Mechanical Issues For A Pi CNC

The Raspberry Pi platform has become popular in the maker community for various CNC projects. The single board computers are readily suited to acting as a server for a small CNC setup or 3D printer, though it’s fair to say that for heavy work they probably aren’t quite up to the task of driving the steppers in a serious rig directly. [Danny] set out to try to build a CNC plotter of his own, using a Pi Zero, and learned a few things along the way.

The plotter uses 3D printed parts combined with brushed DC motors which are geared down. Potentiometers are added to allow the Pi to keep track of the location of the pen. This enables the position to be corrected through feedback.

While the plotter does move and accept commands, it does have some issues. There is significant play in the gear train which [Danny] suspects of causing the poor output results. If you’ve got any ideas as to how this could be improved or overcome, throw them down in the comments!

We’ve seen another take on CNC control with the Raspberry Pi, too. Video after the break.

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Facebook Wants to Teach Machine Learning

When you think of technical education about machine learning, Facebook might not be the company that pops into your head. However, the company uses machine learning, and they’ve rolled out a six-part video series that they say “shares best real-world practices and provides practical tips about how to apply machine-learning capabilities to real-world problems.”

The videos correspond to what they say are the six aspects of machine learning development:

  1. Problem definition
  2. Data
  3. Evaluation
  4. Features
  5. Model
  6. Experimentation

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Electric Bike From The Ground Up

Electric vehicles are getting more traction these days, but this trend is rolling towards us in more ways than just passenger vehicles. More and more bikes are being electrified too, since the cost of batteries has come down and people realize that they can get around town easily without having to pay the exorbitant price to own, fuel, and maintain a car. Of course there are turnkey ebikes, but those don’t interest us much around here. This ebike from [Andy] is a master class in how to build your own ebike.

Due to some health issues, [Andy] needed a little bit of assistance from an electric motor on his bike, but found out that the one he wanted wouldn’t fit his current bike quite right. He bought a frame from eBay with the right dimensions and assembled the bike from scratch. Not only that, but when it was time to put the battery together he sourced individual 18650 cells and built a custom battery for the bike. His build goes into great detail on how to do all of these things, so even if you need a lithium battery for another project this build might be worth a read.

If you’ve never been on an electric bike before, they’re a lot of fun to ride. They’re also extremely economical, and a good project too if you’re looking for an excuse to go buy a kit and get to work. You can get creative with the drivetrain too if you’d like to do something out of the box, such as this bike that was powered by AA batteries and a supercapacitor.

Printed Part Gets Classic Truck Rolling

When working on classic vehicles, and especially when modifying them outside of their stock configurations, things can get expensive. It’s a basic principle in economics: the rarer something is the more money somebody can charge you for it. But if you’ve got the skills and the necessary equipment, you can occasionally save yourself money by custom-fabricating some parts yourself.

After changing the gear ratio in his 1971 Ford F100, [smpstech] needed to adjust his speedometer to compensate. Unfortunately, a commercial speedometer reducer and the new cables to get it hooked up to his dash would have run into the hundreds of dollars, so he decided to try designing and 3D printing his own gearbox. The resulting development process and final product are a perfect example of how even a cheap desktop 3D printer, in the hands of a capable operator, can do a lot more than print out little toy boats.

The gearbox contains a large ring gear driven by a smaller, offset, spur gear. This compact inline package drops the speed of the input shaft by 25.5%, which [smpstech]  mentions is actually a bit slower than necessary, but it does give him some wiggle room if he decides to change his tire size.

Even if you’re not looking for a speedometer reducer for a nearly 50 year old truck, there are some lessons to be learned here in regards to 3D printed car parts. The first version of his gearbox, while functional initially, ended up looking like a deflated balloon after being exposed to the temperatures inside the F100’s engine bay. His cheapo PLA filament, which is probably fine for the aforementioned toy boats, simply wasn’t the right material for the job.

[smpstech] then reprinted the gadget in HTPLA, which needs to be annealed after printing to reach full strength. Usually this would involve a low-temperature bake in the oven, but he found that simmering the parts in a pot of water on the stove gave him better control over the temperature. Not only did the HTPLA version handle the under-hood conditions better, it was also strong enough that he was able to use a standard die on the connections for the speedometer cables to create the threads instead of having to model and print them. Definitely a material to keep an eye on if regular PLA isn’t cutting it for you.

This isn’t the first time we’ve seen 3D printed parts used to get a vintage vehicle back on the road. Building these custom parts would have been possible without a 3D printer, of course, but it’s a good example of how the technology can make these types of repairs faster and easier.

[via /r/functionalprint]

Regenerative Braking Charges Your Phone

Way back when, if you wanted lights on your bike, you’d head off to the local bicycle store and purchase yourself a bottle dynamo. This would consist of a magneto that was attached to a bracket on the back of the bike and would rotate by rubbing against the rear tire, generating power for the lights. These fell out of favor over the years as batteries got better and cheaper and people grew tired of the increased drag and maintenance required. Despite this, the idea of generating power onboard a bicycle has never really gone away, and [Javier] has decided to have a crack with his imPulse project.

The formerly popular bottle dynamo had one advantage over contemporary models located in bicycle hubs – they were geared down to allow the generating device to make multiple turns for each revolution of the bicycle wheel. This is useful to allow the generating device to operate in its ideal range of rotational speed. Going for a more modern take, however, [Javier] has decided to leverage a stepper motor as his generating device of choice. Further taking advantage of modern technology, the imPulse system is designed to fit on to the caliper mounts of modern bicycles with disc brakes, allowing easy fitment while also leaving room for a geared-down drive.

[Javier] hasn’t just stopped at power generation, however – there are also plans for lighting systems and power distribution to enable the generated power to be used for a variety of purposes. It even has turn signals – though that’s not the first time we’ve seen them on a bike! Video after the break.

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Ask Hackaday: Is There a Common Mechanical Parts Library?

Like many stories, this one started on the roof. This particular roof is located in Michigan and keeps the rain and snow off of the i3Detroit hackerspace. Being an old industrial building, things up on the roof can start getting creaky, and when an almighty screech started coming from one of the rooftop vents as it swiveled in the wind, Nate, one of the group’s coordinators, knew it was time to do something about it.

Previous attempts to silence the banshee with the usual libations had failed, so Nate climbed up to effect a proper repair with real bearings. He dug into the unit, measured for the bearing, and came down to order the correct items. That’s when it struck him: How many should I order? After all, bearings are useful devices, not just to repair a wonky vent but especially handy in a hackerspace, where they can be put to all sorts of uses. Would extra bearings be put to good use, or would they just sit on a shelf gathering dust?

That’s when Nate dropped us a line and asked a question that raises some interesting possibilities, and one which we couldn’t answer offhand: Is there a readily accessible online library of common mechanical parts?

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Sunday: Breakfast at DEF CON

Nurse your hangover by having Breakfast at DEF CON this Sunday. You’re invited to this yearly ritual with Hackaday and Tindie. We’re celebrating the beginning of the end with coffee and pastries beginning at 10:30 am in the Hardware Hacking Village.

Head over to the Breakfast at DEF CON event page and hit the “follow event” button to keep on any new info about the event.

Extra internet points go to those who bring some hardware to show off… and especially for anyone who is making this the end of their Saturday rather than the beginning of Sunday. We had tons of great hacks show up last year and want to outdo ourselves this time around.

Come hang out with too many Hackaday and Tindie folks to list here. Also don’t forget to check out the SMD Challenge throughout the weekend.