With liquid nitrogen and a soft blasting medium, the deburring of die-cast parts can be carried out fully automatically and gently. Costs and reject rates can be drastically reduced.
Zinc is an inexpensive metal with a low melting point. It begins to flow at 420 degrees Celsius, so it can be processed with relatively little energy input. Die-cast parts made from zinc alloys are therefore ubiquitous in our everyday lives: toy cars, door locks, car parts, fittings, plugs, housings and zippers are just some of the things that are made from zinc.
Explosive deburring with a lot of waste
During die casting, it is almost impossible to avoid small amounts of liquid metal penetrating into the cracks between the individual parts of the mold. On the finished piece, this material forms thin burrs over the seams, which have to be removed after casting. Other metals used in die casting include aluminum, titanium and magnesium.
Parts from smaller series are usually deburred by hand - a time-consuming and expensive process. Instead, explosion deburring is widely used for mass-produced goods: A controlled explosion in a protected chamber briefly generates temperatures of up to 2,000 degrees Celsius, burning off the thin burrs. However, the force of the detonation or the high temperature can also damage the workpiece itself. The reject rate can reach up to 40 percent because molded parts become distorted.
Cold replaces detonation
In contrast, deburring using cryogenic nitrogen works without damage: the workpieces are placed in a rotary drum made of wire mesh. Simple mass-produced items such as plugs or toy cars are tipped into the drum, while complex parts are attached to frames. Liquid nitrogen is then fed into the drum.
There, the gas expands and allows the temperature to drop to minus 60 degrees Celsius. The delicate burrs are deep-frozen and embrittled almost immediately, while the cold has much less effect on the molded parts with their larger mass. The burrs can now be separated from the cast parts with little force. The mechanical action required for this is exerted by small plastic beads.
Similar to sandblasting, plastic granulate is shot onto the parts in the drum at high speed. The brittle burrs break off and are completely removed. The parts themselves, however, remain intact. The soft plastic does not even leave marks on the surface. The method is therefore technically far superior to conventional processes. It achieves better and at the same time reproducible deburring quality, even on complex molded parts with internal burrs.
Reduce unit costs
"The customers of die-cast parts, for example in the automotive industry, are making ever higher demands in terms of quality and precision," explains Thomas Böckler, Application Specialist at Messer. "On the other hand, the manufacturers themselves are also interested in high-quality and efficient processes. For electronic components, for example, which may only cost a few cents, manual deburring is out of the question. However, they are very sensitive to distortion. Our process offers the optimum solution here. In addition, the unit costs per kilogram of die casting are significantly lower compared to explosive deburring."
It is easy to find out whether it is worth investing in a cold deburring system. "First, we carry out a free deburring test with the customer's products," explains Thomas Böckler. "They can then assess whether the result meets their expectations and we can calculate whether contract deburring or an in-house system offers the optimum solution."
For more than 125 years, Messer, the today’s world's largest privately owned company for industrial gases, medical gases, specialty gases, and gases for electronics, committed to its guiding principles of safety, focus on customers and employees, responsibility for our society, sustainability, trust, and respect. Messer's Gases for Life and patented gas applications are essential for environmental protection, climate protection, decarbonization, and innovation.
