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Stewart Platform reinvents the wheel so you don’t have to

StewartPlatform

[Dan Royer] has noticed that most university projects involving a Stewart platform spend more time building a platform than on the project itself. He hopes to build a standard platform universities can use as the basis for other projects.

Stewart platforms are six degree of freedom platforms often seen hefting flight simulators or telescopes. The layout of the actuators allows movements in X,Y,and Z as well as pitch, roll and yaw. While large platforms often use hydraulic systems to accelerate heavy loads quickly. [Dan] is looking at a smaller scale system. His platform is built of laser cut wood and uses six steppers to control motion.

One of the harder parts in designing a platform such as this is creating a mechanical system that is strong, precise, and smooth. With so many linkages, it’s easy to see how binding joints could bring the entire thing to a grinding halt. [Dan] is currently using RC helicopter ball joints, but he’s on the lookout for something even smoother.

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Fail of the Week: Laser cutter that makes jagged edges

fotw-dvd-part-laser-cutter

This Fail of the Week is really only a failure because of the standards to which [eLabz] holds himself. The rig pictured above is a laser cutter built out of DVD drive parts. It goes above and beyond most of the optical drive CNC projects we see around here — it actually makes cuts! But [eLabz] looks on it as a failure because the steps of the driver motors are visible as jagged edges in those cuts. We see this more as a pausing point in the development process before the next refinement is made.

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Omniwheel robot build uses a bit of everything

building-an-omniwheel-robot

Machinist, electronics engineer, programmer, and factory worker are all skills you can wield if you take on a project like building this omniwheel robot (translated).

The omniwheels work in this tripod orientation because they include rollers which turn perpendicular to the wheel’s axis. This avoids the differential issue cause by fixed-position wheels. When the three motors are driven correctly, as shown in the video below, this design makes for the most maneuverable of wheeled robots.

An aluminum plate serves as the chassis. [Malte] milled the plate, cutting out slots for the motor with threaded holes to receive the mounting screws. A few stand-offs hold the hunk of protoboard which makes up the electronic side of the build. The large DIP chip is an ATmega168. It drives the motors via the trio of red stepper motor driver boards which he picked up on eBay.

So far the vehicle is tethered, using a knock-off of a SixAxis style controller. But as we said before, driving the motors correctly is the hard part and he’s definitely solved that problem.

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Bluetooth stepper motor driver

bluetooth-stepper-motor-driver

[Dan] salvaged some parts from an old printer a while back and finally found some time to play with them. One of the things he was most interested in is the geared stepper motor seen above. He was able to get it running with an Arduino in no time so he decided to take the project a little bit further. What he ended up with is a stepper motor driver which can be controlled over Bluetooth.

The motor can’t be driven directly, but with a simple motor driver like the L293 chip [Dan] used it’s not hard to interface them with your control hardware of choice. From there he added an ATtiny85 which will take care of the stepping protocol necessary to move the motor. The Bluetooth module he’s using functions as a serial device, making it really simple to interface with the uC. [Dan] uses a pin header to connect the module, so switching to a different type of serial device in the future will be quick and painless.

After the break you can see him sending step commands to the driver board.

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Working 3D printed stepper motor

Stepper Small 1

Most 3D printers use stepper motors to control the movement of the extruder head. If you could actually print those motors it would be one more big step toward self-replicating hardware. Now obviously [Chris Hawkins'] working 3d printed stepper motor wasn’t built 100% through 3D printing, but the majority of the parts were. All that he had to add was the electronic driver pieces, magnets, wire, and a few nails.

The coils are made up of nails wrapped in magnet wire. The rotor is a 3D printed framework which accepts neodymium rare earth magnets. The axle is pointed which reduces the friction where it meets the cone-shaped support on either side of the frame. The IC on the upper right is a transistor array that facilitates switching the 20V driving the coils. The board on the lower right is a Digispark, which is an ATtiny85 breakout board that includes a USB edge connector for programming and a linear regulator which is how he gets away with feeding 20V as the source.

Don’t miss the demo video after the break where you can see the motor stepping 7.5 degrees at a time.

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CNC ping pong printer uses simple construction

spherebot

This is one of the simplest CNC builds we’ve seen but it still functions quite well. It’s a clone of the EggBot, but is aimed at printing on spherical Ping Pong balls rather than oblong eggs. [Chad] calls it the Spherebot, but you should be careful not to confuse it with the morphing sphere robot which can walk around like a hexapod.

The project is both mechanically and electronically simple. The body of the printer is made up of three acrylic plates, which we’re sure were clamped together when drilling holes to guarantee proper alignment. Threaded rod and nuts are used to mount the plates to one another, as well as to hold the sphere in place while printing. One stepper motor turns the ball while the other pivots the pen mount. A servo motor is responsible for lifting the pen. The entire thing is driven by an Arduino along with two stepper motor driver boards. Don’t miss [Chad's] presentation embedded after the break.

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SCARA arm 3D printer

scara-3d-printer

[Quentin Harley] must really have wanted to test his snuff when it comes to mechanical engineering. He’s been hard at work for a couple of years now designing his own SCARA arm 3D printer. That link leads to a recent summary article in which he shows off the build as seen above. It’s not fully functional yet, but he’s at the point where it’s time to develop the driver circuitry and firmware so he’s close. His blog is dedicated to this single project so click around and see what he went through along the journey.

The SCARA arm is seen in blue, using a couple of stepper motors to move the extruder mount along the x and y axes. The bed itself moves along the Z axis via two precision rods with a threaded rod in the center. As you can see, some of the parts are made of wood, and he used PVC for the cross supports between the upper and lower base platforms. But the majority of the build uses 3D printed parts, including the arms, drive gears, and mounting brackets.

[Thanks Peter]