Not trying to hijack George's Bakers, Herr Dr. Wolbier, or Lyn Bates repsonse:

Please visit the Vibrating screen manufacturers

association web site before you advance.

www.vsma.org

You may find that building a flat screener is is much

easier to accomplish as you are in the begining stages and flat

screeners will provide a better cut as well.







■

Quy,

It is usual to position the mechanism shaft horizontally through the centre of gravity of the machine (or slightly uphill), and this will produce a relatively even circular motion along the full length of the screen. For normal sizing applications the effective weight of material acting upon the screen decks will only have a very small effect upon the centre of gravity, and is usually ignored.

It is true that shifting the mechanism excessively towards the feed end will produce an oval motion with the major axis more vertical at the feed end and more horizontal at the discharge end. Some manufactures have built screens deliberately this way for specific reasons – but for normal applications (assuming good throw, speed and inclination set up); a uniform circular motion will achieve good results.

The vertical location of the mechanism shaft is once again ideally on the centre of gravity, but this is not so important, and often this is not practical. However in your case with a four deck screen it should be easy to position close to the C of G.

Placing the mechanism above the centre of gravity will produce an oval vibrating pattern with the major axis leaning downhill at the feed end, and leaning uphill at the discharge end. Placing the mechanism below the centre of gravity will have the reverse effect with the ellipse axis pointing uphill at feed end, and downhill at the discharge.

With regard to the influence of support springs upon screen motion. Assuming that the supporting elements have been correctly selected for good isolation (nice and soft), they will have no noticeable effect on the screen motion. The vertical location of the springs is not so important; with the usual position at the lower corners. However in the case of very tall screens (as presumably your four deck model will be), raising them up closer to the C of G would perhaps provide better stability. ■

Originally Posted by quydaohoang

Dear George,

Dear John,

I planing to make a 6x12 4 decks screener, circular type. Now is time to decide:

1. Where to put the couterweight mechanism on to the side plate.

2. How is the influence of the screen support (spring brace) position.

For the 1st question:

- Horisontally:

I intend to put the counter weights either on the CG OR move a bit upto 5"-10" to the feed box. My understanding of this are:

1. To compensate the loading at the feed end and that the screen is in circular movement at "all point" with load when CW is at CG with load.

You need to locate it in the centre of gravity, above or below the CoG.

2. If the counter weight still closer to the feed box than the CG with load, then the movement of screen would be "more vertical" at feed end and "flater" at dischage end. This action shall be better for screening efficiency.

No - you will have irregular movement of the screen - most probably rocking motion

Do my understanding are in line with what you are trying to share in this forum? Then what is the side effect of running the screen without load? Should the side dampeners be there to fix this action?

Please rephrase the question

- Vertically:

as the space of the 4 decks screener allowed, I can put the counter weight right at the CG of the screen box.

To handle the 2nd question:

I do not see any formular/princple to handle this. I ordered the Mash Mellow rubber spring and follow all the instructions of spring sizing. It sounds like that the spring selection only deal with asorbing the vibration from screen to structure. There still be the question:

Does the forces from screen spring counter influence to the screen movement?

Yes, if they are nor properly selected.

In case it does not much influence then: should I move vertically the cneter line screen sits 5'', 10" higher than the CG What is the rule of thumb on this?

You need to select correct springs - Marshmellow catalogue specifies the selection procedure, it does not really matter if they are positioned higher or lower.

Looking forward to your comments.

Brgds

Quy

Please see the comments/answers to your questions in red.

Regards

Ziggy Gregory

www.vibfem.com.au ■