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  1. #61
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    The Scorbot came in today. I am actually kind of impressed with it. It has some nice parts on it as well. All of the gears and there are quite a few are steel. They show no signs of wear. Low mileage on this one. That said the gripper motors encoder wires were snipped. Looks like it may have gotten damaged at some point by pulling to wires off the encoder solder card. Instead of breaking out the soldering iron, they broke out the snips.
    The base for the bot and the turntable are some type of resin, but everything else is steel. Timing gears are aluminum. The only plastic parts I see are the idler/tensioner pulley.
    I think I will start out by identifying and running the motors that are connected. The base of it or the turntable would be a good starting point for building a more up to date style arm. Some of the gearing and pulleys would be beneficial for that too depending on the design. Not sure what I will do with it at this point.

    Lee


  2. #62
    Gold Member daniellyall's Avatar
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    Default Re: Robotic arm tool changer?

    As long as you use a quality motor driver, it's surprising what a motor can do with a quality motor driver, the motors for my wheelchair lift are half the size of my fist and can lift 500 pounds, it's made in japan

    <img src="https://ivxo1q-dm2305.files.1drv.com/y4mENMmTr_Cabc7pR0FUdB6gtbADq2JbuG4_rGy0eBQvLJx19pTi6TqMUIJN0xgOyDIc0gWoxYhS38HpbSTFGdfaK-o42IOU6jczrhDpfpCOTNGL1X6hvZCbgj0y35gqmq1YGTrWwShYGV-C7lXA2esy0Pi_WfnBSyroDLSGXwce4uSr1U7op7srdi78rispHCa_K4aFlTlJPVkkNWMfgh_Tg?width=60&height=60&cropmode=none" width="60" height="60" />

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  3. #63
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    There is no doubt about it.
    These geared DC motors can be a beast.
    I use a rather large one for my spring winder just for the reduction and low RPM that I needed. I think it is strong enough to pull a vehicle out of the mud, but slowly.

    I also figured out how they damaged the gripper arm on this. They did not have the limit switch stops set correctly and it allowed the encoder end of the motor to contact the base timing pulleys. Nothing is burnt or anything, so should be an easy fix.

    Lee


  4. #64
    Gold Member daniellyall's Avatar
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    Default Re: Robotic arm tool changer?

    These might be useful https://hackaday.io/project/11224-mechaduino

    Its along the line where you wont to go with Arduino

    <img src="https://ivxo1q-dm2305.files.1drv.com/y4mENMmTr_Cabc7pR0FUdB6gtbADq2JbuG4_rGy0eBQvLJx19pTi6TqMUIJN0xgOyDIc0gWoxYhS38HpbSTFGdfaK-o42IOU6jczrhDpfpCOTNGL1X6hvZCbgj0y35gqmq1YGTrWwShYGV-C7lXA2esy0Pi_WfnBSyroDLSGXwce4uSr1U7op7srdi78rispHCa_K4aFlTlJPVkkNWMfgh_Tg?width=60&height=60&cropmode=none" width="60" height="60" />

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  5. #65
    Gold Member daniellyall's Avatar
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    Default Re: Robotic arm tool changer?

    Lee here is the arduino that goes with the winder I posted Thomas Hopman FabAcademy Final Project Page

    <img src="https://ivxo1q-dm2305.files.1drv.com/y4mENMmTr_Cabc7pR0FUdB6gtbADq2JbuG4_rGy0eBQvLJx19pTi6TqMUIJN0xgOyDIc0gWoxYhS38HpbSTFGdfaK-o42IOU6jczrhDpfpCOTNGL1X6hvZCbgj0y35gqmq1YGTrWwShYGV-C7lXA2esy0Pi_WfnBSyroDLSGXwce4uSr1U7op7srdi78rispHCa_K4aFlTlJPVkkNWMfgh_Tg?width=60&height=60&cropmode=none" width="60" height="60" />

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  6. #66
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    Thanks, For this, Daniel.
    It will certainly be helpful.
    The plan is if I get an assembly bot designed and working with meager motors and drives, then I may just upgrade the ones that need it later on to have a production assembly station. The same kind of machine could do part changes on the router for that lights out machining I mentioned.
    Lots of plans in the works. Oh and all these smaller motors could easily handle my spring winder needs.
    I already have the drive out of a cheap wire feed welder. Just have to figure out what I want to use for slide on the front plate to operate the tools.

    Lee


  7. #67
    Gold Member daniellyall's Avatar
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    Default Re: Robotic arm tool changer?

    that code you just need to change a couple of settings manly just bobin travel

    <img src="https://ivxo1q-dm2305.files.1drv.com/y4mENMmTr_Cabc7pR0FUdB6gtbADq2JbuG4_rGy0eBQvLJx19pTi6TqMUIJN0xgOyDIc0gWoxYhS38HpbSTFGdfaK-o42IOU6jczrhDpfpCOTNGL1X6hvZCbgj0y35gqmq1YGTrWwShYGV-C7lXA2esy0Pi_WfnBSyroDLSGXwce4uSr1U7op7srdi78rispHCa_K4aFlTlJPVkkNWMfgh_Tg?width=60&height=60&cropmode=none" width="60" height="60" />

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  8. #68
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    Okay guys, one question that I haven't found an answer to.
    The DC motors I will generally be using will have encoders mounted on them. I may place some on joints instead later on, but the questions still pertains to them.
    How do I connect an encoder to an arduino to both control the position of the motor and receive feedback from it?
    Or would I need separate circuits for this? Something like a teach pendant that some bots have?

    I want to be able to physically move the arm and record all encoder positions for that particular move.
    For playback later in a programmed sequence.

    I also didn't actually find how to connect a DC motors encoder to Arduino, but I think that would be similar to using a manual rotary encoder or POT and that is easy to find.

    Lee


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    Default Re: Robotic arm tool changer?

    Lee,

    To use a DC motor, you need to turn it into a servo, which means adding a quadrature encoder, and using a digital PID in your firmware to control it. Reading the encoder requires having the quadrature encoder outputs connected to interrupt inputs of the MCU. You have a real learning curve in front of you....

    Regards,
    Ray L.



  10. #70
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    No doubt about that.
    This is really the long term goal. I don't really require the feedback for initially setting up the sequence. I may wind up going over to Linux if I know it well enough and decide to use larger motors.

    There are a lot of different little software programs coming out soon that may be good for these things. Open source of course.

    I have received quotes on some of the commercial CRA software and it ranges from about 3K to 10K. Nice stuff, but useless without the hardware interface.
    So, this will be a long term project.

    Lee


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    Default Re: Robotic arm tool changer?

    Quote Originally Posted by LeeWay View Post
    No doubt about that.
    This is really the long term goal. I don't really require the feedback for initially setting up the sequence. I may wind up going over to Linux if I know it well enough and decide to use larger motors.

    There are a lot of different little software programs coming out soon that may be good for these things. Open source of course.

    I have received quotes on some of the commercial CRA software and it ranges from about 3K to 10K. Nice stuff, but useless without the hardware interface.
    So, this will be a long term project.
    One of the LinuxCNC developers has a Scorbot and has a Linuxcnc config/kinematics configuration for it. (so can run Gcode)

    He is using Mesa hardware to run it but the encoders are quite low resolution and its not high performance device
    so its probably usable with those low cost HBridges you mentioned, 2 or 3 parallel ports and software encoder counters
    and PWM generators

    Last edited by PCW_MESA; 12-10-2016 at 02:13 PM.


  12. #72
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    Thanks for this. I did see some stuff about it on Github.

    Thankfully my first project will not require any of the more involved stuff. I will only need to move tools in and out of place on something like a lathe faceplate for the spring winder. I will need a pincer tool to make 90 degree or more bends. A left and right hand coiling tool. A shearing tool.
    This will not only get me going with the Arduino, but will also involve hardening and tempering my own tools once I get the sizes and locations down. The motors will actually be the last thing to go on the machine.
    The real machines use cams and things to actuate tools with a large motor, but those can be adjusted a lot for different springs, materials and tools.
    I will not need the same kind of versatility.

    Lee


  13. #73
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    I decided to relist the Scorbot and extras back on Ebay. Rather than salvage all the hardware and motors or get it running, someone else might be better suited to reuse it as is with Arduino.
    I think a different style of arm will be better suited to an assembly station. In fact those industrial types arms are available with controllers and software that are right in my price range. Under 5K. Some half of that.
    Made by big brands too like Bosch, Epson Seiko, Yamaha Etc.

    Lee


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    Default Re: Robotic arm tool changer?

    Katia is looking better and better! I did see a used Universal Robot UR3 for $8000 in NY state.

    Steve



  15. #75
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    That is a good price on the UR3. They are over $30K right now. Must be something wrong with it.

    These Scara arms and like are generally fairly small. Maybe a yard span. They do have larger ones. They don't really need to be collaborative if they are set in a work cell like an assembly table. Just don't get in their way.
    The collaborative aspect as well as easy setup for different jobs is certainly worth a premium, however they also represent the top of the line systems.
    They are a few that are lesser in cost and one French robotics company mentioned they have no plans to sell to the US market.
    There are many lower cost arms that are simply not released yet. Not sure what all of them are waiting on, but it seems to me that the first would gain some sales just by being first. Many mention the software will all be open source too and that right there is probably the bottleneck for all of them.

    Lee


  16. #76
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    Okay guys.
    The other little bot arm arrived. It actually came with most of the covers for it. It is a Thermo Scientific Dimension 4 flip mover. Moves medical specimens and sample trays around.
    That means it will be pretty precise.
    It only has the two motors shown in the Add. Bottom one that controls the arm is a Nema 23 stepper with a US Digital encoder. 4 wire stepper. 5 wire encoder. Pretty standard stuff, right?
    The same motor also operates not only the arm position, but the upper joint position as well. Not quite sure yet how it manages that. I haven't taken it apart.
    I did see something that I have never seen before though. This stepper has three additional wires coming right out the side of the motor. They are twisted and go to the circuit board. The circuit board connections are relatively simple. There is a blank spot for an additional motor if I choose to use it, but probably won't.

    Thoughts on those extra three wires?

    The upper claw motor is just a nema 17 and it also has a US Digital encoder. Little smaller one.
    I will take it apart while snapping good photos of it.
    It only has like a 13 pin connector. 3 terminals are large ones and are power I assume. One of those is ground. This uses 24 VDC and 36 VDC at like 4 amps. I'll bet the lower volatage is the little motor and one of the bigger terminals and the one left the higher voltage.
    Then like 10 normal pins in the middle. Only about 5 of those are even used. So relatively few control pins to figure out.
    Here is an image of that connection.


    Robotic arm tool changer?-s-l1600-jpg

    Lee


  17. #77
    Registered jfong's Avatar
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    Default Re: Robotic arm tool changer?

    My best guess is the 3 wires is for a temp sensor. A brake is normally just 2 wires.



  18. #78
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    These are touted as very fast precise movements with minimal controls to help eliminate setup and down time. We will see.
    I will probably get to do a little testing on it this weekend.
    It all looks easy enough for even me to figure out. Good thing. No documentation to speak of online.
    I did request a manual from them, so we will see whats up with that approach.

    I was thinking the larger silver cylinder was either a brake or a clutch, but not other markings are on it that I can see until it comes apart. Hope it's not a heavily would spring. Those are not cool to find unexpectedly.

    Lee


  19. #79
    Gold Member LeeWay's Avatar
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    Default Re: Robotic arm tool changer?

    This plate mover arm is pretty interesting. There are only 6 actual control wires. This board can only accept the equipment onboard already with the exception of another possible motor. Possibly for a different end effector.

    These parts and the board all all high quality stuff.
    I will not be able to use the board at all though.
    I will need to control at least two more motors with it.

    The arm or shoulder joint on here is something I would noot have expected.
    It is designed to keep the claw 90 degrees to the table or always vertical no matter the arm angle. The arm is turned with the geared motor, but on the outside there is a timing pulley and belt. The timing pulley is on roller needle bearings.
    This pulley is actually bolt to the base and is stationary. The belt then maintains the claw position as the arm is turned.
    Pretty cool, but not useful for me. The end effector should rotate independently of the arm.
    I do think the silver canister is a brake of some sort. I haven't taken that assembly apart yet. Needed better allen wrenches. I will let you know what that looks like.
    There is also a fairly large resistor on here. Maybe for braking?

    Lee


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    Default Re: Robotic arm tool changer?

    Lee, any progress with the robot arm?



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