The Best Threaded Holes For Resin Parts

November 1, 2022 by Danie Conradie 21 Comments

Threaded inserts are great for melting into FDM prints with a soldering iron. The process isn’t so simple for resin prints, since they don’t generally soften with heat. Off course, you can also print the threads directly, screw a bolt into an un-threaded hole, or tap a hole. Following his usual rigorous testing process, [Stefan] from CNC Kitchen investigated various ways of adding threaded holes to resin prints.

After establishing a pull-out force on PLA using threaded inserts (205 kg) and tapped holes (163 kg), [Stefan] tested parts printed with Prusament Tough Anthracite resin. Un-threaded and tapped holes failed at 44 kg and 55 kg respectively, while printed threads were almost twice as strong, reaching 106 kg before breaking. Stephan also tried gluing inserts into the parts using resin and CA glue. The resin didn’t cure properly in the opaque parts (6 kg) while CA was comparable to plastic threads, failing at 52 kg.

Chart of results — TLDR: Print your threads for best results

[Stefan] also tested regular ELEGOO Translucent resin. The higher hardness of the cured resin allowed the parts to hold on to around 100 kg for un-threaded and tapped holes, while printed threads reached 120 kg. Threaded insert glued with resin did better on the transparent parts thanks to improved UV penetration, but were very inconsistent. Inserts glued with CA performed about the same as on the Prusament parts, failing at 56 kg.

In an attempt to improve the performance of the inserts [Stefan] printed some parts with stepped holes to match the geometry of the inserts, which had the advantage of preventing the insert from falling through during gluing. It only made a marginal difference on the Prusament parts but boosted the strength of CA-glued inserts on the ELEGOO resin to 82 kg. Two-part epoxy was also tried, which matched the un-threaded holes in strength.

So for resin parts you’ll probably be best served by just modeling the threads in CAD and printing them directly. If you need to be able to repeatedly screw and unscrew fasteners in a hole without stripping, threaded holes with CA or epoxy might be a better solution.

Continue reading “The Best Threaded Holes For Resin Parts” →

3D Printed Strain Wave Gearbox

October 31, 2022 by Danie Conradie 19 Comments

3D-printed gearboxes are always an interesting design challenge, especially if you want to make them compact. [ZeroBacklash] created a little strain wave gearbox (harmonic drive) for when you want to trade speed for torque on NEMA 17 stepper motors.

Strain wave gears work by deforming a stationary flexible spline into an ellipse so the teeth engage the internal teeth of the output spline. Add a couple of extra teeth on the output side, and you get a high-reduction gearbox with fewer parts and reduced volume than equivalent spur gearing. Keeping the flexible spline stationery is achieved by making half of it engage with a stationary spline with the same number of teeth.

In this case, there are 60 teeth on the input side and 62 on the output, giving a gear ratio of 30:1. The flexible spline is deformed using a set of bearing balls and an elliptical plug on the shaft of the motor. It makes for a compact design that matches the frontal size of the stepper motor and is only about 27 mm long. [ZeroBacklash] has not released any design files, but the idea should be simple to replicate.

We’ve featured a couple of 3D printed harmonic drives of different sizes, but they usually use a pair of ball bearings as the wave generators, which doesn’t lend itself well to smaller designs.

3D Printed Heat Exchanger Uses Gyroid Infill For Cooling

October 31, 2022 by Danie Conradie 33 Comments

3D printing allows the physical manufacturing of some unique geometries that are simply not possible with other processes. If you design around these strengths, it is possible to create parts that significantly outperform more conventional alternatives. With this in mind [Advanced Engineering Solutions] created a metal 3D printed heat exchanger that is half the size and four times the efficiency of the one it was designed to replace. Video after the break.

Gyroid infill splits an internal volume in two, perfect for heat exchangers.

Made from an aluminum alloy using a Laser Powder Bed Fusion (LPBF) machine, the heat exchanger is intended to cool transmission oil on military helicopters by using fuel as the coolant. Looking somewhat similar to a Fabergé egg, it uses gyroid “infill” for the actual heat exchange part. An interesting characteristic of gyroids is that it creates two separate intermeshed volumes, making them perfect for this application.

It was printed in one piece, without any removable support, just an internal lattice that supports the gyroids at the inlet and outlets. The only post-processing required was threading and surface cleanup on the ports. Since metal 3D printing is still too expensive to really allow many iterative prints, a significant amount of design and simulation time was put in before the first print.

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Stop Silicone Cure Inhibition, No Fancy Or Expensive Products Required

October 30, 2022 by Donald Papp 16 Comments

Casting parts in silicone is great, and 3D printing in resin is fantastic for making clean shapes, so it’s natural for an enterprising hacker to want to put the two together: 3D print the mold, pour in the silicone, receive parts! But silicone’s curing process can be inhibited by impurities. What’s cure inhibition? It’s a gross mess as shown in the image above, that’s what it is. Sadly, SLA-printed resin molds are notorious for causing exactly that. What’s a hacker to do?

Firstly: there are tin-cure and platinum-cure silicones, and for the most part tin-cure silicone works just fine in resin-printed molds. Platinum-cure silicones have better properties, but are much more susceptible to cure inhibition. Most workarounds rely on adding some kind of barrier coating to molds, but [Jan Mrázek] has a cheap and scalable method of avoiding this issue that we haven’t seen before. Continue reading “Stop Silicone Cure Inhibition, No Fancy Or Expensive Products Required” →

Playing With The Power Of Full G-Code Control

October 30, 2022 by Danie Conradie 5 Comments

Slicing software needs to maintain a balance between ease-of-use and control, while handling handle any STL file you throw at it. If you eliminate the need to convert an existing 3D model, and create G-Code directly, you gain a lot of design freedom, at the cost of increased design effort. By taking advantage of this freedom and making it more accessible, [Andrew Gleadall] and [Dirk Leas] created the FullControl Design Library.

Each model is a mathematically generated extrusion path with a host of adjustable design parameters and print settings. This allows you to print things like a single-layer non-planar part, or 90° overhangs without any support (video after the break). The website was built using the python version of the original Excel-based FullControl Designer (unreleased at the time of writing), and threejs for the 3D visualization.

Go browse the library, play with some parameters and see what strikes your fancy. For ideas, help and updates, keep an eye on the FullControl Subreddit.

Continue reading “Playing With The Power Of Full G-Code Control” →

3D Printer Slicing In The Manufacturing World

October 29, 2022 by Al Williams 10 Comments

It is no secret that the way you build things in your garage is rarely how big companies build things at scale. But sometimes new techniques on the production floor leak over to the hobby builder and vice versa, so it pays to keep an eye on what the other side is doing. Maybe that was the idea behind [Carolyn Schwaar’s] post on All3DP entitled “Beyond Cura Slicer: 3D Printing Build Prep Software for Pros.” In it, she looks at a few programs that commercial-grade 3D printers use for slicing.

The differences in the software we typically use and those meant to work with a dedicated high-end machine are pretty marked, but maybe not in the way you would expect. While you might expect them to have tight integration with their target machine, you might not expect that they usually offer less control over parameters than a product like Cura. As a quote in the post points out, Cura has over 400 settings. Commercial 3D printers don’t have time to tweak those settings endlessly. So the emphasis is more on canned profiles that just work.

Not all of the programs are tied to machines, though. Commercial CAD offerings are becoming more capable with 3D printers and can sometimes slice and send jobs to printers directly. Regardless of software type, though, everyone needs certain functions: design, repair, simulation, build plate layout, and more.

If you are looking for a hobby-grade slicer other than Cura, we’ve been using SuperSlicer which is a fork of PrusaSlicer, which is a fork of Slic3r lately.

3D Printing Gets Small In A Big Way

October 26, 2022 by Al Williams 8 Comments

If you have a 3D printer in your workshop, you probably fret more about how to get bigger objects out of it. However, the University of Amsterdam has a new technique that allows for fast large-scale printing with sub-micron resolution. The technique is a hybrid of photolithography and stereolithography.

One of the problems with printing with fine detail is that print times become very long. However, the new technique claims to have “acceptable production time.” Apparently, bioprinting applications are very much of interest to the technology’s first licensee. There is talk of printing, for example, a kidney scaffold in several hours or a full-sized heart scaffold in less than a day.

Another example application is the production of a chromatography instrument with 200 micron channels and 20 micron restrictions. This requires a printer capable of very fine detail. There are also applications in semiconductors and mechanical metamaterials. Of course, we always take note of photolithography processes because we use them to make PC boards and even integrated circuits. A desktop printer that could do photolithography might open up new ideas for producing electronic circuitry.

If you want to play with photolithography today, [Ben Krasnow] has some advice. Of course, there are several ways to produce PC boards, even with a garden-variety 3D printer.