Practical 3D Printing: Finishing The Part

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Finishing The Part

06.04

00:00	With the print complete we're on to the post-processors and any finishing touches, which as always varies considerably for different parts.
00:07	Depending on the application, some parts will be ready to use straight out of the printer, whereas others will require post -processors applied by the manufacturer or even ourselves once we've received it.
00:19	Let's continue with our intake manifold worked example to show some common actions here, picking up immediately after the part was finished printing.
00:27	As we know the beauty of SLS is there are no support structures to be removed from the part, but with that said, upon removing the part from the build chamber the manufacturer will remove all the excess powder, collecting what they can to recycle.
00:43	This de-powdering is often done with a brush initially and then through media blasting with small glass beads and the help of compressed air.
00:52	What happens next depends on the post -processing requirements that we selected for the print.
00:57	In our example we chose smoothed, sealed and dyed, but there's other options like priming and painting, added threaded inserts or even a range of quality checks.
01:08	Let's start with smoothing which can be done a few different ways.
01:11	One common option is media tumbling, where the part is placed in a vibrating tumbler with small ceramic chips.
01:18	After a few hours this produces a smooth satin finish on the parts.
01:24	For our example the manufacturer Prototech used the vapour smoothing process.
01:29	The much-like Acetone-vapour smoothing process which we discussed in the FDM section of the course, where the part is exposed to solvent vapour.
01:38	The combination of heat and solvent vapour selectively melts the surface, smoothing and sealing it.
01:45	Prototech reached out, and expressed some concern that during the process the deep internal areas of the vacuum rail on our manifold might not be roomed and sealed as well as the rest.
01:56	Protontech has Since this isn't a visible area and will only be exposed to airflow we were happy to proceed.
02:02	It's more important for the outside surfaces and also the inside of the runners to be smoothed and also the outside to be sealed to protect it from grease, oil and fuel in the engine bay.
02:13	Following this process the part was dyed black.
02:16	The natural white color of the part would quickly get dirty and discolor in an application like this so it's really just for aesthetic purposes.
02:24	This is done simply by submerging the part in a solution of dye and hot water for about 10 minutes or so and really only dyes the surface of the part to a depth of around half a millimeter.
02:35	Alternatively the parts can be primed and painted just as we discussed with our FDM parts.
02:41	Check back to that section of the course if you want a refresher.
02:44	While SLS and MJF parts are reasonably watertight there are other coatings available for the purposes of increasing these properties for parts that might be regularly exposed to water like on the outside of a vehicle in wet climates.
02:59	At the pointy end of the spectrum we have electroplating or metal coating which can be done with materials like copper, gold, nickel, chrome or stainless steel.
03:09	These go some way in bridging the gap between plastic and metal parts improving the strength and durability while also providing an excellent surface finish.
03:18	That covers off the surface finishes but we still need to discuss threaded features.
03:24	As we know printing threads directly and chasing them with a tap, forming threads from scratch or using nut pockets or threaded inserts are all options for thermoplastic materials used in SLS.
03:36	The details around these are much the same as what we discussed in the FDM section of the course.
03:42	So, again check back to the threaded features module at the end of that section if you're hazy on the details.
03:48	If we'd printed threads directly or made holes for the threads at this point we'd turn to our taps, to form or tidy them up.
03:56	Prototech, the manufacturer of our intake manifold worked example, offers tapping and inserts as a post processing option which we've used to make our lives easier.
04:06	Recalling the earlier CAD and printing modules in this section of the course, we sized the holes for mounting the throttle bodies appropriately for threaded inserts and created a technical drawing designating the holes that required them.
04:19	So, all we needed to do was select the tapping and inserts option from the post processing list, and attach our drawing.
04:27	Again, Prototech was nice enough to capture this for our course.
04:31	First they confirmed the holes are the correct size for the threaded insert piece.
04:36	Then just like we've covered in our practical skills a technician uses a soldering iron with a special tip to heat the insert until it begins melting the surrounding plastic and pushes it down into the hole a specified amount.
04:48	Finally, any plastic that was displaced by the insert is cut away to leave the surface clean.
04:54	We received the parts with the inserts in place and unsurprisingly the throttle is mounted up perfectly and securely.
05:01	Before we install the parts for use on the engine we should ensure all the powder has been properly cleaned out as we really don't want any left overs going through the engine.
05:11	A quick blast with compressed air gets this job done.
05:14	That brings us to the end of our post processes and finishing touches for SLS prints.
05:19	So, let's summarize the main takeaways.
05:23	Unsurprisingly, the post processing process for SLS prints are much the same as FDM prints as we're working with similar thermoplastic materials.
05:31	The key difference being that the manufacturer will usually apply these for us as part of their service although naturally this comes at an additional cost.
05:40	After de-powdering the printed part this could include media tumbling or blasting or vapour smoothing and sealing.
05:47	Following this the part may be dyed, primed or painted for aesthetic purposes or given functional coatings like electroshoots.
05:54	Finally, threaded features are created whether that's via tapping or the use of inserts.