Where does Tool Wear come from and how to avoid it

Aluminium HPDC dies endure extreme conditions, facing thermal, mechanical, and chemical stresses with every production cycle. These stresses can lead to various forms of wear, compromising the die’s lifespan and the quality of the parts produced. Let’s dive into the main factors influencing die wear and explore practical solutions to extend die life.

There are three major culprits:

• Chemical Attack

• Erosion and Abrasion

• Thermal Fatigue

Adhesive wear or soldering occurs when aluminium adheres to the die surface, making it challenging to release parts and increasing maintenance downtime. In addition, areas around the gate suffer from erosion due to the direct metal impact, while cavitation wear results from void collapses within the die material. But this article is not about these two factors. The easiest way to avoid these is using Rheocasting.

This article is about thermal fatigue, which causes cracks on the tool steel’s surface. These heat checkings are filled with aluminium with each shot. The crack imprints must be deburred from each part in the post-processing, which triggers additional costs.

Where are these cracks coming from?

The surface getting in contact with the aluminium heats the most. Each millimetre below sees a lower temperature until you reach the cooling system’s temperature. The temperature difference between the surface and the cooling channels defines our temperature range in the tool. When we multiply that with Young’s modulus and the thermal expansion coefficient, we can calculate the stress:

σ=E⋅α⋅ΔT

So, each degree of temperature difference you save reduces the stress on the tool’s surface. As mentioned in Gold Nugget 22, tool steels are designed to consistently reach 150 to 250°C. Therefore, avoiding cold cooling water is the first step to significantly improving your tool’s lifetime. Usually, these require a redesign of the cooling channels to achieve a consistent temperature throughout the mould. However, when you use a lot of cold water, you will need that new tool very soon anyway.

The second step is to improve the spraying process. Cooling hot spots by spraying cold water on them is a terrible idea. Because of the Leidenfrost effect, you will not reach the hot surface, therefore not impacting the hot spot. Instead, you cool colder areas even further down. This can result in water not evaporating until the melt hits it, causing porosity issues or preventing the lubrication from forming a protective layer, bringing soldering issues to your die far away from the hot spot.

What are the most effective solutions to prevent tool wear?

Training your development and production teams on the principles of thermal fatigue will yield the highest ROI in prolonging the tool’s lifetime. The Process Optimisation Workshop from Casting-Campus GmbH is the perfect opportunity for that.

This workshop can also explore micro-spraying, which eliminates water usage entirely. By implementing the “no water” rule, even Gigacasting tools can reach over 100,000 shots. We can also explore heat treatments that heal your tool before the cracks form. You will also get more tips and tricks for your HPDC production and information on why Rheocasting extends the tool’s lifetime even further.

Schedule a Free Consultation down below to discuss your production issues and level up your product portfolio!