Sacrificial Bridge Avoids 3D Printed Supports

[Tommy] shares a simple 3D printing design tip that will be self-evident to some, but a bit of a revelation to others: the concept of a sacrificial bridge to avoid awkward support structures. In the picture shown, the black 3D print has small bridges and each bridge has a hole. The purpose of these bits is to hold a hex nut captive in the area under the bridge; a bolt goes in through the round hole in the top.

Readers familiar with 3D printing will see right away that printing the bridges might be a problem. When a printer gets to the first layer of the bridge, it will be trying to lay filament in empty space. By itself this is not usually a problem as long as a bridge is short, flat, and featureless. Unfortunately this bridge has a hole in it, and that hole means the printer will be trying to draw circles in mid-air, rather than simply stretching filament point-to-point across a gap. One solution would be to add a small amount of support structure, but that just moves the problem. Removing small supports from enclosed spaces can be a real hassle.

To solve this [Tommy] added what he calls a “sacrificial bridge”, shown as blue in the CAD image. He essentially gives the hole a flat bottom, so that the printer first lays down a thin but solid bridge as a foundation. Then, the portion with the round hole is printed on top of that. With this small design change, the print becomes much more reliable with no support structure required.

There is a bit of post-work involved since each hole needs to be drilled out to punch through the thin sacrificial bridge underneath, but it definitely beats digging out little bits of support structure instead.

This 3D Printer Enclosure Takes Ventilation Seriously

A lot of work has gone into hacking common items (like IKEA Lack tables) into useful and effective 3D printer enclosures, but [Stefan.Lu] has taken a harder look at the whole business. He decided to start with some specific goals that were unmet by current solutions. In particular, he wanted to allow for proper ventilation and exhaust. Not only do some filaments smell bad, but there is ongoing research around UFP (ultra-fine particles) emitted from the 3D printing process. Just in case UFPs turn out to be this generation’s asbestos or something equally terrible, [Stefan.Lu] felt that a bit more work and expense up front would be worth it to meet his goals of a ventilation-friendly enclosure.

In addition to ventilation and exhaust, [Stefan.Lu] wanted to locate the printer at a comfortable working height, and preferred not to build things entirely from scratch. He did it for well under $200 by using a common storage rack shelf as the foundation and acrylic panels for the sides, and a few thoughtful uses of basic hardware. The angled metal supports made for easy attachment points and customization, and a combination of solid shelf plus anchoring to the wall put an end to vibrations. The side panels are secured by magnets, and [Stefan.Lu] points out that if you don’t have access to a laser cutter, cast acrylic withstands drilling and cutting better than extruded acrylic.

The final touch was a fire alarm, which is an excellent precaution. 3D printers are heating elements with multiple moving parts and they often work unattended. It makes sense to have a fire alarm around, or at least not enclose the device in highly flammable material in the first place.

Low-Tech Chair Enters the Matrix

This video demonstrates a really interesting experiment: sticking a Vive Tracker onto an ordinary chair in order to sync it up perfectly with its VR counterpart. The result? A chair that is visible in VR as a virtual object, but has a 1:1 physical world version occupying the same space. This means that unlike any other virtual object, this chair can be seen, touched, felt, moved, and actually sat in while the user is immersed in VR.

The purpose of this experiment seems to have been to virtually explore seating arrangements for real-world environments, and spawned a theatre planning tool by design studio [Agile Lens]. But we wonder if there’s unrealized potential in the idea of connecting physical objects that can be touched and held (or sat on) with their VR counterparts. Video demos of the chair test are embedded below.

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Mini Spool System for 3D Printing Pen Tidies Things Up

3D printing pens may be toys to some, but they can be genuinely useful tools to repair 3D prints, rescue a support structure, or weld together different pieces. However, [BManx2000] found that the way the filament simply sticks out of the back of a 3D printing pen like a bizarre tailfeather was troublesome.

The solution? A Mini Spool System for 3D Printing Pens, with which you can use your 3D printing pen to weld together the parts after printing them. The unit holds 1.75mm filament coiled under its own tension in a tidy package that doesn’t interfere with feeding. Since different 3D pens are shaped differently, the interface to the pen is a separate piece that can be modified or changed as needed without affecting the rest of the design.

We’ve seen some interesting innovations with filament holders before, like this entirely 3D printed filament holder, but a mini spool for a 3D pen is definitely a new one.

Books You Should Read: Feynman’s Appendix to the Challenger Disaster Report

It isn’t really a book, but Richard Feynman’s Appendix to the Challenger Disaster Report is still definitely something you should read. It’s not particularly long, but it’s educational and relevant not just as an example of critical thinking in action, but as a reminder not to fool oneself; neither individually, nor on an organizational level. Sadly, while much was learned from the events leading to and surrounding the Challenger disaster, over thirty years later many of us can still find a lot of the same things to relate to in our own professional lives. There isn’t a single magic solution, because these problems are subtle and often masquerade as normal.

Feynman and the Challenger Disaster

Richard Feynman (1918-1988) was a Nobel Prize winning physicist and one of the best-known scientists of his time. In 1986 he somewhat reluctantly agreed to join the Rogers Commission, whose task was to investigate the Challenger disaster. The space shuttle Challenger had exploded a little more than a minute after launch, killing everyone on board. The commission’s job was to find out what had gone wrong and how it had happened, and figure out how to keep it from happening again.

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7-Segment Digits Slide Stylishly on This OLED Clock

Over at Sparkfun, [Alex] shared an OLED clock project that’s currently in progress but has a couple interesting twists. The first is the use of a small OLED screen for each digit, to which [Alex] added a stylistic touch. Digits transition by having segments slide vertically in a smooth animated motion. It’s an attractive effect, and the code is available on his github repository for anyone who wants to try it out.

[Alex] also found that by using an ESP32 microcontroller and synchronizing the clock via NTP over WiFi, the added cost of implementing a real-time clock in hardware becomes unnecessary. Without an RTC, time would drift by a few seconds every day and require a reset. At the moment the clock requires the SSID and password to be hardcoded, but [Alex] would prefer to allow this to be configured via a web page and could use some help. If you have implemented a web server on the ESP32, [Alex] would like to know how you handled multiple pages. “I’ve been scratching my head throughout the build on how to get this done,” he writes. “With the ESP8266, there’s on(const String &uri, handler function), but that seems to have been removed on the ESP32.” If you can point [Alex] in the right direction, be sure to pipe up.

OLED displays and clocks often go together, as we have seen with projects like the DIY OLED Smart Watch, but it’s nice to see someone using the OLED’s strengths to add some visual flair to an otherwise plain display.

Spray Paint Goes DIY Virtual with a Vive Tracker

Here is a virtual spray painting project with a new and DIY twist to it. [Adam Amaral]’s project is an experiment in using the Vive Tracker, which was released earlier this year. [Adam] demonstrates how to interface some simple hardware and 3D printed parts to the Tracker’s GPIO pins, using it as a custom peripheral that is fully tracked and interactive in the Vive’s VR environment. He details not only the custom spray can controller, but also how to handle the device on the software side in the Unreal engine. The 3D printed “spray can controller” even rattles when shaken!

There’s one more trick. Since the Vive Tracker is wireless and completely self-contained, the completed rattlecan operates independently from the VR headset. This means it’s possible to ditch the goggles and hook up a projector, then use the 3D printed spray can to paint a nearby wall with virtual paint; you can see that part in action in the video embedded below.

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