Digitalfire Ceramics Technical Articles

Make Your Own Ball Mill Stand

Section: Glazes, Subsection: General

Description

Pictures of a ball mill rack that you can make yourself

Article

No industrial plant that mixes its own raw glazes would be without a ball mill. Yet potters lack them for a couple of reasons: Expense and awareness.

A ball mill is a porcelain jar half filled with spherical porcelain balls. Liquid glaze is poured in, a lid secured, and it is rotated on a motorized rack for 1 or more hours. The tumbling of the balls within grinds particles smaller and smaller. The creamier glaze applies better, has more stable viscosity, fires more consistently and cleaner with less specks and imperfections (eg. pinholes and blisters), and melts better. Ball mills also enable you to employ native materials.

Jar: Jars need to be heavy and thick. They are expensive, a 1 gallon jar typically costs about $100 US. These jars are not easy to make. They must have a water tight lid. A jar must be a true cylinder or it won't rotate smoothly on the rack. They are not glazed on the inside. They are best made by casting a low shrinkage porcelain. It would be extremely difficult to dry and fire a thick thrown perfect cylinder shape made from a plastic porcelain. However you can use a plastic material jar. The grinding action between the jar walls and balls is lost but the balls will still crush the particles between them if you mill for much longer periods. Typically small jars have a range of ball diameters from 1-4 cm. The pebbles cost about $6 US per pound and you need about 8-10 lbs for a 1 gallon jar. Plainsman has a stock of pebbles and they are about $5 Canadian per pound.

Rack: A rack (or stand) is $700-1300 US. However you can build your own for very little if you base you design on that shown here.

Front and Back View Unit weighs about 50 pounds. The lower assembly is welded from angle iron, the upper from 1/8" flat steel.

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Figure2

Motor One rod is longer and extends out the other side of the bearing for the large pulley to mount on. It is driven by a 1/4 hp 1725 rpm electric furnace motor (this type of motor is mass- produced and inexpensive).

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Figure 2

Pulleys & Rollers The pulley ratio is about 5.5:1. The large is a self locking mount type. Rod is 1" cold roll. Hydraulic hose with slightly less than 1" inside diameter has been pulled over the rod to grip the jar and make it run smoothly. Apply grease to the rod if the hose is difficult to pull on.

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Figure 2

Casters Use a caster wheel welded sideways at both ends to keep the rotating jar on center (the jar needs an unobstructed shoulder to ride against these casters).

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Figure 2

Bearings Four pillow block bearings hold 1" cold roll steel rods in place. The rods are far enough apart so that the shoulder of the jar runs low enough to contact the caster wheels.

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Legs and Feet Thread bolts into the feet as shown so the rack can be leveled and to prevent it from rocking on the floor.

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Figure 2

General Notes

• Use a porcelain jar if possible since much of the grinding is done between the balls and the jar. If necessary you can use a plastic lidded jar. Wine making carbuoys are good since they are very straight cylinders that will roll without hopping in the stand.
• The jar must be cylindrically true or it will rock and hop while turning.
• Fill the jar half way with balls.
• The jar should not turn too quickly (about 30 RPM).

In Bound Links

• (Glossary) Ball milling

  A device used to reduce the particle size of mater...

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