How To Identify Plastics Before Laser Cutting Them

March 14, 2015 by George Graves 30 Comments

If you own a pickup truck, you’ll quickly find yourself making friends with people who just happen to need help moving next weekend. Trust me, it’s almost magical. And if you own a laser cutter (or work in a hacker/maker space that has one) you’ll get some odd requests to cut or engrave plastic items of unknown type. Before you do, you should read this (pdf) chemistry lab written by [David A. Katz] to learn how to identify what type of plastic it is.

There are several reasons why you don’t want to cut or engrave some types of materials. A few make a gooey mess that you’ll regret even trying. Others make a horrendous odor. Some hackerspaces will even charge you extra if you stink up the place (aka: malodorous material charge.) Some tend to catch on fire. Yikes.

But that’s not the worst of it. Some types of plastic release potentially deadly hydrogen chloride gas. It’s bad for the optics, it’s wreaks havoc on the electronics and mechanics of the machine, and could do a really good job of messing up your lungs forever. In the video after the break, you can see the flame test for such plastics in action at the NYC Resistor as they test several common items using nothing more than a blow torch and some copper wire. In short, if the flame test produces a green flame, do not put it in the laser.

If you want to see a good list of what is and what isn’t ok to cut, head on over to ATXHackerspace’s wiki. They will give you a nice run down with lots of notes and helpful hints as well.

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Lift Kits For Car Jacks Do Exist

March 14, 2015 by Rich Bremer 72 Comments

When needing to change a tire or work under our vehicles we humans reach for a trusty jack. The standard jack in your trunk or mounted behind the seat of your truck works fine 99% of the time. But what happens when the vehicle in need of repair has a lifted suspension, raising the frame in relation to the ground and making the stock jack now too short?

Off-Road enthusiast [am4x4] had that problem and came up with a neat solution. He made a lift kit for a roll-around mechanics jack! He started with a 1.5 ton jack from Harbor Freight. This jack had 2 small casters in the rear and one wide roller in the front. This combination works great on concrete but [am4x4] needed this to work out in the dirt so a few mods were in order.

First the front roller was scrapped and replaced by two large 8 inch diameter tires. To get these to fit the bolt holes for the roller were enlarged to the same diameter as the wheel bearings. A new solid axle was then made from 5/8 inch solid rod. Those may look like pneumatic tires but they are actually solid rubber and only cost $6 each, also from Harbor Freight. These tires not only raise the jack up several inches but also increase the surface area contacting the ground. This better distributes the weight of the vehicle and prevents the jack from pushing itself into the ground.

In the back, the small stock casters were removed and replaced with larger, heavier duty ones. Even with the larger casters, the jack leans rearward. [am4x4] plans on making an extension to level the jack out but for now, it works well and is definitely a conversation piece at the off-road get togethers.

Nerdalert: German TV Producers’ Amazing Vectorscope Animations

March 14, 2015 by Elliot Williams 21 Comments

German weekend late-night comedy show “Neo Magazin Royale” has a bunch of super-nerds behind the screens in the production studio. This is apparently what they do when they’re (not) working: making test screens that render as multiple animations on their test equipment.

While others out there are limited to displaying cool graphics on oscilloscopes, these guys have vectorscopes and waveformer monitors. A vectorscope is like an oscilloscope in X-Y mode, but with one screen that decodes the color space and one screen for the audio (in stereo). A waveform monitor that plots out the brightness levels of a test image. Normal studio techs use these to calibrate their colors, brightness, and audio levels.

Apparently, these guys programmed a custom test screen that would: a) encode a small animation of a 20-sided die spinning around the show’s logo in the color channel b) encode the show’s logo in the left and right sound channels, and c) their production company’s logo in the screen’s brightness.

At the end of the video, the director Patrick (in the glasses) admits that they’ve spent about three months working on this project and everyone starts laughing. “And who gets anything from this? Nobody!” says the show’s host.

One way to rectify that, though. Post the source code!

Replacing Dead Battery Pack Cells Saves You Some Coin

March 14, 2015 by Rich Bremer 43 Comments

No one will deny that cordless drills can be super convenient. Sure, they need to be charged once in a while but that’s not a big deal. The big deal is when the batteries no longer hold a charge. Buying a new battery pack from the drill OEM is not cheap. If you need several, it’s almost cheaper to buy a new drill/battery combo.

It is not uncommon for only one cell is bad in the battery pack. Getting a replacement cell makes economic sense. And at about $1 per cell, even replacing all of the cells in the pack is way cheaper than the alternatives. [ksickafus] had a battery pack that did not work and not only did he replace all the cells, he wrote a great instructable about it.

The process started by removing the cells from the plastic container. Since they were soldered together they came out in one unit. The cluster of cells was then laid down on a piece of paper and the perimeter of each cell was marked to document the cell orientation. Next, the leads connecting each cell to its neighbor were noted on the same sketch.

The new cells were then laid out on the template to make sure they were in the same orientation as the originals. [ksickafus] uses braided shielding as his new tabs to connect the cells together and learned from experience that flux is necessary for this type of repair. Once everything is soldered up, it’s time to re-assemble the cells in the plastic case and give it a charge. If you do this at home, make sure you keep an eye on it the first time so nothing goes wrong!

If replacing NiCd’s with NiCd’s isn’t cool enough for you, maybe popping some LiPo’s in your drill would be up your alley.

LEGO Based 3Doodler Uses Regular Filament

March 13, 2015 by James Hobson 9 Comments

As part of a university research project, [Vimal Patel] was asked to make something out of biodegradable 3D printer filament. The theme of the project is called Monomateriality — making products out of a single material to aid the manufacturing process, and after the product is used, ease of recycling.

He started by experimenting with the 3D printer filament in the UP 3D printers the university had on hand. But he wasn’t content with the layer-by-layer deposition method that all FDM printers use. He was more curious about free form deposition modeling — extruding material along multiple axes at once.

Unfortunately the project budget didn’t afford him a 6-axis robotic arm 3D printing setup like this to complete the project. But he was able to build his own custom extruder using a hot glue gun, and some LEGO. It’s kind of like a 3Doodler, but much more bulky.

Using standard LEGO parts he was able to build an attachment for the hot glue gun to feed the 3mm diameter biodegradable filament through the nozzle. He’s uploaded the design files over at rebrickable.com to share with the world.

While the end product he designed (a bicycle helmet) isn’t too realistic, [Vimal’s] more excited at the accessibility of the making process — after all, you just need a hot glue gun and some LEGO.

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Vise Reborn As A Roll Bender

March 13, 2015 by Rich Bremer 7 Comments

Have you ever tried bending a metal rod into a consistent curve? Maybe you bent it over your knee or broke out a bucket or something. Doing it by hand never really gets the arc perfect. Handyman [Joe] found himself needing to bend a bunch of 1/4″ metal rod into various diameter rings. He didn’t have any tools to bend or roll metal and instead of fretting about it, he put on his ingenuity hat and built a perfect tool for the job.

That perfect tool is called a Roll Bender and it uses 3 rollers to bend metal into an arc of consistent radius. The straight piece of metal is passed by the rollers many times. The distance between the rollers is continually adjusted to reduce the radius of the arc of the metal until it reaches the correct size.

[Joe] started out with an old drill press vise. A piece of plate steel was welded to the stationary vise jaw to provide a platform for a grooved pulley to be mounted. On the clamping jaw, a piece of angle iron was attached to support two very large bearings. The metal rod is clamped between the two bearings and the grooved pulley. A key made from a socket and some scrap metal as a handle allow the user to rotate the pulley by hand while the distance between the rollers is adjusted by the vise’s crank. Doing this moves the rod back and forth between all 3 rollers to gradually mold the once-straight rod into a full ring.

We’ve always been fond of machines that do the bending for you. Even if they haven’t been invented yet.

DIY Surface Grinder For Making Precision Parts At Home

March 13, 2015 by Rich Bremer 31 Comments

Surface Grinders are machines that can make a surface of a part very flat, very smooth and very parallel to the face of the part that is mounted to the machine. Surface grinders usually have a spinning grinding wheel suspended over a moving bed. The bed moves the part back and forth under the grinding wheel removing an extremely small amount of material at a time, sometimes down to just a ten-thousandth of an inch (o.0001″) in order to make a precision part.

[Daniel] is a tool guy and wanted a Surface Grinder. He didn’t need a super-accurate commercial grinder so he decided to make one himself. It’s a doozy of a project and is made up of quite a few other tools. [Daniel] already had a mini CNC mill and decided this would be a good platform to begin with. The mill was rigid and already had automated X and Y axes, after all. For the grinder motor, nothing made more economical sense than to use a regular angle grinder, but there were two significant problems. First, no company made wide grinding wheels for an angle grinder. [Daniel] had to modify his spindle to accept an off-the-shelf surface grinding wheel. The second problem is that the new grinding wheel had a max RPM rating of 4400. The angle grinder can reach 10,600 RPM. In order to slow down the angle grinder, a speed control was taken out of an old variable-speed router and integrated with the angle grinder. Problem solved. A mount was then made to attached the angle grinder to the Z axis of the mill.

A magnetic chuck mounted to the mills bed is used to hold down metal work pieces. There is a lever on the chuck that when moved in one direction it creates a magnetic field to hold a ferrous piece of metal firmly to the chuck during machining. When the lever is moved in the other direction, the part is released and can be removed from the Surface Grinder.

To use his new Surface Grinder, [Daniel] creates a CNC g-code file to move his work piece back and forth underneath the grinding wheel. Being able to control the depth of cut and feed rates with his CNC machine removes human error from the grinding process and leaves a consistent finish on the part. Check out the video after the break.

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