Lost Wax Casting / Investment Casting
Terms in this set (12)
Method of metal casting in which a molten metal is poured into a mold that has been created by means of a wax model.
To form metal into complex shapes
Materials for the casting
Metal: Steel (4-5 hours to cool)/Aluminium (2 hours to cool)
1. Create a mold for the wax using aluminium
2. Inject wax to mold wait for it to cool
3. Once wax model is ready, they stamp on a code to tell the foundry worker what type of metal to use when they cast the part
4. Using a hot iron, they attach wax component to create a metal delivery system; channels that will funnel the molten metal into the mold's cavity
5. Dip the wax assembly to a ceramic solution called slurry (done by hand)
6. To strengthen the slurry, they coat it in a fine zirconium sand, and let it dry
7. A machine then coat it with coarser sand until the ceramic shell coating the wax assembly becomes about 3/10 of an inch thick
8. 5 days later, de-wax the mold by placing it in a hot steam chamber called an auto-glave for 5-10 minute
9. Once the mold is dried out the part could now be casted
10. First they put the cold mold into an oven, and heat it up for 2-3 hours
11. Pour the metal into the cavity and let it cool at room temperature
12. Once cooled and solidify, the mold is destroyed using a vibrating hammer which takes 5 minutes
13. Saw off the metal delivery system
14. Grind surface smooth
15. Sizing (steel- heated, aluminium- cooled)
- Many Intricate forms with undercuts can be cast.
- No sand inclusion
- A very smooth surface is obtained with no parting line.
- Dimensional accuracy is good.
- Certain unmachinable parts can be cast to preplanned shape.
- It may be used to replace die-casting where short runs are involved.
- This process is expensive, is usually limited to small casting, and presents some difficulties where cores are involved.
- Holes cannot be smaller than 1/16 in. (1.6mm) and should be no deeper than about 1.5 times the diameter.
- Investment castings require very long production-cycle times versus other casting processes.
- This process is practically infeasible for high-volume manufacturing, due to its high cost and long cycle times.
- Many of the advantages of the investment casting process can be achieved through other casting techniques if principles of thermal design and control are applied appropriately to existing processes that do not involve the shortcomings of investment castings.
Why do you heat the ceramic mold first before pouring the molten metal?
So that the heat won't shock the mold and break / crack it
Why do they make the mold larger than the actual part?
Because metal shrinks when cooled
Types of wax
- Flexible modelling wax
- Ornament Wax
- Paraffin Wax
- Rosin Wax
- Micro Yellow Wax
- Montan Wax
What type of production method is Lost Wax Casting?
Batch production - because of the production time and the hand finishing
Give 2 examples of Lost Wax produced products
Jewellry and complex machine parts
Will 3d printing make Lost Wax Casting obsolete?