The Hardware Components
The Lasersaur is built from a number of subsystems. For readability these subsystems are color-coded throughout the documentation. Also the following names are used whenever possible. We have organized both the CAD model and the BOM to reflect this convention.
frame-gantry: #83bbff frame-outer: #546883 frame-door: #828ca3 frame-panels: #431424 frame-table: #443858 x-cart: #9e4301 x-drive: #bc652e y-cart: #650b01 y-drive: #b72e22 optics-laser: #b9d551 electronics: #9b982b air-assist: #a3b693 extraction: #a8968b
The mechanics comprise both stationary and dynamic parts. The primary building blocks of both the frame and the gantry are T-slot aluminum extrusions. They are widely used in the automation industry and many suppliers offer them. The Lasersaur is designed around extrusions with 20mm side lengths. All the mount assemblies are built from angle brackets and custom-cut acrylic pieces.
The linear motion assemblies for the x- and y-axis roll directly on the aluminum extrusions. Unlike many gantry designs, no proprietary rails and carriage assemblies are used. The Lasersaur carriages are build from standard-sized ball bearings (with nylon coating), cap screws and custom-cut acrylic pieces. Bot axes are minimally constraint and are quite forgiving in terms of inprecisions of the frame.
The drive mechanisms are based on timing belts and stepper motors. We use 12-tooths pulleys, 5.08mm XL belts and 2000 microsteps steppers/drivers. This results in a theoretical resolution of 0.03mm/step.
- overall dimensions: 1700x1080x350mm (67x42.6x13.8")
- work area: 1220x610mm (48x24")
Optics and Laser
Lasersaur uses a stationary laser source and flying optics to direct the laser beam to the location of interest. Three mirrors and one lens plus the various mounts make up the optics subsystem. The optics components are from a modular system (Thorlabs). This makes it easy to experiment with further improvements like different laser sources and beam expanders. Mirrors and lenses have a 1" diameter and can adapt well to stronger lasers.
The system is designed with a DC-excited CO2 laser tube in mind but can be adapted for other sources relatively easily. The space dedicate to the tube can accomodate up to 1.4m tubes which makes it compatible with typical low-budget CO2 lasers up to 100W.
A typical low-budget CO2 laser system (like the one listed in the BOM) consists of 3 components: laser tube, power supply and water chiller. We have a dedicated space for the power supply inside the Lasersaur. The water chiller is external to the box.
The system is controlled by a vanilla Arduino Uno in conjunction with two GeckoDrive G251X. A custom Arduino shild (laa-shld) connects all the components and simplifies wiring. Each of the Geckos drives a Lin Engineering stepper motor. For the x-axis we use a lightweight Nema 17 and for the y-axis a Nema 23 with rear shaft.
The Arduino also controls the laser intensity via a digital PWM line and monitors limit switches and door sensor. We have a few GPIO available to also control the water chiller, air assist, and fume extraction. Many of the non-essential control functions are subject to firmware support.