Week 3: Computer controlled cutting

.SVG

I pressed on "select .svg file" and opened the one I wanted. I then edited speed, force and origin position of the blade and pressed on "send file to printer" button.

.PNG

Differently I could have wanted to use a .png file, but steps to follow are the same. In case I wanted to save .camm file instead of sending it to printer, I would have had to press on "module"-->"add server module" in the upper fields of the screen. Then choose "file"->"save". As a new block appears on the screen and it's necessary to put it in the right position (to do that check input and output of the block to insert and of the ones already linked). Once file is saved, shell commands described earlier have to be run:

Below there's drawing-sticker comparison:

Parametric design: sketching with equations on Solidworks 2016

After kerf testing, we had to develop a parametric design of a press-fit kit to create for third week assignment.
It took me one day or two clearly understand what a "parametric design" really was but after many examples, tutorials (a nice one here) and support explanation (here) I passed from theory to practice.
I decided to use Solidworks because I'm familiar with this software but I had never used Equations to drive my sketch so I thought it would have been easier to check if the assembly of my sketch worked well
I intended to first test a simple joint and only after to design a press-fit parametric kit.

Testing parameters with kerf and joint

Opening a new Part, you can start setting sketch parameters right-clicking the Equations folder in the FeatureManager design tree, and select Manage Equations or by going in Tool-->Equations.
I show below the parameters I set: and then I made a simple joint sketch: NB: in quotation window it's important to type "=" before parameter's name.
If quotations and parameters are properly defined, if you change parameters value, dimensions of the sketch will change.

It is necessary to save drawing as a .dxf file to send it to the lasercutter and to do so you need to extrude your sketch before (you have to select faces to export as dxf file).

First attempt I made was with 0,1mm kerf (I hadn't test prototype material real kerf).
I opened .dxf file on Illustrator and I edited some file features to make it suitable for the laser cutter:

• Changed boundaries RGB and thickness (because laser cutter software recognize specific values- that can be changed anyway)

• Grouped (Select element and Ctrl+G) and moved closer:

• edit printing features:
  

1-Select printer ( your laser cutter name in orange square): 2-Tick Ignore artboard: 3-Untick Auto-rotate: 4-Click on Setup to run laser cutter's software ( Job Control in my case): (sorry that on my lab notebook Job Control is set in Italian language) 5-Clicking on Preferences it's possible to make changes based on document dimensions (written above Setup) to workspace area. NB: I usually leave 5mm margin more or left. 6-Set material and click JC button (means "print")

Job Control will open automatically and your work will be already on work area.
By double-clicking on free space you can edit material and set action (cutting or engraving) RGB, power, speed and ppi (that's why we changed RGB of .dxf file on Illustrator before).
To connect to the printer you have to press on USB sign in bottom right of the page: Then drag and drop your work till the laser pointer. Pressing Ctrl+I you'll see your work preview. If you see like this: it means the color you used on Illustrator doesn't correspond to any action on Job Control, otherwise you'll see something like this: If material features are properly set, you can run your work pressing "Ready" button on bottom right.
IMPORTANT: make sure laser focalization is ok!

Brief explanation on how to set Trotec 400 Speedy flex

I think most of laser cutters require the same process to be launched. This is Speedy 400 Flex keypad.

• Switch the machine on turning on-off key clockwise beyond "I" sign;
• Wait till the work surface area goes down completely;
• Push the Up button of work surface area in the keypad till it is 5 cm distant from laser head;
• Put the focalization tool as shown below.

• Keep on pressing little until the tool drops of the head guide;
• The focus is set.

NB

• Be careful not to hit laser head in positioning material
• It's always better to fix material to the work area borders with masking tape (which can be easily cut by laser light)

....Joint result: First attempt

Since I hadn't check real kerf of MDF (I used this material for prototyping), joint didn't work.

....Second Attempt

So I used electronic calipers to check MDF kerf: since the measurement resulted 0,1 mm bigger than file size, kerf was 0,05mm.
I so changed parameters value on Solidworks: I also realised (with great help from Simone Guercio) that in joints height kerf has to be added/subtracted two times and so I defined two new parameters: I repeated the step to cut new .dxf file and the result finally matched with no play.

Parametric lamp socket: are we sure kerf really exist?

After testing joint on MDF and plywood kerf in group, I started designing my parametric modular project.
My concept was to make a lamp socket that could change shape thanks to internal structure (made of concentric disks that could be combined vertically in multiple ways) and outer different coverings.
Instead of writing my parameters on Solidworks 2016 I wrote a .txt file with variables and relative values and then imported it on Equations folder in FeatureManager.
I admit some parameters were added while sketching cause you better understand how to relate dimensions just when your sketch gets sharp.
For example, when I first draw my lamp socket, I used (circles width)+kerf as parameter but then I couldn't move easily among covering sketch definition (cause I needed diameters value to create joints), so I assigned "d", "d2" and "d3" different values to which I after added kerf. To export .dxf file to be sent to the laser cutter, I had to extrude each circle of different height otherwise it would have been just one solid body with one face (actually their real thickness correspond to plywood one).

External covering design took me more time due to these problems:

• I couldn't imagine a nice shape to give them(and you see that still I haven't found one);
• I had difficulties in replicating circles dimension while spacing them vertically;
• I wanted to be see immediately if the circles I was repeating really corresponded to previous ones.

After several attempts I found a way:
I made a new part sketch with vertically spaced parametric extruded circles (using Reference Geometry-->Plane function): ...and I had this result: NB: extrusion height is equal to material thickness. I then chose the plane that split in half the three solid bodies and opened a new sketch on it: NB: to do that is important to put the circle center on origin.
I draw a free curve without parameters making sure that lines of future joint were corresponding. I couldn't manage to make it parametric only by hiding circles extrusions and give a quote to sides so I extruded the new sketch and exported it as a .dxf file. Now I could open it in a new part ( File-->Open... and choose .dxf where format is asked) and add parameters: Once variables were added I extruded it again to have .dxf file to be cut.
I followed the same procedure in sketching the second shape (that suited different circles order):

As you can see in the pictures above, I didn't use material thickness as variable for joint of female component but I subtracted double of kerf value. If you're asking yourself why, I will try to give you an explanation but during this week so many theories arose among my fablab walls that I come to the conclusion that, due to the fact that everyone of us managed to get to a result with his/her own opinion about how kerf should be used, due also to all those irritably different kerf values we found, to lack of calipers precision and to my past experiences with laser cutting, KERF IS JUST DISCRETIONALY RANDOM VARIABLE.
So basically, we may say that it doesn't exist. But let's say I'm wrong with this last opinion and assume kerf has a defined, unique value for all plywood panel we used (even if humidity made them boat-shaped and impossible to be cut with same settings along all width and lenght).
...But what does kerf really represents? As our instructor explained us, it corresponds to laser light beam radius. So, each time we cut something, 2*kerf value material is burnt and taken away from cut pieces. Therefore we have to consider that in joint sketches.
The rule I come out with was that in drawing male components I had to add twice kerf to desired length, while I have to take the same quantity away to female components dimensions.
Since I easily made mistakes in calculating this relation every time, I helped myself like this: We found best cutting settings to be 40% speed and 80W power with 0.045 mm kerf during our test. So I used this kerf value in Solidworks equations. Anyway, once I sent my .dxf file to laser cutter (as explained above) I found put that coverings (female components in my case) were too tiny to fit with circles.
I immediately understood there was something around kerf and in fact, in the end anyone of us found different kerf value for his/her panel with same speed and power. That's the biggest point I have to solve about this week but, since deadline was approaching, I empirically changed values of interest on Illustrator to find the exact dimensions for my joint (and I also changed a covering shape to look nicer) because I wanted to have a prototype of my project idea: