Background | Matt Lemay is part of Autodesk’s Customer Success team, focused on Additive Manufacturing & Generative Design. While “customer success” can mean just about anything these days – for us the theory is simple: helping customers win will help Autodesk win – a rising tide lifts all boats right?
Renishaw Canada Solution Center | Renishaw is a leading manufacturer of advanced metal additive manufacturing systems and an expert provider of customer tailored solutions. We partnered with Renishaw Canada to deliver the workflows shown below – Mark Kirby’s (Additive Manufacturing Business Manager) expertise in connecting additive & subtractive manufacturing, and their state of the art Solution Center, were critical in helping us to create the project below.
The Case for Design for Additive Manufacturing
Additive Manufacturing (AM) is growing at a rapid clip. The driving force behind this, is the competitive separation that AM can create: With AM, Manufacturers can:
- Improve Product Performance | reducing weight, improving CFD performance, improving cooling (see: Light-weight Airline Seat Can Save Airline $200 M)
- Enable Mass Customization | no two customers are the same, so why should the products that we sell them be? (see: How Generative Design helped Under Armour make it’s first 3D Printed Trainer)
- Enhance Supply Chain | reducing assemblies and creating On-demand Manufacturing (see: Port of Rotterdam’s RAMLAB and Autodesk pioneer ‘on-demand’ additive manufacturing for ship repair)
In order to gain these advantages, new design considerations need to be made. In most cases, additive manufacturing costs more than traditional manufacturing, especially at scale – so adding more value to your products with the factors listed above is the best way to make a business case. Runze Huang PhD (Strategic Researcher at Northwestern University) presents this topic perfectly in his blog: AM Disruption at Different Scale, where:
“AM technology determines your bottom line…But value added of product determines your top line!” Runze Huang, PhD
The Case for Generative Design
Since additive manufacturing allows us to create products that were never thought possible, we also need a new set of solutions that help us re-imagine our designs to match new production potential. Enter Autodesk generative design, a technology within Fusion 360, which allows users to quickly generate 10’s, 100’s, or 1000’s of CAD-ready, higher performing design options, based on real-world manufacturing constraints. General Motors recently announced that they leveraged generative design to consolidate a traditional assembly from 8 parts to 1 (improving supply chain), create a 40% lighter design that’s also 20% stronger, all while generating over 150 feasible design options. More details here: How GM and Autodesk are using Generative Design for Vehicles of the Future
“We subscribe to the ‘design thinking’ philosophy where quantity is valued over quality in the ideation phase and we think AGD is a HUGE leap forward in design,” said Kenny Cornett, owner of Innovation Forge. “With AGD, we have brought that philosophy to our CAD work and we can now identify form and function early on and use the natural synthesis from a multitude of design options to find the best path forward.”
Cast Study | End-to-End Additive for Hydraulic Manifold
Why Additive needs Subtractive
Some consider additive manufacturing and subtractive manufacturing as competing technologies. In actuality – they are supplemental, and having Subtractive Post processing combined with Metal Additive is in most cases, required.
The reason for that is because Laser Powder Bed Fusion (LPBF) has it’s limitations. While it can produce “impossible to make geometries”, internal lattice structures, and organic designs – it also doesn’t match up with Subtractive Manufacturing in capabilities like surface finish.
- According to industry data, the usual surface roughness values for selectively laser melted parts vary between 15 µm and 40 µm (Metal-AM.com). Depending upon the application, critical geometry may need finishing or polishing
- Additive also has limitations with features like Holes – threaded holes will need to be drilled and tapped afterwards, and holes requiring tight tolerances may need to be machined as well
New Considerations with Generative Design
As if combining two highly specialized technologies in Additive + Subtractive wasn’t enough – organic geometry created through Generative Design can add some additional challenges to the production process
While Organic Geometries created by Generative Design can lead to amazing increases in Product Performance:
1. How do we connect Additive Manufacturing & Subtractive Manufacturing?
2. How do we plan for post-processing with Generative Design?
3. How do you hold those parts during machining post-processing?
4. How do you align to those parts for your Work Coordinate System?
Mesh to Solid | Connecting Additive & Subtractive data
When planning for Additive Manufacturing, with Subtractive Manufacturing post-processing, we need to make both an Additive Manufacturing ready model and a Subtractive Manufacturing-ready model. In either case, data will have to be manipulated. For those working with STL data in Additive this has been traditionally painful – once a file has been converted to an STL mesh, it can be very challenging to do conventional CAD operations needed to plan for Subtractive Manufacturing. This is the importance of Autodesk Netfabb’s and Autodesk generative design within Fusion 360 solutions for Mesh to BRep. Unlike Topology Optimization which usually creates a Mesh, Autodesk’s generative design technology creates a CAD-ready SAT file, allowing engineers to add post-processing allowances, close holes to be drilled later, etc.. More details on Mesh-to-BRep functionality, here.
(Left, Generative Design creates 10’s or 100’s of CAD-ready geometry allowing for the ability to make post-processing adjustments easily, early-on in a workflow. Right, Autodesk Netfabb allows for Mesh to Solid conversion for CAD adjustments at anytime)
Planning for Post-processing in Generative Design
Generative Design technology works by taking input geometries as Preserve or Obstacle geometry, and using Form Synthesis to generate CAD-ready geometries, comparing across a range of materials, that achieve a stated performance increase. For example, minimize mass while keeping a Factor of Safety of 2, for Aluminum, Titanium, Stainless Steel, and Inconel. We can use the input geometries to our advantage, by specifying machining allowances as geometry within the Generative Design process.
In the image below, we are using geometry for our Machining allowances as an extra set of Obstacle Geometries – making it so Generative Design will not add any material in those areas.
We then take that with the output results, to generate two models:
- Additive-ready, which has machining tolerances added to it
- Subtractive-ready, which has the final expected geometry after machining
Workholding for Additively Manufactured parts
Now that we’ve generated and printed our organic geometry, we also have to be able to hold in for subtractive post-processing. Since we can shift between Mesh and Solids at anytime, we can use our geometry to create 3D-printed Conformal Jaws as work-holding. We can do that by using our Additive-ready model, and subtracting it from blocks of CAD geometry.
(3D Printed conformal jaws used to tightly hold the printed part for Subtractive finishing. Shown at the Renishaw Canada Solution Center)
Aligning to Parts
Machine alignment is the process of picking up known points, to specify a machine’s WCS (Work Coordinate System) on a part. This is the basis for toolpaths to reference as a 0,0,0 point. For traditionally produced parts you can align to corners or known points. With Additively created organic geometry it can be more challenging, where there might not be regular CAD geometry to align to. Here we have two options:
(1) we can add additional geometry, just for alignment
(2) we can use alignment tools.
To add additional geometry for alignment, since we can convert between a Mesh and a Solid at anytime, we can use known geometry to add to a design. In Fusion 360 – there are a set of geometries available with the solution that can be easily used for probing, these can be added to your “Additive-ready” part to set the Work Coordinate System. Within just Fusion 360 – we can create generative design input geometries, generatively-design the part, post-process, set probing strategies for CAM, and generate CNC toolpaths. For more details on probing, check here: Fusion 360 WCS Probing Tutorials
Since we have both Additive & Subtractive ready models to start machining, we can specify the Additive ready as the “Stock” Geometry and Subtractive ready as the “Setup Geometry”
Next, we can start creating toolpaths. That is where my “knowledge” ends, but if you need some more information on getting started with CAM, check out some of the great content created by my colleagues Tim Paul, Marti Deans, and Lars Christensen: Fusion 360 CAM Adoption Portal
See for yourselves! The results combine the geometric complexity of Additive Manufacturing, with the surface finish and precision of Subtractive Manufacturing.
This article was originally posted on LinkedIn – connect with me there for the latest happenings / news from Autodesk around additive and generative adoption.
– Matt Lemay, Adoption Specialist – Additive & Generative
Disclaimer | This was meant to focus on design strategy and to be solution agnostic (although I have shown the process through Autodesk’s Additive Manufacturing software). Please feel free to share, criticize (even better, praise), or recommend topics of importance to you in the comments below.