RecyclingofPatternWaxes

Our Technical and Marketing Director - Mr. Rajesh Zade’s article on Recycling of pattern waxes published in INCAST Magazine USA.

Most of the investment casting foundries who are mass-producing commercial investment castings expect that the pattern wax they are using must be recycled and reused. Companies with competitive pricing, trust that they can save major production costs by using recycled pattern waxes.
Considering cost reduction and environmental concerns, we must give priority to the recycling of the waxes. The following are a few possibilities regarding recycling and reconstitution of the used waxes.
Filled pattern waxes and unfilled pattern waxes are recycled differently. Unfilled waxes do not contain any kind of filler material so they are easily recycled. Comparatively, filled waxes are more difficult to recycle, as they contain filler materials that must be removed by means of a filtration system.
To make it simple and effective, the pattern wax manufacturer can provide recycling services for used pattern wax, but in cases where this is not possible, due to extensive shipping costs, the recycling of the waxes can be done in- house very cost effectively.

For Proper Recycling of the Pattern Wax, We Must first Analyze and Understand Ash
The residue of contaminated material in pattern wax, which does not burn completely at temperatures above 9000C, is considered ash. When checking ash content in autoclaved material, the ash particles appear reddish in color, as depicted in Figure1. After passing a magnet over the ash, most of the ash particles are attracted to the magnet. This indicates that when we do autoclave dewaxing, the ash particles are iron or iron oxide along with the ceramic particles. This is shown in Figure 2.

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Figure 1: Ash particles from autoclaved wax

Common Precautions to be Taken for Recycling and Reconstitution of the Unfilled and Filled Pattern Waxes
1. First you need to setup a wax testing
laboratory where you can check the thermal and physical properties of the wax.
2. Avoid wax contamination during pattern production, assembly, shell building, dewaxing and storage.
3. Maximum contamination takes place during the dewax process. Observation shows that there is less contamination when using flash fire dewax than that which occurs in wax removal using an autoclave. Autoclaves for this purpose are the major reason for wax contamination with ceramic particles and iron particles due to rust forming in autoclave system.
4. To avoid this, the autoclave chamber should be kept clean and dry when not in use.
5. Using compressed air, any loose ceramic and dust particles must be removed from the shell’s surface prior to dewaxing.
6. After dewax, the wax must be pumped to a wax-processing tank automatically.

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Figure 2: Ash particles, attracted to magnet

7. After every cycle the ash percentage and other properties must be analysed and controlled.

Recycling of Unfilled Pattern Wax
Compared to other waxes, unfilled pattern waxes are readily filtered. Use a wax tank having oil bath heating. Maintain the temperature suggested by the wax manufacturer to separate the water from the wax. After water settling, drain the water from the bottom valve and then shift the wax to other tank with oil bath heating. In this tank hold the wax at the temperature specified by your wax supplier to settle down the wax impurities. The holding/settling time should be approximately 24 hours, but depends on the ash content of the wax. Once settled, the wax is filtered through a micro filtration system. Check the ash of the filtered wax and if it is in your acceptable range, you can use this wax after reclamation.

Recycling of Low Filled Pattern Waxes
Low filled waxes contain filler percentage less than 20%, in this case we can separate the filler material and then filter the unfilled separated wax. This unfilled wax can be

settled and filtered as per the process mentioned above. After filtration and reclamation, fresh filler material should be added prior to use.

Recycling of the High Filled Waxes
Most filled pattern waxes contain more than 20 to 45 percent filler material. As a result, they are difficult to recycle since filtration is not possible. It is difficult to separate this density of filler material from the waxes. In this case separating the impurities with settling is the effective solution. Though we could not achieve a low ash content in these waxes after settling, we can definitely reduce the ash content and use these waxes for production for those jobs, where complete wax removal from the cavity is possible while dewaxing.
Steps for Recycling of the Filled Pattern Waxes
1. While continuously stirring, hold the wax at 1000 C to remove themoisture content of the wax.
2. After moisture removal, hold the wax at 1200 C. Stop the stirrer to allow the impurities to settle.
3. Provide sufficient time for the settling.
4. For this settling tank, two outlet vales should be provided. Valve No. 1 at the bottom of the tank. Valve No. 2 at 150 mm height from the tank bottom.
5. After sufficient time has passed to allow the filled wax to settle, remove the wax using valve No. 2.
6. This wax is passed through a magnetic separator to remove iron particles.
7. Filter this wax by a stainless steel wire mesh of 60 to 100 mesh.
8. Check the ash percentage and other properties. Adjust the properties and ash percentage by adding the fresh wax.
9. This Wax can be used for commercial jobs having maximum wax draining/dewaxing efficiency.
This is a basic overview of the recycling possibilities for pattern waxes. For detailed information, please email us at sales@saffroshine.com

Figure 3: Unfilled Pattern Wax Recycling

Figure 4: Reclamation of Low Filled Pattern Wax

Figure 5: Recycling of High Filled Wax