At least smaller than what I imagined possible and I was printing small stuff before I got a Zero. I’ve been refining my processes printing small fasteners as they are challenging to print well and in use they give feedback of qualities achieved in smoothness of operation and holding power. The Zero has been great for rapid iterative testing and refinement. It’s also pretty good at precise repeatable motion although I suspect even the cheapest Ender 3 clone could achieve impressive results with the approach I’m developing.
Here’s a print done on my essentially stock Zero with an 0.4 mm nozzle. The thread pitch is 0.4 mm. This has good usable strength despite being printed vertically. It was printed hot for PLA, 230 C, and the layer adhesion is great. I need to set up a testing rig to quantify strength and see what further optimization possible. These were sliced in vase mode with an extrusion width of 0.20 mm and over extrusion to fuse adjacent extrusions and minimize seams. The trick to getting strong parts with vase mode is putting micro cuts in the model to create a convoluted perimeter instead of just getting a simple loop around the apparent perimeter as shown in the bottom image from the slicer. The power of this technique has me thinking about setting up a dev environment for Orca or Prusa slicers and seeing if I can add a hybridized conventional and vase mode slicing option with parametized zig zagged paths especially with respect to overhangs, interior holes and other features that might benefit from this approach.
Typically mine are hollow although asymmetric cut patterns can be used to drive one or more extrusions to the core. The flow rate can also be dialed up to get a more complete fill but that must be balanced with the tolerance modeled between male and female threads as increased flow thickens everything. I have thought about using a script to modify the sliced gcode and every nth layer add a move to the center from the nearest point and then extrude the expected needed volume to fill the core.
I’d be surprised if any of my slicing parameters are stock. I think I have the speed of external perimeters set to 150 or maybe 200 but it is irrelevant as the motions are so tiny the speed is controlled by accelerations never approaching the speed limit. I think my acceleration for that print was 10k and the nut and bolt together print in about 110 seconds at a 0.05 mm layer height.
0.4 mm thread pitch is very impressive with a 0.4 mm nozzle, but so is printing a fastener that’s almost the diameter of the 1.75 mm filament. I love seeing people using 3D printers to do creative things, but I particularly love seeing people 3D printing creative and cutting edge mechanical parts and other functional stuff. Engineering is how I express my creativity, and there is definitely an art to it. Well done. Thanks for sharing.
Printing horizontally also has drawbacks. Print resolution is better in Z than the XY plane typically by a factor of 2 or more so printing horizontally requires a larger tolerance between male and female threads which reduces thread engagement which reduces the amount of torque the threads can take. The threads at the top in Z are printed as isolated islands which makes their quality and strength worse. Max torque is further impacted when the bolt is clipped to eliminate the need for support by the fraction of the bolt clipped off the bottom. Also clipping the head of the bolt decreases the functionality of hex head bolts and wrecks some types such as socket heads. Resistance to cross threading is also impacted by horizontal printing.
My approach should work great for larger fasteners. I first started doing fasteners in the range of 4 to 7 mm where it worked quite well before pushing it smaller. I haven’t yet tried but expect the quality will improve as size increases. I’ve made further improvements and will post new photos in another day or two.
I was very impressed with your method that has a continuously printed helical thread. That’s going to be very strong and uniformly so, as well as accurate, but seems more applicable to small fasteners. I did consider that horizontally printed larger fasteners would have little dots of plastic at the top of each thread peak which would not print well and would have poor layer adhesion, but that seemed less of a problem than slicing 20% off the diameter of the thread on one side so it could lay flat on the build plate. In my comment under the video, I stated that I’d leave the bolt head intact and would design rectangular print-in-place support for the flat side of the removed side of the threads.
Vase mode is going to be best for small fasteners, without question. I can see pros and cons of horizontally printed larger fasteners.
Apologies if you consider this a thread hijack. If so, let me know and I’ll gladly delete my comments.
No apology needed. Discussion is good. The video you posted is a good method for some cases and somebody should benefit from it.
I want to start doing measured strength testing soon. I think the layer adhesion I am getting is excellent when printing hot in vase mode with small extrusions but I need better testing to be certain and to fine tune the ideal print temperatures and flows of the various filaments I use.
Here are drivers one with a bolt loaded and the other with a nut prior to assembly. The drivers were modeled similar to the fasteners with radial cuts to force a radial extrusion path. They were sliced in vase mode with a 0.18 mm extrusion width but printed with a 0.4 mm nozzle which resulted in the tiny holes between the ribs. Each driver weighs a bit less than a gram but feels solid and mates to the fasteners surprisingly well.
Here is a close up of the M14 from a different angle such that the lighting better reveals the trapezoidal thread form which handles more torque than a triangular thread. This radial extrusion pattern allows the steeper overhangs of this thread to be printed cleanly even when printed hotter for better layer adhesion.
I’m loving this thread. Very impressive. Those gray parts look like they were resin printed. I’m not sure if I have an application for this but having seen the results, I’d like to try printing fasteners. Thanks for sharing this.
They were modeled in openscad. The threads were done using the BOSL2 library. These threads are similar to ACME threads, except ACME threads use a 29 degree angle and these have a 10 degree angle for a closer to square profile.
I like the feel of these fasteners printed with radial extrusion. They can spin with minimal play, especially at larger sizes. Typically parts like this need to be modeled with a tolerance such that the nut diameter is 0.6 mm or more larger than the bolt diameter to compensate for the tendency of circular extrusions to draw inward as they are laid down and as they cool. This effect increases with overhang deforming threads so the tolerance often needs to be greater than used for vertically printed round pins and holes. Tolerances can also be affected by print speed, temperature, filament and layer height. As fit loosens triangular threads rapidly lose engagement and torque capacity, so achieving an appropriate tolerance can be a critical and fussy process leaving many with the impression that FDM printing threaded fasteners is stupid. But with these radially extruded fasteners the tendency of the extrusions to draw inward and shrink is lessened and the effect is reversed such that the hole is pulled slightly larger not smaller and male and female parts can be modeled to the same size without a tolerance factor. Tightness of fit can be increased with over extrusion but the need to fuss with it is greatly lessened. In this case as a first guess based on experience with parts at other sizes I modeled these parts with a 0.38 mm spacing at their closest for extrusions and had the slicer use a 0.42 mm extrusion. As I try to show in this video, the result is good with little need to tweak.
Once you get the parameters dialed in you could provide a great service to the 3D printing community by sharing your results on Printables. A 3mf slicer file with the settings would be great and a full set of 3D printable STL files for various diameter nuts and machine screws of different lengths would be even better.
There is a certain coolness factor in 3D printing the entire project, including matching fasteners. I would like to try this. I’m now actively looking for a project where I can use 3D printed fasteners.
As for projects for printed fasteners, this one that you @Liberty4Ever have already seen is a good one that I enjoyed making and using. Advice before purchasing - #20 by HandyDoodads It uses two custom fasteners, a double ended male fastener with a flared waist allowing two sections of internally threaded rod to be joined nearly seamlessly and a bolt with a head which attaches the internally threaded rod to an end frame with the head recessed into the frame. The fasteners were designed to be snug eliminating the need for loctite or lock washers. In this case the primary loading is perpendicular to the fasteners and the maximum loading is modest so the strength of these printed fasteners is good enough. The structure is sufficiently overkill for the intended use that the parts other than the vase mode fasteners and threaded rod were printed with 1 perimeter and 5% infill and the entire project only used about 500 g of filament. Steel hardware would add cost and possibly increase complexity of the design and assembly. Might also detract from the aesthetics and likely only gain unneeded strength.
I’m now thinking optimizing this approach will be more challenging then when I started this thread. In the past few days the weather here has significantly warmed. My printer is in our attic, a passively heated room that was 45 to 50 F much of the winter. For the past week at temps of 60+ F I noticed changes in printed overhangs. What I had attributed solely to the different extrusion pattern was in part due to the Zero’s excellently performing part cooling and aux fans when run full blast in a cold environment. To compensate for the warmer temps I began by decreasing the extrusion temp and discovered that as the extrusion temp falls the accuracy of extrusions smaller than the nozzle diameter declines. So I also increased the modeled thread angle from 10 to 20 degrees. In this fussing I learned this radial extrusion pattern decreases thread size radially more than I thought and thus engagement and torque capacity are likely worse than I imagined. I have yet to do quantified strength tests which will be essential to understanding and balancing the various trade offs in geometry and slicing parameters.
In preparation for strength testing I implemented another approach to making micro cuts in the model’s perimeter which has extrusions meeting at the core when sliced in vase mode.
Then I discovered that the longer extrusions to the core also shrink more resulting in a little more thread deformation and increase the tendency of overhangs to curl up. So I increased the thread angle from 20 to 25 degrees for better threads and could end up at the ACME angle of 29 degrees for trapezoidal threads.
I still think this approach can be worthwhile but it will be fussy to optimize fasteners for core strength versus thread strength and for strength in tension vs compression or shear. For strength testing I have been looking at Digital Force Gauges, probably 110LB/500N, on Amazon. Among the lower cost ones I’ve only seen hand pull gauges. I want the gauge inline with a mechanical load for consistent repeatable tests and I am considering 3d printing an adapter for inline testing with a cheap hand pull gauge. Any thoughts or suggestions will be appreciated.
Here’s something I just did utilizing this approach for making small custom printed fasteners. It’s a screw assembled axial roller bearing, 18 mm od, 5.5 mm thick, 5.1 mm id. The fastener mainly needs to hold it together when unloaded as when the part is under load the fastener is unloaded. The glop in the photos is the lubricant which is super helpful to stick these tiny parts in place during assembly. The entire thing weighs about 1 gram.
In my comment under the video, I stated that I’d leave the bolt head intact and would design rectangular print-in-place support for the flat side of the removed side of the threads.
… bad jokes aside, that is some incredibly detailed printing, impressive work!
