Week 4. Computer-controlled cutting

Go to:
  1. Kerf. Group assignment
  2. Parametric Design
  3. Vinyl Cutting
  4. Results

1. Kerf. Group assignment

Group:

Equipment:

Epilog Fusion M2 40 (75W) Epilog Mini 24 (60W) Roland GS24

Before touching laser cutter read the Manual. At least the Safety and Main features part.
Important!

About the machine

Epilog Fusion M2 control panel

Epilog Fusion M2 40 and Epilog Mini 24 are CO2 laser cutters operating in infrared range. The cutting starts from the upper-left corner of the drawing until it's defined differently. By Up and Down buttons you can choose parameter you want to set. Then you can adjust it by joystick.
FOCUS is the distance between the laser source and the surface of the material. To set the same distance every time we use an aluminum spacer which we put on the laser source and then we lift/lower the working space until the spacer touches the surface of the material. Don't forget to press on the middle of the joystick to set the zero (if you don't do that it'll return to the zero point automatically when the cutting starts).
JOG is the position of the laser source. You can't see in infrared range (cool if you can but the most humans can't) so there's a red laser which helps to define the position of the laser source. To turn it on/off press the button with a red light pic on it. With the joystick you can move it to the position where you want start the cutting/engraving (upper left corner of the drawing) and then press on the middle to set the zero.
SPEED, POWER and CONFIG you can adjust here as well but it's easier to set then from the software.

File format we use for laser cutting is PDF. For the cutting the thickness of the lines must be 0.02mm (0.001"). Thicker lines will not be cut in Vector mode. To create my drawings during this week I used Inkscape and Fusion 360

Cutting/Engraving Settings

To put your drawing into cutting you need to open (the PDF file) it on the machine connected to the cutter (special driver should be installed) and press Ctrl+P and open Settings. From the General page you can choose Raster (for engraving), Vector (for cutting) or Combined (for both) mode.
Choose the Resolution as in your original image for better result.
Set the Raster and Vector setting according the material. Below you can find a table with recommended parameters from the manual.

Parameters for Epilog Fusion M2

Parameters for Epilog Mini 24

Kerf

Kerf is the width of material that is removed by a cutting process. Laser beam has width. The width is minimal in focus point. There are different processes going with the material: vaporasing, burning, blasting. So some of the particles stay in the laser beam scattering it.
Kerf depends on the material, speed, power, frequency, moon position and other parameters but there's average value for each material. It's important to take account of kerf in the drawing. You can use the offset tool or make a Parametric Design

Kerf for different materials

3mm Acrylic 3mm MDF

Here you can see that the upper part of the cut piece is slightly smaller than lower.

To measure the Kerf we decided to cut 20 small pieces and measure them all together. The difference between measured number and the number in the drawing will be Kerf*20. We chose 3mm Acrylic and 3mm MDF as our test samples. We used Inkscape to make a simple drawing. The drawing is a rectangle 100x40mm devided in 20 5x40mm pieces.

To measure the Kerf we decided to cut 20 small pieces and measure them all together. The difference between measured number and the number in the drawing will be Kerf*20. We chose 3mm Acrylic and 3mm MDF as our test samples. We used Inkscape to make a simple drawing. The drawing is a rectangle 100x40mm devided in 20 5x40mm pieces.

100x40mm rectangle cut in 20 5x40mm pieces

On the first cut we didn't get through On the first cut we didn't get through. On the second we did, but our first design was 20mm wide and small pieces fell down. We increased the width up to 40mm after.

We placed all pieces together on a flat surface and mesured the result length. Digital meter failed us so we use an analog one later. The length was 98,2mm and the kerf=(100-98,2)/20=0,9mm

We did all the same to 3mm acrylic (including failing the first cut) but on Epilog mini. I find if even easyer than using Epilog Fusion M2 40. Epilog mini has built-in autofocus, so there's no need to worry about this parameter. And the jog is set to the position manually. To move the jog you need to unlock it by pressing button with the lock on it, move the jog to the starting point and press the button again.
The length was 95,3 and the kerf=(100-95.3)/20=0.235mm

Comparing Speed and Power

We had a simple design created with Inkscape and saved as pdf for the cutting, 0,02 mm line width. We used 3 mm MDF.

First cut was done using the pre-defined values for 3 mm MDF; Speed 9 % and Power 80 %.

Cut 2 was done with Speed 20 % and Power 80 %.

Cut 3 was done with Speed 30 % and Power 80 %

Cut 4 was done with Speed 30 % and Power 90 %.

Cut 5 was done with Speed 20 % and Power 90 %.

Result was that only the Cut 1 was cut through, the others not. So the Speed is real important value to choose correctly. Too much speed cannot be compensated with little more power.

2. Parametric Design

I started by drawing a test pice in Inkscare just to test the pressfit joint. The design is a crest with 0.1mm step between teeth. I cut it from 6,5 mm cardboad and it was the first issue. 6,5 mm cardboard was a tough guy. I failed to cut it 5-6 times. I even removed numbers from the drawing because the laser just burned areas with a small details (even with power compression on).

I found parameters when I could cut the whole piece by running the job for tHree times without burning. But in the end even the smallest joint was loose but I got the Idea (not to use 6,5mm cardboard at the first place).

I used Fusion 360 to make the design for this week. I've like Hexagonal form so i had an idea how to start. After only 11-12 attemps I drew a proper sketch where I could change parameters of my piece.
Parameters in my design:

The constant values define the dimensions of the part. Width of the slot depends on the material thickness.

Then I created a drawing from the design and saved it as a PDF file (unmark lineweigth) for lasercutting. And I cut it from 3mm MDF on the Epilog Fusion M2 40 (75W). It was a perfect fit. Round corners of the joint helped to press one part into another. The connection was just right.

Settings for the cut

Changing the parameters will change the design.

Sketch Dimension and type the parameter name.

It seems you are using an outdated browser that does not support canvas :-(

Then I found 4 mm cardboard. I changed the design by changing the parameters (kerf 0.4, material thickness 4mm, depth 15mm) and cut it as well.

Perfect fit again. But only hexagonal form is a bit boring.

I added legs with the same parametric slots.

But I haven't found the same cardboard so I used 4mm box from Lenovo Thinkpad. It has 3 layers instead of 2. So it was challenging to cut it. In the end at some points the very last layer of the cardboard wasn't cut. The properties of the cardboard are differend as well. It's not so elastic. So, the fit wasn't perfect. But I'm satisfied with the result.

Some details on the bottom layer are required but I think it came out nice. The construction is quite stable.

3. Vinyl Cutting

Fo vinyl cutting I decided to prepare something from a rester image. I chose a photo of a Banksys's graffity from my own collection.
To convert a raster image into vector in Inkscape:

Open or import Image to Inkscape

Press Alt+Shift+B

Choose one out of tree options, set the treshold as you like (I used Brightness cutoff with the threshold 0,270), press ok and close the window. Then move the image and you will see the result.

Here we can see the all contours I got. Now we need to clean the mess.

I removed all parts which seemed to be too small.

After editing and simplyfing (Ctrl+L) the contour it looked like that. It's fair to say, that the vector image I got in the result is remotely similar to the original one.

Now it's time to cut our image fron black vinyl on our Roland GS24.To cut the image

  1. Open the inkscape .svg file
  2. Open the lever on the left hand side of the machine
  3. Put the vinyl roll in the designated place behind the machine and put the edge in its place
  4. Pinch rollers should be aligned on grit marks
  5. Close the lever
  6. Switch on the vinyl cutter.
  7. Choose between roll (the machine assumes you are using a big enough roll), edge (the machine will look for the edge to start) or piece. I chose Edge
  8. Check the drawing is positioned on the bottom left hand corner of the document. What I actually did, was resize the document to the size of the drawing: From the Document Settings menu, click resize the document to the image size. Then, in the printer settings dialog, (shown in the image on the right), set the correct length for your case. For the width you need to keep the one given by the machine (Get from machine)

Rollers on the marks.

Pen force about 0,5

This is the result after removing all extra parts with the tools on the picture. I placed a transfering sheet on top of the whole piece and removed the original substrate. Now it's ready to be put on my fridge.

4. Results of the week