Design for Additive Manufacturing(DFAM) for Metal Printing
Hello, good morning. Good afternoon, everybody. This is Vaman Kulkarni and right now aconsultant. But before this last 2 months back, I retired as director from Honeywelltechnology solutions. I was with Honeywell for last 14 years as responsible for all themechanical systems and before that I was with the gas turbine such establishment DRDO for21 years. So, that has been my quick background.
So, today's topic is on the design for additive manufacturing, popularly known as DfAM.This is very relevant, because additive manufacturing is becoming more relevant in thecurrent situation and scenarios, it can bring a lot of benefits. So, we will see some of that, andthen mainly concentrate on the approach which we need to follow and the tools which areavailable for the DfAM.(Refer Slide Time: 01:18)
Quickly looking at the benefits of additive manufacturing overall. It definitely reduces thecycle time for product development. So, we can quickly make the prototypes and test it,validate it, and then make quick design changes and then finalize the design. So, that is a bigbenefit of additive. In addition to that, because of the process itself, it enables wider design
space. It opens up the design space, because the way it is done is we are building the partlayer by layer using the CAD model.
So, we do not have as such any manufacturing constraint which used to be a bigger need tobe considered earlier when reducing doing the design and because of that, we can design alightweight part, we can get a better performance and then we also can consolidate the part.So, that it reduces the assembly related challenges as well as the time involved in the part inthe assemblies.
Definitely it is almost like 100% of the material is used to build a part, there is we are notgoing to take out any metal material except for the some of the finishing things, it could be ashigh as 95 to 98%. The complex parts, which used to have a lot of tooling requirement or thecasting and forging things. So, that is disabled as and hence we get a better cost advantagethrough the additive manufacturing.
We can reduce the inventory because we can build the part on demand. So, the inventoryrelated cost can definitely come down. That there are quite a few applications I talked aboutthe prototype earlier, we can also build quickly the toolings which are required, either for thecasting or the forging related dye tools, as well as the assembly and fixture tools. So, thoseare the additional benefits we get, we can quickly take advantage of additive manufacturing.
New designs that is where we are going to concentrate today and converting that into aproduction thing both for the legacy parts as well as the new product designs. We can takeadvantage even for the production of these things. It is also been used today for many of thepart repair activities for both worn-out parts, as well as some deviations would havehappened during the regular manufacturing and then we can address that as part of the partrepair activities.
The right side, I would like this chart, which is from Renishaw’s Staircase model, whichclearly talks about the applications. On the top you can see the design for additivemanufacturing. So, that is where we will concentrate to more today. It can really open up thedesign the benefits of additive manufacturing, rather than just taking the existing part andthen re-manufacturing.
There are advantages of that which you can see in the bottom today. That is without anyconstraint that is being deployed. We need to address some of the replacing the direct partreplacements. That is due to the sum of the supply chain related challenges, which we haveand then which we can overcome by using additive manufacturing, and there could be a lot ofissues in the today's assembly related challenges.
So, without changing much of that design, we can consolidate and then come up with adesign. There are some good examples of those applications.(Refer Slide Time: 05:24)
So, we have been familiar with design for manufacturing for the conventional things. Andnow, we are talking about the design for additive manufacturing. This chart shows the basicdifference between DFM and DfAM. Typically, while designing itself we consider themanufacturing related inputs and the constraints and then come out with the design, but whenit is reviewed by a manufacturing expert. He might again give some more additional inputsaying that we need to simplify certain things.
Because it is difficult to manufacture all the yield could be very low when you do it using aconventional subtractive way of manufacturing. So, in the DfAM many of those things areremoved. In fact, you can see that the step 3 is totally removed from the DfAM and in thedesign itself, we have to unlearn some of the constraints which we put for ourselves asdesigners while coming out with the design. So, that is the major difference between theDFM and the DfAM.(Refer Slide Time: 06:40)
Why DfAM? As I told there are quite a few benefits of additive manufacturing, if you reallywant to make best use of additive manufacturing a DfAM plays a big role. The basicadvantage is it is a free form of fabrication, which AM allows. So, we can leverage that tomake either a part consolidation or come out with a design which gives an improvedperformance, it could be in terms of the losses or the efficiencies, which you can provide.
This we are not able to do it the conventional things because of the manufacturingconstraints. We can also reduce the weight considerably by having topology optimized partsas well as lattice structure. So, these are the things which can is possible when we deploy theDfAM. The key thing as a designer is we have to unlearn some of the things which has beentaught to us as part of the DFM activities.
Because additive manufacturing, we can come up with the out of box innovative designs.There are additive manufacturing related inputs which the designer needs to considerespecially when he is designing gait, he needs to ensure that there are minimal supports,especially in the overhang regions where we need to give the support, how we can minimizethat, because those are the supports which we need to take it out.
And also, it is a wastage of material and we may have to do some post finishing operationswhere we provide the supports. So, keeping that in mind, we have to ensure the design itself.So, that we can have the design with minimum supports and we need to ensure that there is aminimum post processing needed to finish the product. We need to ensure that when we
come out with the design, the part should be manufacturable consistently using the additiveand it should be reliable.
So, this is one of the questions which is being repeatedly asked for additive manufacturedparts, but if we have a design addressing that, then we will be able to address most of thequestions which comes out for the additive manufacturing.(Refer Slide Time: 09:22)
So, let us get into the details of the typical DfAM approach. The way I have classified thisDFAM approach is the first one is the system design. The second one is the part design itselfand the third one is the AM process design. In the system design, it is basically we choose apart which can be produced through AM and what are those component boundaries for thiscomponent.
So, the problem sort of gets defined as part of the system design. We also look at theinterfaces, and then the bigger assembly where it goes in. So, that we can consider theconsolidating the parts and the material what could be used. So, it is more like identifying thepart defining the boundaries, that is what is done out of the first step, which is a systemdesign.
In the part design, we start actually creating the initial design. This includes the conceptualdesigns, and then carrying out some of the analysis for either for the flow thermal ortemperature related or the structural related analysis to make sure that it meets all those
requirements. And then we also verify that design, and before we start looking at the additivemanufacturing, way of producing these parts.
So, that is all part of the part design. In the process design, we take this design, and then weevaluate it for making it out of additive manufacturing. Then we also start looking at what isthe best way to produce this part a what is the ideal orientation, which will ensure that it willhave some minimum supports and then we also optimize in terms of the build time and thecost, what is ideal.
And maybe AM simulation will help us to make sure that the part can be produced withquality and without any failures as you move along. So, there are same simulation tools,which helps us. After doing all that, then we start producing the parts. So, that is typically theoverall approach.(Refer Slide Time: 12:03)
We will get to the little more details of these things. I will talk about few pointers as well aswith an example here and then at the end, we have some couple of case studies, which we canquickly run through. As I told you, the first thing is we have to choose a component for AM,keeping in mind what benefits AM would bring, if we make this part as an AM producedpart. We talked about the advantages earlier.
So, we need to ensure that some of these things we can incorporate in the design, then we saythat as this is the good part to be printed. In some cases, we may select a part, but there couldbe some risk which will be involved in this. Basically because of the criticality of the part and
then we may have some questions regarding reliably producing this part. Finally, inespecially in the aerospace is scenarios, the part needs to be qualified and then certified, therecould be more effort and testing involved to validate some of those things. It also should bealigned to the organization's business value.
That is where we come up with the cost model and then see that it is aligned with ourmanufacturing and manufacturing strategies as well as the function driven strategies where itbrings in some of the differentiators to provide a better performance compared to thecompetitor products.(Refer Slide Time: 13:44)
So, in some cases, we see that there is no benefit of using additive manufacturing. It could bea very simple part and it can be done very easily with conventional manufacturing. It may notbe cost effective to go through the additive approach and if we go through additive it couldtake more time compared to the conventional things and especially if it is a high-volumesimple part, then it may not be economical to produce it by AM.
So, in that case, we may say that additive is not suited for that component. In some cases, wesee that the part itself may be very difficult to produce it out of additive manufacturing. Itcould be because of the today's size limitations what we have the build volume typically whatwe can do today is about 400 millimeters by 400-millimeters by about 500-millimeter height.
Of course, there are new machines which are coming up which can handle up to 1000millimeters also, but still to be established. There could be a material limitation also, today
materials are limited to nickel alloys or titanium alloys, aluminum alloys, stainless steel,anything which is related to the magnetic alloys and hardened steel could be difficult to do itout of additive manufacturing and because of the strength related things, conventionally it isdone through a forging.
We may not be able to match the material properties with additive manufacturing or highspeed rotating parts that are still technology needs to be established, especially in terms of thecentrifugal forces and then, how it works out on the additively build parts, keeping some ofthese things, we may say that, they could be very difficult to produce these part out ofadditive manufacturing.
We also have to keep in mind the post processing which are involved. If there is lot of postprocessing to be done on an AM build part to meet the final product requirements, then also itis not worth pursuing out of additive manufacturing.(Refer Slide Time: 16:04)
Once we select a part, then we start defining the design problem. When we say defining theproblem, it is sort of defining the boundaries in terms of the interfaces with the adjacent parts,where it should fit in. So, it also defines the interfaces with the adjacent components or wealso have to understand what current challenges are if it is done out of the conventional. So,that we can address those things when you are designing it out of additive manufacturing.
Once we have an understanding of the bigger assembly, we can also look into the partconsolidations. So, typical design steps are indicated here. We come up with the concept and
then we look at the assembly with that concept and then we look into see whether any partscan be eliminated any fasteners or joints or even the adjacent parts can it be included as partof this design.
Then we see whether that new design is acceptable with the reduced parts and then we startlooking at which are those functions which we can further optimize to get a betterperformance. If it is a heat exchanger for example, we can see how we can improve the heatexchanger efficiency by coming out with the AM designs or if it is a duct where the pressureloss is to be minimum.
So, how we can make care habited designed to minimize those pressure losses. So, those arethe things what we will look at and then we finalize on the optimization function. Then, wealso see that what is the best material which we can produce this, keeping in mind what it canoffer.(Refer Slide Time: 18:16)
So, once we do those sort of defining the problem, we also have to define the load cases andthe material load cases. Typically, we may have some of the thermal requirements, structuralrequirements, floor requirements. So, those are the things which we have to finalize, beforewe start doing the detailed design. As I told we also have to finally decide on the possiblematerials what we will be using.
We need to make sure that the other constraints which we have for this AM which canproduce to the AM in terms of build size or surface finish those are the things which we sortof define as part of the load cases.(Refer Slide Time: 19:11)
So, then we start looking at the part design where detailed part designers as part of theadditive manufacturing DfAM approach. So, in the part design, as I indicated, we come outwith the initial design which is more like a conceptual. So, in addition to the conceptualdesign, it will also have form fit and function things incorporated as part of initial design. Weneed to think out of the box when we make this initial design.
We need to understand the challenges which we have with the conventional approach andhow we can work on through the AM design. We also have to ensure that in terms ofperformance, we are getting a better performance. It could be aerodynamic, you can see aturbine blade which I have shown there, the airfoil as well as the cooling passages inside theinternal cooling passages. How those things can be optimized so that we get a betterperformance and as well as we are able to meet what the temperature what the material canwithstand.
So, those design optimization for the performance are carried out and then we look at it fromthe structural design point of view. The key thing when you look at the structural design pointof view, which is different from the conventional way is, we can take a lot of weight from thepart through additive manufacturing. We can make it lightweight.
So, that is the big advantage of additive. This is enabled by topology optimization. Topologyoptimization has been used for more than 10 years now, but whatever design comes out fromtopology optimization, which are not able to produce it using the conventional approach andagain, we had to do a lot of compromise, but today with whatever design which we come outusing the topology optimization. It can be produced through the additive manufacturingwhich still we may have to do some small refinement to make it suitable for additivemanufacturing.
So, the design which comes out on topology optimization. In the today's limitations, wecannot directly take it to a CAD software like NX, Catia or Pro-E. So, that is the we had tobuild a remodel it in the CAD software which again is little time consuming, but the otheroption is we can build in some certain rules inside those CAD tools. So, that we can convertthat model into the CAD software.
So, those are the things what we can do and maybe once we define those rules, we canautomate it and then we can take the model into the CAD tool. So, some work needs to bestill done in that but topology optimization is definitely the way to go about few parts I haveshown here few brackets, in fact, these the middle ones are the brackets which are used inA320 and then the A380 aircrafts and then the bottom is one of the engine mount bracket,which we can typically optimize it to reduce the weight by more than 30%.(Refer Slide Time: 23:05)
So, once we have the initial design, we have to interpret the design, so that it is compatiblefor manufacturing by AM. So, there are a lot of design rules which we can come out. In fact a
lot of work have happened in this direction, but it is still very specific to the organizationswhich has spent a lot of time and effort, it is not openly shared. Also, these design rules arearrived at keeping the infrastructure what organizations have.
When I mean infrastructure, it is the machine what they have been using the material whatthey have been using. So, keeping those into consideration the design rules have beendeveloped. We can use those design rules and then see whether the initial design can beproduced out of AM. We also have to keep in mind the limitations of the AM in terms oftolerances, the surface finish, the minimum wall thicknesses, what can be done.
The diameters what can be produced to the accuracies? So, we need to keep those things inmind and maybe the initial design may need to be fine tuned from those considerations. Theother big thing which we have to keep in mind is to take a big advantage of additivemanufacturing is to reduce the weight by incorporating the lattice structure or the gridstructure, that are the lattice structure design has been there for quite some time.
But the question is how to produce the parts? Now with AM since we can produce theseparts. We can have the lattice structure which is either periodic or pseudo periodic orcompletely random, since it can definitely be produced through the AM. The lattice structurescould be homogeneous or it could be heterogeneous. The challenge of producing these latticestructures in the additive manufacturing is the thin lattice structures.
Especially the ultimately this the CAD model has to be converted into an STL format, whichis the format the AM machines will use it and there are some constraints in translating thesemodels and we may lose some of the geometries as part of that. We need to keep that in mindespecially, when we have the thin lattice structures. The typical software's which areavailable for lattice design is Netfabb and materialize.
In fact, those many people are having using these software's to come up with the latestdesigns which can be produced with the additive manufacturing.(Refer Slide Time: 26:01)
As part of the design for additive manufacturing one is the functional complexities which wecan incorporate. You can add some additional functions to get the additional benefits ofadditive manufacturing. A simple example is a structural component can also be used as aconduit or an airfoil. So, that we can do those additional functions. Similarly, the swirler inthe combustion chamber, which helps in improving the mixing efficiencies.
So, that is the other example of adding additional functions. So, those are the things also weneed to keep in mind while producing the part. There are some examples you can see thecombustion mixer as which is a GE9X part which GE has come out and it is going to be aproduction part. In addition to this, we can also think of having a varying property across thematerial length and breadth of it.
It can be done either having a multi material designs or it can be done by intentionallyincorporating the porosities through which we can address can change the density of thematerials. So, this is a new area which is been explored and a lot of work is happening in thisarea to take advantage of additive manufacturing through which it is possible to producethese varying properties in the same designs. So, the functionally graded AM is a big areawhich a lot of work is happening today.(Refer Slide Time: 27:50)
The lattice designs, we talked about a typical example here. This is for a conduit which isalso acting as a sort of heat exchanger. So, the conventional design is the baseline is the onewhich is on the top where it is just a smooth hollow design. There are 3 designs which havebeen considered can see the how we can increase the surface area by incorporating the latticedesigns.
We also have to keep in mind the pressure losses. The CFD design shows in terms of the heattransfer rate as well as the pressure drop and then based on this we can select the designswhich definitely gives advantage here both in terms of improving the thermal efficiencies, butwithin the pressure drop what we can allow for.(Refer Slide Time: 28:47)
So, there are in the design we also get some of the manufacturing related benefits what wehave especially we talked about the part consolidation. An example there what you can see isthe heat exchanger which is made out of aluminum, this is 163 parts is converted into onesingle assembly. So, lot of part consolidation reducing the weight by 40% and then the costby 25%.
So, once we have this part consolidation it also helps in reducing the inventory because wejust have a complete assembly as one part. The other benefit of additive is in terms ofreducing the material wastage. The wastage of material could be as low as less than 5% justfor the supports which we are talking about. In some cases, additive manufacturing is an idealcase when we have to have a quicker turnaround time and small production.
This is ideally suited for aerospace industry which has a lifetime of more than 30 years. Youmay have issues with the current supplier and he is not able to produce or he has closed theshop. Whereas, we can quickly take the design and reproduce it, in fact recently there was apart Honeywell got FAA certified. This is the critical part; this is a bearing support which isthe design is almost more than 40 years old.
But then there was an issue with to the current supplier and then quickly we can reproducethis part through the additive manufacturing and we did not look at the defect much bought it,but we ensured that it can be produced through the additive manufacturing the consistence inthe reliable way and this part has been certified. So, those are the typical scenarios where youcan take advantage of additive manufacturing.(Refer Slide Time: 30:57)
So, once we have this design, which is locally into from the manufacturing point also, we goback and then we re-verify make sure that it is meeting the original design intent. So, that iswhere we do the aerodynamic analysis, the thermal analysis and ensure that we meet theperformance and structurally the party is able to withstand the structural loads the thermalloads, it is able to withstand.
We also ensure that the surface finish what we get out of additive manufacturing either it isgood enough or what post processing needs to be incorporated. When we do the CFDanalysis, some of those effects of surface finish on the performance could be difficult tosimulate and have a quantifiable impact. So, those are some challenges of course, the CAEtools have been rapidly developing.
It where we can almost the final details can be simulated and then the impact can beanalyzed, we do not need to have any special tools for this verification, we do theconventional answers Nastran, Abacus.(Refer Slide Time: 32:21)
Those other tools which we use it for all the analysis. So, coming to the last part, which is theprocess design, which is more related to the additive manufacturing related things. The firstthing which immediately had to be done is the evaluation of the support structure. So, wehave to ensure that the design is reviewed by AM expert who will ensure that the supportswhich have been thought about is good enough to withstand the structural notes.
At the same time the support should not be too strong. It is difficult to take out those partsand there is a lot of wastage of materials. So, we also look at the AM the design and whatpost processing needs to be done subsequently after the part is produced by AM to meet thefinal part requirements. So, that the challenge in terms of creating the support structure todayis it is typically today is based on the experience.
So, there are some tools for providing some of the guidelines, but it is definitely not the best.The experience plays a big role here in identifying the right place where we need to give thesupport and what is the minimum support which is required? We have to ensure that asupports do not collapse during the printing process. It is having enough for structuralstrength and at the same time it can be easily removed.
So, the tools plus the experience is a one which helps in the today's evaluating these. Thetools which enables the support structure design is Magics, Netfabb, NX, simplify 3D. Theseare the tools which automate the support structure but still needs to be vetted by AM expertwho would run through this in a lot of cases in the past.(Refer Slide Time: 34:39)
The next thing which you have to keep in mind is the pre preparation to print the part. Mostof this is machine related. We need to set up the machine. The machine parameters play bigrole here. We get lot of guidelines from the machine manufacturers and then that further finetune to attain the final finished product requirements.
So, typically the machine settings can be divided into four headings which is energy related.Energy related is more like the energy source whether it is the laser beam or the electronbeam, the power source, the spot size, the pulse duration which decides on the exposure ofthe laser to the material, it could be scan related in terms of the scan speed, the scan spacingand the scan pattern itself.
Certain things could be powder related which depends on the powder size, the powderdistribution, and then the layer thickness itself and then the temperature later which is thetemperature of the powder bed and then the feeder. In some cases, the bed is preheated beforewe start the processing. So, those are the things which we need to keep in mind whilefinalizing on the machine settings.
Once we finalize on this typically almost all the air machines, if you run it through asimulation, it indicates what build time it is going to take the build the part. How much itcould cost? This cost is purely only for the printing perspective, it does not consider the otherpart of the cost models, which we have to do it separately to evaluate the business case.
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