Most inexpensive 3D printers use a type of lead screw to move some part of the printer in the vertical direction. A motor turns a threaded rod and that causes a nut to go up or down. The printer part rides on the nut. This works well, but it is slower than other drive mechanisms (which is why you don’t often see them on the horizontal parts of a printer). Some cheap printers use common threaded rod, which is convenient, but prone to bad behavior since the rods are not always straight, the threads are subject to backlash, and the tolerances are not always the best.
More sophisticated printers use ACME threaded rod or trapezoidal threaded rods. These are made for this type of service and have thread designs that minimize things like backlash. They typically are made to more exacting standards, too. Making the nut softer than the rod (for example, brass or Delrin) is another common optimization.
However, when lead screws aren’t good enough, mechanical designers turn to ball screws. In principle, these are very similar to lead screws but instead of a nut, there is a race containing ball bearings that moves up and down the screw. The ball bearings lead to less friction.
Misumi recently posted a few blog articles about ball screws. Some of the information is basic, but it also covers preloading and friction. Plus they are promising future articles to expand on the topic. If you prefer to watch a video, you might enjoy the one below.
Continue reading “Mastering Ball Screws”
[Christian] wrote and sells some CAM/CNC controller software. We’re kinda sticklers for open source, and this software doesn’t seem to be, so “meh”. But what we do like is the Easter egg that comes included: the paths to mill out the base for a clock, and then the codes to move steel ball-bearings around to display the time.
Of course we’d like to see more info (more, MORE, MOAR!) but it looks easy enough to recreate. We could see redesigning this with marbles and a vacuum system, for instance. The seats for the ball bearings don’t even need to be milled out spheres. You could do this part with a drill press. Who’s going to rebuild this for their 3D printer? You just have to make sure that the machine is fast enough to move the balls around within one minute.
Continue reading “CNC Clock Mills Itself, Displays The Time”
[Martin Raynsford] figured out a way to sneak some learning into a fun package. He did such a good job the test subjects didn’t even know they were teaching themselves just a tiny bit of CNC programming.
The apparatus above is a marble maze, but instead of building walls [Martin] simply etched a pattern on the playing field. The marble is a ball bearing which moves through the maze using a magnetic CNC gantry hidden underneath. Where does one get ball bearings of this size? If you’re [Martin] you scavenge them from your laser-cut Donkey Kong game.
He showed off the rig at the Maker Faire. It takes simple commands as cardinal directions and units of movement. The ‘player’ (remember, they’re secretly learning something, not just playing a game) inputs a series of movements such as “N10,E10” which are then pushed through a serial connection to the Arduino. It follows these commands, moving the hidden magnet which drags the ball bearing along with it. It’s simple, but watch the clip after the break and we think you’ll agree the sound of the stepper motors and the movement of the ball will be like crack for young minds.
Continue reading “Magnetic CNC marble maze”
[Lior Elazary] designed and built this clock to simulate the function of a CPU. The problem is that if you don’t already have a good grasp of how a CPU works we think this clock will be hopelessly confusing. But lucky for us, we get it, and we love it!
Hour data is shown as a binary number on Register A. This is the center column of red parts and is organized with the MSB on the bottom, the LSB on the top, and left-pointing bits function as digital 1. The clock lacks the complexity necessary for displaying any other time data. But that’s okay, because the sound made by the ball-bearing dropping every minute might drive you a bit loony anyway. [Lior] doesn’t talk about the mechanism that transports that ball bearing, but you can see from the video after the break that a magnet on a circular path picks it up and transports it to the top of the clock where gravity is used to feed the registers. There are two tracks which allow the ball to bypass the A register and enter the B register to the right. This works in conjunction with register C (on the left) to reset the hours when the count is greater than 11.
If you need a kickstart on how these mechanical adders are put together, check out this wooden adder project.
Continue reading “Mechanical CPU clock is just as confusing as its namesake”
This collection of gauss weapons use rare earth magnets to accelerate projectiles to damaging speeds. They work using the same concepts as a coil gun, but instead of just one projectile travelling along a length of guide track, there are many projectiles that work in a chain reaction. A series of magnets are placed at equal distances along the track. Each has a couple of large ball bearings on the muzzle side of the magnet. The first ball bearing is fired using mechanical force – like a spring mechanism – and accelerates as it approaches the magnet due to the attractive force of that magnetic field. When it impacts the magnet it sends one of the ball bearings on the opposite side down the track where it will accelerate when it nears the next magnet in the chain. The weapon above achieves a final projectile speed of about 68 miles per hour, breaking six fluorescent tubes in a row on at the right side of the apparatus.
Still prefer rail guns that use electromagnets? Check out this gauss pistol kit that is about as powerful as a BB gun.
This kinetic sculpture is a ball bearing’s paradise. Not only do they get a cushy ride around two lift wheels but there’s a variety of enjoyable obstacles they can go down. The first is a vortex made from a wooden flower pot which sends the balls randomly down one of two possible exits. From there it’s on to enjoy a ride on a flip-flop, a divide-by-three (takes weight of three marbles before it dumps them all), a zig-zag track, or a divide by twelve mechanism. We’re sure this is a riveting read, but don’t miss the video after the break where [Ronald Walter] shows it in action and takes it apart to illustrate the various features.
If you’re wondering about the digital logic terms used, we’ve seen wooden devices that use these concepts in the past.
Continue reading “5/8″ ball bearing playground”
We’re going to let you decide which of these two projects is a delight, and which is amusing.
The project on the left is a desktop kinetic sculpture. We like it because of its size and simplicity. A single AA battery drives the gear head motor that provides the lift for the metal balls. There are several different routes for them to take in returning to the lift wheel, each route determined by a mechanical combination of the metal spheres. This is more of a month-long build than some of the other kinetic devices we’ve seen which could take a lifetime.
The offering on the right is a perpetual motion machine. Well, it will be once that guy gets the kinks worked out. You can see him explain how he intends this works in the video after the break. We’re not betting on perpetual motion, but if we did, our money would be on something like the Steorn Orbo replica and not on this.
Continue reading “Kinetic project duo to delight and amuse”