My goal today is to create a mold to practice with pewter. I will mix investment, pour it around the wax model-tree, let it dry and burn it.
The first step is to mix the investment. I got X-Vest investment powder which is asking for 320ml of water for 1KG of investment powder. I guess this means a factor of 0.32. I used around 300g of powder and therefore 96ml water. It is recommended to use a mixer to thoroughly mix the powder and water but I don’t have one right now. So I guess my first try will be suboptimal but at least it will allow me to learn the benefits of each refined step later. For now I will also not vacuum the investment neither before or after pouring into the mold. I will see how well the piece turns out and potentially vacuum the next time. If I am making finely detailed rings it will probably be necessary. I took around 10 minutes to measure the powder / water, mix it and pour it into the flask that contains the wax tree. The instructions say the investment needs to dry at least for 2 hours … I am excited to take off the plastic base and burn this thing! Here are some pictures of the steps:
One big lesson learned today is that I will have a lot of wasted metal because of how I designed the tree and especially the stem diameter and length. I will have to optimize this or the flute will get even more expensive …
The flask is now in the burnout oven. I programmed two steps: 60 minutes from ambient temperature to 800 degrees celsius (1475 degrees fahrenheit) and then 90 minutes at that constant temperature (800°C / 1450 °F). Following the BlueCast instructions (supplier of the investment) this is the “fast burnout” mode. I can see the glow in the oven through a small hole on top and the display says it reached the target temperature. Cool!
The oven worked perfectly and automatically cooled down after the 150 minute burnout process. It took around 30 minutes until I was able to touch the flask and check it out. The wax seems to be completely gone which is good news. Unfortunately there are some hairline cracks that are visible. I don’t think they will influence the casting too bad but they shouldn’t be there. Next time I will use a mixer, vacuum the mixture and use the slower burnout process. Anyway … tomorrow is the pewter casting day!
