Features:
A cavity or apparent lack of flesh containing sand particles on or within the surface of a casting
Causes:
A. Bad drawing of flow path or mould, with drawing crack and sand falling
B. Improper design of flow path, sand hole caused by hot metal flushing during pouring
C. Improper design, long molding time, long baking time and “moisture migration” result in low strength of local molding sand and formation of sand holes
D. Low moisture content of molding sand
E. There is “falling sand” in the mold cavity, for example, the mold chamber is worn, the sprue cup sinks, and there is falling sand when the mold (compactor) is pressed to the gate or above the mold chamber
F. The molding chamber is worn and there is “sand shaking” phenomenon when the back plate is raised
G. There is burr or floating sand in the sand core, and the sand core is not blown clean
H. Sand shoveling during mask core setting or sand squeezing during mold closing
I. Deformation of formwork, resulting in sand squeezing and falling
J. The model panel was not installed flat, resulting in sand extrusion in the mold cavity
K. Disa splint or the sand mold is cracked due to bulge, which compresses and deforms the sand mold, resulting in sand extrusion or sand hole
Plan improvement measures:
A. The scheme is recalculated, and it is suggested to reduce the water inflow of riser as much as possible to facilitate the floatation of sand slag
B. Polish the model and polish the flow path to reduce the sand hole caused by poor draft
C. The comprehensive pouring system is adopted in the scheme design to improve the slag retaining effect of the pouring system
D. If the pouring time is too long or it is unable to punch at the same time, recalculate the scheme
E. Increase bottom or side water injection
F. If the mold parts are worn, replace them in time
G. If there is sand extrusion, confirm that there is no problem with the panel, and make R angle or anti pressure strip at the molding line at the sand extrusion position
H. During molding, if sand blasting and sanding are carried out at the back of the molding plate, confirm the size of the formwork, and repair welding shall be carried out in case of serious wear
I. Reduce the amount of water sheet or blank holder and improve the slag retaining capacity
J. If the mask is adjusted during sand removal, confirm the interference of the core pin
K. Change the position of the water inlet to avoid the parts easy to wash sand (the water inlet shall not be made on the sand core blowing mouth)
L. Make slag collection package in the scheme
M. 4A for cross flow to facilitate scum