Erhart Manufacturing Process
Cast iron manufacturing has such a rich history in craftsmanship and detail that in attempting to create an object from this material, we worked very hard to honor the tradition of what the material is used for and the considerations for casting that have existed for centuries. We really wanted to bring this incredible material to the modern world in form and redefine its aesthetic. The challenge we faced was to bring a modern aesthetic form to an inherently traditional process and then refining our product to find the balance between those two that made it complete.
SAND MOLD GENERATION
To make the mold box, the pattern is first placed in a wooden box where the pattern is attached to the bottom. Once the box is stable, the mold box is moved along the rollers until it reaches the sand dispenser. The first pound or so of sand is usually not well mixed but after that, the rest of the sand gets poured into the mold box. After amassing the amount of sand needed, it needs to be manually leveled. The manual attention is the reason Erhart is able to do so well in the Foundry business, as the manual labor makes it possible to generate a smaller number of castings with higher attention to detail.
On the other side of the foundry, a similar mold making process is set up but out here, the molds are very large, almost four feet by four feet. A giant sand mixer and dispenser runs on rail tracks placed in the main aisle of the foundry, pouring sand into new mold boxes. The leveling and processing of these mold is still a manual job. The mold boxes in this case are made of steel, because of its capacity to carry the heavy weight of sand and large iron casts.
The iron heats up in a furnace up to over 2,000 degrees. The exact temperature of each batch depends on the chemical properties required for specific engineering applications.
The molten iron is transferred to the pourer, and tested for the perfect temperature. Getting the right temperature for the iron is extremely important, because if either too hot or not hot enough, the iron would break during the cooling process, or fail in actual use.
Once the iron is ready, foundry workers holster the pourer into position directly above the mold’s feed. They check the amount of iron left after each pour, making sure there is enough for the next mold.
The foundry workers take precautions seriously. Industrial gloves and boots are a must for those who work the pour. Looking directly at the molten iron is highly discouraged, unless equipped with protective head covering and safety glasses.
The cast object can be large and have multiple bends and crevices that would take a lot of time to make even just by hand. Erhart has a large shot blasting chamber in one corner of the foundry. This chamber looks like a giant vault and is right next to where the molds are broken to release the cast object.
The shot blasting chamber looks like a giant vault . when opened, there is a large circular table attached to the door onto which the cast part is placed either manually or with the help of a crane. The table is covered with many small round pellets that are rapidly fired at the part once it is safely locked in, inside the shot blasting chamber. The parts have to be rotated from time to time so as to make sure all surfaces are evenly processed.