Practical 3D Printing: Step 1: CAD

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Step 1: CAD

06.41

00:00	In this worked example we're going to be making a front strut tower brace using 3D printing to first produce a prototype and then a functional final part.
00:08	This is going to give you a real world look at using 3D printing to create a performance part using CAD and if you follow along you'll end up with a unique looking brace that you can tailor for use on your own vehicle.
00:20	The specific example we're using is for a Mazda RX-7 FD3S and the design consists of aluminium strut tower mounts that will be bonded to a carbon fibre tube to brace them together.
00:32	The aluminium mounts will be printed using SLM additive manufacturing but we'll print a prototype first using our SLA resin printer as a cheap way to check fitment before spending money on a third party manufacturing service.
00:45	FDM printing could be used for the prototype but SLA is simply more suited to the detail of the design in this case.
00:52	The final parts could also be machined but you'll see that the price of 3D printing them is very competitive.
00:58	As the design flexibility for additive manufacturing allows us to use a lattice structure to maintain stiffness and reduce weight and therefore material usage reducing the cost.
01:09	Regardless machining this kind of detail would be impossible or at the very least extremely impractical.
01:16	If you're interested in learning more about how we got to this stage then check out the worked example in the 3D modelling and CAD for motorsport course where we cover this process in detail.
01:26	If you want the complete picture, you'll also be able to cover the 3D scanning process that was done prior to this as a worked example in the 3D scanning course.
01:34	However, I just want to note that this is all possible without 3D scanning it just takes some extra time taking physical measurements from the car to ensure the design will fit.
01:44	With that covered let's discuss the design work that's related to 3D printing with the main topic being our DFM considerations.
01:51	These parts aren't overly large so we shouldn't run into any issues around print volumes.
01:58	Relatively simple with no enclosures, threaded features or geometry with big changes in thickness and a lack of bracing that could lead to warpage.
02:07	The finest detail is in the area with the lattice structure and while we could have used a 3D lattice here, modelling such a structure requires a paid extension with infusion.
02:17	So, to keep things simple and accessible we've gone with a 2D honeycomb lattice that can also be printed without supports provided we print with the base of the mount so the structure is being built up vertically.
02:30	As we mentioned this lattice feature is a key element of this design in that it works to retain structure while also reducing weight.
02:37	A structure like this just isn't possible with other conventional manufacturing techniques.
02:42	Looking ahead we'll be using Craft Cloud services to find a manufacturer.
02:47	Reviewing the design guidelines on Craft Cloud's website the minimum quoted printable wall thickness for aluminium is 0.8mm.
02:55	While designing we've made sure to stick to this so there shouldn't be any issues here.
02:59	But if the manufacturer we end up going with does have any concerns about our design then they'll contact us.
03:05	There's also some engraving features we've added to the surface of the spigot that'll be bonded into the carbon tube.
03:11	These will provide some mechanical interlocking to help with adhesion.
03:15	Again, the design guidelines quote that these shouldn't be less than 0.4mm deep so at 1mm deep we shouldn't have any problems.
03:24	These same spigot features need to tightly fit into the carbon tube.
03:27	So, there are some critical dimensions that need to be accurate.
03:32	Again, from Craft Cloud's design guidelines we can see that the quoted accuracy is plus or minus 0.2% with a lower limit of plus or minus 0.2mm.
03:43	In practice this really depends on the part design and the third party manufacturer we're going to use.
03:48	However, we've made sure the parts are designed 0.2mm smaller than the carbon tube and we can always remove a small amount of material.
03:57	If the fit is too tight or if it's slightly too loose then the adhesive will help fill any small gaps.
04:06	Also with tolerances in mind we've slotted the bolt holes to the strut tops to allow for any inaccuracies.
04:12	And since the studs are on an angle this means that the part can be removed and reinstalled after the carbon tube is bonded in place.
04:19	The exact distance between the strut towers won't cause any issues because of how it will fix the aluminium mounts to the strut towers and then trim the tube to length before bonding it in place on the car.
04:32	Basically, using the car as a jig so we'll know it fits.
04:35	This will be done with the car on a flat level surface to ensure the chassis is loaded evenly and the strut bar isn't stressed until the chassis flexes from this position.
04:45	As these mounting surfaces will be hidden we could inform the supplier that these can be in contact with the support material and this should result in a better surface on the top sides of the part that are visible.
04:56	The final point to make on the topic of DFM is that we're using different 3D printing technology and material to print the prototypes and the final parts.
05:05	These differences would typically come with a different set of DFM considerations and sometimes revisions or modifications to the design.
05:13	In this case nothing needs to be changed and SLA is capable of creating a part that was designed for SLM, at least for this purpose of a prototype anyway.
05:22	The last step in our CAD software to prepare for printing is to export our mesh files ready for slicing or sending to the manufacturer.
05:30	In Fusion this is as simple as using the 3D print function from under the export tab in the mesh toolbar, selecting the object we want to export, one of the mounts in this case, and then choosing the STL binary format and millimeter unit type or whatever the part has been designed in.
05:47	We'll make sure the refinement settings are set to high especially because SLA and SLM have such good resolution and we don't want to lose any detail.
05:56	Then we complete the process.
05:57	For the mount on the other side and finish up.
05:59	That covers all there is to consider around CAD for our first step so let's summarize what we've done before moving on to the next stages of the process.
06:07	3D scanning and modeling was used to create a design for a strut tower brace that consists of aluminum strut mounts and a carbon fiber cross tube.
06:16	The aluminum mounts will be prototyped using an SLA resin printer first before the final parts are printed using an SLM manufacturing process.
06:25	DFM considerations for SLM and SLA have been taken into account as well as the assembly process with the carbon tube and fitting it into the vehicle itself.
06:35	Finally, mesh files have been exported for SLA slicing and sending to the manufacturer.