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V-Slot™ Nema 23 Linear Actuator Build (Belt Driven)

Discussion in 'Other Builds' started by Mark Carew, Nov 14, 2018.

  1. Mark Carew

    Mark Carew OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Builder

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    Mark Carew published a new build:

    Read more about this build...
     
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  2. P01

    P01 Well-Known
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    Hello builders!

    I wold like to use this build (1500mm with NEMA 23) in a research lab.
    I have no experience with linear actuators, so could you please advise me if this design fulfils my requirements.

    The idea is to mount a small monitor (or tablet) on the actuator’s plate and move it in
    a cyclic patterns (constant speed, step displacement, sine displacement, …):

    upload_2018-11-18_18-26-32.png upload_2018-11-18_18-26-48.png

    My questions:
    1. Is this design rugged enough to handle max. 2kg load at max. speed 1m/s?
    2. I would like to accelerate from 0m/s to 1m/s in shortest distance possible. What would be the distance? The same question for slowing down from 1m/s to 0m/s.
    3. How precise would be the positioning of 2kg load? For example, moving it 1000 millimetres at max. speed 1 m/s.
    4. What noise shell I expect from linear actuator with the bundled NEMA 23 (in dBA or description)?
    Thank you for any advice!
     
    #2 P01, Nov 18, 2018
    Last edited: Nov 18, 2018
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Contest Winner! Builder

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    Hi P01

    1) It's hard to quantify the Acceleration without trial-and-error (So my 1500mm/s2 guess may be way off, but experience and gut feel, says its close for our NEMA23s and a 2KG load (Not a lightweight at all)
    2) Punching those numbers into the Prusa Acceleration calculator (RepRap Calculator - Prusa Printers) Gives me (See below)
    accel.PNG

    ie, just over 300mm acceleration and 300mm deceleration (leaving less than 900mm of travel at 1m/s)

    This basic acceleration calculation assumes that the motor and driver can keep up though, so:
    3) The next point to think about is the driving characteristics. Here there are too many variables to give an exact Yes/No answer (So if time/budget allows you might want to try this hand-on to experiment with your actual use-case, conditions and setups):
    3.1) The required Motor RPM can be calculated from the Pulley diameter and selected Microstepping
    3.2) Then three different components come into play: Stepper motor, Stepper Driver and Control electronics. All three has to be able to achieve the required max RPM / acceleration (As mentioned above). In this case, keep in mind there are hundreds of steps per mm * 1000mm = couple hundred KHZ step rate - so even your consideration of controller (Grbl can reach between 50-100khz - so probably need something faster) comes into play.
    4) This is probably achievable, but not likely to be easy unless you take slow accelerations or limit the maximum speed a little more

    Hope that helps!
     
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  4. P01

    P01 Well-Known
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    Thank you for the reply. I suppose, it must be quite difficult to predict all the properties of the linear actuator in a specific use-case situation, but reading your answers, I think that it is worth to give it a try. If I finally build one, I will let you know the results. Thank you again.
     
    Mark Carew likes this.
  5. dung pham

    dung pham New
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    Hi, I want to build exactly this v-slot nema 2 linear actuator belt driven, and can move from 0 to 40" or 60". I see the list of parts . In stepper motor, it shows "Note: Stepper motors require special driver circuits to drive them. These drive circuits allow you to step the motor precisely to any position.". Can you please let me know what stepper motor and drive I need to buy and anything else I need to buy to complete this project.
    Qty Part Name Part Link Comments
    4 Low Profile Screws - 25mm Low Profile Screws M5 (10 Pack) SKU 20 - Sold in Packs - You will need 4 Singles
    6 Low Profile Screws - 8mm Low Profile Screws M5 (10 Pack) SKU 946 - Sold in Packs - You will need 4 Singles
    2 Aluminum Spacer - 6mm http://openbuildspartstore.com/aluminum-spacers/ SKU 90
    1 Aluminum Spacer - 3mm http://openbuildspartstore.com/aluminum-spacers/ SKU 175
    3 Double Tee Nuts http://openbuildspartstore.com/double-tee-nut/ SKU 60
    1 3GT (GT2-3M) Timing Pulley - 20 Tooth https://openbuildspartstore.com/3gt-timing-pulley-20-tooth/ SKU 830
    2 Eccentric Spacers - 6mm http://openbuildspartstore.com/eccentric-spacer/ SKU 226
    4 Delrin Solid V Wheel Kit http://openbuildspartstore.com/solid-v-wheel-kit/ SKU 480
    1 Smooth Idler Pulley Kit http://openbuildspartstore.com/smooth-idler-pulley-wheel-... SKU 550
    1 Idler Pulley Plate http://openbuildspartstore.com/idler-pulley-plate/ SKU 570
    1 Motor Mount Plate for Nema 23 Stepper Motor https://openbuildspartstore.com/motor-mount-plate-nema-23... SKU 910
    4 Cable Ties - 4" http://openbuildspartstore.com/cable-ties-10-pack/ SKU 675 - Sold in Packs - You will need 4 Singles
    4 Low Profile Screws - 15mm https://openbuildspartstore.com/low-profile-screws-m5-10-... SKU 922
    1 V-Slot Gantry Plate (20mm) http://openbuildspartstore.com/v-slot-gantry-plates/ SKU 935
    1 3GT (GT2-3M) Timing Belt - By the Foot https://openbuildspartstore.com/3gt-gt2-3m-timing-belt-by... Length Varies - 3' for 250mm, 4' for 500mm, 7' for 1000mm, 11' for 1500mm
    1 Nema 23 Stepper Motor https://openbuildspartstore.com/nema-23-stepper-motor/ SKU 518
    1 V-Slot® Linear Rail http://openbuildspartstore.com/v-slot-linear-rail/ Varies
    4 Nylon Insert Hex Locknut - M5 (10 Pack) https://openbuildspartstore.com/nylon-insert-hex-locknut-... SKU 10-pack
     
  6. Mark Carew

    Mark Carew OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Builder

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  7. P01

    P01 Well-Known
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    Hello, what would be the best way to mount a rotary encoder on the linear actuator? I have two reasons to do it:
    1. To know the exact position of the plate/load, to make sure that the load is able to keep up with programmed acceleration, that there is no slipping of the belt, etc.
    2. As a security measure: to detect if the plate/load is blocked (unable to move).
    So, to mount the rotary encoder (I hope I can include the link):
    https://www.amazon.com/Aideepen-Enc...e=UTF8&qid=1544313625&sr=8-5&keywords=encoder

    I can think of a few options:
    1. To mount it directly on the plate and use some kind of a wheel mounted on the encoder’s shaft to make it spin in contact with the V-slot rail.
    2. To mount it on the V-slot rail (close to the motor), and put a 3GT (GT2-3M) Timing Pulley on the encoder's shaft to make it spin in contact with the belt.
    3. To mount it on the V-slot rail and substitute a Smooth Idler Pulley with the rotary encoder.
    Which option would be the most recommended? Are there any parts in openbuildspartstore to make the mount easy?
    Thank you.
     
  8. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Resident Builder Builder

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    I'd be inclined to find a dual shaft stepper and mount it on the back.
     
  9. P01

    P01 Well-Known
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    Hello Rick 2.0, thank you for the reply. I have not considered the dual shaft stepper mount because, I think, I should be watching the plate/load or at least the belt movement. I will be using the linear actuator in a way that differ from typical cnc use-case:

    1. To move the load between 1kg and 2kg with maximum acceleration that the high torque stepper motor allows.
    2. Try to control the trajectory (I mean acceleration and speed) of the load as precise as possible (to replicate programmed patterns). At least I have to know exact position of the load at every moment to take into account its real trajectory.

    If I mount the encoder on the stepper’s shaft, I will not be able to detect the belt slipping (I do not know if it is real issue or just my imagination).
     
  10. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Resident Builder Builder

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    In that case, due to the forces you'll likely be experiencing at each end, I'd pick up a matching Idler Pulley Plate for the opposing side of the far end and drill out the axle hole both sides for a pair of flanged bearings. Then just use a regular pulley fixed on an axle rod with one end protruding outside the bearings far enough to attach the encoder to.
     

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