and mixing equipment is one of the most critical aspects of sand conditioning, with the manufacturer of the equipment being the best resource for information;
After cooling, the sand, water and bentonite mixture is charged into a sand storage silo to allow time for the bentonite to temper prior to mulling
. This tempering time (in addition to the cooling) has reduced the required mulling
cycle by 20%.
The premix consumption should be higher when bone-dry return sand is involved because the return sand clay would make little contribution to the overall "glue" strength during the limited mulling
Another source of the higher WMS sand fines is attrition of silica grains in mulling
, shakeout and blasting in sand processing.
The total time the water is in contact with the premix and sand is called the "true mulling
time." How long does it take to add premix and water?
This clay addition requires increased mulling
time, which can not be accomplished effectively in many high production sand systems.
are performed on prepared molding sand as it exits the muller and prior to mulling
: in effect, testing after the fact.
The time constant of the green sand mulling
system was also considered.
is fundamental to the success and profitability of a modern green sand metalcasting operation.
This is not necessarily a problem, but it can be associated with brittle sand, since this sometimes occurs with insufficient mulling
due to a high influx of core or new sand and bond.
The degree of mulling
also influences permeability because it affects the distribution of the clay and additives on the sand grain.
For a true study of the test, it was decided the sample variation should be minimized by added mulling
for better homogeneity of the sand.
Our speedmullors use a dynamic mulling
principle to keep the sand in constant motion.
The sand mixture was consistently prepared by mulling
a four-screen silica sand for 10 minutes with 7% bentonite.
Combined with water in the modern mulling
process, each sand grain is smeared with a mixture of water and bentonite clay.