Home » Posts tagged '3dprinting'

Tag Archives: 3dprinting

Additive Manufacturing 101: How to (re)design your parts for Additive Manufacturing

(Image: 3D Hubs)

Redesigned concept of a carburetor (Image: Cassidy Silbernagel)

  Mechanical Design Engineer and Additive Manufacturing Ph.D. student

This is the final article in a series of original articles that will help you understand the origins of the technology that is commonly called 3D printing. First an introduction, followed by the seven main technologies categories (binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, vat photopolymerization) and now a design philosophy for additive manufacturing.

Design for Additive Manufacturing

All of these following principles differ greatly for each technology category. Some are not a concern, others are a major concern. Before you design for AM, you need to know which process you are designing for, and if possible, what machine it will be built upon. Each machine and even different materials differ on some of these aspects.
https://www.linkedin.com/pulse/design-metal-am-beginners-guide-marc-saunders/

Supports / Overhangs

Each technology deals with this differently. Generally, there is a critical angle (typically 45 degrees) that allows no support to be needed such as in the letter Y. Some need supports for all bridges of a certain length such as the middle of a capital H. Others need supports for overhangs such as at the ends of a capital T. How supports are designed or generated and removed needs to be thought of in the design process. By changing or re-orientating the design, you can minimise the need for supports, and change how the supports are removed.

Orientation

Two factors come into play for orientation. First is material properties can differ depending on the direction they are built. This shows some test bars I printed to test how build orientation affects the electrical resistivity of a metal alloy. Strength can differ depending on build orientation so if you have a part that needs to have a certain strength in a certain direction, you will need to know how the orientation affects the strength of the part.


Images: Marc Saunders

The second is that printed features can come out looking differently depending on orientation. If you have a circle you want to print and have it come out circular, you will need to orient the part so that the circle is in the XY plane and not chopped up by the layers.

Minimum feature size / Resolution

This greatly depends on the process you use, and especially the machine you use. Just because two machines from different manufacturers use the same technology, they may not have the same feature specifications. There are also many factors that play into minimum features, and each is different. Here you can see some of the minimum sizes for a typical SLS process in Nylon. This is where you need to find out the machine and material specific specifications if you want to be designing features in the submillimeter range.

Post-Processing


There are many different ways post-processing can affect how you design. If the process relies on supports, they will need to be removed manually, or potentially semi-automatically. If attached to a build plate, the parts will need to be removed. If there is excess powder or liquid trapped, it will need to be removed. If you want uniform or enhanced material properties, a heat treatment or post infusing of a second material may be needed. If you have critical surfaces that assemble, post machining will be required including custom part holding jigs or fixtures. All of these need to be taken into consideration when designing in order to gain the greatest benefits from AM.

Four ways to (re)design parts

Method 1: Send directly for AM

Method 2: Modify for AM

Method 3: Combine and redesign for AM

Method 4: Rethink and redesign for AM

Method 1: Send directly for AM

The first and easiest is to simply take an existing design and without modification create it using AM technology. This is advantageous when the single part is excessively complex making it difficult to produce using traditional methods or made from materials that are expensive where minimal waste is desirable. This can also be desirable when the lead times for a part are excessively long or if the part is no longer manufactured.

Advantages

  • Easiest
  • Less material wastage
  • Direct single part replacement
  • Potential faster lead times
  • Allows easier manufacture of complex design

Disadvantages

  • Narrow scope of use
  • Limited potential gains

Method 2: Modify for AM

The second is to redesign the single part to either improve performance and/or to make the part better suited for AM.

Advantages

  • Improve performance
  • Decrease weight
  • Improve printability
  • Direct single part replacement
  • Less material wastage

Disadvantages

  • Requires same assembly methods and parts

Method 3: Combine and redesign for AM

The third is to combine multiple parts to aid in part reduction, reduce assembly costs, and enhance performance.

Before 3D printing, this fuel nozzle had 20 different pieces. Now, just one part, the nozzle is 25% lighter and five times more durable.

Advantages

  • Allows reduction of parts
  • Reduce assembly
  • Potentially less risk than a complete redesign of overall machine/assembly

Disadvantages

  • Requires more design time
  • Requires testing and validation

Method 4: Modify for AM

The fourth is to completely rethink the assembly and redesign according to basic first principles and design requirements. While this complete redesign can yield the greatest results, it takes the most time and effort to achieve.

 

Image: Optisys LLCThe test project involved a complete redesign of a high-bandwidth, directional tracking antenna array for aircraft (known as a Ka-band 4×4 monopulse array).

Reduce part count reduction from 100 discrete pieces to a one-piece device.

  • Cut weight by over 95%.
  • Reduce lead time 11 to two months. (eight months of development, three to six more of build time)
  • Reduce production costs by 20%.
  • Eliminate 75% of non-recurring costs.

Advantages

  • Allows greatest performance increases
  • Eliminate parts and assembly
  • Reduce weight, cost, lead time

Disadvantages

  • Most amount of design effort