The following is excerpt from our whitepaper: How Additive Manufacturing is Transforming Tooling. Download the full version below.
If you work in or around advanced tooling manufacturing, you have likely encountered the concept of conformal cooling. For those researching it for the first time, conformal cooling is a technique used to accelerate and control the temperature declines in tooling inserts.
In aluminum die casting, for example, the molten metal arrives at the die at a temperature of around 600°C and injects into the part cavity in about 20 ms. The part then solidifies with the help of cooling channels decreasing in temperature to around 60°C within 60 seconds.
When solid, the die separates and pins eject the part from the die. In die cast production, cooling of the die cast insert constitutes around 70% of the cycle time to manufacture a part. By accelerating the cooling rate, tooling designers can speed up production times. They can also increase the lifetime of the cooling inserts and even improve the material properties of the end use part.
Conformal cooling has been around for a while. In fact, in principle, it is similar to a solution used in spacecraft design – regenerative cooling. In regenerative cooling, you flow cold fuel through the rocket nozzle to keep the nozzle from melting.
Copper Thrust Chamber with Regenrative Cooling Channels
The result is a nozzle that is ice cold on the exterior but experiencing full rocket exhaust combustion on the interior. Engineers have utilized solutions like this to have their parts survive even when exposed to environments that exceed the melting point of the metal. So, in a way, the same design solutions used to launch spacecraft to orbit, the moon, and beyond could be used to manufacture the parts that propel your next car to the supermarket!
How to manufacture cooling channels
Engineers have limited design freedom when using conventional manufacturing methods to create cooling channels. Most approaches involve drilling straight, intersecting lines for cooling fluid to flow. However, this type of cross drilling can cause several issues like stress concentrations and leaks.
Conventional cooling example. The simple design demonstrates a single loop for coolant. Image courtesy of Ante Lausic, Lead Process Engineer – Metal AM, GM
In addition, since these cooling channels are formed by straight lines, hotspots often remain out of the coolant’s reach, and the thickest parts of the casting, which also have the longest solidification times, do not see optimized cooling. Since these sections also take the longest time to cool, speeding up the process in these areas can help to speed up the entire manufacturing process. It can also mitigate the risk of opening the die too soon and exposing molten metal to the atmosphere.
Metal AM can be leveraged to print an insert with conformal cooling channels that follow the contours of a part and provide more optimized cooling. By integrating conformal cooling channels, manufacturers can achieve several beneficial results:
- Reduce cycle times
- More uniform temperature gradients that help to eliminate hot spots
- Better, more complex designs that improve the material properties of die cast parts
With conformal cooling, it not only becomes possible to accelerate manufacturing, but engineers may also be able to thermally balance the tool resulting in a casting that solidifies near-simultaneously.
Conformal cooling example. This more sophisticated design matches the surface area to cool faster. Image courtesy of Ante Lausic, Lead Process Engineer – Metal AM, GM
In casting, the last sections to solidify also have a higher concentration of air pockets. By creating a cooling strategy that solidifies the more critical sections faster, conformal cooling can help to move the air pockets away from harmful areas, so by controlling the cooling balance, engineers can improve the material properties of their parts.
Download the full whitepaper to learn how Velo3D is enabling the next generation of conformal cooling, including:
- How Velo3D’s metal 3D printing solution enables larger inserts and design freedom to create larger and more varied conformal cooling channels with different geometries
- How Velo3D enables the printing of larger diameter channels (up to 100 mm) with a higher quality surface finish resulting in a reduced risk of cracking
- How the large-format Sapphire XC enables the manufacturing of larger inserts up to 600 mm diameter at a higher throughput with 8 lasers that achieve a seamless overlay through pre-print and runtime laser calibrations