I see a number of articles on the WEB about using a blue laser around 2 watts for cutting and engraving. A lot of times the laser is attached to a 3D printer. Now I have a 3D printer but I wanted a cutter that was a bit larger and did not want to bother with swapping the laser for the print head. So I built a carriage for the laser based on reprap Prusa technology.
The usable area of the bed is about 16″ by 16″ (400 by 400 mm). Unlike the 3D printer the laser is moved in both the X and Y directions rather than moving the bed in one direction and the laser in the other. A piece of 3/4″ plywood serves as the base and it sits on rubber feet so I can get my fingers under it to pick it up. The carriage and gantry move on 8 mm rods with dual linear bearings. I used two steppers to move the gantry in the Y direction to provide even force at each end of the gantry. There is no Z axis as the laser can be refocused for different height materials. There is a piece of sheet metal on the base that serves to protect the plywood from the laser.
Parts like the motor mounts and bearing supports are 3D printed and are based on the Prusa parts. For the electronics I used the Arduino mega with the ramps 1.4 interface. Since I have 2 steppers for the Y axis the Z axis driver on the ramps was used as it has two stepper connectors. To get this to work I modified the pins.h file in the Marlin software to swap the Y and Z axis.
The laser is turned on by use of the fan circuit in the ramps board. This is really handy as the circuit provides the 12VDC needed by the laser and there is Gcode functions to turn the fan on and off.
There is a bit more work to do on it. The cables need to be properly dressed. Then there is all the safety issues. It needs a lockout switch and an enclosure to prevent any stray laser beams and control the fumes.
Repetier-Host works well for testing and for sending the Gcode files to the cutter. The manual mode lets me move the carriage around and turn the laser on and off. The first test I did was using handwritten Gcode to cut a 20 mm square. For generating more complex designs I have settled on using Inkscape for drawing and have tried both Gcodetools and J Tech Photonics Laser Tool extensions to generate the Gcode. So far I have had better luck with the J Tech tool.
Here is a short video showing cutting the fabric.
I did a number of tests to see what materials could be cut with this laser cutter and what cutting speeds to use. Regular paper cuts very easily. The cuts don’t even have a burnt looking edge like thicker material. Card stock cuts nicely with a slightly slower cutting speed. Cereal box cardboard would take a slow cutting speed and several passes to cut. Normal thickness cotton fabric cuts easily. I haven’t yet tried other types of fabric. Cricut vinyl cuts and you can adjust the cutting speed to cut just the vinyl and not the support material. It will mark wood with nice clean lines.
Above is Cricut vinyl cut with the laser and below is after it has been weeded.
Below is a piece of pine that has been engraved with the laser.
I see many interesting uses for this laser cutter especially once I get better at using Inkscape.
Around about the time I got my 3D printer working I saw that the University of Iowa was offering a Senior College course “Designing and Manufacturing with Computer Modeling and 3D Printing”. That sounded useful so I signed up for it. The most important software tool for 3D printing is the 3D design program and I was looking around for a suitable program to use. Just a week before the course started a friend turned me on to Autodesk Fusion 360. This looked like a nice program and it was targeted to 3D printing users. So I decided to learn it. Then along comes the Senior College course and it turns out to be primarily how to use Autodesk 3DS Max 2016 a much more complicated program. Since 3DS Max is not free like Fusion 360 I decided to concentrate on learning Fusion 360 and take whatever I could get from the course on the overall 3D design process.
The biggest hurdle to get over is figuring out the order things are done in 3D design. In 2D drafting if you wanted to draw a 1x2x0.5 bar with a 0.25 hole that is what you would draw. In the 3D system the general idea is to sketch out the basic form (bar with hole) then go back and add the dimensions and any other features for the design. When designing more complex shapes you really have to think through how best to go about getting the shape you want and the order of the operations. Several times I have gone down a path and had to back up or start over to get where I wanted to go. I was hoping to get some of the how to go about it from the course but 3DS Max is so complex that about all that could be taught was the basic which button to push. It would have been nice if there were some student helpers there that could help with the basic questions about the program.
There is a difference in the process between creating an artistic pleasing shape and mechanical design where you need make a part that has precise dimensions that have to be followed. From what I know so far 3DS Max seems more suited to the artistic process and Fusion 360 to the mechanical design process. Of course this could be because I haven’t found the appropriate functions in 3DS Max. It kind of looks like you may be able to customize the 3DS Max workspace for different processes.
Above is an image of half a flywheel that I am designing using Fusion 360. The goal here is to print this in plastic then use the plastic printed part as a pattern to cast the flywheel in metal. A plastic flywheel would not be too useful.
There are other approaches to 3D printing besides designing an object using a CAD program. Online there are several repositories of things already designed that one can download and print or order a print. I have used this a few times to get parts and accessories for my 3D printer.
Above is a Christmas tree ornament that I downloaded the design and printed.
Yet another approach is making copies of existing objects either full size or miniature replicas.
I used the Autodesk product Memento to generate a 3D mesh of a broken gnomon. Hopefully I can digitally repair this, print a plastic pattern and using the pattern cast a new gnomon in brass.
This process involves taking many pictures of the object from every possible angle then processing the photos using the Memento software. I have yet to figure out exactly how to go about doing the repairs. Memento provides some tools to manipulate the mesh and there are other tools to work with meshes.
Even if you don’t own a 3D printer a working knowledge of 3D design software can be useful. There are quite a number of companies that offer 3D printing services. You can submit your design files online and get quotes and order printed parts. These companies offer quite a number of different materials including metal.
The temperature sensor for my weather station is a commercial wireless temperature/humidity sensor that I have mounted in a commercial solar radiation shield. It has been in operation for a couple of years and seems to be reasonably accurate. The humidity sensor part did fail and the sensor had to be replaced. Despite being in the radiation shield the outdoor environment is hard on humidity sensors.
Above is a picture of the commercial solar radiation shield with the wireless temperature/humidity sensor inside.
Another approach to protecting the sensor for solar radiation is to use a fan to provide a steady flow of external air. Essentially blowing away the hot air around the sensor. The processor that I am using to read the wireless weather sensors also has provisions for a wired temperature/humidity sensor which I have been using to monitor the conditions inside the instrument cabinet. I thought it would be interesting to compare the passive radiation shield with a fan aspirated shield.
I build a simple shield out of some 2″ PVC pipe and fittings.
The picture above shows the parts of the sensor. In the middle is the actual sensor mounted on a small PC board with a RJ11 connector. Above that is a 12VDC wall wart to power the fan. The 40 mm computer fan to the left is mounted in a short section of 2″ PVC and glued in place. A length of telephone cable is used to connect the sensor to the processor. A PVC U fitting and a longer piece of PVC completes the sensor.
Above is a picture of the completed sensor mounted on my instrument platform. The fan draws air up the long tube and out the short tube. With both ends to the tube facing down it should help keep the rain and snow out. The sensor is located near the middle of the U fitting. It remains to be seen how long the fan and humidity sensor will last in this environment.
After it runs for a few days I will compare the performance of the two sensors.
6/22/2016 Comparison data between the two sensors shows that the fan aspirated sensor is affected by the sun more than the sensor in the shield. Next I will try a simple sun shade for the fan aspirated sensor.