Practical 3D Printing: DFM - Design For Manufacturing

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DFM - Design For Manufacturing

05.16

00:00	Many of the same DFM or Design for Manufacturing considerations for FDM 3D printing also apply for SLA.
00:08	For example, the part size limitations based on the printer's build volume, which is often smaller for SLA printers.
00:15	Rather than covering all these again, if you're hazy on the details, be sure to check back to the DFM module in the FDM section of this course for a refresher.
00:25	This module is going to be about driving home some of the key points around the details of SLA printing that we've already covered, as well as introducing a few SLA specific considerations, particularly around the size of features.
00:40	What's always important is that we design parts with the manufacturing limitations, but also advantages in mind, making sure that we're using the right type of 3D printing for the job.
00:51	SLA lends itself to high detail and good surface finish.
00:55	So, if these are the priorities for our project, then we'd typically choose SLA over FDM.
01:01	But there are still limitations on the size of the details that we can include.
01:06	If we go too small, they'll lose definition.
01:08	Another way to look at this is if we have access to SLA printing, then we can include finer details in our design.
01:16	On that topic, let's discuss some typical values that we can apply to certain features.
01:21	Again, you won't have to remember these as we've prepared a DFM guide that you can refer back to for each form of 3D printing that we'll be covering in this course.
01:30	Unsupported walls, which are those that connect to the rest of the part on only one side, should be at least 1mm thick.
01:38	Whereas supported walls, which connect on at least two sides, can get away with being thinner at a minimum of only 0.5mm due to their stronger foundations.
01:49	As you'd expect, the size of features in SLA can typically be much smaller than FDM.
01:55	For example, the minimum hole size can be as small as 0.5mm with quality results.
02:01	Whereas for FDM, this is usually closer to 2mm.
02:05	The same rule follows for most fine details, where a minimum size of 0.5 is suitable for good definition, but this can be pushed as low as 0.2mm in some cases.
02:17	On that note, due to the increased resolution, SLA allows for finer threaded features to be included in the print.
02:24	Although, with that said, the strength of the threads isn't going to be very strong, so we'll still typically turn to nut pockets for more demanding fixtures.
02:33	More specific to SLA printing is escape holes.
02:36	Something we've discussed previously and are required to drain uncured resin from any enclosures or hollowing of the part.
02:43	For these, we should target a minimum of 4mm diameter for these to ensure that the resin can escape easily.
02:50	These escape or relief holes for avoiding potential suction cups on the release film during printing need to be kept in mind during the design phase, as adding these features as an afterthought could be a compromise if they were not factored into the design.
03:04	Clearly, this requires a lot of forward thinking and understanding the manufacturing process to foresee these issues during the design process and typically requires some trial and error, which might lead to revisions.
03:17	Like any manufacturing process, we must also consider the accuracy that's achievable and use suitable tolerances in our design.
03:25	SLA is known for its high resolution, but also its accuracy.
03:29	And will usually provide an accuracy of up to plus or minus 0.2%, so this depends on the size of the part.
03:37	But for typical print sizes around 100mm or so, this ends up being about plus or minus 0.2mm for most parts.
03:45	As always, we need to keep this in mind for any critical dimensions and allow for some tolerances to avoid fit and function issues.
03:53	This might be as simple as opening up the lid.
03:55	Or slotting some holes.
03:56	However, there are features of our design, along with the print settings, that can help avoid inaccuracies.
04:03	For example, trying to maintain a consistent cross-section area will help prevent internal stresses from the curing process that can cause warpage.
04:12	Avoiding large overhangs or other unsupported structures will help here.
04:16	Essentially, we want to design the part with stiffness in mind and that might mean adding some extra bracing to support the structure.
04:24	The main things to understand from this module are that we first must choose the appropriate manufacturing method and materials for the application.
04:32	Then, it's a matter of keeping the limitations and benefits of the process in mind and designing around these to get the most from our project.
04:40	A lot of the same considerations we need to keep in mind for FDM 3D printing also apply to SLA.
04:47	And often we'll find that what's ideal for one aspect leads to compromises in another.
04:53	Specific to SLA, we need to keep in mind how the curing process, print orientation and supports impact our design and the quality of the print.
05:02	And try to design the part to avoid potential issues with warpage, surface finish and even print failures from excessive release forces that could damage the release film as well.