Warpage refers to the somewhat alteration or distortion in the die-cast dimensions. Cast surfaces don’t follow or maintain the intended or specified design measurements. The exterior fails to align with the specs by a fine or visible margin after its removal from molds.
This article highlights the causes, effects, and measures to prevent warpage in die casting.
Causes of Die Casting Warpage
Failure to comply with the solidifying contraction and/or temperature distinction after solidification effectively triggers warpages. However, there are many types of errors to initiate these incidents.
● Inaccurate Design
–Faulty design to cause warpage concerns the mold design, the part’s design, and the process design. Filing all the factors associated with the entire design process is impossible. However, any alteration in design or specification without adjusting other parameters leads to a warpage.
● Compromised Operation
–Likewise, multiple operational factors affect molds’ dimensional stability. The major players are inconsistent temperature, water flow, spraying/lubrication, and speed. Misplaced stress due to uneven stretching and ejection also contributes to possible warpage.
● Limiting Variation
–Improper or incorrect system centering sometimes leads to warpage. Even the limiting variation can’t help much as the alignment becomes distorted. Poor or compromised straightening of operational processes sometimes initiates warpage in aluminum die casting.
Effects of Warpage on Die Casts
The overall warpage effect primarily depends on the defect’s severity. Less warpage is always better than more, exceeding a considerable standard in production. The noteworthy effects include:
1.Surfaces become prone to damage and defects due to the poor aesthetics of metal alloys.
2.Reduced structural integrity for altered dimensions, specifically in fine-tuning casts.
3.Easy wear and tear on sharp changes for the mismatched alignment and outer finishing.
4.Increase production cost due to the required remaking or remelting of die-cast parts.
Preventing Die Casting Warpage
Avoiding warpage in die castings is possible during solidification when the defect is minimal. But the countermeasures for warps are extensive as they involve many operational and design issues. However, the following actions may minimize its formation to a significant extent.
- Ensuring the die-casting molds have their desired interior specifications.
- Reserving the 80% die tolerance for operation while providing 20% to the toolmaking.
- Assigning one specific shrinkage value to a dimension or reviewing the assigned ones.
- Checking the draft allowance assigned to the interior cores as well as shorter walls.
- Reviewing the correct radii and transition measurements for thick-thin wall combos.
- Using intact machine parts to replace worn-out platen, link, support, bar, bushing, etc.
- Proper temperature controlto ensure uniform cooling during and after solidification.
- Having the same length for all the bumper pins with the straight/plain bumper plate.
- Holding optimum and thorough consistency in lubricant spraying and the water flow.
- Maintaining an intact injection-ejection system with proper slide-out measurements.
- Addition of supporting ribs or specific shapes to control difficult-to-hold shape/walls.
- Getting or injecting the molten metal alloy through the gate system as soon as possible.
- Introducing uniform section sizes to minimize the stacking of residual casting stresses.
- Increasing injection pressures to arrange the metal alloy molecular structures properly.
- Attachment of small-sized cast-on bars to different die parts to sustain the dimensions.
Completely avoiding die-cast warps is somewhat impossible due to heavy mechanical complexity. Still, close observation of the solidification and ejection can help detect the formation of warpage easily. It’s crucial to adjust all the relevant parameters upon setting a change in design specifications.