“X” is the unknown quantity “Spurt” is the drip under pressure. Die cast engineers understand the feeling. Especially when the customer is complaining that many of the dry seal pipe thread ports are leaking. High volume mudane alumininum castings like air brake valves will be with us for a while even as sexier electric vehicle castings capture our attention. In all cases it comes down to doing the basics well.

Avoiding leaks in dry seal pipe threads is all about forming a thick skin in the cored passages. In most cases it will be necessary to tap the pipe thread into the casting without premachining. There is no advantage in going to the trouble of engineering the die to form a thick skin layer if you machine it all away. Usually it will be necessary to make the core pin out of maraging material. Normal H13 cores almost instantly split when the internal water passage is close enough to achieve the desired skin thickness. I only manifold cooling water inlet lines because it is important to avoid boiling within cores like this. An outlet manifold hides the evidence that the water flow is insufficient. Cores with this much internal cooling are easily overcooled between shots. Certain brands of die casting machines (like Buhlers) can be bought with timed water cooling valves which can stop the water flow each cycle before the core pin making a dry seal pipe port becomes too cold. Even though it is possible to use hot oil within a pin like this, the 50% reduction in heat removal related to switching from water to oil spoils the thick skin creation that is needed.