BALL MILLING

Tittle: Ball milling

Introduction:

A ball mill is a type of grinder. It is a cylindrical device used in grinding or mixing materials like ores, chemicals, ceramic raw materials and paints. Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium. Different materials are used as media, including ceramic balls, flint pebbles and stainless steel balls. An internal cascading effect reduces the material to a fine powder.

Apparatus and material:

-course sand, stainless steel balls, sieve and mill.

           

Procedure:

1.      Between 300-500 g course sand is weighted

2.      A few stainless steel balls with a various size is put in the mill.

3.      The course sand is poured into the mill

4.      The milling process is started for 15-20 minute with a suitable speed.

5.      Then, sand powder is sieved by using sieve nest.

6.      After that, the sand powder is weight once again based on their diameter.

7.      The particle size distribution  graph (histogram) is plotted.

8.      The process is repeated for another material.

Results:

Num of experiment	Initial reading	1 (350 μm)	2 (300 μm)	3 (250 μm)	4 (200 μm)	5 (150 μm)
10 min speed 5	312.5000	281.8520	14.1100	4.0953	5.7915	1.833
20 min speed 5	400.0000	358.8703	30.1848	3.7835	3.3666	2.4822
10 min speed 3	318.7866	304.7363	9.7152	2.2757	0.1764	0.0000
20 min speed 3	315.0000	296.6660	18.5576	1.4943	0.2741	0.0622

Discussion:

Particle size is important in the formulation of drug. This is because the particle size will determine the rate of dissolution and also disintegration after administered in the body. One of the method to reduce the particle size is ball milling. The ball milling will break the particle to small size or powder. The main factors that influence the particle size reduction for ball milling is speed and also the time taken.

From the results that we get from the experiment, it shows that the higher the speed and the longer the time taken the more the particle reduce the size. As we can see in the table, the amount for the smallest size which is 150 μm higher for speed 5 at 20 minute. None of the particle be reduced to 150 μm for particle that undergo milling at speed 3 for 10 minute. From the graph we can see that the particle more in size 350 μm. This shows that the particle are not completely being reduced into very small particle. Therefore to increase the reduction of particle size, we need to increase the speed and increase the time for ball milling process.

This is due to some errors. For example, the rate of shaking of sieve nest is different and inconsistence. This will make the distribution of particles in the sieve nest is not equal.Besides, the amount of different diameters of ball bearings is not equal for each experiment. This may affect the product. Some of the experiment used on large balls. Mills process usually used different diameters; large diameter balls will tend to breakdown the coarse feed and the smaller balls help to form fine product by reducing void spaces between balls. 

Question:

1.        What are the factors that influence the process of particle size reduction (milling)?

The factors that influence the particle size reduction is the speed and time for the milling process and also the coarseness of the material.

2.      What tools can be used to reduce the size of the particles?

By grinding using mortar and pestle, hammer mills and vibration mills.

3.       What are the factors that influence for choosing tools for reduce the particle size?

Particle size reduction range, nature of grinding material (roots, barks use cutting methods), the purpose of grinding process and the operation cost.

Conclusion:

As the conclusion, the best condition for ball milling are with the speed 5 and with 20 minute time taken. 



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