hotbox processes. Therefore, the core machine must be designed to account for heat expansion. Floating centering points can compensate for any expansion so the location of the corebox and machine are correct regardless of temperature. The core shooter must prevent premature hardening of the sand mixture. Direct air contact is made in the sand funnel and at the shoot tubes, vaporizing water in both areas and stopping the sand from drying. The sand mixture that remains in the shoot unit then comes into contact with the air after shooting. Adding vaporized water compensates for the loss of moisture in the shoot. For machines in which the shoot unit moves to the fill position after shooting, moisture must be added and then covered when filling. As with the sand distribu- tion, vaporization must take place without developing water droplets. Depending on the flowability of the sand and the
position of the shoot tubes, sand channels or bridg- ing may develop in the unit. The sand mixture then will flow only in certain areas. The rest of the unus- able sand will dry and can lead to poor core quality. Sand channels or bridging can be stopped by using an apparatus that turns during the shooting process. This breaks down the channeling and allows the amount of sand delivered to be calculated by measuring the torque required to fill the unit.
Ultrasonic vaporing of the coreshooting unit compensates for the loss of moisture in the shoot during inorganic coremaking.
October 2012 MODERN CASTING | 29
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60