Where is the Complexity of Rheocasting?

Buying the slurrymaker, the machine that makes the semi-solid slurry, is the easy step in getting started with Rheocasting. The machine was purchased, or the test tool arrived at the facility, and the first trial catastrophically failed. After analysing all the parts, the answer was “Rheocasting doesn’t work. We tested the tool in HPDC, and it worked perfectly fine.” However, was it really the Rheocasting process that didn’t work, or was it something else?

20% – The typical HPDC Stuff

Rheocasting is not a standalone process; it is a different melt processing for high-pressure die casting. So, in the first step, you need to do the things right that are also required for HPDC castings.

You need proper melt processing!
Most of the time, an alloy change goes hand in hand with the Rheocasting trials. This alloy needs to be melted in a furnace without contamination from the previous alloy. Then the melt needs to be cleaned and transferred to the holding furnace at the right temperature.
Hotspots need proper cooling!
Material accumulations are always a hotspot as the solidification takes longer. To avoid shrinkage porosity, you need to cool these areas as quickly as you cool the surrounding areas. Otherwise, the likelihood of shrinkage porosity increases.
Get your peripherals in order!
Corner-cutting is quite common for test tools. Instead of installing jet coolers at these hotspots, these areas receive a full wash with water and release agent. And suddenly gasporosity appears somewhere in the casting. Thanks to the Leidenfrost effect, the hotspot stays hot and the surroundings undercool. That then leads to early solidification and gas porosity from the water.

30% – The Rheocasting-specific Adaptions

Rheocasting is based on the HPDC system, but it still requires adaptations due to its semi-solid nature. These adaptations have to be done correctly; otherwise, the trial is a failure.

Tune in the Solid-Fraction!
The laminar fill is the desired goal in Rheocasting for many applications, as it provides outstanding properties and a porosity-free casting. However, if the solid fraction is not high enough (above 35%), you will never reach that status. Also, the solid fraction has to be in relation to the wall thickness.
Adapt your Tooling!
Testing Rheocasting on existing tooling comes with limitations. A wide, harp-shaped HPDC ingate produces multiple melt fronts, which generate metal meetings that cause entraptions. And the thin gate sections before the part starts trigger the sponge effect. When you squeeze a wet sponge, water rinses out, and the sponge stays. In Rheocasting, the liquid section of the slurry is pushed into the casting while the solid particles stay behind. This delivers a terrible quality everywhere.
Process Parameters are different!
Many foundries test Rheocasting by comparing everything 1:1. The same tool, the same gate, the same shot curve. That doesn’t work! The Rheocasting process parameters differ, and for a good reason. In HPDC, you want that turbulent fill. In Rheocasting, you need to avoid it. Why should the parameters be the same? Especially, since the tool is hopefully adjusted.

50% – The Business Development for new Parts

Business development in the foundry industry involves planning whom to invite to dinner and how many copies of the flyer for the upcoming trade show to print. All the parts are perfectly curated on the portals. However, when you want parts for Rheocasting, these portals are empty.

Purchasing is too late!
Rheocasting outcompetes HPDC due to its superior properties. But when the part is on your purchaser’s table, it is already too late. The part is designed for a different alloy with different properties. There is no time to go back to the drawing table and change these things.
You don’t know how to sell Properties!
Rheocasting does not replace HPDC; it expands its scope. So, you need to find these applications where Rheocasting solves pain points. Then you need to show and guide your potential customer to your solution. If it is not automotive, you need to be fast at adaptation, build your own supply chain, and educate your customers on the process advantages. For the first time in years, the discussions are about benefits and not discounts.
You have no clue about Marketing!
Marketing was never needed for foundries. But for Rheocasting, you need a communication channel with people you don’t know. You need to present the capabilities that the process can bring to specific applications to get the attention of the design owners who can make that happen. Without this crucial step, you won’t see many parts to quote on.

And there are way more small things you never thought about that make a difference in the outcome when starting with Rheocasting. And let’s be real, we all want a technology that brings in new profitable business. Rheocasting can do that, but you need to learn the details and put in the effort to succeed.

If you want to learn all the details and become a Rheocasting Expert, join the Rheocasting Masterclass. In this live course, you will understand how to implement Rheocasting profitably. Secure your spot today, before your competitors fill up the course.