Practical 3D Printing: Tapping Threads & Threaded Inserts
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Tapping Threads & Threaded Inserts
05.43
| 00:00 | In the previous module we covered the finishing processes we could use on FDM 3D printed parts in the interest of improving the surface appearance. |
| 00:08 | However, surface finish isn't the only factor that requires post-processing following printing. |
| 00:14 | The other key area that needs attention is around threaded features, which is something that we discussed at the end of the last section of the course, so be sure to check back if the details seem hazy. |
| 00:25 | We've also looked at the use of nut pockets in practice earlier in this section of the course, so in this module we'll specifically cover the practical skills around tapping threads and using heat-set threaded inserts. |
| 00:38 | Let's start by creating a very simple part in Fusion to experiment with the different options of tapping threads into 3D printed parts, chasing printed threads, and using threaded inserts. |
| 00:50 | The first step is sketching a rectangular shape with three hole positions and then extruding it down 15mm or so. |
| 00:57 | Then we can use the hole tool to make each hole. |
| 01:00 | The first will be tapped with a M5 by 0.8 thread. |
| 01:04 | A good rule of thumb to determine the hole size is one commonly used for metal parts, where we subtract the thread pitch from the size of the hardware. |
| 01:12 | For this example, M5 minus the 0.8mm thread pitch leaves us with a 4.2mm hole. |
| 01:21 | Next, we'll create the threaded M5 by 0.8 hole. |
| 01:25 | And the important part here is selecting the modeled preference so the 3D model of the thread is actually created. |
| 01:32 | Finally, we need a hole for the threaded insert. |
| 01:35 | The dimensions of the hole we need to make depend on the threaded insert that we're working with. |
| 01:40 | Generally, the suppliers of the inserts will specify these dimensions, so we can simply follow them. |
| 01:46 | For the M5 inserts we're using from CNC Kitchen, the hole should be 6.4mm in diameter and no less than 10.5mm deep. |
| 01:55 | This hole diameter allows a 6.3mm lead-in on the insert to help square it up to the hole and as we push it in, it also gives it plenty of interference with the 7.1mm diameter of the knurled section. |
| 02:08 | We'll print the part from PLA and the only thing we need to keep in mind from here is the shell thickness or the number of wall loops. |
| 02:16 | With a 0.4mm nozzle, the width of each loop ends up being around 0.5mm. |
| 02:22 | The supplier of the threaded inserts This requires a minimum of 2.6mm for the wall thickness. |
| 02:28 | In other words, we need 6 wall loops, which is quite a lot. |
| 02:32 | This will also be plenty of material for the tapping process as well. |
| 02:37 | After the part is printed, we're ready to start creating our threaded features. |
| 02:41 | Let's look at the pre-printed threads first. |
| 02:44 | If we try thread an M5 by 0.8 machine screw into these as they are, you'll notice that they're too tight and this simply comes down to the thread not being accurate enough, which is why we're going to chase it with a tap. |
| 02:56 | It's best to use what's called a bottoming tap for this, which is essentially a tap with only a very short lead-in for the threads. |
| 03:03 | Because we already have some threads, it's easy to get this tap started. |
| 03:07 | Plastic is very easy to work with compared to metal, even aluminium, so it doesn't take too much effort to cut the thread and it's easy on the tooling. |
| 03:16 | Once we've chased the thread, we can retry our hardware and see how much nicer the threads feel. |
| 03:22 | For the blank hole, we'll start with a tapered or intermediate tap, as we'd use for any metal part. |
| 03:27 | In this part, where the hole goes all the way through, we can get the job done with this tap alone. |
| 03:33 | However, for a blind hole that doesn't pass through the entire thickness of the part, we'd need to swap to a bottoming tap to cut the threads down to the bottom of the hole. |
| 03:42 | Again, we'll check our work with our hardware to make sure everything feels good. |
| 03:47 | Finally, we're on to the threaded insert. |
| 03:49 | Before we heat up the soldering iron though, we need to attach the specific tip to the hole. |
| 03:53 | We need to attach the tip to the soldering iron for our size insert. |
| 03:56 | Moving on, we want the temperature of the soldering iron to be above the melting point of the plastic. |
| 04:02 | Say 30 to 50 degrees Celsius higher than the nozzle temperature for that material. |
| 04:07 | It should go without saying that care needs to be taken with this tool when it's hot to avoid burning yourself or anything else that it comes in contact with. |
| 04:15 | Next, we can use our hands to get the threaded insert started on the tapered lead end. |
| 04:20 | Some cheap inserts won't have this. |
| 04:22 | So, it's just something to be aware of when shopping around. |
| 04:25 | Now, we can position the soldering iron tip into the insert and apply some pressure. |
| 04:29 | Being patient and waiting for the heat to be transferred to the insert and for the plastic to soften. |
| 04:35 | The insert will start to move down into the part with pressure. |
| 04:39 | We want to stop when the top surface of the insert is flush with the surface of the part. |
| 04:44 | Once cooled, which shouldn't take very long, we can check that our hardware threads in nicely and everything feels sturdy. |
| 04:51 | And that's all three methods covered, so let's recap this module. |
| 04:55 | Post printing processes can involve creating threaded features in our parts. |
| 04:59 | This needs to be considered when modeling the parts in our CAD software so we can create the correct hole size or model the thread. |
| 05:07 | We also need to allow for enough shell thickness or number of wall loops in our slicing software when tapping threads or using threaded inserts. |
| 05:15 | If we print the threads, we'll need to chase them with a bottoming tap to clean them out. |
| 05:20 | Alternatively, if we're tapping threads from scratch, we can start with an intermediate or tapered tap and might also follow this with a bottoming tap. |
| 05:28 | Then, using a soldering iron with a special tap, we can carefully press them in so the top surface is flush with that of the part. |
| 05:35 | Just remember to be patient as the insert comes up to temperature and melts the plastic. |
