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Thread: Seeking Help in Manufacturing

  1. #1

    Question Seeking Help in Manufacturing


    I am a small manufacturer of screens - inclined circular motion.

    Could you tell me why the screening media is provided with a curvature across the width of the screen? Why this is done ?

    We tried it by adjusting the height of the screen panel supporting ribs suitably and tried to tension the screen panel by tensioner plate/bolts. But the curve we got was uneven and some portions did not even touch the support ribs. How do we design the proper tensioner plate and the bottom supporting ribs , in ordr to acheive the proper curvature. What is the optimum degree of the curvature from the middle point?

    I would appreciate if you could help!

    regards
    manish

  2. #2
    George Baker

    George Baker

    Vice President- Corporate Communications

    Assinck Ltd. [eDir]

    Assinck Ltd.

    Professional Experience 39 Years / 9 Month George Baker has 39 Years and 9 Month professional experience

    Discussions 883 George Baker acceded to 883 discussions, Articles 0 George Baker wrote 0 articles, Publications 0 George Baker Baker released 0 publications

    Searching nothing specified

    Know-How Screening (373) George Baker used this tag 373 times, Manufacturer (110) George Baker used this tag 110 times, Conveying (28) George Baker used this tag 28 times

    Camber across width of vibrating screen body? WHY?

    The answer is quite functional: We need to put a camber or arch across the width the vibratng screen for only one reason.

    When using WOVEN WIRECLOTH, IT has metal edges or hooks which need to be engaged with the side tension rails. These rails pull "TIGHT , taught, or drum head tension tight" TO ensure the wirecloth is very tight and held down. If you did not have the camber, you would not be able to pull it down tight. The wirecloth must be very tight to ensure long life. If it is allowed to be loose, it will break like a bobby pin bending back and forth a few times. Tighter is better than looser.

    You must be able to tighten down enough to engage the bottom of the wirecloth to the top of the rubber "buffer strips" which go ontop of the arched......longitudinal rails. IF YOU are loose and the rubber falls off.....you have steel to steel contact and premature breakage and failure of the wirecloth.

    GEN RULE OF THUMB: the wider the screen the more longtiduntal support rails you will need. The finer the wirecloth the closer the rails need to be, to avoid sagging and ripping. The finer the cloth diameter the more likely you may need a SUPPORT cloth or SANDWICH SECTION TO avoid premature failure. On 6' and wider screen bodies: the manufacturers typically arch from the one side plate to the centre and bolt down here with countersunk brass receivers and then arch from the centre to the other side. This is called a double camber. You can arch across an 8' screen body in one high single cambered arch. No problem. Except, material gangs up on the sides and causes a mini surge load which creates fines carryover and inefficient screening.

    IF USING perf plate, urethane or rubber segments (ie 2'x2' or square panels) a flat deck is desirable. No tension of this media is needed .........so no arch is needed to help stretch the wirecloth. This style of flat deck media is simply HELD DOWN and runs with the motion of the screen deck.

    IF you tried to stretch a piece of wirecloth on a flat surface - it would be nearly impossible. BUT, if you cut a 45 gallon drum in half and put if on a table top....round side up....and just HUNG on the metal hooks on both sides........YOU WOULD stretch the cloth and have TENSION. Hence, THE need for the arch.

    LASTLY - If you have heavy media like 3-4 inch clear wirecloth on say a top deck, you probably need only 3 rails across the width of a 6 foot wide screen........but if 3/16 inch clear wirecloth, you would probly use 5-7 rails across to support this finer media.

    The arch should be measured out to have a radius that allows gradual slope from side to side while maintaining constant contact of the underside of the cloth the the rubber which is on the support rail.

    Hopes this helps.

    GEORGE BAKER - Assinck Limited/ MODERATOR

  3. #3

    Wink regarding screen

    Thank you Mr.Baker for your timely advice

    A few more clarifications please:

    What is the optimum degree of the curvature . screen width being 5 ft and legth between 8 to 15 ft. The aperture size is between 40 to 6mm?

    next , what is the best design for the side tensioning plates/ channel . ie. how to correctly design it so that it pull the screen down properly while not transmitting load on the tensioning bolts?

    The screen cloth used by us is having an edge preparation of hook type design as commonly used. The problem we have encountered is that for 40mm and 6mm screen we use the same tensioner channel design, it tends to have a different effect on the tensioning -as the diameter of the wire is bigger in 40mm than the 6mm screen. I have seen in many pictures that the tensioner channel is made in a degree in both the sides, what should be this degree of inclination on the top/bottom walls of this tensioner channel?

    For your info , we are using the rubber covers on the longitudanal bars (5 in nos). on each deck.

  4. #4
    George Baker

    George Baker

    Vice President- Corporate Communications

    Assinck Ltd. [eDir]

    Assinck Ltd.

    Professional Experience 39 Years / 9 Month George Baker has 39 Years and 9 Month professional experience

    Discussions 883 George Baker acceded to 883 discussions, Articles 0 George Baker wrote 0 articles, Publications 0 George Baker Baker released 0 publications

    Searching nothing specified

    Know-How Screening (373) George Baker used this tag 373 times, Manufacturer (110) George Baker used this tag 110 times, Conveying (28) George Baker used this tag 28 times

    Tension Rail Design and stuff...

    Hello Again:

    The height of the camber or curvature: Contact Simplicity Engineering by email through their website for this calculation please. Ask for engineering. I personally do not have this measurement, but it must be such that the wirecloth sits down on all support rubbers equally.

    TENSION RAIL DESIGN: It is very important that the BEND ON the engaging edge or lead edge is correct. This edge actually ENGAGES the Seat of the bend in the METAL REINFORCED edge.
    It must be bent in the proper plane to actually engage and SEAT into the metal reinforced edge of the wirecloth screen section. This will ensure proper TENSIONING.

    If this lead edge is too high on the the wirecloth metal edge - IT will open up the HOOKED EDGE OR STRAIGHTENED IT vertically. This will NOT pull the cloth down onto the rubber on the rails and will actually HOLD the wirecloth OFF the rubber strips on the supporting longitudinal rails. The wirecloth will break up prematurely and fail....due to improper tension.

    The design of the METAL reinforced edge is highly important also.
    On say .225" diameter wire and larger - typically a BEND edge with no metal edge treatment is used.

    On say .177" mid range wire diameters.........a metal edge is wrapped onto the wirecloth to protect the wire from gouging and to have a spot for the edge of the tension rail to seat and engage. (Wirecloth will be turned in the metal edge maybe one time)>

    ON say....finer wire diameter the number of turns of the wirecloth inside the metal edge is more times. To STOP the fine wire from pulling out of the metal edge and maintain a decent wirecloth life.

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