DC motor and Limit Switch

Discussion in 'The Projects Forum' started by Golden Bucky, Aug 27, 2013.

  1. Golden Bucky

    Thread Starter New Member

    Aug 27, 2013
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    I need some help - I'm building a machine but I'm not sure of the best way of doing it.

    I have three large wire spools. Two empty and one full. The full spool (approx. 500kg) is much larger than the empty spool (100kg when full). I wish to transfer the wire from the large spool to two of the smaller spools. I want to do this regularly so I want to set up a system that will not have to be monitored but can turn itself off when the smaller spool is full and/or the larger spool is almost empty - whichever happens first.
    I want to keep this as simple as possible. I currently have two parallel spindles - one for the large spool and one for the smaller spool with a third parallel shaft in between - a self-reversing screw shaft - this will run a guide back and forth in order to evenly place the wire on the smaller spool.

    I'm thinking of using two DC motors (I will have to be able to adjust the speed of the motors driving the spool and self-reversing shaft):
    the first motor is to turn the smaller spool, this in turn will pull the wire off the larger spool causing it to turn
    and
    the second motor to turn the self-reversing screw shaft to guide the wire
    and
    2 limit switches - one on the smaller spool and one on the larger spool.

    The idea behind this is that:
    when the larger spool is almost empty the limit switch on it sends a signal back to the motors to cut out
    and/or
    when the smaller spool is full the limit switch on it sends a signal back to the motors to cut out

    Can someone please help me.
    Are DC motors and limit switches the simplest, best and cheapest way of doing this or is there another way?
    If DC motors and limit switches are the best how would I wire it up so that it works like I described above?

    Thanks for your help.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    There is a few things here to consider! It can get complicated.
    And a complete idea of what the system entails probably requires more than a few line description.
    For the shut off when full, probably some kind of limit switch that runs on top of the increasing drum that will switch off when full.
    But on take up spools, often this requires different speed on the take up spool as the diameter of material increases?
    This is where the full demands of the system is needed?
    DC or BLDC motors may be the best/cheapest option.
    If no variable speed is required for any of the drums, with say encoder or some kind of feedback is needed, you may be able to control it with one of the Smart Relay products from Seimens, Omron, Idec, all are mostly identical, just relabeled.
    It will probably entail more than a 'DC motor and limit switch'?
    Max.
     
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  3. Golden Bucky

    Thread Starter New Member

    Aug 27, 2013
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    How do I work out if my wire will be capable of with standing the pull force placed upon it. It has a tensile strength of 2050 - 2250MPa - bearing in mind a moment of inertia of 500kgm2?
    Thanks for your help
     
  4. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Your question falls squarely in the middle of my cup-o-tea. In nearly 3000 posts, I believe this is the first time I can truly call myself an expert ;) on a topic. I'm a controls technician who plays engineer on TV, and most of my experience is in the wire & cable industry. I've designed a few of these rewinder/respooler lines (that's what they're called - this thing you described) - actually I'm in the middle of designing one right now - and here's one such example of my work.

    Ok, sorry for the excitement. On to your situation. Need more info.

    1. How fast (in feet per minute) do you want to run the line? How fast do you need to accelerate from zero to full speed, in seconds?
    2. Do you already have the DC motors? If so, do you have drives? provide specs for both.
    3. Do you want the changeover from one small takeup spool to the other small takeup spool to happen automatically ("flying splice")? or just shut down so that the operator can come over and perform the changeover?
    4. How are the two smaller spools situated? Side by side? Does the traversing screw provide travel across both reels? Please post pictures.
    5. What volt/amp/phase service do you have available?
    6. Do you need a footage count? Speed display? What indications do you need?
    7. Do you ever need to run in reverse?
    8. Do you have a dancer of any kind? festoon? arm? anything?
    9. Is the traversing screw mechanically coupled to the takeup shaft in any way? Please post pictures.
    *please post pictures of anything and everything that you are working with*
    10. Will the entire contents of the large spool fit onto the two smaller spools? If not, what is the maximum rotational weight that will be on the takeup at any given time?
    11. What is your budget?

    There is a whole lot more to this than "whether limit switches are the best option." Limit switches are totally insignificant at this point, so put that out of your mind. Answer the questions, let me guide you. We can get through this (provided you have a budget - this stuff isn't cheap).

    EDIT:
    12. For both the takup and payoff, what is the difference between empty and full belly size? Please provide diameter of empty drum, and full drum.
     
    Last edited: Aug 28, 2013
  5. Golden Bucky

    Thread Starter New Member

    Aug 27, 2013
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    1
    Thanks very much for your time - I really appreciate your help

    In answer to your questions:

    1. How fast (in feet per minute) do you want to run the line? How fast do you need to accelerate from zero to full speed, in seconds?
    1 revolution per second of the large coil would be excellent - I'm working this out at 420 feet per minute (7 foot circumference of the large coil).

    2. Do you already have the DC motors? If so, do you have drives? provide specs for both.
    No, I do not already have motors - I am trying to work out how to size them

    3. Do you want the changeover from one small takeup spool to the other small takeup spool to happen automatically ("flying splice")? or just shut down so that the operator can come over and perform the changeover?
    I want the entire system to shut down once the small spool is full or the large spool is almost empty - whichever happens first

    4. How are the two smaller spools situated? Side by side? Does the traversing screw provide travel across both reels? Please post pictures.
    I will be using one small spool at a time along with one large spool at a time

    5. What volt/amp/phase service do you have available?
    I have 110 Volt, 230 Volt and 3 phase 400 Volt supply

    6. Do you need a footage count? Speed display? What indications do you need?
    I don't need any footage count - just plain transfer from one spool to another

    7. Do you ever need to run in reverse?
    No I don't need it to run in reverse

    8. Do you have a dancer of any kind? festoon? arm? anything?
    No I don't have a dancer or festoon or movement arm
    I have a self reversing screw mechanism - that's all - please see pictures


    9. Is the traversing screw mechanically coupled to the takeup shaft in any way? Please post pictures.
    *please post pictures of anything and everything that you are working with*

    No at the moment the entire unit is dismantled - it has been lying idle for a number of years and I'm in the process of cleaning it up - I need to get pillow
    block bearings among other things for the shafts - small spool and self reversing screw mechanism - please see pictures
    The table as you can see from the pictures needs a new base and a lick of paint

    10. Will the entire contents of the large spool fit onto the two smaller spools? If not, what is the maximum rotational weight that will be on the takeup at
    any given time?

    The entire contents of the large spool will fit onto 5 smaller spools - each smaller spool will be manually lifted off and replaced with an empty spool each
    time the small spool is full - maximum rotational weight on the take up spool at any one time is 220lbs


    11. What is your budget?
    As cheap as possible is the answer to this question - I haven't clarified that one yet - approximately €1500


    There is a whole lot more to this than "whether limit switches are the best option." Limit switches are totally insignificant at this point, so put that out

    of your mind. Answer the questions, let me guide you. We can get through this (provided you have a budget - this stuff isn't cheap).

    EDIT:
    12. For both the takup and payoff, what is the difference between empty and full belly size? Please provide diameter of empty drum, and full drum.
    The full 'drum' is not a drum but a coil of wire which will be placed upon the large spool spindle - please see picture
    The large spool has a weight of 1100lbs, a diameter of 28 inches and a depth of 12 inches - in the picture attached there are two large spools stacked on top of eachother on one pallet

    The small spool has a diameter of 19 inches, a depth of 9 inches

    Please see pictures

    Thanks very much for your time
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I don't see any pictures.
     
  7. Golden Bucky

    Thread Starter New Member

    Aug 27, 2013
    7
    1
    Charles, thanks again for your time. Apologies, please see attached photos. I had a look your Youtube video - it looks fantastic - I'm hoping to put together something on a more basic level tho.
    Please have a look over these attached photos and let me know what you think.
    Thanks again
     
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  8. Golden Bucky

    Thread Starter New Member

    Aug 27, 2013
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    1
    In addition to information already given

    The wire in question is a high carbon wire with a very high tensile strength so this should not be a problem for the wire - I am confident hat the wire will be able to handle the pull as long as there is a slow start up and slow down

    I would like to start and stop the small spool slowly - ideally a slow start/stop lasting approximately 3 to 4 seconds

    I would like to turn the large spool at 1 revolution per second of the large coil would be excellent - I'm working this out at 420 feet per minute (126 meters a minute) (7 foot / 210 cm outside circumference of the full large coil).

    A uniform wrapping speed is not critical - I am conscious that the wrapping speed will change as the diameter of the larger spool decreases and the diameter of the smaller spool will increase. I don't need any footage count - just plain transfer from one spool to another

    Thanks again for your time
     
  9. Golden Bucky

    Thread Starter New Member

    Aug 27, 2013
    7
    1
    As I've mentioned I want to keep this as simple as possible - I am now confident, having looked at the tensile strength of the wire, that the wire won't break provided I have a slow start.
    Both spools with be mounted on bearings so the pulling force on the wire will be limited.

    I'm looking into motor starters - one option I've been told is to pull one of the wires off the stop button and then wire it in series with the normally closed contact of a button actuated limit switch to make contact with the wire (and trigger the switch) when one reel is full and another switch for when the other reel is empty, By connecting both of the switch contacts in series - when one of them is actuated is has the same effect as pressing the stop button on the starter.

    What does this sound like?

    Can I please have some advice on the best type of motor and starter for this application?
     
  10. Golden Bucky

    Thread Starter New Member

    Aug 27, 2013
    7
    1
    Thanks a million for your help

    Just to refresh my point - I've meade one or two changes

    I have two large wire spools. One empty and one full. The full spool (approx. 500kg) is much larger than the empty spool (100kg when full).

    I wish to transfer the wire from the large spool to the smaller spools. I want to do this regularly so I want to set up a system that will not have to be monitored but can turn itself off when the smaller spool is full and/or the larger spool is almost empty - whichever happens first.

    I want to keep this as simple as possible.


    I'm looking to put a motor on the small spool and use this to turn the large spool through the pull of the wire

    I will be using one small spool at a time along with one large spool at a time

    I want the entire system to shut down once the small spool is full or the large spool is almost empty - whichever happens first

    The wire in question is a high carbon wire with a very high tensile strength so this should not be a problem for the wire - I am confident hat the wire will be able to handle the pull as long as there is a slow start up and slow down

    The large spool has a weight of 1100lbs (500kg), a diameter of 28 inches (70cm) and a depth of 12 inches (30cm) - in the picture attached there are two large spools stacked on top of eachother on one pallet

    The small spool has a diameter of 19 inches (48cm) and a depth of 9 inches (24cm)

    I want to unwind the entire contents of the large spool onto 5 smaller spools - each smaller spool will be manually lifted off and replaced with an empty spool each time the small spool is full - maximum rotational weight on the take up spool at any one time is 220lbs (100kg)

    I would like to start and stop the small spool slowly - ideally a slow start/stop lasting approximately 3 to 4 seconds

    I would like to turn the small spool - the one powered by a motor at between 3 to 5 revolutions per second (180 to 300 rev per minuet)

    A uniform wrapping speed is not critical - I am conscious that the wrapping speed will change as the diamter of the larger spool decreases and the diameter of the smaller spool will increase. I don't need any footage count - just plain transfer from one spool to another

    I do not have any motors at the moment so any suggestions would be greatly appreciated

    I have access to 110 Volt, 230 Volt and 3 phase 400 Volt supply

    I don't need the motors to run in reverse just in one direction

    I'm hoping to get this done for as cheap as possible - at most €1500

    Please give me some suggestions on how to start and stop both motors and the best type of motors for the job

    Thanks very much for your help
     
    Last edited: Aug 29, 2013
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    One of the problems when unwinding spools of this weight/inertia is precise control, i.e. the ability to have braking or servo effect which essentially would stop the spool from freewheeling if a rapid stop was called for.
    I have worked on similar systems but I used a Motion card in a PC for servo control.
    But I don't think you want to get into that kind of design unless you had someone to work with locally that was familiar with this type of control.
    So there may have to be some experimentation in order to manage any possible overrun of a full coil.
    Once the machine is built to a point mechanically the effect and effort of unspooling could be obtained empirically by observation and testing to see what kind of motorized unit could be used.
    Max.
     
  12. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Ok, thoughts, in the order I think of them:

    Your level wind is rather unique. It's a pawl & worm shaft drive like what's in a fishing reel. pretty cool. I've only ever seen one other instance of this setup used for this purpose; it's almost always a ball screw or ACME screw. It may make things simpler and cheaper to mechanically couple it to the spindle drive rather than drive it with a separate motor and drive. Or it may not. small DC motor and small drive can be cheap too. You might want to price both options.

    Your goal of 420FPM might be unobtainable for your budget. Not sure though. I consider this "medium speed," which usually requires a dancer and PID control. But with your high tensile wire, you may be able to get away without that stuff. You might just have to build it and see; if it doesn't work, you can always invest additional money and make it right; you shouldn't be out any money.

    For your budget and your high tensile wire, I'm thinking that the best option might be to power only the takeup, and let the payoff freewheel, with a brake for stopping. You could use either a pneumatic brake with air regulator for adjustable torque, or an electromagnetic brake with adjustable power supply. You could set either scheme up to apply a low torque to the payoff while running, to keep the line taut and prevent oscillations in payoff RPM, and then upon stop, apply full torque. This is exponentially simpler than trying to synchronize two powered spindles whose diameters are changing. It will be much cheaper, because you won't need that payoff drive - and that payoff drive was going to be the biggest price tag item because it needs to be ballsy and have regen braking. I think you could probably get away with just one 5HP DC motor driving the whole thing.

    I recommend using a footage counter with relay output for your "spool full, shut down" operation. Reason being, trying to use a limit switch riding on the roll, it is going to have to be a fine tuned adjustment, which is not compatible with the bouncing nature of the surface it will be riding on. Dual batch counters are available in abundance and are not that expensive or hard to program. I assume you know the footage of your large reels; you enter this as preset one, and you enter the desired footage to fill the small reel as preset two, and it will switch the output whenever either of the presets are reached. This is the "tried & true" way it's done in industry.
     
  13. strantor

    AAC Fanatic!

    Oct 3, 2010
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    "starter" isn't the proper term for what you need. "starter" refers to an AC motor control that only "starts." Basically a relay/contactor with an overload. Not a variable speed control.

    What you need is a DC drive, and given that I believe you can accomplish this with a 5HP permanent magnet DC motor, I suggest you look into the KB Electronics KBCC-255. It's the lowest cost 5HP DC drive that I trust.

    About the wiring of the buttons and such, you're still putting the cart before the horse. We have to decide upon what we are actually doing before we design a control circuit for it.
     
  14. strantor

    AAC Fanatic!

    Oct 3, 2010
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    So can we say that the overall effective diameter is 19"-28"?


    If so, then we are looking at a circumference between 60" and 88" and hence a rotational takeup speed of 57-84RPM. Agreed?
     
    Last edited: Aug 29, 2013
  15. strantor

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    o what's man? You give up already?
     
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