The 2010s featured many new technologies that were once labeled ‘futuristic’ technologies, including drones, self-driving vehicles and printing physical parts. Additive manufacturing or 3D printing really took off this decade, but is not a straightforward and simple process. To print reliable parts, an engineer must overcome one of the biggest challenges in additive manufacturing.
Warpage is one of the most challenging mechanical behaviors engineers face when designing and creating 3D printed components, but how does an engineer go about addressing this challenge. This post seeks to answer 3 questions:
- What is warpage?
- Why is warpage problematic?
- How to address warpage?
What is warpage?
Warpage is the tendency of a material to unevenly change shape once exposed to heat or moisture. It is generally known that materials do change shape once subjected to a sufficient amount of heat. Everyday examples include leaving plastic in a microwave too long, a chocolate bar left in your pocket too long and a dry sponge changing shape unevenly when absorbing water. This behavior applies to many materials used by engineers, including steel, aluminum, composite materials and plastics.
Warpage can be purposely achieved by taking a heat source and applying it to one spot on a component. As the heat spreads throughout the component, the component changes shape, but since one spot in was first exposed to the heat, that spot had an effective head start on the shape changing process. This unevenness is shape changing is known as warpage.
Why is warpage problematic?
Warpage can be problematic for multiple reasons, but two are mentioned below:
- Shape – When components are manufactured the final part must be of specific dimensions. Imagine building a multi-story structure with structural beams that do fit during installation or beams that are too thin and risk collapse. Producing a structural component of exact shape is important. When it comes to 3D printed parts, the warpage can lead to many challenges including: part collapse during printing or a final shape inadequate for use.
- Residual Stresses – The final and uneven shape of the component can lead to an unseen phenomenon known as residual stresses. Suppose you have a rectangular prism of aluminum with ends A and B. End A is subjected to a high enough heat source that causes a change in shape, but low enough to leave End B mostly unchanged. The difference in shape changes causes the development of internal or residual stresses. The stresses are important for many reasons. One example is the load bearing capacity might be reached earlier due to the existence of stresses, and once the capacity is reached, fracture can occur.
How to address warpage?
The warpage discussed so far can be simulated with software, for example Simufact Additive. The printing or additive manufacturing process and many of the physical events, including the non-uniform thermal expansion and contraction, can be included in the simulation. The benefit to the engineer is an ability to compute and visually inspect the location of residual stresses and the warpage of the component.
With direct knowledge of the warpage and residual stresses, an engineer or designer can develop optimal, build-up orientation, supporting structures and part geometry, and ultimately avoid components that are excessively warped and stressed.
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