All In A Spin.
Imbalance is the result of the centre of gravity of a body not coinciding with the support point. 
It's a bit basic....if you think about it. So: take it from here.
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Shape Of Plug Weights
- TYPICALLY Cylindrical shaped PLUG WEIGHTS on say an ELJAY horizontal type screen.....these basically change a circle shape ellipse into an elongated cylindrical type shape. Some say this makes for better stratification of material than a straight line stroke.
- 1/2 PIE SHAPED unbalanced plate weights....typically 1/4 to 1/2 inch thick add more equals BIGGER STROKE, decrease or subtract more equals smaller eccentric offset....or less throw.
- T SHAPED unbalanced plate weights.......same theory as above descrip.
AND WHY DO WE WANT STROKE ANYWAYS??? Well, we want to statfiy the coarse up into the air.......so the FINES have an opportunity to work thru the voids created by stratification and attempt to PASS the opening in the wirecloth or rubber or urethane media. RPM is the other critical aspect here......more RPM equals more presentations to the hole openings vs lower RPM. ■
Material Accumulation At Center Of Screen
DEAR SIR,
THANKS FOR REPLYING MY QUERY, I AM TOTALY NEW TO THIS FEILD SO I DONT KNOW WHETHER I AM WRONG?
THE ACTUAL PROBLEM I AM FACING IS THAT I HAVE A CIRCULAR VIBRATORY SCREEN. AND THE EXCITATION FORCE IS BY UNBALANCED WEIGHT MOUNTED ON BOTH SIDE OF VIB. MOTOR. THE VERTICAL AMPLITUDE IS 3 mm & HORIZONTAL IS 4UPTO MY ASSUMPTION THE MATERIAL SHOULD TRAVEL ON OUTER SHELL DUE TO MORE HORIZONTAL AMPLITUDE.
BUT IN PRACTICE IT GETS ACCUMULATED AT CENTER.
SO I AM IN DOUBT WHETHER MY MACHINE IS WORKING OK OR NOT.
MESH - 100 X 42 GUAGE.
HOW CAN I MEASURE THE MACHINE PERFORMANCE ■
Unbalance Weight Shape
is their any effect of shape of unbalance weight on vibration pattern ■