Taking Advantage of DfAM

[SteveCox3D 85]

 

In my previous post on DfAM (Design for Additive Manufacture) I concentrated on how to deal with some of the design principles needed to ensure the manufacturability of a part using Additive Manufacturing (AM), or 3D Printing (3DP).

 

In this post I’m going to concentrate on the way DfAM can take advantage of some of the unique capabilities that AM and 3DP has to offer. There are a number of different advantages available and we’ll look at each one in turn…………

 

“Complexity Comes For Free…..”

 

This is a statement that’s often made about AM/3DP. It’s not always completely true because dealing with complexity in this method of manufacturing can incur longer manufacturing times and sometimes, as the saying goes, “time is money”. However it's true that designs for this type of manufacturing method can be considerably more complex, yet still be feasible to make, compared with those designed for the more traditional methods of subtractive manufacturing, forming, or casting.

 

One great example of design complexity is this Digital Sundial designed by Mojoptix :

 

 

In itself this is a very clever piece of design that uses mathematical formula to generate the geometry which creates a digital time image from shadows cast by the sun. However, that geometry in some areas is so complex, with many thin internal walls, that the only feasible way of making this is using AM/3DP.

 

 

In other applications this design freedom helps to realise complex cooling channels inside parts where efficient heat exchange is one of the key performance requirements. Channels can be provided deep inside parts where they are most effective, as opposed to being provided only where they can be manufactured. The result is that optimal functionality can be the focus for the part design rather than how it can be manufactured using traditional methods.

 

The ability to make thin complex structures that are often “locked” inside parts is one of the aspects that is allowing the use of complex lattice structures for light-weighting of parts made using 3DP/AM. These internal lattices are similar to the internal structures that using infill in Cura produces, however the advantage of these more advanced lattices are that they can be created from understanding the stress analysis of the part as a solid structure.  The lattices created can then be very dense in high stress areas and much less dense in lower stress areas, resulting in significant weight savings.

 

Here’s an example of such a variable structure in a cut-away section of an advanced concept that I worked on for a marine pilot ladder

 

 

I personally think that the use of AM/3DP for light-weighting is one of it’s most exciting possibilities and one that could play a key part in sustainability of design and manufacturing in the future.

 

At the moment AM/3DP is being used for reducing weight in high value/low volume applications such as aerospace, but it the future I expect it to also provide this advantage in higher volume/medium value applications such as automotive.

 

Light-weighting using AM/3DP is a subject that I’d like to return to in more depth in a future post.

 

 

Multi-Material Prints

 

With dual extrusion 3D printers such as the Ultimaker 3 and new Ultimaker S5 it’s possible to combine two quite dissimilar materials on a single layer. That gives the opportunity to create some interesting concepts that can be produced in a single 3D print.

 

One example is this pair of pliers that I designed specifically as a dual material print. The main structural parts are in a rigid material (in this case PLA) and the central latticed core, which behaves like a pivot, is made from a very flexible TPE (thermoplastic elastomer).

 

 

In order to get a good bond between the two materials I didn’t want to rely on material adhesion alone because of the shear forces acting across the joints between the two materials as they are operated. So in this design I incorporated interlocked mechanical connections between the two materials where those features were printed through the layers. This in itself was another example of DfAM, because understanding how the layers would be printed allowed me to design a robust, yet manufacturable, connection between the two dissimilar materials.

 

 

 

In the future we will probably see 3D print heads that go beyond two materials to multiple materials, which will open up further new opportunities

 

 

Part Consolidation

 

Another opportunity using DfAM is to design what would be a multi-piece component to be manufactured in a single pass. This is called part consolidation and it reduces assembly time, and can also provide fully assembled parts that would be impossible to achieve through normal methods.

 

The advantage of these are reduced inventory, reduced weight, elimination of assembly time and some design freedom, but they can sometimes have the downside of reduced levels of serviceability, so that needs to be a consideration.

 

A good example of part consolidation is the antenna bracket below that was created by Airbus for the Eurostar E3000 communications satellite. This was previously a four part assembly with many internal fixings for assembly of the fabricated parts which was replaced with an AM single piece design, which also had the benefit of being both stiffer and lighter than the multi-part assembly it replaced.

 

See this TCT Magazine article for full details

 

Integrated Mechanisms

 

Another opportunity that Part Consolidation can provide is the possibility to create integrated mechanisms that are multi-part assemblies with functional mechanisms that work straight off the printer.

 

Perhaps one of the most famous is the NASA Space Wrench that was 3D printed on the International Space Station as part of their 3D Printing in Space investigations for supporting long-term exploration missions.

 

In a weight-less environment it’s probably not a good idea to have lots of small parts floating around, so this was designed as a working wrench where the ratchet mechanism was created directly inside the part during printing. The first time the wrench is operated any small bonds between the parts are broken and the ratchet mechanism works.

 

 

Another good example of an integrated mechanism is this Platform Jack that can be downloaded from Thingiverse

 

 

Part Customisation

 

Another key advantage of AM/3DP is it’s ability to take advantage of part customisation where every part made differs slightly to suit individual customer needs. Here DfAM plays a role in the area of Mass Customisation where a mass produced part is used with a customised 3DP/AM part to produce something that has the best of both worlds.

 

Mass Customisation earbuds are a good example of this where mass-produced earphone drivers come together with 3D printed tips that have been created from a scan of your particular ear contours.

 

This leads into the ability to satisfy something called “The Market-of-One”. This opportunity is where either mass personalisation, or a fully customised part, is a true one-off product that will perhaps never be repeated, but for which a commercial opportunity exists.

 

In DfAM this customisation can be achieved by using a full parametric design approach where the key adjustable features in a design are defined in a parameter table such as this example below in Fusion 360 :

 

 

This table allows new dimensions to be quickly input into the parameter table and the design then updates automatically to reflect these without the need for any additional design work. The customised design can then be rapidly output to slicing software for final preparation. In this way customised designs can be produced and prepared for manufacture in a matter of minutes.

 

 

Have You Taken Advantage of DfAM ?

 

The difference between what’s covered in this post compared with DfAM in my first post on the subject is that all of the above techniques need to be considered at the concept stage of designing. In this case it needs the AM/3DP mindset to be adopted right at the very outset.  There's an example of that in this video made by HP which shows some of the above DfAM principles I've described combined into a very durable 3D printed part with a high service life

 

It can be quite a difficult transition to make to take advantage of the freedoms that AM/3DP offer, and it maybe needs a degree of innovation and creative thinking to make the most of the opportunity. One of the things that is now starting to emerge are higher education courses and apprenticeships dedicated to the use of AM/3DP, and these will undoubtedly be useful in embedding these opportunities in the design-make workflow for the workforce of the future.

 

At the current stage of DfAM we have merely scratched the surface of what we can do and I’m really excited to see how we exploit the advantages I’ve outlined above in the future. So, I’d be really interested to see and hear from the community how you’ve taken advantage of DfAM, and what your aim was ………….

 

 

 

Edited July 2, 2018 by SteveCox3D

[geert_2 557]

Thanks for this interesting post with practical examples.

 

I especially like the digital sun clock, because it shows an inspiring and creative new way of thinking, breaking out of the box. This is what we need to learn more. At the same time this concept reminds us of the ancient astronomers, who also used such ideas in their temples.

 

Then I have a question concerning the orange plier: this is an interesting concept, but how long does such a mechanism survive in real life? And how well can it handle a load, if you want to fix a bolt or pipe for example? Can it really clamp with force? And how do you come to such a structure, thus how do you develop it? It would be interesting if you could describe the workflow, or the idea-flow.

 

Looking forward to your next posts.

 

Edited July 3, 2018 by geert_2
corrected unclarity

[SteveCox3D 85]

Thanks for the comments @geert_2

 

The interesting thing about the pliers is that the service life could be long because there are no moving parts and the flexible part is working well within it's elastic limit so it's response should remain constant.  I'm used to testing things to determine their service life and this feels like it would cope with a very high number of operating cycles.

 

The clamp force isn't enough to do a mechanical job like tightening a nut, but it does have a soft pinch force like you can get with your fingers.  Someone who I showed it to was very interested in it as a potential application where they were trying to automate strawberry picking which needs a damage-free grip.  So-called "soft robotics" is a new area where robots become less mechanical but have more of a human touch and maybe this would be appropriate for that.

 

I did try some alternative lattice shapes, but this very regular pattern seemed to work best. It's something that I probably need to return to and see what changes I could make.  Simulation of this is quite difficult because it's a non-linear material behaviour, so trial and error 3D printing different patterns is probably the best option to develop the idea further. At least 3D printing makes that easier to do!

[geert_2 557]

On 7/4/2018 at 11:49 PM, SteveCox3D said:

...

Someone who I showed it to was very interested in it as a potential application where they were trying to automate strawberry picking which needs a damage-free grip.  So-called "soft robotics" is a new area where robots become less mechanical but have more of a human touch and maybe this would be appropriate for that.

...

 

Yes, I could see the use for such applications with fragile materials indeed: biological samples, glass bottles,... I hadn't thought of that.

 

For some applications, maybe you could even print these pliers out of one material, and by just varying the geometry get both the desired stiffness and softness where needed? For example, by adding a similar pattern at the clamps, it would get a softer grip around the sample, like rubber?

 

Interesting field of research.