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Linear actuator used for agitation of chocolate tank

Discussion in 'Concepts and Ideas' started by Chuck Pheterson, Mar 7, 2017.

  1. Chuck Pheterson

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    I'm new to Openbuilds and linear actuators and am seeking feedback regarding a solution that I have in mind.

    I am currently using a steam tray (roughly 20 x 13 inches and 4 inches deep) as a chocolate dipping pot for products that I manufacture. The tray is maintained at 95-degrees F to keep the chocolate in a liquid state. When not in use, the chocolate needs to be slowly stirred/agitated to prevent formation of clumps. I believe that a paddle attached to a linear actuator would provide the back and forth motion that I am seeking. The requirements of the project are as follows:

    1. Motor must not be over the chocolate: left or right side of the gantry.
    2. A belt driven gantry seem preferable to screw for sanitary purposes
    3. Paddle must be able to detach from the gantry for ease of cleaning
    4. Gantry should travel the length of the tray in roughly 30 seconds, then reverse direction and travel back in roughly 30. Total back/forth travel time is 60 seconds.
    5. Programmable on/off time would be nice. Continuous stirring is not needed. For example, 5 minutes of stirring per hour would be sufficient. This would also give the motor a rest.
    6. The paddle would be roughly 20 inches wide, by 3 inches tall and made of thin stainless steel. Holes would drilled into so chocolate can pass through easily. Thus, resistance will not be very high.
    7. Some sort of slip clutch or overload shut off would be helpful to protect the motor in the event that the heating element fails and the chocolate solidifies.
    8. The solution should be easily removed from the tank and set aside so that product can be dipped into the tank. Thus, ease of mobility and light weight is important.
    Suggestions would be appreciated regarding available kits that are best suited for this application. Also, suggestions for controllers, limit switches, motors, gantry arm styles, etc. would be appreciated.
     
  2. Josh Rupp

    Josh Rupp Well-Known
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    Chuck, project seems pretty simple, but I think I would have some concerns using a straight up Openbuilds actuator for your purposes. That is not because I don't think it would do the job, but because of the sanitation concerns. I'm an engineer but trade (it's how I bring home a paycheck) and I design solutions like this all the time. While we're not in the food industry, I do understand the design constraints. So with these actuators here, you would have to be concerned with the type of belt and the open wheel design mainly. Since this would be sitting over your vat of chocolate, I would be concerned with these items #1) wearing, and potentially "flaking off" contaminants into your vat, and #2) potentially collecting the chocolate on the mechanism.

    Additionally, I just designed a very similar device that swept back and forth and opted to use compressed air to drive the unit over an electric motor, way more simple. While duty cycle and amount of runtime come into play, it would be worth considering. Do you have compressed air available?
     
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  3. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Rather than over the top, I would suggest the actuator set off to the side below rim level and merely have an arm that extends over the tray. Attach the arm with threaded knob clamps so it's easily removed for cleaning or access to product.

    Timing and motion are easily accomplished through an Arduino controller. Screws should not be seen as a problem as these are not greased screws. The Delrin bearing does not require any lubricant. As the post noted above you have more to worry about with the greased wheel bearings which is why I suggest the entire unit be off to the side below rim level. As for the issue of the heaters not starting, using thermal sensors hooked to shut off relays will be far easier to implement.
     
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  4. Chuck Pheterson

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    Thanks for your reply. My chocolate tank is located at a co-packer's facility. Although compressed air is available, they turn off the compressor after hours and on weekends. Thus, it is not a reliable power source. However, I should mention that my plan is to place the actuator above a lexan lid that will cover the dipping tank except for a slit through which the paddle attaches to the gantry.
     
  5. Chuck Pheterson

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    Thanks for your reply. My chocolate tank is located at a co-packer's facility. Although compressed air is available, they turn off the compressor after hours and on weekends. Thus, it is not a reliable power source. However, I should mention that my plan is to place the gantry above a lexan lid that will cover the dipping tank except for a slit through which the paddle will attach to the gantry.
     
  6. TrishC

    TrishC OpenBuilds Team
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    Sounds yummy :thumbsup: Would love to see this Build posted!
     
  7. Josh Rupp

    Josh Rupp Well-Known
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    OK, the lexan cover may provide the separation you need from contaminates, you will probably be the best judge of that.

    If that's the case, and you're thinking you want to try to use the Openbuilds actuators, I would think that the 500mm C-beam would be a good choice. It comes as a kit, has a nice adapter plate to use as the actuator stage (for mounting the paddle) and would also overhand the vat to allow to make up some kind of mounting structure.

    The only thing to decide would be if you wanted to try and use the Stepper motors that are traditionally used with these actuators, as they're typically intended for programmable applications, constantly changing. Or if you wanted to just use a small AC motor, even small fractional gearmotor to couple to this. Your app is simple, you don't need to go through the process of telling it positions to go to with pulses from a drive. You just need it to operate in one direction to a spot (could be defined by a sensor on the actuator) and reverse directions to another spot. If you did this, a simple Programmable Relay could be your control, and a little easy program in Ladder Logic and you'd be on your way. Ever seen Ladder Logic before? Or maybe I should ask, how much programming experience do you have in general?
     
  8. Chuck Pheterson

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    I have extensive experience with real-time firmware for data communications products (written in C and assembler). I should be able to figure out the syntax and logic required, however, I'm unfamiliar with Ladder Logic and the devices that are required. If pointed in the right direction, I should be able to figure it out.

    Regarding sanitation, it might make sense to run a rail lengthwise down both sides of the tray. Taking this approach, the motor (and belt) could be offset to one side of the tray. The paddle could be attached to the center of a plate that spans between the two rails. This would make sense if the plate/paddle would run in a straight line even through the belt is propelling it from one side. Would this make sense, or would it need to be propelled from both sides to work smoothly?
     
  9. Josh Rupp

    Josh Rupp Well-Known
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    Ladder Logic is just simple Boolean logic at its core, and programmers will have different levels of "extra" stuff. While all will have timers and counters, higher end programmers have fancier function blocks to do more sophisticated control. But in your case, you wouldn't need any of that high level stuff. Either way, it's easy to learn, tons of stuff online, or I could help you out.

    As for the actuator layout, I don't know if two would be necessary. As you said, there shouldn't be much drag on the paddle with all of the holes in it. So to hang a paddle off the side of the actuator would probably be fine. To make it a little more stable, you could upgrade the standard c-beam actuator with the XL or Double wide plate to space out the wheels a bit.

    C-Beam™ Gantry Plate - XLarge
    C-Beam™ Gantry Plate - Double Wide

    If you thought you needed two actuators, you could drive them both with one motor, just couple them with a belt & pulleys. I think you have options, just depends on the space that you have available.
     
  10. Chuck Pheterson

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    Thanks for your feedback. I'm currently thinking that a DC gear motor might be best. It is easily reversible, perhaps without programming. I'll be traveling for the remainder of the week and then delving back into system design. I'll post my thoughts again early next week.
     
  11. Chuck Pheterson

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    I'd appreciate suggestions regarding a small gear motor that would mount onto a standard c-beam actuator and a programmable relay that would permit reversibility and speed control. I suppose that limit switches or sensors will be needed to delimit the endpoint of travel in each direction. Thanks again for your assistance.
     
  12. Josh Rupp

    Josh Rupp Well-Known
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    Two companies that I have used have been Bodine and Oriental Motor. Iodine offers brushed DC motors, and both offer brushless DC options, which are what I typically prefer. I think your app would be better with the BLDC motors too be cause of the constant cycling and change of direction and they're much lower maintenance.

    Bodine - Products
    Oriental Motor - Brushless DC Motors and Drivers Speed Control Systems - 15 W (1/50 HP) up to 400 W (1/2 HP)

    As for Programmable relays, I've used some super cheap ones from made by Teco, but they pretty reliable and easy to program.

    http://www.bb-elec.com/Products/Con...rs/TECO-SG2-V3-Programmable-Logic-Relays.aspx

    Or you could go with a bigger name, still not bad on price such as these small Allen Bradley units. Couldn't go wrong with either.

    http://ab.rockwellautomation.com/Programmable-Controllers/MicroLogix-1100

    If you need more help, send me some specs like feed rate, approximate cycle frequencies, etc.
     
  13. Chuck Pheterson

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    I've given some additional thought to the solution. My chocolate dipping tray is roughly 20 inches (508mm) long. A double wide V-slot gantry with an 8mm screw (I now like that combination), would require roughly 63 revolutions to traverse one direction of the tray in 30 seconds (seems reasonable). Thus, a target rpm for the motor is roughly 126 (one minute to traverse the tray in both directions). I believe that 1/15 hp will be fine given that I'm currently using gear motors rated at only 1/150 hp for driving rotational agitators in smaller tanks. So, I believe the following motor will work nicely:

    Item # BLH015K-20, Brushless DC Motor Speed Control System On Oriental Motor U.S.A. Corp.

    This motor comes with a controller that offers a means to adjust the speed between 5 and 150 rpm. It also has inputs to control start/stop and the direction of rotation. I suspect that I could toggle these inputs via external hardware logic (limit switches and a few chips) to delimit the range of motion of the actuator. No programming should be necessary, unless I am missing something.

    If I do use this motor, or a similar motor, mounting of the motor to the actuator may require a custom bracket if the motor and existing v-slot brackets do not properly align the actuator screw with the motor shaft. From the information on the web regarding openbuild kits, I'm not sure if the current brackets will work.

    Finally, I'd like to incorporate a slip clutch into the solution, if that is the best means to protect the motor in the event that the screw-shaft freezes up for some reason. Perhaps the controller already handles this. I'm not sure if that is the case.

    As always, your thoughts are greatly appreciated.
     
  14. Josh Rupp

    Josh Rupp Well-Known
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    Sorry it took a little to respond, been busy in the evening the last couple nights. Anyhow, I like your choice for a motor, I think that will provide plenty of power. As for your assumptions on the IO available on the drive, it is definitely capable of sending/receiving all of the info that you need to set something up with switches and chips (or relays, whichever you're more comfortable with).

    I took the time to draw up a custom bracket to mount this motor for you and was able to use some stock parts from OpenBuilds for the pulleys and drive belt. Here are the links to that stuff:

    3GT (GT2-3M) 9mm Timing Belt - Closed Loop
    3GT (GT2-3M) Timing Pulley - 20 Tooth - 9mm Belt - 8mm Clamp Bore
    3GT (GT2-3M) Timing Pulley - 20 Tooth - 9mm Belt - .25" Bore

    And here are a few screenshots of the motor mount plate that I drew up. If you like it, I can post a drawing file on here and maybe someone will bite on making this thing for you ;)
    Vat_Assy.PNG Vat_MotorMnt.PNG Vat_MotorMntRr.PNG

    As for your final question about the need for a slip clutch, I actually don't think that is necessary. The drive comes equipped with an Alarm and fault protection, and in the case of an overload, this will trip, requiring either a reset or a reboot to clear the fault. From personal experience with these drives, this protection has been adequate in protecting the motor, and most cases, a well designed machine will hold up beyond the motor fault. So I don't think the clutch is necessary. You'll just maybe want to wire an indicator light the the Alarm output, and then a Reset button to the Input.

    Let me know what you think!
     
  15. Chuck Pheterson

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    Thanks so much for the thought that you have given this and for the image that you have posted. As I look at it, two questions come to mind. I see that you have incorporated a belt to transfer power from the motor to the actuator drive shaft. Until I saw your approach, I had assumed a direct attachment of the motor to the actuator shaft via some sort of collar, perhaps even a slip clutch. Would this approach make sense if the motor and shaft were properly aligned by a custom bracket? Also, until I saw your image, I had envisioned a single double-wide v-slot rail used in a horizontal orientation with the motor directly attached to the screw via a bracket at the end of the rail.This approach would make for a fairly light solution, which is a reasonable objective since the actuator will be removed from the tank and set aside when the tank is being used. Agitation of chocolate is needed only when the chocolate tank is not being used. I'm concerned that it will get covered in chocolate if Ieft in place while dipping is taking place.

    Glad to hear that the motor looks like it will do the job. Regarding control, I've been researching simple PLC controllers and came across the Ace 11. It is under $50 and appears to offer all of the IO that I should need and is programmable via flow diagrams and state machines (as well as ladder logic), which appeal to my computer programming background. Take a look: Ace | Velocio.net
     
  16. Josh Rupp

    Josh Rupp Well-Known
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    I don't have much familiarity with using slip clutches, but from looking real quick, one hurdle I see having to overcome would be the different shaft sizes between the actuator and the motor. You could machine the end of the actuator shaft to match, that would be an adequate solution, just some custom work, that's all.

    So then to comment of the motor mounting as a foldback set (what I showed with a belt) versus inline, I just always have preferred the foldback for a more compact footprint for mounting, and then from the simplicity aspect of the motor mount plate. You could mount the two pieces inline and then couple them as you said, I think it all just comes down to what you want.

    In regards to the actuator design, I just tried to pick something that Openbuilds offered as a kit. These C-beam actuators are a turn-key solution that just need mounted in place. You could put together your own actuator with the pieces that they offer, I was just trying to keep it simple for you. I've personally purchased the 250mm version of this, and it hardly weighs anything by itself. I think it would work for your need to install/remove frequently as well.

    This looks like a fine solution as well. Definitely would do the job. The thing I always liked about the TECO relays that I use is that they have a display on them. That display can either be a programmed HMI to display info to the operator (ie. piece counts, cycles, timers, etc) or the Ladder logic can be accessed and directly edited without a PC. That's a big selling point for me, because I don't want to have to go get a computer to plug into the thing to change a simple timer or something. Just makes troubleshooting easier.
     

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