3D Printed Linear Actuator Is Cheap And Strong

Motors are all well and good for moving things, but they’re all about the round-and-round. Sometimes, you need to move something back and forth, and for that a linear actuator will do the trick. While they can be readily sourced for under $50 online, [Michael Rechtin] genuinely felt like reinventing the wheel, and managed to whip up a 3D-printed design that costs under 20 bucks.

The basic design is simple, consisting of a small motor which is geared down through several stages using simple spur gears. The last gear in the train is tasked with turning a lead screw which drives the arm of the linear actuator back and forward.

For simplicity, [Michael] used a 24V brushed DC gearmotor for its low cost and the fact it already has a step-down gearbox integrated into the design. It’s paired with a couple more 3D-printed spur gears to provide even more torque. Instead of a fancy lead screw, the build instead just uses a quarter-inch bolt sourced from Home Depot, which can be had much cheaper. This pushes a 3D-printed arm back and forth thanks to a nut stuck in the arm. It’s all wrapped up in a neat-and-tidy 3D-printed housing. The design is able to push with a force of roughly 220 lbs. For a more practical idea of its strength, it can readily crush an empty soda can.

The video on the design is great, showing how important features like limit switches are added, and how the wiring can be neatly hidden away inside the housing. We’ve seen [Michael’s] work before, too, like strength testing various types of 3D printed gears. Video after the break.

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The end result - motorized window in a silver stainless steel frame, with the linear actuators and gas struts, shown from the outside half-open.

Swing Gate Motors Come To Help For Opening A Giant Servery Window

[Martin Roberts] wrote to us, telling us about a build that his company, [Ocean View Workshop], was tasked with. Creating a four meter wide window able to open vertically is no small feat, and it had to be custom-built because the local company building such windows wasn’t comfortable working with anything other than aluminum — insufficient for the window’s scale. With massive weight of the glass alone, structural requirements for supporting it, and the mechanical loads to be applied, some careful planning was in order.

To start with, this window had to be motorized, as an average person wouldn’t be capable of pulling it upwards. Not satisfied with the linear actuator choice available, they went to a hardware store and found some swing gate actuators that, in workshop tests, proved themselves to be more than capable of handling way over the weight required. In fact, they were capable of lifting [Martin] himself off the ground without much hassle.

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Building A High-Capacity Linear Servo Actuator

Linear actuators are useful things, moving things in straight lines rather than annoying circles like so many motors. [Retsetman] recently built a linear servo actuator of his own design with accurate positional control.

The design relies on a carriage that moves along a threaded rod, perhaps the most rudimentary design of linear actuator. A large brushed DC motor is used to turn the threaded rod through a 3D-printed 9:1 herringbone geartrain, shifting the actuator back and forth. End stop switches are used to disengage the motor to avoid damage to the mechanism. Feedback is via a ten-turn potentiometer driven off the output geartrain to match the range of the actuator to the rotational range of the pot.

The final build has a stroke of approximately 100 mm, and can lift and hold a 15 kg weight with ease. In a pull test, the actuator failed at a load just shy of 100 kg. If you’re looking for something smaller, though, you can try building a linear actuator out of old DVD drive parts instead. Video after the break.

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1960s Stereo Console Gets An Upgrade

Faced with an old console stereo from the 1960s that was barely functional, [Sherman Banks] aka W4ATL decided to upgrade its guts while keeping its appearance as close to the original as possible. This stereo set is a piece of mahogany furniture containing an AM/FM stereo receiver and an automatic turntable from JCPenny’s Penncrest line. As best [Sherman] can determine, it is most likely a 1965 model. The old electronics were getting more and more difficult to repair and the tuner was drifting off-station every 15 minutes. He didn’t want to throw it away, so he decided to replace all the innards.

The first thing was to tear out the old electronics while retaining the chassis proper. The new heart of the entertainment center is a modern Denon AV stereo receiver. This unit can be controlled over Ethernet, has a radio tuner, inputs for SiriusXM and a turntable, and supports Bluetooth streaming. [Sherman] next replaced the 1965 turntable, and then turned his attention to connecting up the controls and indicators.

The potentiometers were replaced with equivalent ones of lower resistance, the neon stereo indicator was replaced with an LED, but the linear tuning dial proved to be a nearly two month challenge and resulted in a cool hack. In brief, he connected an optical rotary encoder to the tuning knob and used a stepper motor with a linear actuator to control the dial indicator. All this is controlled from an Arduino Mega 2560 with three shields for I/O and LAN. But there was still one remaining issue — without vacuum tubes to warm up, the radio would play immediately after power-on. [Sherman] fixed that by programming the Arduino to slowly ramp up the volume at the same rate as the original tube receiver. And finally, he installs a small HDMI monitor in the corner to display auxiliary information and metadata from the Denon receiver.

Check out the videos below the break. We wrote about a couple of similar conversions in the past: this one from 2018 was also a Penncrest, and from last year this COVID isolation project that emphasized the addition of a new liquor cabinet.

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Mini Linear Actuators From DVD Drive Parts

For many years now a source for some of the smallest and cheapest home made CNC mechanisms has been the seemingly never-ending supply of surplus CD and DVD-ROM drives. The linear actuator that moves the laser may not be the longest or the strongest, but it’s free, and we’ve seen plenty of little X-Y tables using CD drives. It’s these mechanisms that [Nemo404] has taken a little further, freeing the lead screw and motor from the drive chassis and placing them in a 3D-printed enclosure for a complete linear actuator that can be used in other projects. (Video, embedded below.)

There seems to be no positional feedback, not even the limit switch that would grace a typical CD drive, but aside from that it makes for a compact unit. There are two versions, one for a linear bearing and the other for the brass bushes found in CD drives. It’s unclear how strong the result is, but it appears to be strong enough to demonstrate lifting a small container of screws.

Should you need to make your own actuator then aside from the easy-to-obtain old CD drive the files can be found on Thingiverse. And introduce yourself to the world of CD drives for CNC machines by taking a look at this mill.

Thanks [BaldPower] for the tip!

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Riding Mower Repair Uncovers Miniature Culprit

Most people would be pretty upset it the lawn mower they spent $4,000 USD on had a major failure within the first year of owning it. But for [xxbiohazrdxx], it was an excuse to take a peek under the hood and figure out what brought down this state-of-the-art piece of landscaping gear.

It should be said that, at least technically, the Husqvarna TS 348XD in question was still working. It’s just that [xxbiohazrdxx] noticed the locking differential, which is key to maintaining traction on hilly terrain, didn’t seem to be doing anything when the switch was pressed. Since manually moving the engagement lever on the transmission locked up the differential as expected, the culprit was likely in the electronics.

Testing the dead actuator.

As [xxbiohazrdxx] explains, the switch on the dash is connected to a linear actuator that moves the lever on the transmission. The wiring and switch tested fine with a multimeter, but when the actuator was hooked up to a bench power supply, it didn’t move. Even more telling, it wasn’t drawing any power. Definitely not a good sign. Installing a new actuator would have solved the problem, but it was an expensive part that would take time to arrive.

Repairing the dead actuator seemed worth a shot at least, so [xxbiohazrdxx] cracked it open. The PCB looked good, and there were no obviously toasted components. But when one of the internal microswitches used to limit the travel of the actuator was found to be jammed in, everything started to make sense. With the switch locked in the closed position, the actuator believed it was already fully extended and wouldn’t move. After opening the switch itself and bending the contacts back into their appropriate position, everything worked as expected.

A tiny piece of bent metal kept this $4,000 machine from operating correctly.

As interesting as this step-by-step repair process was, what struck us the most is [xxbiohazrdxx]’s determination to fix rather than replace. At several points it would have been much easier to just swap out a broken part for a new one, but instead, the suspect part was carefully examined and coaxed back to life with the tools and materials on-hand.

While there’s plenty of folks who wouldn’t mind taking a few days off from lawn work while they wait for their replacement parts to arrive, not everyone can afford the luxury. Expedient repairs are critical when your livelihood depends on your equipment, which is why manufacturers making it harder and more expensive for farmers to fix their tractors has become such a major issue in right to repair battles all over the globe.

The Black Magic Of A Disappearing Linear Actuator

Many of the projects we serve up on Hackaday are freshly minted, hot off the press endeavors. But sometimes, just sometimes, we stumble across ideas from the past that are simply too neat to be passed over. This is one of those times — and the contraption in question is the “Kataka”, invented by [Jens Sorensen] and publicised on the cover of the Eureka magazine around 2003.

The device, trademarked as the Kataka but generically referred to as a Segmented Spindle, is a compact form of linear actuator that uses a novel belt arrangement to create a device that can reduce to a very small thickness, while crowing to seemingly impossible dimensions when fully extended. This is the key advantage over conventional actuators, which usually retract into a housing of at least the length of the piston.

It’s somewhat magical to watch the device in action, seeing the piston appear “out of nowhere”. Kataka’s youtube channel is now sadly inactive, but contains many videos of the device used in various scenarios, such as lifting chairs and cupboards. We’re impressed with the amount of load the device can support. When used in scissor lifts, it also offers the unique advantage of a flat force/torque curve.

Most records of the device online are roughly a decade old. Though numerous prototypes were made, and a patent was issued, it seems the mechanism never took off or saw mainstream use. We wonder if, with more recognition and the advent of 3D printing, we might see the design crop up in the odd maker project.

That’s right, 3D printed linear actuators aren’t as bad as you might imagine. They’re easy to make, with numerous designs available, and can carry more load than you might think. That said, if you’re building, say, your own flight simulator, you might have to cook up something more hefty.

Many thanks to [Keith] for the tip, we loved reading about this one!

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