Causes and Prevention of Burrs in Zinc Alloy (ZAMAC) Die Casting

 Burrs are a common problem in zinc die-casting processing, affecting appearance, fitting accuracy, and subsequent electroplating/surface treatment effects. This article analyzes the causes, detection, and prevention of zinc die-casting burrs to understand the solution process for zinc alloy manufacturing.

I. Definition and Causes of Zinc Alloy (ZAMAC) Die Casting Burrs

Burrs are small overflows or protrusions on the edges of castings or machined parts, which can lead to assembly interference, surface electroplating defects, poor feel, and safety hazards. In severe cases, rework or scrapping is required, increasing costs and delivery time.

The causes of zinc die-casting burrs include the following:

Improper mold fit and clearance: Excessive clearance between the mold cavity and core or wear of the locating pins causes molten metal to overflow and form burrs. 

1.Injection parameters and molten metal behavior: Excessive casting pressure, insufficient mold temperature, or improper gate/runner design can cause molten metal impact or backflow, resulting in localized flash.

2. Insufficient venting and ventilation: Poor venting from the cavity vents or irregularly shaped structures can cause gas to be compressed, leading to molten metal extrusion and the formation of burrs or flash.

3. Alloy composition and melt viscosity: Zinc alloy melts have high fluidity, but abnormal viscosity, impurities, or gas content can easily result in unstable flow patterns, leading to burrs.

4. Mold wear and decreased machining accuracy:** After prolonged use, wear on the mold lines, locating pins, guide pillars, and guide sleeves can cause incomplete closure, resulting in gaps and burrs.

5. Uneven cooling and solidification: Excessively rapid or slow cooling in certain areas can cause uneven shrinkage, resulting in shrinkage cavities and cracks accompanied by burrs or flash.

6. Inappropriate post-processing and cutting parameters:  Inappropriate trimming, turning, or punching parameters can leave new burrs or enlarge existing ones.

7. Surface Treatment Magnification Defects: Insufficient deburring before electroplating or spraying makes surface burrs more noticeable after treatment or leads to coating peeling.

Of course, product defects can be avoided during zinc alloy product manufacturing through the following methods: 

Manual Inspection: Visual inspection and magnifying glass examination: Locate common flash locations.

Tool Inspection: Compare mating surfaces with mold tolerances to determine the source of burrs.

Cross-sectional Analysis: Observe the internal flow lines and structure at the cut burr area to determine casting defects.

Production Tracking: Record injection parameters, mold temperature, and mold life to identify abnormal correlations.

In summary, burrs on ZAMAC zinc alloy caps originate from a combination of issues in multiple areas, including molds, casting processes, melt quality, and post-processing. These problems can be solved through systematic improvements, starting with preventative measures: optimizing mold design and maintenance, fine-tuning casting parameters, improving the gating system, controlling melt quality, enhancing venting/cooling, standardizing post-processing, strengthening pre-plating inspection, and training the team. This holistic approach can reduce defects, improve quality consistency, increase surface treatment yield, and reduce rework costs.