Practical 3D Printing: Design For Manufacturing

Back to course

Watch This Course

$199 USD $99.50 USD

-OR-

Or 8 easy payments of only $12.44 USD Instant access. Easy checkout. No fees. Learn more

Enroll Now
8 easy payments of only $12.44 USD

Course Access for Life

60 day money back guarantee

Design For Manufacturing

10.15

00:00	DFM or design for manufacturing is important to consider for any project we're working on where we want to successfully produce a real part.
00:08	Each manufacturing process, including each type of 3D printing, involves its own set of DFM considerations, some general and some unique.
00:17	The main things we need to keep in mind are the limitations of the manufacturing process so we don't end up designing something that's incredibly difficult, extremely expensive or simply impossible to produce.
00:28	It's also just as important to understand the strengths and benefits of the process as well so we can play to these and end up with the best possible product.
00:37	Either way, it's going to require a sound understanding of the manufacturing process.
00:42	This module will be about understanding the DFM considerations for FDM or FFF 3D printing and we'll continue on this topic when putting it all into practice in the next practical section of the course.
00:55	So, let's crack into these considerations, the first of which is the fairly straightforward topic of print size limitations.
01:01	Every printer will have a limited volume that it can print.
01:05	The term volume is used here to describe the 3D space defined by the maximum x and y dimensions, which is essentially the printable area on the bed and the maximum z-axis height.
01:17	We discussed this in the earlier printer performance and metrics module, but most consumer FDM printers will typically be between 100 and 200.
01:32	There's a lot more options available, all with different price tags.
01:36	While some might have different limits on each dimension, for example a larger print bed width than z-axis height, all that really matters is that we know what these limits are for the printer that we intend to use as we design the part.
01:50	It's also worth keeping in mind that getting a larger part 3D printed by a third party manufacturer can be exponentially more expensive.
01:58	Not just because of the amount of material used, but at a certain size the manufacturer will also need to use a larger and more expensive machine and they'll need to charge that out at a higher rate.
02:10	Another thing that's important to understand is that these dimensional limits don't exactly translate to the overall dimensions of the part.
02:18	For example, if the printer is limited to a 250x250x250mm print volume, and our part is 300mm in one dimension, we still might be able to print it.
02:30	That's because the diagonal dimension on the print bed is just over 350mm, whereas the diagonal dimension across the entire volume is just over 430mm, so if we get creative with the print orientation, we can manage to print a much larger part.
02:47	But the downside here is that the print orientation will likely end up compromising other qualities like the layer orientation, and therefore the mechanical properties, or the surface finish.
02:59	That brings us to the next DFM consideration, the mechanical properties.
03:03	This is something we've covered in some detail in the print orientation module, so check back if you need a refresher.
03:10	With this, it's important to understand the loads our design will be subject to, if any, and then choosing a print orientation method.
03:17	to align the strength of the part in this direction.
03:20	This won't always be possible, and again, there will often be compromises, which is why all these factors need to be considered together and as early as possible in the design process.
03:31	If we can't achieve the mechanical properties we want given the constraints, then maybe we need to consider adjusting the design using another material which may prompt a change in printer or even a move to a completely different manufacturing process.
03:45	Another consideration to include is the dimensional accuracy that's achievable with the printer we plan on using.
03:52	As you might expect, some printers, usually by way of better build and component quality, are capable of achieving more accurate results than others.
04:01	It probably won't be surprising that this is generally accompanied by a higher price tag.
04:06	That said, FDM will usually provide an accuracy of up to plus or minus 0.3%.
04:12	So, this depends on the size of the part, but for typical print sizes around 100mm, this ends up being about plus or minus 0.3mm for most parts.
04:24	This is relatively good for plastic 3D printing, although it still falls short of typically injection moulded parts and CNC machining.
04:32	So, we need to keep this in mind for any critical dimensions and allow some tolerance to avoid fit and function issues.
04:40	This might be as simple as opening up or slotting some holes, but in extreme cases, we might need to reconsider the design.
04:48	In saying that, print orientation can go a long way here.
04:52	We discussed this in a previous module, so again check back if you need to refresh it.
04:56	But essentially, we're aligning critical dimensions with the print bed, preventing the effects of gravity and helping with accuracy.
05:04	Another example would be aligning holes with the vertical axis.
05:08	If the holes are horizontal during printing, then there's a higher chance that they'll be out of round.
05:13	For holes where the accuracy of the diameter measurement is critical, it can be best to print them undersized and then drill them out with the correct diameter drill bit afterwards.
05:22	Clearly, any warpage is going to reduce accuracy as well.
05:26	We know how the print settings can cause this.
05:28	But what about the design? The same ideas apply.
05:32	Warping is caused by internal stresses from temperature differentials across the part, usually with the part cooling unevenly.
05:40	While the build plate temperature, cooling fan speed, and enclosure temperature, all impact this, so does the geometry of the part.
05:47	Thin areas with low volume and lots of surface area will cool faster, but also heat faster.
05:54	Avoiding extreme changes in geometry is ideal if possible.
05:58	But, like rounding edges in our design can help lower mechanical stress concentrations, it also helps with thermal stresses.
06:06	In the same vein, minimizing the need for support material in our designs can also be a step in the right direction.
06:13	Sometimes though, there just aren't any workarounds that we can use, so we just need to be aware of the potential discrepancies in design for them, whether this means allowing for looser fits or slotting holes.
06:24	All of what we've discussed have been general ideologies we can keep in mind while designing.
06:30	However, there's still some specific values that we can apply to certain features as well, and while these do vary between different setups, there's still some typical values that we can use.
06:40	Keep in mind that you won't have to remember these, as we've prepared a DFM guide which details these for each form of 3D printing that we'll cover in this course.
06:50	The first feature on the list are walls, of which there's basically two variations, unsupported and supported.
06:57	An unsupported wall is one that connects to the rest of the part only on one side, whereas supported walls connect on at least two sides.
07:05	Often we'll find that supported walls can be printed thinner due to their stronger foundations.
07:11	However, for FDM, the same limitation is applied to both variations, in that the walls should generally be at least 0.8mm thick.
07:20	The minimal hole size should be about 2mm if we want a quality result.
07:25	For accurate small holes though, it's possible to undersize the hole slightly, and then use a precision drill bit to open it up to the desired size.
07:33	The same rule applies for most fine details, where a minimum size of 2mm is suitable for good definition.
07:40	Likewise, embossed features where the details are proud of the face, or engraving where they're into the face, should be at least 2mm in depth or height to be clear and visible.
07:52	However, we can get away with only a 0.6mm width on these features.
07:57	More specific to FDM printing is horizontal bridges, something that we've discussed before.
08:03	This is where we can essentially span gaps between vertical structures without the need for support material.
08:09	The maximum span of these bridges should be around 10mm.
08:13	Chances are, any more than this simply won't work and the bridge will sag or collapse.
08:18	On the topic of support, any continuous overhanging structure will need to be supported at 45 degrees, although we'll typically set the threshold a little bit lower at around 30 degrees from vertical in our slicing software unless we're really trying to push the limit.
08:34	Moving on, we need to discuss infill density, which, rather than being so important, so much of a limitation of additive manufacturing, is more of an advantage over alternative techniques.
08:44	Infill density describes the fullness of the inside of the part.
08:48	Basically, the space between the walls of the part, and this doesn't always need to be completely solid.
08:54	In fact, more often than not, it'll be built up of a structure that results in pockets or voids between printed material.
09:01	We'll usually end up with between 10-50% infill density.
09:06	An example of this structure would be something like a honeycomb inside a beehive.
09:11	But, in reality, there are lots of different ways this structure could be built up, and this is easily set up in the slicing software as we'll see in a coming module.
09:19	This is a great way to reduce weight and also material usage, which, as we know, lowers the part price, but clearly this needs to be considered along with the strength of the part.
09:29	We'll wrap up there and quickly summarise the main points from this module.
09:34	Design for manufacturing requires a sound understanding of the manufacturing process, and keeping the limitations and also the advantages in mind during the design process to ensure that we get the best results.
09:46	For FDM 3D printing, there are fairly clear limitations around the dimensions of the parts we're able to print, but the print orientation can be used to our advantage here.
09:56	We just need to keep in mind any compromises to layer orientation and therefore surface finish, mechanical properties and the accuracy of the printed part.
10:06	Minimising the effects of gravity, warpage and support, should be kept in mind when designing our parts.