Ceramic Industry

BCR - Custom Designed Extrusion Dies

August 6, 2000
A custom-designed die.
Brick and tile manufacturers have traditionally used single-use dies to form their products. The dies are an inexpensive way to obtain the shapes and sizes desired. However, they tend to wear out quickly because of the abrasiveness of the brick and tile material. Once they wear out, they must be thrown away, and a new die must be purchased. Plants using particularly abrasive materials might go through 20 to 25 shaper caps per year, spending thousands of dollars in downtime and replacement parts.

There is an easier and less expensive way to form brick and tile shapes. Custom designed dies, developed to work with each specific plant's materials, can help brick manufacturers make high quality products without frequent replacements. Such dies can also help eliminate problems such as crazing, core cracks, laminations and web pulling.

Die Considerations

Many elements need to be considered when choosing a custom designed die-including the length of the die unit, interior extrusion angles, and any extra features that might be beneficial.

Using the correct die unit length will help compact the clay column to achieve better green strength and a more uniform density, allowing the brick to dry more evenly. Die length is determined by and designed around a particular plant's material.

But while the length of a die unit has a significant impact on compaction and extruder amperage, chances are it won't cure every problem. Using different interior extrusion angles at different places within the unit might be another solution. It's surprising what a difference a one to two degree change in an extrusion angle can make. On some units, diversion bulges can be installed to help even out the clay flow. A balanced column, within 1à2 in. or less in 6 feet of column, helps the brick or tile remain straight after drying and firing procedures are completed. (When analyzing for balance, simply split the column into three equal segments, and if those segments remain within a 1à2 in. tolerance of each other as the column is pushed out approximately 6 feet, a balanced column will be maintained.)

Anti-twist baffles can be specified to help deter auger twist in the clay column. The baffles can also help reduce or eliminate laminations within the extruded product. There are, however, certain instances in which they will eliminate one problem only to cause another. For example, some materials that have little or no plasticity create problems when balancing a column. The die manufacturer should be able to determine whether baffles can be successfully used in a given application.

The lubrication system is an important part of die design and has been proven to increase the wear life of the die unit. However, forcing lubrication into the column can cause laminations, especially on materials that have little plasticity to begin with. In a custom designed die, the lubricant is equally distributed around the column rather than being forced in. Either oil or a water-soluble die lubricant can be used. However, not all brick and tile materials are compatible with the water-soluble lubricants, and in some cases they can increase extruder amperage or cause the column to stick instead of slide.

Even a die that is custom-designed and evenly lubricated will eventually wear out. However, unlike a single-use die, custom designed units are for the most part totally relineable.

Production Advantages

The initial cost of a custom-designed die can be substantially higher than a single-use unit. However, the savings in downtime and replacement parts quickly enable custom-designed dies to pay for themselves. Custom designed dies can also provide the following advantages:

  • lower amperage on the extruder motor

  • better recovery rates

  • longer wear life

  • * better lubrication distribution

  • better column balance (if maintained properly)

  • relineable wear parts that are competitively priced with single-use units

  • better green strength by means of more equal column density.

    The goal is to make the best quality product at the lowest possible cost. Custom-designed units can help manufacturers achieve that goal by making a plant more competitive and more efficient to operate in the long run.

    For More Information

    For more information about custom designed dies, contact Reymond Products International, Inc., P.O. Box 202, Midvale, OH 44653; (330) 339-3583; fax (330) 339-6809.