The folks at the Lansing, Michigan hackerspace built themselves a 40 Watt laser cutter. It’s an awesome machine capable of cutting plywood and acrylic, and is even powered by a RAMPS board, something normally found in 3D printers. They wanted a little more power out of their 40 Watt tube, though, and found pulsing the laser was the best way to do that.
Unlike the fancy Epilog and Full Spectrum Laser machines, the Buildlog.net 2.x laser cutter found in the Lansing Hackerspace didn’t use Pulse-Per-Inch (PPI) control until very recently. When a laser tube is turned on, the output power of the laser is much higher – nearly double the set value – for a few milliseconds. By pulsing the laser in 2-3 ms bursts, it’s possible to have a higher effective output from a laser, and has the nice added benefit of keeping the laser cooler. The only problem, then, is figuring out how to pulse the laser as a function of the distance traveled.
To do this, the laser cutter must accurately know the position of the laser head at all times. This could be done with encoders, which would require a new solution for each controller board. Since laser cutters are usually driven by stepper motors controlled with step and direction signals, a much better solution would be to count these signals coming from the CNC computer before it goes to the RAMPS driver, and turn the laser on and off as it moves around the bed.
A few tests were done using various PPI settings, each one inch long, shown in the pic above. At 200 PPI, the laser creates a continuous line, and at higher PPI settings, the lines are smoother, but get progressively wider. The difference between PPI settings and having the laser constantly on is subtle, but it’s there; it’s not quite the difference between an axe and a scalpel, but it is a bit like the difference between a scalpel and a steak knife.
It’s an impressive build for sure, and something that brings what is essentially a homebrew laser cutter a lot closer to the quality of cutters costing thousands of dollars. Awesome work.
Finding new uses for your tools and equipment can be very exciting. [Foamy] wrote in to tell us about a blog post by [qbotics] that demonstrates etching designs into denim with a laser cutter. What a cool unexpected use for a laser cutter!
According to the Epilog laser cutter’s website, “we have engraved everything from denim to acrylic with fantastic results”. This inspired the author of “Science with denim” to try engraving jeans. After some experimentation, [qbotics] found that setting the 75W laser cutter to 15% power at 100% speed worked best. The results are quite impressive; the engraved pattern looks like naturally faded jeans. Amazing.
In the past, we have seen lasers engrave everything from calculators to wood. We would be curious to see if some of the DIY laser cutters could engrave denim as well. Give it a try and tell us about it!
[Bradley Gawthrop’s] biggest gripe about his laser cutter is the lack of Mac support. We don’t think we’d have any gripes if we owned one of these (yeah, that’s a lie…) but we can understand his second biggest issue which is the inability to see the work piece once it’s inside the machine. He figured out a very easy way to light the area as the cutter gets to work.
It occured to him that the optical head is always directly above the part of the work piece he was interested in seeing. He had been using a flashlight to shed some light, but what if he just added lighting to that head? The circuit is certainly nothing hard; some LEDs, resistors and a power source will do the trick. But routing the power is where things get more difficult. You need flexible wiring strung just right so as not to restrict motion on the X/Y axes. Most of his time was spent routing some 14 gauge stranded speaker wire for this task. He added his own 5V DC supply to power the adhesive LED strip which enjoys a resting place on the bottom rail of the head unit. Boom, problem solved.
[Daniel] sent us his entry to the Epilog laser cutter challenge on instructables. He made a book scanner, mainly out of found parts. The bulk of the project was salvaged from dumpsters, though if you’re not comfortable with that, the free section of craigslist might be able to do the job. The cameras are loaded with CHDK, using StereoData maker, and custom software to compile the images into PDFs. They did a fantastic job of documenting every step of the construction, including helpful tips for some of the more complicated parts. There are several videos in the instructable, so be sure to check them out. We’re particularly amused by the extra step of making the photo captions visually interesting. At 79 steps, it’s a long read, but well worth it.
[Murray484] submitted his instructable on how to create a stepper motor controller from an old scanner. He removed the motor and controller from an old scanner then harvested the parts. He’s pretty much starting over, taking the ULN2003 chip from the scanner motor controller and putting it on a fresh board. He then wired it all up, installed the software and got it working. Finally, he built a container out of cardboard for it all. Though he could have made it nicer looking and used higher quality building materials, he was trying to make this a “green” project for the epilog laser cutter contest. He’s done a good job recycling, this could be pretty useful.
[Madaeon] pointed us toward this entry for the Instructables Epilog challenge. While this may not be extremely complex, or have as many wires as our typical post, it is a fantastic example of thinking outside the box. How many lemon batteries have we seen? A lot. This one stands out as being more elegantly displayed and functional at the same time. In its final form, you sprinkle lemon juice on it’s petals and it lights up. If you ever find yourself in the position of teaching someone about electronics, remember this project. Sometimes aesthetics can make a dull simple project take on a life of its own.
While we hope you enjoyed our How-To: Etch a printed circuit board, toner transfer certainly isn’t the only way to get the job done. [Garrett] from macetech has recently been playing around with using an Epilog laser to etch PCBs. He started by applying a thin even coat of flat black spray paint to the copper board. The laser is used to remove paint in areas that you want the copper removed. Once that’s done, you proceed with etching as usual. He eventually removed the paint mask using acetone. The result has very fine, sharp traces, but most people that have tried this agree that using spray paint is less than ideal.