Compliant Robot Gripper Won’t Scramble Your Eggs

gripper

[Chiprobot] has created an amazing compliant gripper.  Designing robot hands (or end effectors) can be a perilous task. It is easy to give robots big, good, strong hands. Strong grippers have to be controlled by sensors. However, sensors can’t always be relied upon to ensure those hands don’t crush anything they touch. Hardware fails, software has bugs. Sometimes the best solution is a clever mechanical design, one which ensures a gripper will conform to the object it is gripping. We’ve seen “jamming” grippers before. (so named for their use of a granular substance which jams around the object being gripped).

[Chiprobot's] gripper is something entirely different. He designed his gripper in blender, and printed it out with his Ultimaker 3D printer. The material is flexible PLA. Three plastic “fingers” wrap around the object being gripped. The fingers are made up of two strips of printed plastic connected by wire linkages. The flexible plastic of the fingers create a leaf spring design. The fingers are attached to a linear actuator at the center point of the gripper. The linear actuator itself is another great hack. [Chiprobot] created it from a servo and an empty glue stick.  As the linear actuator is pulled in, the fingers pull around  any object in their grip. The end result is a grip strong enough to hold an egg while shaking it, but not strong enough to break the egg.

We would like to see the gripper gripping other objects, as eggs can be surprisingly strong. We’ve all seen the physics trick where squeezing an egg with bare hands doesn’t break it, yet squeezing an egg while wearing a ring causes it to crack much… like an egg.

[Read more...]

RepRap Wally Can Print Larger Versions of Itself

Reprap Wally

SCARA based 3D printers seem to be all the rage these days, and with good reason. This RepRap Wally doesn’t use any linear rods or timing belts — in fact, it can even print larger versions of itself with each iteration! Well, minus the electronics of course.

It was first spotted out in the wild at the NYC Makerfaire, and looks to be a pretty slick design. Using fully 3D printed limbs, the steppers move the arms using a fishing line. To reduce the load on the joints, a bowden extruder is also used. The really cool part of this is the z-axis, it uses a 4-bar linkage to stay level, but because of this, it also moves along an arc in the y-axis as it raises or lowers. This is accounted for in the firmware — otherwise you’d have some rather interesting curved prints!

Stick around after the break to see it in action, it’s a nice change to watch from the standard gantry style printers.

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Accurate temperature control of your 3D printer extruder

[Tim] is working on building a 3D printer and using it as an excuse to learn as much as he can. The first big issue he tackled was accurate temperature control, so he made an interesting write-up on how to characterize the thermal properties of an QU-BD extruder’s hot end and use that information to create a control algorithm for the heater.

The article starts with a basic thermal model and its corresponding formula. [Tim] then runs several tests where he measures the heater and extruder tip temperatures while switching on and off the heater. This allows him to figure out the several model parameters required to design his control algorithm. Finally, he tweaked his formula in order to predict the short term future so he can know when he should activate the heating element. As a result, his temperature is now accurately controlled in the 200°c +/-1°c window that he was shooting for.

RepRap Simpson puts a new spin on delta RepRaps

ReprapSimpson

Just when you think you’ve seen it all in the 3D printer world, something new pops up! [Nicholas Seward] posted a video of RepRap Simpson, his latest project.  Simpson is a delta robot – but unlike any delta we’ve seen before. Previous offerings vertical rails on which the arms travel. As you can see, this design mounts three articulated arms directly to the base of the printer, using steel cables as part of the joint mechanism.

Judging by [Nicholas'] posts on the RepRap forums, Simpson’s grounded delta design has already gone through a few revisions. The basic geometry though, has remained the same. [Nicholas] calls this edition a “Proportional Gear Drive Joint Simpson”. The name may not roll off the tongue, but the movements are incredibly smooth, organic, and fast.

As with any delta design inverse kinematics play a huge role in the software. [Nicholas] is trying to simplify this with an optical calibration system. For the adventurous, the equations are posted on the forums, and a python Gcode preprocessor is posted on Thingiverse.

Even Simpson’s base received special attention.  It’s built from a water jet cut piece of basalt.  We like the use of opposed helical gears on the large joints, as well as the guitar machine heads used to tension the cable drive. One thing we are not sure of is the longevity of system – will cable stretch play an issue? Will the printed parts suffer wear from the cables? Only time will tell.

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Students build a 3D printed plane

3d printed plane

A student team has successfully designed, built, and flown a 3D printed RC plane using only $16 of plastic with a consumer-grade 3D printer (Makerbot), plus the necessary electronics and motor.

The folks over at the Wright Brothers Institute (WBI) have a great program called the AFRL Discovery Lab which brings teams of students, businesses, researchers, and government together to work on a specific challenge or opportunity.

One of the programs this year was the Disposable Miniature Air Vehicle, or DMAV for short. The student interns [Nathan, Ben, and Brian] spent the first 5 weeks at Tec^Edge designing the plane. The team went through 5 revisions before they settled on a design they believed could fly. The final plane weighed 1.5 pounds, and on its first flight… plummeted into the ground. Good thing they printed a second copy! After some more practice [Stephen] got the hang of it and was able to fly and land the plane successfully.

According to the WBI, this is the first functional aircraft that has been fully 3D printed (sans electronics) using FDM technology, and the first low wing 3D printed plane to be flown. Hate to burst their bubble, but 3D printed quadcopters have been around for quite a while!

Test flight video is after the break.

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Rubicon gives the Makerbot Digitizer a run for its money

rubicon

Look out MakerBot, there’s a new 3D scanner on the block and it’s about 10% of the cost of the Digitizer. Enter the Rubicon 3D Scanner which just hit Indiegogo, a device much closer to being worth its price $199.

Just like the pricey Makerbot Digitizer it’s a very simple design made up of a webcam, two laser lines, and a stepper motor controlled turn table. Still very easy to make yourself, but at $199, it’s not a bad price for an all-in-one kit, especially compared to the Digitizer. The newcomer claims a much faster scan time (3 minutes versus 12), and the same stepper rotation (800 steps or 0.45 degrees per step). There are no details about making the design open source, but after some digging in the RepRap forums we found some discussion on that topic from designer [Robert].

It scans objects up to 160mm in diameter and 250mm tall, however it has the ability to scan marginally larger objects if the camera is moved farther back. The funding for the Indiegogo campaign will go towards a custom arduino-esq PCB with a motor driver built in – personally we would be interested in just getting the PCB and 3D printing the rest of the scanner ourselves!

More information is found in the video after the break. [Read more...]

A deck screw extruder

deck

A lot of great ideas happen in the middle of the night, and for [Werner] it’s no different. One night he came up with an idea for a new 3D printer extruder, and after a very basic prototype, we’d have to say he might be on to something. It’s basically a deck screw acting as a worm gear to drive filament, but this simple idea has a lot of really cool advantages.

There are two really interesting features of this extruder, should [Werner] ever decide to flesh out his idea into a real prototype. First, the stepper motor for this extruder can be extremely small and mounted directly above the extruder. This opens up the doors to easily creating multi-extrusion printers that can handle more than one filament. Secondly, using a deck screw as a worm gear means there is a huge area of contact between the plastic filament and the driver gear.

Whereas the usual extruder setup only makes contact with the plastic filament along one or two splines of a hobbed bolt, [Werner]‘s design drives the filament along the entire length of the deck screw worm gear. This could easily translate into much more accurate extrusion without all the fiddling around with springs and hobbed bolts today’s extruders have.

In any event, it’s a very interesting idea, and we’d love to see [Werner] or someone else make a functioning extruder with this design.