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Tweakie.CNC – CNC Homebuilt router, mill, engraver, vinyl cutter.

CNC machine construction and operational details together with examples and samples of things that can be made and techniques used for small CNC machines. Low Power Laser as he said “

To drive the laser I am using an adjustable, constant current source which is capable of driving a 2 to 2.5 Volt diode at any current between 5 mA to >500 mA thus catering for most commonly available types. The laser diode used here is being driven at 170 mA which according to the manufacturers specification will produce 150 mW of laser output power (before the lens).

The drive PCB also incorporates a ‘TTL modulation input’ which will allow pulsed operation up to 15kHz and providing the pulse width is small enough and the PRF high enough (check with the diode manufacturers specification) the laser drive current, and subsequent output power, could be increased accordingly (an additional heatsink may also be required for this type of operation). I am, however, operating it in CW mode and as the specification for the modulation input is <0.5 Volt for off and >2 Volt for on, this has meant that I can switch the laser on and off using a signal derived from the Z axis direction pin of the LPT port. Therefore, by disabling any Z axis movement and manually focusing the laser onto the surface of the work I am able to use the same GCode file (vector graphics) albeit with a reduced feedrate that I would otherwise have used for conventional point engraving (+Z moves turn the laser off and –Z moves turn it on again).