3. Computer controlled cutting¶

In the third week we worked as a group and also indiviually. The objective of the group assignment is to explore the characteristics of the laser machine so we did two tests (). As for the indiviual assignment we did a press-fit construction kit design and then cut it using the laser machine.

Task 1 (group assignment)¶

Theory part¶

As a group, we were asked to characterize the laser machine’s focus, power, speed and joint clearance by conducting an experimental test. Before presenting our outcome, we would present first the laser machine.

What is laser machine? and what is the working principle of it?¶

A laser cutting machine is a machine that uses a laser beam to cut or engrave materials such as wood, plastic, or metal. It works by directing the laser beam through a series of mirrors and lenses to focus the energy onto a small spot, melting or vaporizing the material based on instructions from a computer. It is easy to use, accurate and fast. However, there are some limitations such as material thickness

Some applications of the laser machine:¶

Home decoration
Customizing objects by engraving or custom cutting
Prototyping
Cutting process of various materials in industries (automotive, medical, sports, etc.)

There are different types of laser machine, there is CO₂ laser machine and fiber laser machine. The one which is available in the lab is CO₂ laser machine. The table below shows its specifications:

Name	GV1309 Laser machine
Laser power	100 Watts
Working area	1300 mm x 900 mm
Machine type	CO₂ Laser

It is important to note that this laser machine does not cut all types of materials, it is limited to specific materials. The table below will show which materials it can cut:

Materials it can cut	Thickness
Cardboard and paper	5
Wood	12
Acrylic (PMMA)	20
Leather	6
Fabric	6
Rubber (Non-chlorinated)	8
Foam	30

NOTE ALL UNITS ARE IN MM

It can also engrave some materials such as, glass, ceramic, stone, anodized aluminum and painted metals.

Questions and answers¶

Mention three main safety measures when operating a laser machine?¶

Never leave while the machine is operating. Stay close until it finishes the cutting process.
Make sure there is a fire extinguisher near you before starting the machine.
Make sure the area aroung the cutter is free of flammable materials.

Which Materials are prohibited to laser cut using the laser machine in your lab? Give example of two and why?¶

The first material is PVC because When laser cut, PVC releases chlorine gas, which is highly toxic and can cause serious health issues if inhaled. It also damages the laser machine components, especially the optics and metal parts, by causing corrosion.
The second material is PC since polycarbonate tends to burn rather than cut, producing excessive discoloration, fumes, and poor-quality edges. Additionally, it releases toxic gases, which are harmful to both the user and the laser cutter’s ventilation system.

Why fire blankets are used? Are there other emergency Aids and Measures in the lab?¶

Fire blankets are made from glass fibre fabric, with a thin fire-resistant coating. They work by stopping the air flow to the fire, starving it of oxygen – one of the vital ingredients that fire needs to keep burning. Yes, there are emeregency aids in the lab. Near the door there is a fire extinguisher and behind the laser machine there is a vaccum to prevent waste accumulation because it is not recommended to keep the wastes of some materials.

How to avoid burned out edges?¶

Burn marks are caused by the intense heat of the laser beam. So, it is important to use proper setting. Chossing the right speed and force iss essential. So, if you want to cut wood you should either conduct an experiment to find out the proper settings or you can find some data online that helps you to ensure proper preparation.

How to avoid having certain material crumbling?¶

To avoid this problem, it is recommended to use a tape around the work piece to make sure there is no gap between the base of the machine and the work piece.

Practical part¶

We were asked to conduct 4 tests. One for the speed, one for the power, one for the focus and the last one is for joint clearance.

Speed and force test¶

To conduct the speed and force test we have used the 2D software Cuttle to create the below sketch:

Then we have exported the sketch as DXF and sent it by mail to fablabbh.share@gmail.com.

We have used RDworks application to import the design and upload it to the machine.

Step 1 Click on Files > Import

Step 2 Choose Desktop > Polygon

Step 3 Use different colors to change the speed and the force, and to do that we have selected each polygon and used different color for each one of them so we can change its speed.

Step 4 Click on speed > change the speed to 25 mm/s > click on Ok

Step 5 We have repeated the steps for the remaining 4 polygons at the top.

Step 6 To do the force test we have applied different forces for the 5 polygons at the bottom. To do that, we have used the same steps except that here we changed the force not the speed.

NOTE: For the speed test the force remained unchanged as 60 and for the force test the speed remained unchanged as 25 mm/s. The below image shows the final outcome.

Step 7 Click on Download

Now, we are done with RDworks and we have to set our laser machine so that it starts printing. So First we need to power the laser machine.

Second We have to start the laser machine by rotating the button to the right

Third We have to set our workpiece and we need to make sure that the edge of the workpiece is touching the edge of the machine bed

Fourth We have to press on Files > Enter

Sixth We need to make sure that the distance between the laser beam and the workpiece has the thickness of the piece shown below:

Seventh In the control panel we have to press on Origin > Frame to ensure that the design is within the machine’s working area > Start

The final outcome is shown in the below image:

COMMENT: in the speed test we have not noticed that much difference but when it comes to power test we have notied that when we set the power at 20 the laser beam could not actually cut the cardboard which means that it requires a force higher than 20.

Focus test¶

To do this test we have changed the Z value by pressing either on Z↑ in the control panel to increase the height of the bed machine or pressing on Z↓ to lower the height. If we increase the height this will make the focus less and if the focus was too low it will not cut the cardboard. On the other hand, if the focus was very high it might burn the cardboard. So, we found that if we set Z value as 3000 mm, it will work perfectly.

Joint clearance test¶

The last test we did was for the joint clearance and for that we used the parametric design in cuttle to make things easier. So, we did a simple design and different thickness values to test which value would be suitable. The first value was chosen to be as 1mm The same thickness as the cardboard.

We noticed that all the thickness worked perfectly because the cardboard material is flexible and the difference in the values of the thickness was not huge.

Task 2 (indiviual assignment)¶

Press-fit construction kit¶

Indiviually, we were asked to design a press-fit construction kit design using any 2D software. So, I used Fusion 360 to make the design because I felt it would be more comfortable than the others softwares. Before starting the design we had to find an inspiration or something that we would love to design. So, I searched online and found a design that attracted me and I decided to go with it. The below image will show the design.

As the image shows there is one square and one joint to link the squares together. For this kind of design there are some features in Fusion that would really help me like the parametric design, mirror and the rectangular pattern

Step 1 So, I started by choosing the right plane and I sketched half of the shape without specifying any dimension and then I draw a vertical line to help me with the mirror feature.

Step 2 Then, I started choosing the parameters to do the design with high accuracy.

Step 3 In Fusion, I have entered the parameters with the values

Step 4 Then, I started specifying the dimensions using the parameters

Step 5 ** I have used the mirror feature to make the exact shape on the other side

Step 6 I used trim to eliminate unwnted lines

Now, I have the square I need for the design.

Step 7 Sketching the arc using the same parameters

Step 8 I have used Rectangular pattern to have the same shape multiple times. For my design I needed 6 squares and 8 arcs. So, I have changed the quantity and diplacement

Step 9 I followed the same step above for the arcs but I increased the quantity to 8 and then I got the final sketch as shown in the image:

click here to download my original file design

click here to download my design

Step 10 I have exported the file as DXF file

Step 11 I have named the file and saved it to my desktop

After that, I have sent the file by email to the same email mentioned in the group assignment and I have followed the same steps we followed earlier. The speed was set to be 25 mm/s and the force was set to be 60

Below you can see how the laser machine works:

via Imgflip

The result is shown in the below image:

Step 12 I have assembled the design so that it looks like the photo I found earlier online.

Vinyl cutting¶

In this week, we were also introduced to a different machine which is called vinyl cutting. Vinyl cutting is a process in which graphics, letters and other vector designs are accurately cut from material using a cutter or plotter. It is mainly used to create custom stickers and make iron-on designs for t-shirts. The one which is available in the lab is called Cricut Explore Air 2. The machine cuts over 100 materials such as ncluding cardstock, vinyl, iron-on, glitter paper, cork, and bonded fabric.