Cutting SMT Stencils with a Laser

Prototyping your own PCBs? At a loss for how to apply your SMT electronics? Well — do you have access to a laser? [Felix] shows us a definitive way to use a laser cutter to engrave SMT stencils with ease.

The real trick here is to engrave — not to cut. Typically if you’re using enough power to cut straight through the plastic, you’re going to get melting and burning of the edges — which won’t work well for a SMT stencil. So what [Felix] found is to engrave at approximately 20-30W @ 400-450mm/s. He’s using Mylar as the material.

The results are pretty awesome — but if you’re without a laser, he also has an excellent tutorial on DIY metal SMT stencils by chemically etching soda can metal!

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Robot Arm Wields Laser, Cares Not For Your Safety

Here at Hackaday we’ve covered a bunch of DIY laser diode projects. And for good reason, they are just cool. We’ve seen people add lasers to their 3D printers, stick one in a milling machine, use a highly modified scanner and even build a simple XY gantry specifically for the task. To say the least there is definitely a wide range of methods for moving around a laser but we’ve never seen anything like what [Sp4rky] sent in to us. He and his friends outfitted an old educational robot arm with a laser.

The robot arm is a 5 axis Armdroid 5100 picked up from eBay for a couple hundred dollars. It didn’t come with a controller but all of the stepper drivers were housed in the base of the arm. After a little tinkering around with the inputs the team was able to get the arm to move by sending serial commands from a PC, through an Arduino Mega which then sends the appropriate signals to the uni-polar stepper drivers. That was the easy part of the build.

The hard part was getting the arm to hold the laser at a consistent angle and height above the table. Inverse Kinematics to the rescue! Since the desired position of the laser, as well as the length of the arm segments is known, mathematical formulas can be derived to determine the necessary arm segment and joint positions while moving the laser around. The process flow starts out with an image in Inkscape, g-code is then generated with this plugin, then sent to the Arduino running a modified version of GRBL that has the inverse kinematic formulas. The Arduino directly controls the stepper drivers and the robotic arm moves. The Arduino also controls 3 constant-current laser drivers made from LM317 regulators. Three laser drivers, why?

Triple Laser Robot[Sp4rky] got his laser diode modules out of surplus medical equipment and, unfortunately, the rated optical wattage was quite low. Since he had 3 diodes, he decided to try to combine the 3 low power beams into one high power beam. This can be done using a prism. A prism splits sunlight into a rainbow of colors because each wavelength(color) of light that passes through the prism is bent a different amount. Since the laser diodes only put out one wavelength of light, the beam bends but does not split or diffuse. A 3D printed bracket points each laser diode at a 3-sided pyramidal prism which sends the combined beam of light straight out the bottom towards the object to be cut or engraved.

This project is cool enough that we would have covered it even if [Sp4rky] wasn’t burning a Hackaday logo. Although it doesn’t hurt for anyone wanting their project to get covered!

Playing Space Invaders with Real Fire and Lasers

Making a Space Invaders game is up there on the list of most unconventional things you could do with a laser cutter. In watching the tiny little ships burst into flames, [Martin Raynsford’s] modification has got to be one of the more dangerous looking ones we’ve seen as well.

[Martin] always had the desire to make a tangible version of the classic game. Since his Whitetooth A1 laser cutter already contained the bulk of the moving hardware needed, not to mention an actual high powered laser to “pew pew” with, he decided it was the perfect starting point for such a project. The game is played looking down into the cutter since the laser of course fires in that direction, however a basic webcam is mounted to the laser assembly so that you can view the game on a computer screen at the proper perspective. An Arduino Mini is responsible for stepper control, allowing the player to jog back and forth and fire with a keyboard. [Martin] added an extra gear to the z-axis bed-leveler so that it could drive rows of paper invaders left and right across the bottom. Paperclips wedged into slots along a modified backboard hold each of the paper slips in place. This works ideally since they can be reloaded easily and won’t be maimed during use.

Due to the heat of the laser, landing a well positioned shot will likely nuke all of the nearby invaders as well, making for a theatrical inferno and easy win. Now to step up the difficulty level and figure out how to make them fire back…

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Laser-Cut Clock Kicks Your CAD Tools to the Curb and Opts for Python

In a world deprived of stock hardware other than #6-32 bolts and sheets and sheets of acrylic, [Lawrence Kesteloot] took it upon himself to design and build a laser-cut pendulum clock. No Pricey CAD programs? No Problem. In a world where many fancy CAD tools can auto-generate gear models, [Lawrence] went back to first principles and wrote scripts to autogenerate the gear profiles. Furthermore, not only can these scripts export SVG files for the entire model for easy laser cutting, they can also render a 3D model within the browser using Javascript.

Given the small selection of materials, the entire project is a labor of love. Even the video (after the break) glosses over the careful selection of bearings, bolt-hole spacing, and time-sensitive gear ratios, each of which may be an easy macro in other CAD programs that [Lawrence], in this case, needed to add himself.

Finally, the entire project is open source and up for download on the Githubs. It’s not every day we can build ourselves a pendulum clock with a simple command-line-incantation to

make cut

Thanks for the tip, [Bartgrantham]!

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Measure Laser Wavelength with a CD and a Tape Measure

Obviously the wavelength of a laser can’t be measured with a scale as large as that of a carpenter’s tape measure. At least not directly and that’s where a Compact Disc comes in. [Styropyro] uses a CD as a diffraction grating which results in an optical pattern large enough to measure.

A diffraction grating splits a beam of light up into multiple beams whose position is determined by both the wavelength of the light and the properties of the grating. Since we don’t know the properties of the grating (the CD) to start, [Styropyro] uses a green laser as reference. This works for a couple of reasons; the green laser’s properties don’t change with heat and it’s wavelength is already known.

It’s all about the triangles. Well, really it’s all about the math and the math is all about the triangles. For those that don’t rock out on special characters [Styropyro] does a great job of not only explaining what each symbol stands for, but applying it (on camera in video below) to the control experiment. Measure the sides of the triangle, then use simple trigonometry to determine the slit distance of the CD. This was the one missing datum that he turns around and uses to measure and determine his unknown laser wavelength.

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A Motor, an Arduino and a Whole Bunch of Laser Cutting

[Guido] was recently commissioned to build a kinetic sculpture for a client who wanted something unique. What he came up with is really awesome.

It’s called ORBIS: The Wooden Kinetic & Lighting Sculpture. It mounts to the wall and provides a focal point for the room – a bright flashy spinning one at that! Does it just stay there and do random things? Nope, of course not! [Guido] built it with a unique control box, two Arduino 2560’s and an Xbee to communicate between them.

Orbit Kinetic Sculpture

He was told to design it using old and new technologies so he’s got a rotary phone dial on the side of the box which allows the user to change through the different modes.

Switches on top also let you change the color of the sculpture and the speed at which it moves around. Since it’s wireless it can be easily set on the coffee table and become an instant conversation starter.

See it in action after the break.

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How to Identify Plastics Before Laser Cutting Them

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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