10 Casting Defects

Identify and fix 10 casting defects with these pictures, descriptions, and causes.

1. Bent or Twisted Defect

Bend or twist casting defects occur when the part bends or twists out of desired shape.

Potential Causes

• Poorly designed mold
• Improper ejection from mold
• Part design does not meet casting design requirements (e.g. not enough draft)

2. Misrun or Short Pour Defect

Misrun or short pour casting defects can be identified by holes or areas where the metal didn’t fill the mold, creating an incomplete part.

Potential Causes

• Not enough metal fed into the mold
• Poorly designed gating system/mold
• Improper temperature control by foundry
• Part design may not meet casting design requirements (e.g. too thin of walls)

3. Parting Line Shift Defect

If the mold cope and drag misalign, you may notice an offset/uneven appearance to your casting, occurring at the parting line.

Potential Causes

• Improper mold set up
• Improper mold design
• Improper mold maintenance

4. Flash Defect

Casting flash occurs when metal leaks out of the mold, creating excess surface area.

Potential Causes

• Improper mold maintenance
• Mold reaching end of life

5. Porosity Defect

Metal casting porosity is localized round holes in the part.

Porosity is perhaps the most well-known casting defect. There are several distinct “types” of porosity.

Potential Causes

• Poorly designed gating system/mold
• Metal casting method

Unlike hydrogen gas porosity, this type of porosity can be caused by your metal casting method. For example, sand castings and die castings typically have more porosity defects than permanent mold castings. Why? In sand casting, metal is dumped into the mold. In die casting, metal is high-pressure injected into the mold. In permanent mold casting, metal is gravity-fed, controlled by a tilt pour press. This creates less turbulence during the pouring process, resulting in less porosity.

6. Hydrogen Gas Porosity Defect

Hydrogen gas porosity appears as small holes throughout the metal casting.

Potential Causes

• Improper metal maintenance

7. Inclusion Defect

Inclusion defects occur when small particles trapped in the mold or metal create porosity or poor surface finish on a casting.

Potential Causes

• Sand
• Impurity in metal
• Poorly maintained metal melt process
• Poorly maintained mold

8. Shrink Defect

Shrinkage appears as dips, sinks, and voids in a casting.

Potential Causes

• Poor mold design
• Improper temperature control by foundry
• Part design may not meet casting design requirements (e.g. drastic changes in wall thickness)

9. Crack Defect

Cracking defects are lines splitting the casting surface.

Potential Causes

• Poorly designed mold
• Improper temperature control by foundry

10. Rough Surface Finish Defect

Surface finish defects occur when the casting has a high RMS surface finish that is out of spec.

Potential Causes

• Poor maintenance of mold
• Metal casting method
• An indicator of other defects such as inclusions or porosity

The average as-cast permanent mold surface finish is?200 to 400 RMS. This is smoother than?sand casting?(typically 300 to 560 RMS), but rougher than?die casting?(typically 20 to 120 RMS).

Stop Casting Defects

The best way to avoid defects is to choose an experienced supplier who will produce quality castings from the start! Contact us to learn more.

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