Repairing A Gear With A Candle (and Some Epoxy)

March 19, 2024 by Al Williams 19 Comments

You have a broken gear you need to fix, but there’s no equivalent part available. That’s the issue [Well Done Tips] faced with a plastic gear from a lawnmower. While we’d be tempted to scan the gear, repair the damage in CAD and then 3D print a new one, we enjoyed hearing about his low-tech solution. In addition to the write up, there’s a video showing the process you can watch below.

The idea is pretty simple. Using a piece of pipe and melted candle wax, he prepared a mold of an undamaged section of the gear. Then he cast epoxy resin in place to recreate the missing pieces. There are a few tricks, like putting holes in the remaining part of the gear so the epoxy flows into the existing part. Depending on the gear’s purpose and original material, you might be able to just use it as-is. However, you could also use the repaired gear as a template to create another mold and then cast an entire gear from resin or even metal if you can cast metal.

You can argue whether resin is better or worse than PLA, but of course, it depends on the kind of resin—photopolymers are different from epoxy resins you’d use for this sort of thing. If you think you might like to make your new gear out of aluminum, you might find some inspiration in a previous post.

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Stripped Clock Wheel Gets A New Set Of Teeth, The Hard Way

March 29, 2023 by Dan Maloney 13 Comments

If there’s one thing we’ve learned from [Chris] at Clickspring, it’s that a clockmaker will stop at nothing to make a clock not only work perfectly, but look good doing it. That includes measures as extreme as this complete re-toothing of a wheel from a clock. Is re-toothing even a word?

The obsessive horologist in this case is [Tommy Jobson], who came across a clock that suffered a catastrophic injury: a sudden release of energy from the fusee, the cone-shaped pulley that adjusts for the uneven torque created by the clock’s mainspring. The mishap briefly turned the movement into a lathe that cut the tops off all the teeth on the main wheel.

Rather than fabricate a completely new wheel, [Tommy] chose to rework the damaged one. After building a special arbor to hold the wheel, he turned it down on the lathe, leaving just the crossings and a narrow rim. A replacement blank was fabricated from brass and soldered to the toothless wheel, turned to size, and given a new set of teeth using one of the oddest lathe setups we’ve ever seen. Once polished and primped, the repair is only barely visible.

Honestly, the repaired wheel looks brand new to us, and the process of getting it to that state was fascinating to watch. If the video below whets your appetite for clockmaking, have we got a treat for you.

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Clever Mechanism Powers This All-Mechanical Filament Respooler

March 25, 2023 by Dan Maloney 12 Comments

No matter how far down the 3D printing rabbit hole we descend, chances are pretty good that most of us won’t ever need to move filament from one spool to another. But even so, you’ve got to respect this purely mechanical filament respooler design, and you may want to build one for yourself just because.

We were tipped off to [Miklos Kiszely]’s respooler via the very enthusiastic video below from [Bryan Vines] at the BV3D YouTube channel. He explains the need for transferring filament to another spool as stemming from the switch by some filament manufacturers to cardboard spools for environmental reasons. Sadly, these spools tend to shed fibrous debris that can clog mechanisms; transferring filament to a plastic spool can help mitigate that problem.

The engineering that [Miklos] put into his respooler design is pretty amazing. Bearings excepted, the whole thing is 3D printed. A transmission made of herringbone gears powers both the take-up spool and the filament guide, which moves the incoming filament across the width of the spool for even layers. The mechanism to do this is fascinating, consisting of a sector gear with racks on either side. The racks are alternately engaged by the sector gear, moving a PTFE filament guide tube back and forth to create even layers on the takeup spool. Genius!

Hats off to [Miklos] on this clever design, and for the extremely detailed instructions for printing and building one of your own. Even if you don’t have the cardboard problem, maybe this would help if you buy filament on really big spools and need to rewind for printing. Continue reading “Clever Mechanism Powers This All-Mechanical Filament Respooler” →

Radial Vector Reducer Rotates At Really Relaxed Velocity

December 5, 2022 by Ryan Flowers 15 Comments

When [Michael Rechtin] learned about Radial Vector Reducers, the underlying research math made his head spin, albeit very slowly. Realizing that it’s essentially a cycloidal drive meshed with a planetary gear set, he got to work in CAD and, in seemingly no time, had a design to test. You can see the full results of his experiment in the video below the break. Or head on out to Thingiverse to download the model directly.

[Michael] explains that while there are elements of a cycloidal drive, itself a wonderfully clever gear reduction mechanism, the radial vector reducer actually has more bearing surfaces, and should be more durable as a result. Two cycloidal disks are driven by a planetary gear reduction for an even greater reduction, but they don’t even spin, they just cycle in a way that drives the outer shell, setting them further apart from standard cycloidal drives.

How would this 3D printed contraption hold up? To test this, [Michael] built a test jig with a NEMA 23 stepper providing the torque, and an absurd monster truck/front loader wheel — also printed — to provide traction in the grass and leaves of his back yard. He let it drive around its tether for nearly two weeks before disassembling it to check for wear. How’d it look? You’ll have to check the video to find out.

If you aren’t familiar with cycloidal drives, check out this fantastic explanation we featured. As for planetary drives, what better way to demonstrate it than by an ornamental planetary gear clock!

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Simple CNC Gear Production With Arduino

October 10, 2022 by Al Williams 21 Comments

We’ve seen plenty of people 3D printing custom gears over the years, but [Mr Innovative] decided against an additive process for his bespoke component. He ended up using a simple CNC machine that makes use of several components that were either salvaged from a 3D printer or produced on one. Using a small saw blade, the machine cuts gear teeth into some plastic material and — presumably — could cut gears into anything the saw blade was able to slice into, especially if you added a little lubrication, cooling, and dust removal.

If you’ve built a 3D printer, you’ll see a lot of familiar parts. Stepper motors, aluminum extrusion, straight rods, bearing blocks, and rod holders are all used in the build. There’s also a lead screw and the associated components you usually see in a printer’s Z-axis. Naturally, an Arduino drives the whole affair.

The saw blade was custom-made from a washer, grinding an edge and using a 3D printed template to cut teeth in it. We might have been more inclined to use a cut-off wheel from a rotary tool, but this certainly did the trick. An LCD accepts the gear diameter and number of teeth. The stepper rotates the correct number of degrees and another stepper lowers the cutting head which is spinning with a common DC motor.

As impressive as this machine is, the fact remains that a 3D printer can produce more complex designs. For example, a herringbone pattern can help with alignment issues. It has been done many times. You can even use a resin printer, although you might prefer to stick with FDM.

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New Gear Saves Old Printer

July 5, 2022 by Jenny List 18 Comments

As the digital photographic revolution took off, and everyone bought a shiny new film-less camera, there was a brief fad for photo printers. The idea was you’d have the same prints you’d always had from film, but the media for these printers would invariably cost a fortune so consumers moved on pretty quickly.

Now the pop up in second-hand stores and the like, which is how [Amen] acquired a Canon Selphy 740. It didn’t work, and on investigation it was found that a particularly tiny plastic gear had failed. Most people would have tossed the printer in the trash, but they instead opted to CNC-machine a new gear. It’s not everyday you tackle a job this small, so it makes for an interesting tale.

While the first instinct might be to reach reach for a CAD package, [Amen] instead wrote a script to create the raw GCode. The machining is done with a 0.2 mm bit ground to the desired profile. The result: a gear that gets the printer working again. It’s a dye-sublimation printer that leaves a negative image in the cartridge, allowing negative prints to be made with a bit of cartridge rewinding. And for those who might have ended up with a Selphy of their own, there’s a further post about using cheaper aftermarket cartridges.

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3D-Printed Gear Press Can Squash Stuff, Kinda

June 16, 2022 by Lewin Day 2 Comments

A press is a useful thing to have, whether you like destroying stuff or you simply want to properly install some bearings. [Retsetman] decided to build one from scratch, eschewing the typical hydraulic method for a geared design instead.

The benefit of going with a gear press design is that [Retsetman] was able to 3D print the required gears himself. The design uses a series of herringbone gears to step down the output of two brushed DC motors. This is then turned into linear motion via a rack and pinion setup. Naturally, the strength of the gears and rack is key to the performance of the press. As you might expect, a fair few of the printed gears suffered failures during the development process.

The final press is demonstrated by smooshing various objects, in true YouTube style. It’s not really able to destroy stuff like a proper hydraulic press, but it can kind of crush a can and amusingly squash a teddy bear. If you’re really keen on making a gear press, though, you’re probably best served by going with a metal geartrain. Video after the break.

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