Still laser cutting all of your parts in 2D? Not the folks over at [Just Add Sharks]. With a few lines of code and an in-tact Wii-Mote, they’ve managed to rig their laser cutter to dynamically refocus based on the height of the material.
The hack is cleanly executed by placing the Wii-Mote both at a known fixed distance-and-angle and within line-of-sight of the focused beam. Thankfully, the image-processing is already done onboard by the Wii-Mote’s image sensor, which simply returns the (x,y) coordinates of the four brightest IR points in view. As the beam moves over the material, the dot moves up or down in the camera’s field-of-view, triggering a refocus of the laser as it cuts. Given that the z-axis table needs to readjust with the contour, the folks at [Just Add Sharks] have slowed down the cutting speed. Finally, it’s worth noting that the Wii-Mote was designed to detect IR LEDs, not a 10600-nanometer laser beam, but we suspect that the Wii-Mote is receiving colors produced by the fluorescing material itself, not the beam. Nevertheless, the result is exactly the same–a dynamically refocusing laser!
Now that [Glowforge] has released a continuously-refocusing laser cutter implemented with stereoscopic cameras, it’s great to see the community following in their footsteps with a DIY endeavor. See the whole system in action after the break!
The glowforge only has one camera in the head which means it’s probably doing something similar to this rather than stereo vision. Still it inspired me to make something like this so I’ll keep guessing until mine actually arrives.
I made an autofocus for mine using the stepper out of a DVD drive. I step down until the air nozzle hits the work and keep stepping while the stepper motor is stalled then I rewind 1.5mm because I know that the focus point is 1.5mm below the end of my air nozzle. That way I do not need an up down table and can stick anything up to 35mm thick in there, that s the travel of the DVD stepper screw. I use a 8 pin PIC to do it.
I should add that my focusing lens is in the top of my air nozzle.
Same as here, did you write the project up anywhere, got some pics to share?
This is continuous and non contact so I’m not sure a stepper respond fast enough but I’m interested in seeing your arrangement and maybe a 9G servo could respond fast enough to move the lens around.
can you comment on the detector you used to detect the air nozzle hits the piece? Was it based on monitoring the pressure of the gas assist?
I found some information about this, it basically drove the stepper motor into the material until the motor stalled, the software carried on driving it to the end of the travel (even though it couldn’t move any further) and then backed off 20mm. A neat little hack.
Fluorescing? You mean burning?
This might not work well with acrylic, often there is little to no light emitted from the cutting or engraving. Though it should work fine with most woods and other organics like leather.
Incandescing?
Scintillating?
There’s no visible light, but since the Wiimote detects infra-red, it should pick up the heat from the part being cut. The article is a little inaccurate when it’s talking about ‘colours’ being picked up – it’s actually the spot of heat that it’s seeing.
It would be interesting to see how it copes with the flashes you get from the metal grille below the part, though.
Wrong “infrared”. The camera in the wiimote is near-IR, probably sensitive up to about 900nm. “Heat” is typically 6000nm-14000nm and will not be detected by this camera. You could use one of the FLIR lepton cameras, they are sensitive from 9-14um, but their 9fps frame rate would make it pretty useless.