Proper Content of Active Bentonite

Reachtop always look into the very fine details of the quality controlling during the whole manufacturing process.Follwoing is the view on proper content of active bentonite.

The proper content of active bentonite in the moulding sand is just as important as choosing the correct type of bentonite. Below are mentioned the reasons why it is important to use high-active bentonite in the moulding sand. The positive effects are to

• obtain high green compression strength in order to produce stronger moulds that are easier to convey and to avoid mould deformation in the parting line.

• maintain a high green tensile strength in order to avoid tear-off at stripping and weakened sand cods in the mould cavities.

• obtain a higher wet tensile strength in order to avoid mould scabbing in the water condensation zone and sand expansion defects.

• ensure good moulding sand plasticity to avoid sand “spring-back” and that the sand starts flowing through the injection slot and down into the moulding chamber between the shot operations.

• stabilize the mould cavity to avoid such casting defects as shrinkage and other porosities, casting expansions, sand ero-sion and sand inclusion.

The recommended content of active bentonite measured by means of the Methylene Blue test must be:

>7% for mould height up to 600 mm.

>8% for mould height from 600 to 850 mm.



Reachtop is specialized in ductile iron grooved fittings and couplings. The company has passed ISO9001 quality system, and grooved products has been approved by FM,UL,CE. With DISA moulding line, Inductotherm furnace and Inductotherm pouring system, the steady high quality and timely delivery will be guaranteed.

Sand control plays an important role in process control.



Keeping a continual check on sand properties will secure:

•Reduced scrap.

•Better pattern draw.

•Higher moulding plant efficiency.

•Reduced moulding material costs.

•Reduced fettling costs and time.

Reachtop establish an efficient process control system for the cooling, mixing and aerating operations of the sand. 

The use of clay of good quality in an automatic moulding system is one of the most important requirements. Normally, the following qualities are required of good-quality bentonite:

•it should develop good bonding properties when mixed or mulled with sand and water in the correct proportion.

•it should be able to resist reasonable heat influence so its bonding strength and plasticity properties are maintained.

•it should give the moulding sand the correct consistency (mouldability) so that the sand can be conveyed, stored and handled in the correct way during processing.

•it should enable the moulding sand to compensate for the thermal expansion of the silica grains, which counteracts casting expansion defects.

•it should give the moulding sand the correct stability and plasticity so that perfect lifting of pattern plates can be accomplished.

•it should make it possible for the sand to resist the influence from the heat shock so that it is still economical to reuse the moulding sand.

•in moulding sand mixtures it should maintain sufficient sand bonding properties in dry and hot condition so that the metal can be poured without any risk of casting defects and so that the poured moulds may be correctly conveyed, and still it should be economical to reuse the return sand.

•the moulding sand mixture should collapse readily after cast-ing and be reused.

•it should be economical in terms of price, transport, delivery and storage.