Rice Lasersaur
Student built open-source laser cutter
During the fall 2012 semester, I signed up for a class offered by the Rice University art department titled "The Art of DIY". It focused on developing problem solving, technical, and team skills in order to complete complex projects. The capstone assignment for this class was to build a 100 Watt laser-cutter with a working area of 1220x610 mm^2. The
particular model that we built is called the "Lasersaur". Its design is constantly
being improved by a community of builders who build upon each other's
knowledge. Working on this project gave me the urge to become more
involved in other open source projects. I like how open source
communities use the internet as a way to democratize technical
know-how.
After taking an inventory of all parts, construction of the work area frame began. The aluminum extrusions used to make the frame are joined by angle brackets, screws, and metal inserts that go in the grooves. The aluminum extrusions come together in a way that is kind of like a mixture between Legos and Ikea furniture. They are also great for achieving adequate tolerances because all parts come pre-cut and have well defined straight edges.
The part pictured to the left serves as a track for the linear motion of the Y gantry.
The base of the machine was then constructed. The vertical extrusions will support the frame pictured above. The metal members that are raised from the wooden table are are supposed to support the medium being cut by the laser. Tinted poly-carbonate sheets are placed to isolate the working area from the laser diode and electronics.
The linear motion frame is place on top of the base. Subsequently, the top layer of the outer frame is assembled. The door is then hinged and supported hydraulically. At this point, all structural members have been installed. We decided not to skin the cutter so that we would have easy access to all the mechanical and electric components that make up the cutter.
The motor that drives the Y gantry can be seen on the upper left corner. It has shafts that extend both directions so that the cart is pulled evenly on both sides. The Y gantry has bearings that sit on the frame. Both end of the Y cart are then attached to the belts that extend from the motor. The X cart sits and rolls on the Y gantry. The X motor is also located on the Y gantry and it drives the X cart back and forth.
The frame is skinned with aluminum sheeting. This will protect the user in case of a stray laser. Tinted poly-carbonate is placed on the door so that one can safely look at the cutting job. An emergency shut down button is placed on the lower right corner of the front.
The 100 Watt laser diode is secured on the rear part which also houses the power supply, motor controllers, and arduino board. The diode is cooled by a constant steam of water that runs through the coils that can be seen in the picture.
The "cutting head" consists of a mirror that aims the beam downwards to a lens that focuses the beam to a very small area. The cylindrical housing of the lens is nozzled at the bottom. This allows us to run pressurized air through the housing which then exits at high velocity toward the spot being burned. The air stream greatly reduces the fire hazard associated with burning things with a laser.
This was the first thing that the laser etched out. It can be observed that the laser did not cut all the way through and the line thickness is too big. This resulted from an unfocused lens. The lens height must be adjusted in such a way that the focal point sits on top of the surface that is being cut.
We then tried to cut out the same R design from a carbon fiber nomex sandwich board. The polymer matrix of the carbon fiber sheet causes it to be very reflective. While cutting, much of the light was scattered upwards so we were not able to achieve a proper cut. A practical solution would be to coat reflective materials with something that is not reflective.
The cutter was used to make this Christmas ornament out of cardboard. Now that the laser is focused, the line thickness decreased and the material will be cut even at low power levels. Upon close examination one can notice a waviness in the cut. We believe this to be caused by uneven acceleration of the X and Y motors. The waviness is most noticeable at the beginning of the vectorized tool paths.
The linear motion mechanism consists of two independent stepper motors that control the x and y motions. each motor drives a system of nylon timing belts that are attached to the x and y carts. Stepper motors are used in laser cutters because they allow for very fine control of shaft rotation. The motors are controlled by an arduino; a very versatile open source micro controller.