GroupTask

This week's group assignment is about learning, testing and verifying all the processes involved in computer-controlled cutting, for example, studying the parameters of the laser cutter or knowing how to set up our vector files so that they are ready for cutting. In this new round, with Fab Lab ESAN, we will look at the Trotec cutter and its functionalities.

The first group work we did was in Fab Lab Peru, access was very restricted. The documentation of that work is in 💻Mayra Ascencio's web page 💻. And for the second attempt, as always, the group work was developed with Mayra, and the documentation is here. This time we still did not have access to the ESAN lab, our node at that time, because of the confinement due to Covid-19, so it was developed remotely.

Laser cutting

"Trotec Speedy 400".

A_ Which materials can be cut:

Our node has the speedy 400 version of C02 and can cut/engrave the following materials:

B_ Warning:

Materials that cannot be cut:

PVC: It is counterproductive for the machine due to the corrosion of its laser system and is toxic, hydrochloric acid and toxic gases are produced in thermal processing. *Do not cut PVC materials on any laser cutter.

Metal: speedy machines can cut up to 0.5mm but are not recommended for the CO2 speedy 400.

Stone: It can be engraved, but not cut.

Glass: can be engraved, but not cut. *Avoid reflective materials, some cutting heads are affected by reflective materials that can cause damage to lens systems.

Parameters

The parameters are those data that the machine needs to recognize when we send our files, these must be the correct ones to generate clean cuts and/or engraved correctly.

Technical ranges of Trotec Speedy 400

Feed Rate: 4.3 m/s

Rango de velocidad: 1-100

Rango de potencia: 1%-100%

Rango Frecuencia: 1000-60 000 Hz

Trotec Parameters

It is very important to make previous tests before sending our final cut since what we want is to make sure that our configuration will be the optimal one. We also do this as a precaution, if we choose the wrong parameters we could cause accidents or on the contrary not succeed with the execution of our work. Here we share an example, these are the steps we follow to generate cuts in a 3mm cardboard in 30x60cm format.

Software and operationof the laser machine:

Software JobControl

This program allows us to control our laser machine, it supports designs drawn in programs such as CorelDraw, Photoshop, AutoCAD, etc. Its operation is quite simple and fast. Below we briefly share the steps we followed to install this program on our PC.

RGB Color
In JobControl, Trotec's software, we have 16 default colors that are the only ones we can use in our vector designs. That's why our team looked up the RGB code for each one and created a template with these colors to have on hand, the template allows us to assign the colors to the vectors of our designs if we want to configure them at the time of cutting with the laser machine.

Operation
Most basic machine parts:

Lens and mirror
In principle the beam leaves the laser tube and travels straight to the focusing lens, bounces off the center of the mirrors and passes through the center of the lens. Lenses are used to focus the laser beam in CO2 laser machines.

Lens placement

Activated carbon and filter
An extraction system helps filter dust and fumes from the work surface and activated carbon filters out all odors created during laser processing.

CO2 tube
A laser tube is responsible for emitting and transporting energy in the form of light to generate the laser beam used for engraving or cutting. It is an airtight container that contains mostly CO2, and other gases such as Nitrogen, Hydrogen or Helium.


Schematic explanation


More information: Manual Trotec

Cutting, engraving and kerf

Design considerations for Test or any laser cutting

We in the group realized that when you design drawings or test catalogs you have to be very careful. It won't do any good to do a kerf test, or a fit test if you draw the measurements wrong or make a mistake in the scale, because when you cut it and go to verify the measurements with your calibration tool, you will not get the measurements you expected or you will never know the true variation of measurements between the file and the reality, because the file never had the measurements well done.

Therefore, the following is recommended:

A_If parametric software such as SolidWorks or Fusion 360 is used:

You can restrict the measurements so you can easily modify them if you made a mistake. And by clicking on each part you can know the measures you have placed.

B_If you use Rhinoceros you can use the following commands to check that your lines are fully closed and the measurements are correct:

Zoom: Zoom in and see your closed lines.

Join: With this command you can join curves so that your individual lines become a polyline.

Extend: With this you can extend one line to another and thus close corners.

Trim: With this command you can cut exactly two lines at their intersection.

If you want to verify the measurements, it is recommended to use the different drafting and dimensioning options provided by Rhinoceros in your drawing to know if you have drawn accurately.

*If you use Rhinoceros or any other vector program such as illustrator, CorelDraw or Inkscape, you must also verify that you do not have double lines, because the cnc cutters will recognize the two lines or three or four (whichever there are) and will go through the same place every time.

A_You can use the following command in Rhinoceros:

SelDup

This command only works in the perspective view and is used to identify and select duplicate lines or objects in our design. Once we select the lines for example, we just delete them and we will have a clean file of duplicate lines.

B_Identify duplicate lines before cutting:

Remember that some laser cutting software has within its tools a command that allows us to detect duplicate lines.

Test engrave 30 x 60 cm

MDF

List of parameters used

• Power:100
• Speed:0.6
• Frequency:5000

- Final engraving test
Cardboard

List of parameters used

• Power:85
• Speed:1
• Frequency:5000

- Final engraving test

Acrylic

List of parameters used

• Power: 98
• Speed: 0.45
• Frequency: 5000

- Final engraving test

Test encastre-corte. Comb.

MDF

List of parameters used

• Power:100
• Speed:0.6
• Frequency:5000

- Screenshot of the file with the design dimension.

- Final engraving test

Cardboard

List of parameters used

• Power:85
• Speed:1
• Frequency:5000

- Screenshot of the file with the design dimension.

- Final engraving test

Acrylic

List of parameters used

• Power: 98
• Speed: 0.45
• Frequency: 5000

- Screenshot of the file with the design dimension.

- Final engraving test

Test kerf flexible

MDF

List of parameters used

• Power:100
• Speed:0.6
• Frequency:5000

- Screenshot of the file:
- Final engraving test

Conclusions:
With the designed patterns we observed that MDF, despite being a rigid material, had the option of achieving flexibility with ease.

Cardboard

List of parameters used

• Power:85
• Speed:1
• Frequency:5000

- Screenshot of the file:

- No Final engraving test

Conclusions:
Cardboard did not prove to be a very useful material to use for the patterns; when trying to cut it, it was destroyed.

Acrylic

List of parameters used

• Power: 98
• Speed: 0.45
• Frequency: 5000

- Screenshot of the file:

- Final engraving test

Conclusions:
Unlike the other materials, acrylic was more flexible when the patterns were more defined, in tests we found that some patterns worked and others did not.

Recommendations

Have design considerations while generating the file:

Using a parametric program will help to make modifications quickly if there are any errors and having a unified geometry will help the job to be finished in less time, on the other hand, if we have loose lines, the laser cutting time would be double or more.

Danger of catching fire:
If we set the parameters out of range, we may set the material on fire.

Special fire extinguisher for laser machines: CO2 fire extinguishers
Mask use and how to take care of emissions health.
Always extract either with a filter or towards the window, to avoid intoxication by the gases generated by the laser cutting machine.

The first try:The right one

As a first step, you should always calibrate the laser focus with the tool that comes with the laser cutter. Otherwise, the whole exercise could be inefficient.

I designed parametric parts with Rhinocecros and Grasshopper. In this exercise I parameterized the insets and also the number of sides of the geometries, as well as the number of geometries in each row and column. You can have triangles, hexagons, octagons, etc.

After trying to cut for the first time, it was possible to obtain the cutting of the parametric pieces in cardboard and gray PET material, in order to obtain a set of assemblable pieces. The parameters used were:

Cardboard parameters

• Power:85
• Speed:1
• Frequency:5000

The secondtype of joint

To test another type of joint this week I used a parametric design platform called makerspace, which is excellent for designing boxes for laser cutting. You can customize the dimensions, material thickness and the amount of joints you need on each edge of the object.

It's time for the fun part and that's manufacturing. Then I set everything up and the cutting began. I did some tests and then cut the optimized file to save time and resources.

Testingoperation

As a first step I made a test of a small rectangle. And I activated the machine in cutting mode. Previously it was necessary to check the blade accessory to make sure it cut correctly. The first test was successful.

The vinyl cutter works on the y, x, and y axes and with the correct blade can cut designs accurately. It is important that the vinyl to be cut is securely attached to the plate where it is adhered for cutting.

AboutLearning

- Both the laser cutter and the vinyl cutter are computerized numerical control machines, so they must be designed precisely for optimal cutting.

- Also, always be careful with the electrical system where you are going to connect the laser cutter, to avoid power surges. Finally, the laser cutter emits emissions, while the vinyl cutter does not. The space should always be properly ventilated.

- It is not advisable to cut materials containing PVC, due to the toxic emissions it emits when cut.

My Verdictfrom what I learned

- Due to the pandemic, I was only able to have the vinyl cutter for a short time, I would have loved to cut more designs.

- Parametric design and grasshopper are highly powerful 3D digital design tools. For this exercise they were excellent allies.

Files