Milling and Molten Iron: How to Use Your PCNC Machine for Mold Making

Since our customers are always telling us about their latest projects and all my coworkers have an affinity for making stuff, I shouldn’t have been surprised by all the cool things you can do with a mill.

This weekend, I learned how Tormach machines fit into mold making at the annual “Pour Your Heart Out” iron pour, hosted by Sector67 and FeLion Studios, a couple local makerspaces. To my surprise, it combined my favorite two things – fire and making things. Here was the general process:

Make a Sand Mold

Since we were working with molten-hot iron, we had to use sand molds, which are like a block of sandstone. Some people carved their mold by hand, which can be very artistic and beautiful.


But most interesting to me, you can also machine design directly into the sand mold, or create a model which you create a mold around.


Apply a Graphite Wash

Once the molds were done, the volunteers applied graphite washes to the molds and set them on fire with blow torches. The purpose of this is to make the molds easily separate from the iron, kind of like greasing a baking sheet, but way more fun.


Pour the Iron

The experts were tending the furnace all morning, which included combining scrap metal and coke into the molten hot material known as charge. A whole team of volunteers broke 1.5 tons of scrap metal to be melted for the pour.


When there was enough iron combined and melted, the pouring began!


It only took about half an hour for the iron to cool in the sunny, 40-degree Wisconsin afternoon, and we had our cast iron parts.