Always follow the recommended powder water ratio's and measure both the powder and water accurately.
Always add the powder to the water:
This has 2 effects –
Conventional Mixing | Time (min) |
---|---|
Add Power to Water | - |
Hand Mix | 1 |
Machine Mix | 2 |
Vacuum Bowl | 1½ |
Pour Flasks | 1 |
Vacuum Flasks | 1½ |
Total Mixing Time | 7 |
Vacuum Mixing | Time (min) |
---|---|
Add Power to Water | - |
Mix Under Vacuum | 4 |
Pour Flasks | 2 |
Hold Under Vacuum | 2 |
Total Mixing Time | 8 |
1. Weight powder & measure water
8. Allow to stand - 90 mins
1. Weight powder & measure water
6. Allow to stand - 90 mins
Why do you need to vacuum the slurry?
When mixing the powder & water if it is not mixed and poured in a vacuum, air will become entrapped in the slurry.
If a vacuum mixer is not used, the mixing bowl must be vacuumed before pouring the flasks and the flasks must also be vacuumed after they have been poured.
If this process is not followed the castings will have bubbles on them as the air bubbles in the slurry will stick to the wax pattern and will be directly transferred to the casting.