Thinking about making a custom, 3D-printed part. However, it would require making a thread (6-32 or 8-32, I can’t remember off the top of my head).
Anyways, would this be a feasible task? I know that delrin can be threaded into, and like the filament used in 3D printers, delrin is made of plastic. If this is something that can be done, what filament was used, and with what print settings?
Thanks
Delrin is an entirely different material to PLA or ABS and is much easier to machine and is supremely stronger, and would definitely be capable of holding a thread. Delrin is known as an “engineering plastic” for these reasons.
I think it is important to make the distinction between an “engineering plastic” and a material like PLA or ABS.
In regards to tapping a thread into 3D printed material, I don’t think that the type of plastic is the issue, it is more method of printing. A printer that uses PLA or ABS prints in layers, meaning that these layers are points of weakness, the thread would have to go through these layers and would be reliant on these for strength. If a part is 3d printed with the hole that is going to be tapped already on the model, there will be concentric circle infill around this and this is the major point of weakness. Ideally the thread and print head nozzle diameter, would have to be selected to ensure that the edge of the thread was not a the point where two of the concentric circles join.
I think it could be feasible, but it would most likely be unsuitable for a high stress/load component.
What you could do is design the component in such as way, that you can use a nut embedded in the print to hold the thread. Make a nut shaped/sized hidden void in the middle of the print. Just before the printer, starts to make the lid of the void, pause the print and place a nut into void. It will then print over the nut and enclose it inside the print
Unless you are looking to use a very course thread, don’t tap into the 3D printed part directly. Instead, use threaded inserts such as Helicoils:
I’ve used Helicoils before in FDM 3D printed parts with good success.
Depends on your printer, some may even be able to print the threads for you.
If you plan on drilling and tapping, you have to make sure the hole placement will have enough “stuff” for you to tap the threads into. As most 3D printers, use some form of internal honeycombing technique on the parts to conserve filament.
If the part is designed right what you ask is possible, however you must consider if the materiel your 3D printer uses is strong enough for the task.
I don’t know how good of an idea this is for a 3d printed plastic part but: Make a hole in the 3d printed part from one side that is the size of the outside of a nut that matches the size you need (in the CAD file of the part itself), or just make a circular hole the size of the diameter of the nut. After this is done secure it in place using epoxy or other methods (3d print over it lol). This would mimic tapping it, although I have absolutely no Idea how well it would work (might be worth trying). I now this is completely anecdotal evidence but, I did this on a wood part for a non-FRC related project and it seemed to hold up pretty good. Good luck!
Oh wait, I didn’t mean 3d printing the thread. I meant making the 3d printed part, then using a tap/die set to make the threads.
Of course, the layers are going to be an issue with this, but if this is possible, then I got access to at least 3 or 4 3d printers with the part I’m thinking about 
What are you planning on doing with said part if you don’t mind me asking?
My team has a tradition for keeping things secret, but I will say that this is going to be interacting with a piston from FESTO, which has around 55-58 lbs of force. At this point, it’s dependent on how strong the part is going to be.
Last year we used brass threaded inserts that we installed using a soldering iron to heat the insert and press into place in the 3D printed part. Worked well for us…
What kind of printer are you using?
Although rather impractical, 3D printing can work for printing threads as long as they are reasonably large. I obviously wouldn’t suggest using them for anything that requires strength, but for securing motor controllers etc, 3D printed nuts and bolts could make a lightweight replacement for steel (Or just use zipties and double sided tape!)
I built my own 3D printer a few years ago, so I often print quite pointless things, such as nuts and bolts.
On our 2015 robot, the big yellow gear is an FDMed ABS plastic part with a tapped hole used for a set screw. Here’s another. These parts were modeled with holes sized for 75% thread, printed with 2-3 shell layers and 20-30% infill, and carefully tapped. Worked fine for this extremely low-load application.
This resource is great for understanding the distinction between types and grades of plastics. Hangs in my office.
If used as a rod end, I don’t really think a 3D printed part will work, because all the force, is trying to pull the thread out the the 3D printed part, the chance of success is dependent on how long the thread is.
Could you run a hex hole in the opposite side of your part and then place a nut in that hole? We used this for a camera mount where the nut was press fit into a hole and it allowed the bolt to thread through from the other side.
My team did this with PLA for a part that supports the entire weight of our FTC robot (~12 lbs) over four screws that are roughly that size. It’s been working just fine for us, but we don’t have nearly as much force on it as you intend to. It was printed on a Makerbot Replicator 2x and I think we used the standard settings for temperature and layer height, but we increased the infill to maybe 20 or 30% and the number of shells to 3. I think the infill won’t really matter for tapping something; the number of shells is going to determine the thickness of the plastic around the holes that you want to tap.
Here’s a picture of the part with the screws in it. Our mountain-climbing mechanism goes on the top and the bottom attaches to our robot’s bellypan.
https://drive.google.com/file/d/0Bzk1HN8KHMZwdVhlQmFZdlp5RVE/view?usp=sharing
THIS. Probably my favorite way to fake threads in a 3D printed part.
Helicoils (as Arthur mentioned above) are also good. I prefer to use the standard threaded inserts from McMaster usually though: McMaster-Carr
They do not require the special helicoil insert tool.
A T nut seems like it was invented for this. Just print the hole the diameter of the T Nut and you’re golden
Yes, this is by far the most effective means of including threads on printed parts.
IMO, the best way (without a helicoil or nut insert) to have an axial loaded internally threaded screw hole in 3D printed parts is to just have an undersized pilot hole and use a coarse thread deep V-groove (not machine thread ) screw that can cut its own thread on 1st installation. Some plastic compatible lube my help avoid tearing up the material as screw forms the thread.
This should also allow for best results when multiple cycles of assembly and disassembly will be needed.
Deck screws come to mind, with a well tapered point. Their coarse thread will give deeper engagement with the plastic and put the plastic adjacent to the hole into tension as the screw enlarges the initially undersized pilot hole as it forms the threat rather than cuts material away.
-Dick Ledford
This really depends on your application. We 3D printed the shooter release mechanism on our 2014 practice robot so we wouldn’t have to machine two. We printed ‘threads’ (they really didn’t turn out well) and forced a nylock nut on the back of it and it lasted all season.
However it’s important to note the part was being loaded in shear and not in tension. **I would not recommend loading a 3D printed / plastic thread in tension for an application that applies a load of more than a few pounds. ** Conversely, I don’t see any problem with using this method to load fasteners in shear. I’ve done this before for personal 3D printed projects and didn’t even bother tapping the hole, I just drilled out the hole with the tap drill and drove the bolt in. YMMV.