Re: 4-Bearing, Single Shaft Screen
Ryan
It on depends what you want to screen and where are the natural frequencies of the screen.
Advantage of 4 bearing screen is that bearing load is relatively low but you can't change your stroke.
Regards
Ziggy Gregory
ziggy.gregory@vibfem.com.au ■
Re: 4-Bearing, Single Shaft Screen
Ryanb,
If you need technical assistant about bearings, pls feel free to let me know.
Our engineer will design, select and calculate quickly.
Regards
Cathy Zhang
THB BEARINGS CO.,LTD
Tel: 86-21-61517512
Fax: 86-21-61212665
Mob: 86-013651887840
E-mail: thb-cathy@thb-bearings.com
http://www.thb-bearings.com ■
Dynamics
Hello ryanb,
imo you need to mathematically model the dynamical behaviour of your screening machine, either by some differential equation(s) or by some modeling software. You will arrive at knowing where to put the operaional settings in order to fulfil all those demands. You could even find the local max points = optima of your system. But a f&f - formula for an optimum performance system, I'd like to know such a thing myself... Short way know-how is not free of charge, I feel.
Regards
R. ■
Re: 4-Bearing, Single Shaft Screen
Thanks Everyone,
Roland, I understand that these answers may not be free of charge, but am looking for all available options to a solution. If you have some suggestions, I'm all ears.
Thanks again. ■
Re: 4-Bearing, Single Shaft Screen
Ryan
Solution to your problem is very simple - you have to have an impact test done to identify location of your natural frequencies and then you can determine screen running speed.
Regards
Ziggy Gregory ■
Re: 4-Bearing, Single Shaft Screen
Could you provide more information on how one of these "impact tests" are conducted, or can you direct me to someone with the ability to do such a test?
Thanks,
Ryan ■
Re: 4-Bearing, Single Shaft Screen
Ryan
Any decent engineering consultancy shall be able to perform the test - I do not know where are you located so can't give you any names. If you send me the results I can tell you what to do with the screen
Regards
Ziggy Gregory
ziggy.gregory@vibfem.com.au ■
Re: 4-Bearing, Single Shaft Screen
Ryan,
As Ziggy has advised the stroke of a four bearing screen is fixed by the eccentric shaft, and in your case the 6mm eccentric will = a 12mm dia stroke. This is quite large and suggests that the screens have been manufactured for big aperture scalping applications (say 100 to 150mm openings), and may not be efficient for a smaller sizing job.
The correct speed will be related to the screen stroke, and in the absence of the manufacturers recommendation, I would suggest perhaps 700 rpm for the 12mm dia stroke.
The four bearing screens would have been factory balanced, but any considerable changes to the screen weight (say by heavier or lighter meshes, or by eliminating a mesh on any deck) may require rebalancing.
An excessive change in screen weight can make screen balance impossible without a change in counterweight arm size.
To rebalance:
Clean the meshes and counterweight arms of all built up material.
Start the screen while empty and place finger tips on the screen frame near the bearings. As it gains momentum, a balanced screen will run smoother and smoother as it reaches operating speed.
ADD WEIGHT to the counterweight arms if the point of balance occurs before the screen reaches operating speed, then changes to an unbalanced condition at operating speed.
REMOVE WEIGHT from the counterweight arms if the unbalanced condition decreases as the screen gains momentum but never reaches the balance point, as that point is above the proper running speed.
Always use an equal amount of weight on each counterweight arm.
PLEASE NOTE THESE COMMENTS ONLY APPLY TO 4 BEARING SCREENS
(DO NOT TRY THIS AT HOME WITH CONVENTIONAL 2 BEARING DESIGNS) ■
4-Bearing, Single Shaft Screen
I have two different size screen boxes that implement a 4 bearing screen design with a 6mm eccentric. Is there a formula for calculating shaft rpm/screenbox weight/counterweight to achieve optimum performance? I can not seem to find a balance that works without either causing damage to the machine frame or breaking the main shaft. ■