as sinking outputs or sinking and sourcing inputs
    Logic Range = Inputs and outputs tolerant to +24 VDC, inputs TTL compatible

    And then below is the data for "MDM1"

    https://motion.schneider-electric.co...on-input-ip20/

    Control Type = Step/direction input
    Control Method = Clock and direction inputs
    P1 Connector Options = Power & I/O Flying Leads, Pluggable, Wire Crimp

    So good call guys. Looks like you need to pick the correct one.

    I'm pretty good at looking at torque vs speed curves and doing the math with inertia and lead, etc., but I can miss things on the electronics side. Certainly, the feedback from RCaffin, and jfong, was appropriate, so again, good call guys.

    Quote Originally Posted by RCaffin View Post
    The MDrives - an interesting thing. Way back in the dark ages CNC machines had lots of dedicated electronics (huge boards of chips) but no 'PC controller'. One compromise to handle this was to drive the CNC in a completely different way: you sent a message to the X motor controller to tell it to go to point X at speed S with accel and decell as specified. Then you sent a similar message to the Y axis controller, and then to the Z axis controller. Then you broadcast a Start signal. All this communication was done over SERIAL lines. That was fine for a straight line move, but it could not handle arcs and spirals. In effect, that was back in the days of crank-starting your motor car. Today we have starter motors ... and tomorrow electric cars ...

    But some older companies had thriving product lines for ancient machines, and they are unwilling (or too short-sighted) to replace that older technology with more modern concepts. They are scared of abandoning a dying product line. The result is that they are being replaced by more modern companies with more modern concepts and hardware (at a lower cost). It is what happens in any technology.

    What will replace a PC controller and the Step/Dir interface in the future? Dunno. Could be a long while though.

    Cheers
    Roger
    Roger, are you saying that Schneider Electric MDrive is older technology with a dying product line? Or is this a general statement referring to something else?

    There are many reasons why you could have different control inputs. Their target market could be factory automation for some models, for example, move a beer bottle over, wait for it to be filled, move it back.

    It was my understanding that the MDrive was a step up from traditional steppers. These are "smarter" steppers with built in drivers optimized for the motors. From what I've seen in videos, you can't loose steps on these motors, they will adjust the speed if the load is too great. If the OP can find an appropriate model on EBay, I think that would be a good choice.

    As far as why they aren't widely used, I think it is because unless you find a great EBay deal, they are alot more $$$ to buy direct than a traditional setup.

    Correct me if I'm wrong.



    Quote Originally Posted by arizonavideo View Post
    With the Nema 23 steppers most are really not a good match with small mills. The 150 oz to 300 oz range are a little small so only a few are larger and most have fairly high inductance so are poor at high speed unless you run a 80V driver.

    The one stepper that stands out is the 570oz 5A stepper. It has a really low inductance so is way faster at high speed and has more power than you need.

    Run it at 4A on the X and Y and you will get 150 IPM at 50V all day long.

    Really no reason to spend more. For normal use it will be fast and you should never loose steps.

    Best stepper ever.....

    For small mills at 50V
    I don't think 150 oz to 300 oz is a little small for this kind of application, but that would only hold true if the inductance was low and they could hold torque over a long speed range. Obviously, the ones you have looked at don't do this, and at speed they don't have what is needed.

    Really, you're looking at less than 100 oz in that is needed at final speed for a small mill. The initial torque at low speed doesn't matter, you won't use it. Of course, this depends on the lead you are using. That's why I mentioned the MDrive as being a potentially good choice. It has low torque but a fairly flat curve to a high RPM. The ballscrew inertia and motor inertia are low, and at accelerations 0.2G and below, not much torque is needed as far as I can tell, unless my initial look has missed something.

    I don't see the OP ever using anywhere near the 570 oz in at low RPM on X and Y, however with a low inductance, and at 50V, I absolutely do not in any way disagree that this could be an excellent overall choice based on performance at higher RPMs.

    Do you have a torque vs speed graph for comparison to other options?

    Really, not disagreeing with you in any way, just pointing out that it is only the torque available at top end speed that bears relevance, which I'm guessing you know well, but the OP might be questioning. If you disagree, let me know.

    As far as the discussion about encoders is concerned,

    Well, I wouldn't bother with it, so I agree with Ger21 on that, but as 109jb has stated perhaps it's not much money, and if you want to do it, well, why not.

    I don't see alot of value added, but.....some interesting points all around.

    Certain jfong has a good insight into how electronics work, far better than mine. Really, all of the interested parties' comments are from people whos opinions I value based on other threads I have read or participated in.

    I was thinking, didn't Jim Dawson say he had some kind of linear encoder in his machine with his custom control software? Probably not relevant, but interesting nevertheless.

    I really wouldn't worry about encoders on steppers, but if the price isn't prohibitive, well you could, and if you can find a deal on a "smart" stepper like an MDrive, well, you could do that instead, or, you could just get the steppers that arizonavideo said, and those have proven to give a good result.



  3. #39
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    Default Stepper Options

    Plenty of Schneider and similar types of drives are used in industrial machines. You wouldn't really see them in CNC mill/gantry type machines (you certainly could) but mostly in manufacturing type assembly lines. Basically moving something from point A to B all day long. They sometimes use industrial communications systems like CANbus, rs485 etc which are better immune to noise on a factory floor. You wouldn't want to run 5volt step/direction signals hundreds of feet. Lots of specialized applications for these types of integrated motors/drives. They are usually connected to PLC controllers.

    You can also query the motor for info such as what position, motor temperature, any errors since the communication interface is bi-directional. You can't do that through just step/direction.

    Not all of the Schneider mdrive product line have closed loop encoders on them. They all have smart controllers but some are only open loop. Again check datasheet and interface options. We used to use these motors at my old old job.

    My newest eBay toy are Applied Motion TSM stepper motors with closed loop encoders. Full PID servo capability. RS485, analog and step/direction. Going to use them for a 3d printer.

    Last edited by jfong; 08-27-2017 at 02:30 AM.


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    Default Re: Stepper Options

    Quote Originally Posted by jfong View Post
    LinuxCNC reading quadrature encoder signals with a parallel port might be a little slow. It's probably reliable to about 25khz pulses, only good for low resolution encoders. Better yet would be one of the Mesa FPGA cards. The FPGA can be programmed with quadrature counters with digital filtering. I've done that with Xilinx FPGA's.

    Microchip has some micro controllers that have built in quadrature decoders. Really easy to use. Good for several MHz counting. I don't think Atmel has mcu that has built in quadrature but the last time I looked was a couple years ago. You would have to do the counting with hardware interrupts which is good for about 200khz on a atmega328

    I have C code and Verilog fpga quadrature code if you need them.
    Agreed. I was just pointing out the lowest cost method. I bought some 100 ppr encoders and have a parallel port to test. With 4x encoding and 0.2" pitch screws each encoder count would "theoretically" be 0.0005". My initial plan will be to detect if the actual position is off more than 10 counts (0.005") from the commanded position, and if greater, halt the machine. With 400 counts per rev, 0.2" per rev, and my maximum rapids of 150 ipm, I should only be at 5 kHz on the encoder inputs so I think should be ok with parallel port. Time will tell, but right now I have so little time to do anything in the shop so it will be a while.



  5. #41
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    Default Re: Stepper Options

    Its the inductance.

    The 570 has 2uH and almost all the smaller ones are higher so at the same voltage are slower.

    A little extra power lets you run the ball nut tighter and end bearings and often you have tight spots in the ways to get past.

    So from a cost stand point you can just run the 570 at 3A or 4A and they make less noise and less heat over a 390 oz with higher inductance.

    The break point is 50V. The 80V driver are more money so you save some by staying at 50V.

    Quote Originally Posted by NIC 77 View Post
    So I spent a few minutes on this

    https://motion.schneider-electric.co...-control-ip20/

    Above is the part # data sheet from the first EBay add I posted a link to. The same data sheet I posted earlier. So this is for "MDI1" It says for

    Control Type = Programmable Motion Control
    # of I/O = 4 I/O points, programmable as sinking outputs or sinking and sourcing inputs
    Logic Range = Inputs and outputs tolerant to +24 VDC, inputs TTL compatible

    And then below is the data for "MDM1"

    https://motion.schneider-electric.co...on-input-ip20/

    Control Type = Step/direction input
    Control Method = Clock and direction inputs
    P1 Connector Options = Power & I/O Flying Leads, Pluggable, Wire Crimp

    So good call guys. Looks like you need to pick the correct one.

    I'm pretty good at looking at torque vs speed curves and doing the math with inertia and lead, etc., but I can miss things on the electronics side. Certainly, the feedback from RCaffin, and jfong, was appropriate, so again, good call guys.



    Roger, are you saying that Schneider Electric MDrive is older technology with a dying product line? Or is this a general statement referring to something else?

    There are many reasons why you could have different control inputs. Their target market could be factory automation for some models, for example, move a beer bottle over, wait for it to be filled, move it back.

    It was my understanding that the MDrive was a step up from traditional steppers. These are "smarter" steppers with built in drivers optimized for the motors. From what I've seen in videos, you can't loose steps on these motors, they will adjust the speed if the load is too great. If the OP can find an appropriate model on EBay, I think that would be a good choice.

    As far as why they aren't widely used, I think it is because unless you find a great EBay deal, they are alot more $$$ to buy direct than a traditional setup.

    Correct me if I'm wrong.





    I don't think 150 oz to 300 oz is a little small for this kind of application, but that would only hold true if the inductance was low and they could hold torque over a long speed range. Obviously, the ones you have looked at don't do this, and at speed they don't have what is needed.

    Really, you're looking at less than 100 oz in that is needed at final speed for a small mill. The initial torque at low speed doesn't matter, you won't use it. Of course, this depends on the lead you are using. That's why I mentioned the MDrive as being a potentially good choice. It has low torque but a fairly flat curve to a high RPM. The ballscrew inertia and motor inertia are low, and at accelerations 0.2G and below, not much torque is needed as far as I can tell, unless my initial look has missed something.

    I don't see the OP ever using anywhere near the 570 oz in at low RPM on X and Y, however with a low inductance, and at 50V, I absolutely do not in any way disagree that this could be an excellent overall choice based on performance at higher RPMs.

    Do you have a torque vs speed graph for comparison to other options?

    Really, not disagreeing with you in any way, just pointing out that it is only the torque available at top end speed that bears relevance, which I'm guessing you know well, but the OP might be questioning. If you disagree, let me know.

    As far as the discussion about encoders is concerned,

    Well, I wouldn't bother with it, so I agree with Ger21 on that, but as 109jb has stated perhaps it's not much money, and if you want to do it, well, why not.

    I don't see alot of value added, but.....some interesting points all around.

    Certain jfong has a good insight into how electronics work, far better than mine. Really, all of the interested parties' comments are from people whos opinions I value based on other threads I have read or participated in.

    I was thinking, didn't Jim Dawson say he had some kind of linear encoder in his machine with his custom control software? Probably not relevant, but interesting nevertheless.

    I really wouldn't worry about encoders on steppers, but if the price isn't prohibitive, well you could, and if you can find a deal on a "smart" stepper like an MDrive, well, you could do that instead, or, you could just get the steppers that arizonavideo said, and those have proven to give a good result.


    youtube videos of the G0704 under the name arizonavideo99


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