Water Soluble Waxes for Hollow Parts
A suitable wax for all core configuration types, water soluble waxes are used as a specialty wax in the manufacturing of soluble cores - this is done in cases where an intricate and very precise cavity is required. Some formulations of this specialty wax may also include fibers, ensuring both an increased strength and an increased resistance to cracking.
Most soluble waxes comprise of a filler, binder(polyethylene glycol also known as PEG) and effervescing carbonate.
Consisting of a fine powder material and being an inorganic material, the filler is mainly used in order to improve the shrinkage characteristics of the wax and the overall structural strength of the wax blend. Fibers (more accurately fibrous materials) are also added in some cases in order to improve both the elasticity and strength of the wax.
Used in various combinations, PEG helps to achieve the desired melting point characteristics, harness and viscosity.
The Effervescing Carbonate
The effervescing agent (being an inorganic material) in the wax is Sodium Bicarbonate , and it aids in breaking down the soluble wax during the leaching process and also acts as a bulking agent.
Because of the inorganic characteristics of soluble waxes, proper heating, segregation (the removal of the non-soluble wax pattern from the soluble wax) and agitation is of the utmost importance.
At ChinaSavvy we use various combinations of raw materials in order to create the wax best suited for your project and which delivers the desired characteristics. Working to ISO 9001:2008 standards, the following properties are taken into consideration in terms of quality control:
- The viscosity or hardness
- The drop or melting point
- The point at which it congeals
- The penetration
- Its ash content
The Benefits of Water Soluble Wax
When handles correctly, this type of wax applied in investment or lost wax casting gives manufacturers a number advantages, namely:
- Water soluble waxes have good injection characteristics.
- It can be leached easily from patterns.
- This type of wax delivers a good surface finish.
- Because the filler conveys a greater stability and minimizes cavitation, an excellent dimensional stability can be achieved.
- It also has the benefit of producing a wider range of core geometries.
This specialty wax is also different from other types of waxes in that it has a high viscosity or thickness, a different range of melting characteristics, a higher filler ratio and a tendency to entrap air.
How this Specialty Wax is used
Because this specialty wax is different from other types of waxes used in investment casting, ChinaSavvy employs special procedures in order to ensure only the highest quality castings.
Melting wax in a tank or kettle at between 80° C (176° F) and 85° C (185° F), the liquefied wax is slowly and continuously agitated at around 10 - 15 rpm. This is done in order to ensure an even temperature throughout as well as to prevent the filler from settling.
The designs of both our tanks and agitators are of such nature as not to entrap any air through cavitation. Extreme care is taken when filling the transport container as well as the press wax tank, ensuring that no air is introduced into the mixture.
We also ensure a balanced press temperature profile, making sure that the injection nozzle, tank and transfer system are kept at the same temperature.
Our sprue diameter in the die is maximized, considerably larger than when using pattern wax, while minimizing the sprue length. Furthermore, the injection nozzle is maximized, helping to ensure better results.
The die used is also heated at the start of the casting process, effectively helping to minimize chipping to occur at the edges, and in order to deliver an improved surface finish. By injection soluble wax at the highest possible pressure and lowest possible temperature, better casting results are also obtained.
Water soluble waxes are typically injected under:
- A pressure of 300 < 500 psi (20 < 35 Bar)
- A temperature of between 55 °C and 65° C (131° F and 149° F)
The Process in Short
First, the water soluble wax is injected into a die, taking special precautions and applying various specialized techniques as described in how the wax is used. Once the injection process is complete, the soluble core is left to solidify.
After part has solidified, it is placed it is placed on a pattern die, where after the pattern wax is injected around the soluble core. Once ready, the pattern (containing the pattern wax and soluble core, is placed in a bath, causing the soluble core to leach out and leaving the wax pattern behind.
The investment casting process now continues as normal.
Back to Main Page: Investment Casting.
Further Suggested Reading:
- The History of Investment Casting
- How precise is Investment Casting?
- Split Wax Molds for Hollow Cast Parts
- What Metals can be Investment Cast?