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Oscillating linear actuator - design input appreciated

Discussion in 'General Talk' started by andyfaff, May 17, 2015.

  1. andyfaff

    andyfaff New
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    I am intending to build an oscillating linear actuator. It has the following requirements:
    1) accelerate and move with a constant velocity over a distance of up to 50 mm. Decelerate to stop and repeat in the reverse direction.
    2) The frequency of oscillation is to be between 0.5 and 1 Hz. The required max velocity is then something like 100 mm/s (50 mm to be covered in 0.5s).
    3) The actuator carriage will have a load of approx. 160g.
    4) This oscillation will be continuous for a period of around 2 hours. Then it'll be stopped for ~4 days.

    I was thinking of basing the project on the V-Slot MiniV modular linear actuator. I was going to use a 64 oz in. NEMA 17 stepper motor to drive the motor, with an Arduino controlling the motor via a motor shield.

    Any feedback is appreciated. I'm looking for input on:
    1) is this speed/duty cycle possible with openbuild hardware?
    2) What pulley size should I use?
    3) Is the motor suitable? (What sort of motor should I look for)
    4) Should I run double v wheels on open rail to reduce friction?
     
  2. Ronald van Arkel

    Staff Member Resident Builder Builder

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    Well, what you are looking for is industrial, not hobby stuff like from OpenBuilds, however, OpenBuilds stuff is real good for experiments.

    That speed you mentioned isn't possible with ACME, think more about 2000mm / min., so 33.33mm / sec., higher speed will give too much resonance and the Delrin (from Dupont) Acme nut will only last for a short time, without having play on it, if you want it to kick in at directly the highest speed. This also requires a good driver that can provide the juice. Making a 8mm Acme block out of brass would be better but isn't sold on OpenBuilds (I'm think of making my own one of these days).

    Now, I see you are talking about the belt system, there the speed will be possible but only if you have a curve in your acceleration and deceleration. If it needs to start at 3000mm / min then you have to look for an industrial solution. A NEMA17 motor would do fine, no holding torque needed, and combine it with the 14 tooth pulley for acceleration and deceleration. Nr. 4 I can't answer, have to see the design first.

    Play around a little with this calculator: http://prusaprinters.org/calculator/ to get an idea about how to use the motor with the driver. Ow, and higher voltage is better for response.
     
  3. andyfaff

    andyfaff New
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    Thanks for your help. The key for me is to have the constant velocity over 50 mm each direction, but it's ok to have a trapezoidal velocity profile. I would like to minimize the time spent accelerating and decelerating though.

    I was thinking of making something like , but with the wheels running on double openrail instead.
     
  4. Ronald van Arkel

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    I would just use V-Slot. What length does the 160g have, or what object will be mounted if I may ask?
     
  5. andyfaff

    andyfaff New
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    ~120mm * 120 mm, see attached photo. I am making an oscillating slit aperture. The aperture is made out of two bits of boron carbide (one of which is missing in the picture), which are separated by ~0.3mm. The mount is made from 3D printed plastic. The two pieces of B4C makes up most of the mass. I'll have to remake the holder depending on what hole pattern is required from the carriage.
     

    Attached Files:

  6. Ronald van Arkel

    Staff Member Resident Builder Builder

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    Right. I would use 20*40 V-Slot with two Mini V Wheel Plates at the extremes under the mount that you printed. Use a timing belt tension spring as well, this could help for a more stable movement.
     
    GrayUK likes this.

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