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Electrostatic force

Discussion in 'General Electronics Discussion' started by abrohit, Oct 23, 2010.

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  1. abrohit


    Oct 23, 2010
    How to increase electrostatic force?
    I am from grinding wheel industry, on one process grains are placed on the belt conveyor. Below this conveyor aluminum sheet is connected with 11 KV power supply. Then backing disc is brought near the conveyor. then grains are lifted towards the backing disc by electrostatic force. i am actually facing the problem of grain lifting problem in heavy grains. Can anybody help in this. how to increase this electrostatic force? i can't increase the voltage.

    Can i trial for different material instead of aluminum
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Thinner belt?
    Different Universe?
  3. Resqueline


    Jul 31, 2009
    Initial charging of the particles using the opposite polarity?
  4. abrohit


    Oct 23, 2010
    How can i charge these particles, these particles are the grains used for making grinding wheels.
  5. Resqueline


    Jul 31, 2009
    The (non-conductive) particles are initially at ground level as it is now. Surrounding them with an opposite polarity 11kV instead will transfer some of that charge to them.
    This will effectively double the voltage differential and so has the potential of doubling the force. The particles can't tell the difference between 22kV and +/-11kV.
    Of course, w/o any more specific knowledge of your setup I can't say if this solution is feasible at all for you. Halving the distance will of course have the same effect.
  6. abrohit


    Oct 23, 2010
    yes halfing the distance works but still the force is not sufficient. Any change in material of plate or something else that can help?
  7. shrtrnd


    Jan 15, 2010
    I started two suggestions to abrohit post, then deleted them, because of conjecture about what the system is actually composed of.
    Can you be a little more specific about physical construction of your system?
    I'm assuming aluminum was used because it's non-magnetic. Most electrostatic mats I've seen are coils covered in composites. The aluminum was probably used to extend the life of your system (wear and tear of grit from your process), but it's probably reducing the effectiveness of the static field.
    I think you already pegged the problem, you could use a change in material.
    But there's not enough info here, for responsible suggestions.
  8. awright


    Oct 10, 2009
    I am not an electrostatics (or an electronic) engineer. I am only a hobbyist, albeit one who has dabbled in electronics from before transistors became available. However, I am an avid denizen of independent local used book stores and one of my treasured finds is, "Electrostatics and its Applications," edited by A.. D. Moore, (John Wiley & Sons, 1973, ISBN 0-471-61450-5). I urge you to find a copy - preferably through your local independent bookstore (they need our support) but alternatively through a search service like Abe Books. I have used the information in the book to do home-brew electrostatic painting of steam radiators. It was a hair-raising experience but it did get the paint into the intricate inner recesses of the radiators and I lived to write this.

    It has a chapter on Electrostatic Coating which includes a two page section 11.4.1, "Electrostatic Formation of Sandpaper." Two pages is too much to attempt to reproduce here, but I'll mention a couple of its main points.

    VOLTAGE: It mentions about 100 KV applied between two metal plates separated by about 4 inches.

    MATERIAL: "A continuous belt of semiconducting material passes over a group of rolls and is in contact with the upper surface of the lower electrode plate." Both electrodes are "...usually ... metal sheets encapsulated in a semiconducting material." The lower belt is the carrier for the abrasive grains to be transferred to the glue-coated upper belt.

    I interpret the function of the semiconducting material to be to have enough conductivity to allow enough current to flow to charge the abrasive particles on top of the semiconducting belt without allowing enough current to flow laterally away from the charging area to either short the charging electrode to ground or leak the charge off the abrasive grains before they can be transferred to the glue-coated belt above. The text says nothing about the nature of the semiconductive materials. You might experiment with spraying your lower belt with CRT screen "anti-static spray" to provide a little conductivity.

    The accompanying figure (in the book) shows the lower electrode charged to high voltage (either positive or negative) and the upper plate, above the glue-coated belt, grounded.

    The text mentions that the primary advantage of the electrostatic method over simple mechanical spreading of grains is that the electrostatic transfer leaves the particles embedded endwise in the glue with sharp ends protruding most effectively.

    I don't think the type of metal used in the plates has any influence beyond its compatibility with the semiconductive encapsulant of the plates.

    I'm sure there are other books available on the topic. I presume that you have done a Google search. Another thought would be to contact the abrasive product manufacturers like Norton. Sometimes they have informative booklets bragging about their technologies.

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