Rod and Ball Mill

MACSALAB Rod / Ball Mill Vessels are available in Grade 304 and 316 Stainless Steel, Rubber - lined Mild Steel as well as Ceramic (Alumina).

Rods are available in Stainless Steel and Arlicite.

Grinding Spheres (balls) are available in Steel, Zirconia and Alumina. Quantity and sizes to client’s specifications.

	5 Litre	10 Litre	30 Litre
Flange - Outer Diameter	230 mm	292 mm	392 mm
Internal Diameter	160 mm	200 mm	300 mm
Overall Length	250 mm	320 mm	450 mm

                                                   

MACSALAB Drive Rolls for Rod / Ball Mills are Rubber coated and manufactured in Double and Triple Roll models. The Rolls are 120 mm diameter x 1200 mm long and powered by a 0.37 KW 220 Volt Motor with a variable speed controller.

Ball/Rod mill Literature

 

The Ball/Rod mills are meant for producing fine particle size reduction through attrition and compressive forces at the grain size level. They are the most effective laboratory mills for batch-wise, rapid grinding of medium-hard to very hard samples down to finest particle sizes.

 

A horizontal rotating cylinder (vessel) is partially filled with balls/rods (grinding media), usually stone or metal, which grinds material to the necessary fineness by friction and impact with the tumbling balls/rods. A rotating drum throws material and balls/rods in a counteracting motion which causes impact breakage of larger particles and compressive grinding of finer particles. Attrition in the charge causes grinding of finer particles.

These units are primarily used in the gold, copper and platinum industries with applications also in the lead, zinc, silver, alumina and nickel industries

Factors affecting grinding efficiency:

• Amount of material
• Amount of grinding media
• Speed of the Mill

Some guidelines for Steel and rubber lined vessels are given in the table below.

Volume	Recommended Batch size	Quantity of grinding media	O.D (mm)	Recommended Vessel Speed
5 Litres	1.25 Litres	2.5 Litres	230	54-69rpm
10 Litres	2.50 Litres	5.0 Litres	292	49-62rpm
30 Litres	7.50 Litres	15 Litres	392	42-54rpm

Additional information

Try to limit the size of the batch to 25% of the total vessel volume which is sufficient to fill the voids and slightly cover the grinding Media. Any larger batches cause the balls to spread out throughout the mass of solids so they cannot make effective contact with each other, because of the layers of material between them. This greatly reduces the grinding efficiency of the mill and in some cases makes it impossible to attain the desired results.

The only occasion for larger batches than 25% of total volume, is on products that are soft and easy to grind and the grinding media do not have to make close contact with each other.

The Feed size should preferable be 8 mesh or smaller, although many operations start with much larger pieces. Having the feed material as fine as possible enables the use of smaller sizes of grinding media, which are always best for fine uniform grinding and dispersions. For hard material it is especially advantageous to start with a fairly fine product.

For most efficient results the mill should be at least half filled with grinding media.

Pebbles may be used where product contamination by iron from steel balls must be avoided.

 

The following rules should be carefully adhered to regardless of the type of grinding medium used:

• There should be enough material to cover the grinding media
• Grinding time must be watched carefully to avoid excessive grinding
• The smallest grinding media should be employed. They not only reduce the danger of overheating but, provide faster and better results.

 

When steel balls are used the optimum sizes recommended are between 12.7 and 16 mm but sizes as small as 6.35 mm will give exceptional fine grinds.