Better Lasing With Pulses

laser

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.

 

Creating PCBs with 3D Resin Printers

PCB

The folks over at Full Spectrum Laser are Kickstarting their own 3D printer – a stereolithography machine like the Form 1 and B9 Creator printers. During their testing, they discovered a new application for these SLA printers that should prove to be very useful for the makers and builders using machines – manufacturing PCBs with UV-sensitized copper clad boards.

Full Spectrum Laser’s printer – the Pegasus Touch – uses a near UV laser and a galvo system to build objects in UV-curing resin layer by layer. In retrospect it seems pretty obvious a UV laser would expose UV sensitive boards, but this discovery simply reeks of cleverness and is a nice ‘value added’ feature for the Pegasus printer.

The Pegasus printer has a laser spot size of 0.25mm, meaning the separation between traces on Pegasus-produced PCBs will be just under 10 mils. That’s a bit larger than the limits of laser printer-based PCB fabrication but far, far less complicated. Making a PCB on an SLA printer is as easy as removing the resin tank and putting a sensitized board on the build platform. Draw some traces with the printer, and in a few minutes you have an exposed board.

We’d really like to see if this technique can also be used with other SLA printers. if anyone out there would like to experiment, be sure to send the results into the tip line.

Video from Full Spectrum Laser below.

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