This week I did vinyl cutting and laser cutting as well as developed skills in 2D and 3D design. I started using Inkscape and CorelDraw and FreeCAD this week. As this was my first experience in FreeCAD, first of all I watched some tutorials to get used to the tools and options. I did fully parametric design this week, which was exciting.
And the last but not least, this was my first experience with the vinyl cutter and laser cutter. It is a big responsibility to run both machines, so it’s important to read the user manuals and acknowledge the safety rules, before starting the cutting process.
After choosing the material I want to cut on, I followed those steps for tsting the cutting force.
And the original file of my drawing is here
As I am going to cut a construction kit, which will have joints , it’s essential to design and cut kit parts properly, so that connections will be not too loose and not too tight. For that I did a tolerance test for the cardboard, which I was going to use. I measured thickness in different parts of the sheet using caliper and the minimum result was 3.8mm. I designed a comb-style part with different widths of holes started from 3.8mm to 3.5mm, and the step is 0.05mm. I did the whole design parametrically, which will allow me to use the same file for other thicknesses and if I decide to change the step value.
This time I used FreeCAD as a design tool, to be familiar with one more programm as well. Here is the step by step guide for designing tolerance test kit
Before starting to use the laser cutter, I have read the manual of the machine and with the instructors we got acquainted with the parts of laser cutter and principles of working with it. The most important things are to keep the machine tidy and maintained, and follow safety procedures.
In the manual there are recommended speed, power and frequency for different materials.
The power level directly controls the amount of energy in the laser. As power increases, the energy in the laser increases.
The amount of energy needed to penetrate will vary between materials and their thickness.
Since the laser cuts in a thin conical shape, more power will result in more perpendicular walls and a deeper cut, but will also mean more material removed.
High energy could also make more smoke and charred edges.
So, power is a necessity to reach a required cutting depth, but it is quite destructive to our materials. To make clear edges and less smoke, we should adjust the speed.
This setting changes the speed that the laser carriage will move.
The key to speed is that the longer the energy is exposed to a part, the more energy it will receive. Remember that high exposure to energy could result in smoke and charred edges.
Therefore, we use speed to control the length of time energy is on a point, thereby reducing the exposure to energy, yet still having the required amount to make a cut and avoid flames.
Increasing speed will also make the time of the project quicker. However, too much speed limits energy exposure and could make the cut too shallow.
As a conclusion we can say, that
To not waste a lot of cardboard, before cutting my drawing, I did cut one small rectangle with recommended parameters, to see if everything works well. The cut was perfect, so saved the same parameters for my actual job. Here are the results of my work, and as you can see the best parameter for thickness for this sheet is 3.55mm, even though the actual thickness is 3.8mm.
We used information from thsi source to find the kerf of the laser. We designed in CorelDraw and cut a rectangle with 10 rectangles in it. Thus, we have 11 line cuts.
After cutting, we merged together the small rectangles and measured the length of them together by caliper and got 119.27mm. Then we measured the size of the “frame” rectangle (120.30), subtracted from that oor first value and divided to 11.
So, the kerf of the laser is 0.09mm
As I did for the tolerance test kit, this time as well I saved the file as .svg and did laser cutting.
I have imported the svg file of my construction kit to the CorelDraw program on a computer, which is connected to the laser cutter. Then changed parameters of the document as shown in the screenshot below.
I made two types of parts: small pentagons and bigger octagons. After cutting with the same parameters as I had during the test, I took my created parts to my kids. They enjoyed playing with it and used their imagination to have different objects. We ended up having a pen box, a deer and there is more still to come.
Inspired by what I’ve done so far and being already confident with FreeCAD, I designed the same kit with chamfer joints.
I had more experience using the laser cutter during my Final project. I have done laser cutting of the leather as well as engraving on the wood. You can check out the whole process in my Final project page.
February 3, 2022