TPM Metalcraft Minute
Your Source for Investment Casting Knowledge
The 4 Main Departments in Investment Casting
What do I do with this shell now?
The Dewax Process
Once a tree has received all the required coats of slurry and refractory, it is allowed to sit for a final dry. This final dry is 24-48 hours dependent upon the part dimensions & complexity. The final dry allows for all the remaining moisture to be removed from the porous ceramic shell. The shell will crack or present other casting defects if it is not completely dry before going into the flash fire. At TPM we use a moisture meter to verify that the shell is completely dry before performing the dewax process.
TPM uses a flash fire to dewax the tree. The dewax process is the removal of the wax tree and wax parts from the ceramic shell resulting in a perfect mold of the desired final part. Water expands greatly when subjected to rapid heat. This is why we want to have a fully dry shell before flash fire or the result could be catastrophic. Most foundries use an autoclave to dewax, which uses steam and pressure to melt the wax from the shell. The question is "Why would you want to introduce moisture to a tree we spent so much time drying?!" We choose flash fire as there is no extra moisture introduced and we are ready for the foundry in a more timely manner.
Fully Dewaxed Tree
After 25 minutes in the Flash Fire we have a fully dewaxed tree. The end result is a perfect mold of the final parts we wish to cast. It is very important to keep the open end of the mold covered as we do not want any debris to enter the mold. This empty mold will next go through a Pre-Heat process before being filled with molten metal. The foundry processes will be discussed next month.
Fully Dewaxed Tree
Investment Casting 101
TPM can visit your location and conduct an Investment Casting 101 Lunch & Learn. We have had a few customers who have taken advantage of this and the reviews have been great. The goal of the presentation is to share the capabilities and benefits of Investment Casting process. We also discuss part design and what makes a great casting.
The TPM team prides ourselves on our knowledge of the Investment Casting process and would like to help you understand what makes a great casting, and how TPM can work with you on future projects. Please contact Antonio Garcia if you are interested in having TPM host an event at your location.
- Tree Pre-Heat
- Pouring Metal!
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