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Metal 3D Printing With Generative Design - A Fusion of Design for Additive and Subtractive Manufacturing


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Posted (edited) · Metal 3D Printing With Generative Design - A Fusion of Design for Additive and Subtractive Manufacturing

Introduction

 

Marco Polo, Christopher Columbus, Vasco da Gama, Amerigo Vespucci, James Cook. What do they all have in common, and what could they possibly be doing in a post related to 3D Printing and Generative Design?

 

The obvious answer to what they have in common is that they were all explorers, many of them from an era known as The Age of Discovery. The reason they relate to this post is that Generative Design has been created for “design explorers” and it provides a method for navigating a route through to the discovery of the kind of design outcomes the like of which we may never have seen or used before.

 

Using Generative Design we are able to engage in design exploration to assist us in seeking out new ways to solve engineering and product design problems, perhaps as part of our own “age of discovery”. It provides us with the opportunity of exploring what lies beyond the boundaries of traditional designing, especially where light weight, high stiffness and minimal material usage is important.

 

Multiple Manufacturing Methods

 

When it comes to engaging in that exploration though there can be a perception that Generative Design is only for pushing the boundaries for additive manufacturing parts. That perception is often shaped by some of the more complex, high-profile examples of Generative Design that people have seen, and the fact that when it first emerged it was initially focussed on additive manufacturing as the method of delivering its outcomes.

 

However, that is no longer the case and Generative Design can now produce solutions that are far more inclusive when it comes to the types of manufacturing techniques that we intend to use to produce our final design.

 

It is now capable of delivering designs that can be ready for manufacturing using methods such as 2D cutting, 2.5-axis, 3-axis and 5-axis CNC machining, as well as being able to produce outcomes for die-casting which can easily lend themselves to being used for manufacturing using other methods of moulding.

 

To illustrate that point here are the results of a Generative Design study that returned a number of different solutions. All of them are valid design options, each tailored to a specific manufacturing method, and all of them were produced from a single set-up in Generative Design.

 

1231207566_ManufacturingOutcomes.thumb.jpg.e19cfa4804b74d2fb7b0cecc48e2e033.jpg

 

 

Exploring a Fusion of Manufacturing Methods

 

As part of encouraging the spirit of exploration introduced at the start of this article, I would like to introduce how fusing together additive and subtractive manufacturing methodologies within Generative Design can be beneficial. It also serves as an example of how Fusion 360 lives up to its name through the way it brings both manufacturing methods together within the Manufacturing and Generative Design workspaces that exist within it. When using Generative Design I would encourage you to consider that just because the manufacturing outcome for a study is targeted at one particular manufacturing method it does not always have to mean that it is the sole preserve of that method, and what follows is an example of a type of “manufacturing fusion” workflow.

 

Additive Manufacturing Without Complexity

 

Additive manufacturing is often described as a way of making things where “complexity comes for free”. Whilst that's never been entirely true it's a statement that has served as an enduring strapline for advocates of the technology. The truth of the matter though is that some additive manufacturing methods cannot deliver on that promise of high geometric complexity, yet they are still able to offer a very effective way of making things.

 

Additive manufacturing with some materials and some techniques is restricted by the fact that unsupported overhangs are not only undesirable, but may not even be possible.

With FFF 3D printers it is now possible to use material filaments that are densely loaded with metal powder carried within a polymer binder. Using these materials, parts can be 3D printed on desktop machines and then subsequently put through catalytic de-binding and sintering processes to get to a final metal part that is very close to being 100% dense. There are several examples of this kind of system available, but here I'm going to concentrate on an application using BASF Forward AM Ultrafuse 316Lmaterial on an Ultimaker S5

 

637762914_Ultrafuse316LReel.thumb.jpg.149c200d97d674accd6d84240c432961.jpg

 

Ultrafuse 316L offers the opportunity to create 316L stainless steel parts through 3D printing but, at the time of writing, there is no effective removable support material that is compatible with this particular 3D printing filament. Overhanging areas can also be the cause of significant issues with part stability during the de-bind and sintering stage of the process, however, I still wanted to explore how that kind of material and additive manufacturing method could be used for creating a part that had been produced using Generative Design.

 

Generating a Fusion of Subtractive and Additive Manufacturing

So, I took a slightly different approach in Generative Design when it came to specifying the manufacturing outcome in order to do this. Because of the need to produce a design that was free from overhanging areas the manufacturing objective I chose to use was 2.5-axis CNC machining since, by its very nature, it should generate a design that conforms to that requirement.

When specifying the manufacturing objectives for 2.5-axis CNC machining in the Generative Design study set-up there is the ability to define the minimum tool diameter that will be used. Whilst you would normally specify the real dimensions for the CNC tool that you are going to use, the software does not actually constrain you to using real-life tools. So, it doesn’t really matter for instance that you are unlikely to be using a 0.4 mm diameter tool for 2.5 axis machining but, if you are looking to create a solution for FFF 3D printing, that dimension could be used to represent the diameter of the material extrusion from the nozzle being used.

 

1370026628_ToolDiameter.thumb.jpg.69cd4c7062e07e99ed7e82bfe2167ab3.jpg

 

 

So, using that thinking, here's a study that I ran for the design of a gripper arm. It’s one that is based on the design that can be found in Sample projects section in the Fusion 360 Data Panel:

( Project => Simulation Samples,  Folder => 1 – Hands-On Exercises,  Design => GripperArm).

 

 

392564615_GenerativeDesignSetup.thumb.jpg.a1461c03a5e1890da32b4bd0c8eae6ef.jpg

 

In this case I set up the study and included the 2.5-axis CNC machining manufacturing objective in the full knowledge that I intended to use the outcome instead for an additive manufacturing method. In this case I set the tool diameter at a fairly modest 2 mm (even though a CC Red print core with a 0,6 mm diameter would be used for the 3D printing) and a wall thickness of 2.5 mm to provide a usable condition for 3D printing. Had I wanted an outcome with more complexity I could have reduced that specified tool diameter even further.

 

804156682_CNCToolSettings.thumb.jpg.63513aabc7671aacb604df38a1d2ebeb.jpg

 

The tool direction was set at Z to ensure that no overhangs would be created for the 3D printer to deal with and 316L stainless steel was included in the materials selected for the study.

 

This is one of the solutions generated for a 316L stainless steel part using 2.5-axis machining which looked looked worthy of further investigation and potential for 3D printing.  As you can see from the image there are no overhangs in the design, so I decided to export this outcome and made only very minor changes to it before using it for 3D printing.

 

709221755_SelectedOutcome.thumb.jpg.86eb2667562dfe0c651e61f5cffa3df7.jpg

 

3D Printing and Post-Processing

 

What resulted was a very straightforward, support-free 3D print that was optimised for using Ultrafuse 316L on an S5 printer.  The print was completed using the Ultrafuse 316L material profile from the Cura Marketplace with 100% solid infill, which gave a print time of just over four and a half hours.  It's important to remember that scaling factors need to be applied to the size of the part at the slicing stage to take into account the shrinkage experienced through the de-bind and sinter stage.  These scaling factors for the X,Y and Z axis can be found in the FASF Forward AM guidelines for this material. 

 

1338508211_InPrint.thumb.jpg.5c94aec1bf95cc62e03d7c95af33f261.jpg

 

Some light post-processing was done on the top and bottom faces of these parts after 3D printing to smooth them down using a fine grade abrasive paper.  The material is quite soft in this so-called "green" state and very little effort is needed in order to be rewarded with high quality surfaces after the de-bind and sinter process.

 

1995731207_3DPrintedPair.thumb.jpg.ec00f7583ac10fd9a91ee9bfec9a2905.jpg

 

These 3D prints were then put through the de-bind and sinter process to finish up with generatively designed 316L stainless steel parts that had been successfully manufactured using a desktop 3D printer.

 

1628406600_DebindandSinter.thumb.jpg.b52887a1040d30fe2d02416bac31069a.jpg

 

Conclusion

 

So what are you waiting for? Open up Fusion 360 and become a “design explorer” using all of the tools that Generative Design offers. See how you too can combine additive and subtractive manufacturing objectives into your explorations and discover the potential benefits of using the capability of the multiple manufacturing objectives that Generative Design provides and how it can help with Design for Additive Manufacturing (DfAM). 

 

Also, if you are looking to create 3D printed metal parts consider investigating the BASF Forward Ultrafuse 316L option.  It was very rewarding to run through this process from start to finish and look at the parts at the end with the satisfaction that I had produced my very first metal parts using an Ultimaker 3D printer! 

 

104308507_FinalGripperArmAssembly.thumb.jpg.c5b63b352fe3878c51ed6964421a5474.jpg

 

Note The above post is an edited version of this article published as part of Autodesk University 2020 which is taking place online on 17-19th November 2020

 

Meltio M450 DED.jpg

Edited by SteveCox3D
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