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Solenoid; high-speed push and pull

  1. Jan 16, 2012 #1
    Hi all.
    I am going to build an industrial quality knife-tool to cut cardboard, and I would like to ask you all for any advice, experience and warnings you might have. I'm in the need of a motor to oscillate a knife at a frequency of 200-300 Hz, with a stroke of 1.2mm +/- 0.6mm. The knife it self will probably weigh about 25 - 35 grams (the part the motor has to drive), depending on the outcome of the final construction.
    Would it be best to use two solenoids to achieve push and pull, or would it work with a combined push & pull function at this frequency?
    There is also the issue of heat; any parts should not exceed 50°C. I realize this could be a problem, but I hope some heat sinks will take care of this problem. Any comments?
    I also need to rotate this knife, this could be achieved by rotating the whole system, but it would be nice to combine push/pull and rotation into one motor. Do anybody know of such a motor in sale anywhere, that would meet the formentioned criteria?

    Any comments and suggestions is welcomed here!
     
  2. jcsd
  3. Jan 16, 2012 #2
    200-300Hz is awful fast for a solenoid. They have substantial mass in the plunger and you would be fighting it. I doubt it would be a winning battle.

    If you just needed to make a really high speed cut (i.e. on a piece of moving material), I'd suggest two air cylinders operating in tandem with an offset knuckle in the middle. As one air cylinder drives, the knuckle is forced downward into the work and is pulled away just as sudden by the travel of the cylinder. For the next punch cut, the other air cylinder drives the knuckle.

    For a continuous action, I suggest an offset cam on a motor. You can drive it much faster than a solenoid. If you need to engage / disengage the cutting action, you want to do it at the top of the cam's motion. This is the instant at which the blade is turning about. In ye olden days, the motor would continue to run, and a clutch would disengage at the top of travel and a second clutch would arrest the motion. Now, there are brush less motor controls that can stop on a dime. Or, you can likely turn the motor off and brake it's windings at this low a speed.

    Mike
     
  4. Jan 17, 2012 #3

    jim hardy

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