Cable Bots, Arise! Domination of the Universe is at Hand

Most CNC robots people see involve belts and rails, gantries, lead screws, linear bearings, and so forth. Those components need a rigid chassis to support them and to keep them from wobbling during fabrication and adding imperfections to the design. As a result, the scale is necessarily small — hobbyist bots max out at cabinet-sized, for the most part. Their rigid axes are often laid out at Cartesian right angles.

One of the exceptions to this common configuration is the delta robot. Deltas might be the flashiest of CNC robots, moving the end effector on three arms that move to position it anywhere in the build envelope. A lot of these robots are super fast and precise when charged with carrying a light load, and they get put to work as pick-and-place machines and that sort of thing. It doesn’t hurt that delta bots are also parallel manipulators, which means that the motors work together to move the end effector, with one motor pulling while the matching motor pulls.

But while Cartesian CNC bots are sturdy workhorses, and deltas are fly-weight racehorces, neither can really cut it when you want to go gigantic. In terms of simplicity and scale, nothing beats cable bots.

Cable Bots

Cable bots use wires or strings pulled by reel-mounted motors, with dimensions limited only by the room to mount the motors and the tensile strength of the cables used. When the strings are tensioned you can get a surprising degree of accuracy. Why not? Are they not computer-controlled motors? As long as your kinematic chain accounts for the end effector’s movement in one direction by unwinding another cable (for instance) you can very accurately control the end effector over a very wide scale.

The following are some fun cable bots that have caught my eye.

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Winch Bot Records Hacks and Cats

Some people are better than others when it comes to documenting their hacks. Some people, like [Micah Elizabeth Scott], aka [scanlime], set the gold standard with their recordings. Hacking sessions with the Winch Bot have been streamed regularly throughout the build and this is going to lead to a stacking effect in her next projects because the Winch Bot was designed to record hacking sessions. Hacking video inception anyone? Her Winch Bot summary video is after the break.

The first part of this build, which she calls the Tuco Flyer, was [Micah Elizabeth Scott]’s camera gimbal hack which we already covered and is a wonderful learning experience in itself. She refers to the gimbal portion as the “flyer” since it can move around. The Winch Bot contains the stationary parts of the Tuco Flyer and control where the camera will be in the room.

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Mini Delta Gets a Hot End Upgrade

3D printers are now cheaper than ever and Monoprice is at the absolute forefront of that trend. However, some of their printers struggle with flexible filaments, which is no fun if you’ve discovered you have a taste for the material properties of Ninjaflex and its ilk. Fear not, however — the community once again has a solution, in the form of a hot end adapter for the Monoprice Mini Delta.

The Mini Delta is a fantastic low-cost entry into 3D printing but its hot end has a break in the Bowden between the extruder and nozzle. This can lead to flexible filaments not being properly guided through the hot end and a general failure to print. This adapter allows the fitting of the popular E3D V6 hot end, and is similar to modifications out there for other Monoprice printers.

Overall, 3D printing has long benefited from the efforts of the community to bring both incremental improvements and major leaps forward to the technology. We look forward to seeing more hacks on the Monoprice range!

Mini Delta 3D Printer in Action at the Monoprice Booth

When I was at Bay Area Maker Faire a few weekends ago I stopped by the Monoprice booth to chat with [Chris Apland], their head of 3D Printing. Earlier in the week, the company had just announced preorders for their new $169 delta-style 3D printer called the MP Mini Delta.

[Brian Benchoff] covered that launch and I don’t have a lot of details about the machine itself to add. I saw it in action, printing tiny waving cat models. The stock printer can use ABS or PLA and has a build volume of 110mm in diameter and 120mm tall and these preorder units (being sold through Indegogo) will begin shipping in August.

What was of interest is to hear the shipping estimates the Monoprice team is throwing around. Chris told me that their conservative estimate is that 20,000 of these printers will ship through this preorder, but he is optimistic that by the end of the fourth quarter they’ll be closer to 100,000 units. That is incredible.

Part of the promise here is the out of the box functionality; [Chris] mentioned having a printed cat in your hands within 5 minutes. If it can actually do that without the need for setup and calibration that’s impressive. But I know that even seasoned printing veterans are interested in seeing how fast they can run this tiny delta and still turn out quality prints.

You’ll find the video interview after the break.

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Printing Bed Off-Kilter? Blu-Tack To The Rescue!

For all their applications, 3D printers can be finicky machines. From extruder problems, misaligned or missing layers, to finding an overnight print turned into a tangled mess, and that’s all assuming your printer bed is perfectly leveled. [Ricardo de Azambuja’s] new linear delta printer was frustrating him. No matter what he did, it wouldn’t retain the bed leveling calibration, so he had to improvise — Blu-Tack to the rescue.

It turns out [Azambuja]’s problem was so bad that the filament wouldn’t even attempt to adhere to the printing bed. So, he turned to Printrun Pronterface and a combination of its homing feature and the piece-of-paper method to get a rough estimate of how much the bed needed to be adjusted — and a similar estimate of how big of a gob of Blu-Tack was needed.

Pressing the bed into place, he re-ran Pronterface to make sure he was on the level. [Azambuja] notes that you would have to redo this for every print, but it was good enough to print off a trio of bed leveling gears he designed so he doesn’t have to go through this headache again for some time.

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Dawn of the Tripteron 3D Printer

Cartesian 3D printers were the original. Then delta printers came along, and they were pretty cool too. Now, you can add tripteron printers to the mix.  The tripteron is an odd mix of cartesian and delta. The system was invented at the robotics laboratory at Université Laval in Quebec, Canada. The team who created it say that it is “isotropic and fully decoupled, i.e. each of the actuators is controlling one Cartesian degree of freedom, independently from the others.” This means that driving the bot will be almost as simple as driving a standard X/Y/Z Cartesian printer. The corollary to that are of course delta robots, which follow a whole different set of kinematic rules.

trioptera-renderA few people have experimented with tripteron printers over the years, but as far as we can see, no one has ever demonstrated a working model. Enter [Apsu], who showed up about a month ago. He started a post on the RepRap forums discussing his particular design. [Apsu] works fast, as he has now demonstrated a working prototype making prints. Sure they’re just calibration cubes, but this is a huge step forward.

[Apsu] admits that he still has a way to go in his research – especially improving the arm and joint implementation. However, he’s quite pleased that his creation has gone from a collection of parts to a new type 3D printer.  We are too — and we can’t wait to see the next iteration!

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The Triple Delta Robot Arm (and Leg)

delta By now you’d think we’ve seen just about every means of robotic actuator possible. We have Cartesian bots, Stewart platforms, SCARA bots, Delta bots, and even some exceedingly bizarre linkages from [Nicholas Seward]. We’re not done with odd robotic arms, it seems, and now we have Delta-ish robots that can move outside their minimum enclosed volume. They’re fresh from the workshop of [Aad van der Geest], and he’s calling them double and triple Deltas.

Previous Delta robots have used three universal joints to move the end effector up and down, and side to side. They’re extremely fast and are a great design for 3D printers and pick and place machines, but they do have a limitation: the tip of a single Delta can not move much further than the base of the robot.

By adding more parallelograms to a Delta, [Aad] greatly increases working volume of a his robots. One of the suggested uses for this style of bot is for palletizers, demonstrated in the video below by stacking Jenga blocks. There is another very interesting application: legs. There’s footage of a small, simple triple Delta scooting around the floor, supported by wire training wheels below. It makes a good cat toy, but we’d love to see a bipedal robot with this style of legs.

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