2. Computer Controlled Cutting Assignment

Computed Controlled Cutting Assignment

The Challenge for this assignment was two-fold: first, using the Vynil Cutter and second, making a press-fit kit, which I chose to make using the laser cutter.

Vynil Cutting

I decided to go as simple as possible with the Vynil cutter, and since I needed some decorations for my laptop, I readied a couple images for cutting using the fab modules app, The process was quite easy and simple to get through.

The tricky part came when It was time to take it out of the Vynil and paste it into the laptop. First mistake: I sent another image to the plotter without actually verifying the position for the blade, meaning I actually had to re-cut the eagle, not so good-work.

The second mistake I made was actually not being patient enough when the time came to paste the objects into the laptop. Why? The parts (being more specific, the eagle) were quite small,and some details (like the head and beak) did not bonded properly to the surface, so, when I removed the transfer tape, the results were not optimal. the second figure was not so complicated, so it was simpler to get it pasted.

Finally, here are both figures in place, the one of the eagle´s heads and one of the claws are gone by now.

Laser Cutting

The real challenge, on the way to getting a press-fit kit done, was how to design the kit in order to take into account the thickness for various materials.

The first idea I had was to make a press-fit molecule kit, so simple molecules could be represented (for instance, Hydrocarbons) I was aiming to make a methane-like structure, or some other simple Hydrocarbons

So, I would need a couple pieces for the carbon atom, since I needed a 3D figure and the laser cutter would only provide for 2D cutting, some pieces for the chemical bonds and other set of pieces for Hydrogen Atoms.

Afterwards, I started designing, but as I was going on tinkering with CAD software I started to work on how to make the designs parametric.

Since the simplest way of getting parametric was setting the model geometry as a function of a given variable (the parameter) I picked up where I left off in the last assignment and started coding in OpenSCAD:

Then, after becoming aware of the inherent limitations of the software (only exports on STL, so the model would not be cut) I switched to kokopelli, starting from Jin Jo Lee's script for making shapes for cutting, I adapted it to work with rectangles instead of squares, as it was originally scripted, bur something went wrong, a rectangle was not placed properly in the array!

After reading, re-reading, and testing the script, I got to make it work just fine

Next on my list was using grasshopper to see how different is was to produce parametric forms for cutting. But I could not make it work, so, after some researching, I went to Inventor.

getting parametric with inventor

The capabilities of Inventor to constrain measurments as mathematical functions (for instance d1=3*d0 + 1) was exactly what I needed to get the job done, in the picture above I am adapting the model for a 5.6mm thick MDF sheet. The original measurment was set fot 2.5 mm

However, designing with Inventor forced my to add an additional step to the workflow, given that Inventor will not export its sketches to DXF for laser cutting, I had to save them as DWG (AutoCAD format) and then open them for export using Draftsight:

Importing to Draftsight

This added up to the workload, since the exporting process sent all the lines in the same layer, regardless of them being drawing or construction lines. A line-clean up was in place, and it had to be done anyway since it is necessary to check for double lines or ghost lines before actually cutting.

After this being done, I exported the files to Corel Draw for cutting:

pieces exported to corel Draw

Cutting was actually the easiest and quickest part of the assignment.

But, as the model came to life, some design problems started to appear:

laser failure

First, in the model I drew a set of lines in the middle of one piece in order to make it flexible, the lines were too tightly drawn, and the MDF burnt, I corrected by removing most of the lines, but to no avail, the piece was just as rigid, A bigger model with more lines would be more suitable.

The second mistake was the scale, the pieces were too small to be fully useful.

cut pieces

Third, some slots were just too wide to make a good match, so the couplings were, at some cases, too loose.

As I was starting to assemble, I realized that in order to make the assemblies stand I needed a different kind of piece to make this happen, farewell hydrocarbon models. There is a lot of room for improvement.

Below are some photos of shapes I made tinkering with the kit:

The design files for the construction kit can be found Here.