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Computer Controlled Cutting

Last edited by Behnaz Norouzi

PARAMETRIC DESIGN

Understanding the Laser Cutter Kerf

From Neil's Global Lecture (2019):

  • "The laser cutter has a beam size. The typical size in inches is 0.010 inch (0.254mm). So when it cuts, there is a gap of that size, So if you want to make a part of a certain size, if the laser goes on the line, it means that you are cutting into it about half of 0.01 inch (0.005 inch= 0.127 mm). And for the kind of joint of Making, that is the tolerance of the joint. So you need to account the size of the beam in your design."

“KERF IS NOT AN ABSOLUTE RELIGION” (Neil). Kerf depends on lots of settings, including:

  • Air Flow (Air coming from the nuzzle is pushing down and the exhaust is pulling the air out).
  • Type of the Joint
  • Material Properties and Cutting Settings (Speed, Power, Frequency)
  • Cutting a Straight Line or a Curved Line
  • Cutting in the x or Y Dimension
  • Material Thickness

References: 1, 2, 3.

General rule for taking kerf into account for slots and tabs (Your considerations might vary depending on your design purpose):

  • “when it comes to kerf, the best rule of thumb is, ‘insides in, outsides out’” (2018).
  • When we laser cut slots, the slot size will be bigger than the original design >> If you want to have the same size as the size of the slot in your original design: material thickness – kerf
  • When you have tab, the tab size will be smaller than the original design >> If you want to have the same size as the size of the tab in your original design: material Thickness + kerf
  • A picture, drawn by me, which hopefully helps in better understanding kerf:

Teaching_Kerf_2022Version

Understanding Parametric Design

From Neil's Global Lecture (2019):

  • “Parametric design is needed so that when you change the material with different thickness and change the value for material thickness in your parametric design, the whole design recalculate.”

  • REMEMBER: Your press-fit construction kit must not only be parametric, but also account for the kerf of the laser cutter as well as the thickness of the material in your parametric design. You can also have other parameters, of course! But these two above mentioned parameters are must-to-have for this week’s assignment.

  • You should be able to assemble your press-fit construction kit in multiple ways. SO, designing a simple box with slots and tabs would not be enough for passing this week’s assignment.

  • IMPORTANT: Use a CAD software for parametric design. DO NOT USE INKSCAPE FOR PARAMETRIC DESIGN.

  • A nice example of press-fit construction kit

  • REMINDER: You have already learned about the sketch parameters and constraints in the computer-aided design week; You probably need to get them in use for your parametric design.

If you design in Fusion 360:

  • For creating drawing from your design:
    • After you finish your design, extrude the object, and then create drawing with the scale of 1. (Design >> Drawing >> From Design)
    • Consider having the same size as your final product in your design before you create drawing.
    • Select and delete extra elements added automatically after creating drawing from design. Then, export PDF.
    • Open in Inkscape and the only thing that you should change is the line width for cutting the vector!
    • Save as PDF again and send the print order. (**)
  • You can also right click on the sketch and save as DXF. You can open DXF files with Inkscape.

Remember: First, find the kerf value together with the right settings for the material that you will use for your press-fit kit. Then, make a prototype with two pieces of your design and test how they press fit together to ensure everything is OK; and now you are ready to make your kit!

LASER CUTTING

Fab Lab Oulu's Documentation

Understanding Laser Parameters

  • Remember not to use more than 50% of speed for engraving small objects. It might cause problems to the machine because the laser head has to move very fast back and forth in a small area.
  • Remember not to change DPI for the big laser cutter. It might cause an accident for the laser head and result in breaking some parts! Only use 300 and 600 DPI with this machine. You can test different values for DPI with Epilog Mini or Emblaser 2, for example.
  • Raster Setting: Speed, Power, DPI, Engraving Direction, Dithering
  • Vector Setting: Speed, Power, Frequency, Air assist
  • Read More about laser parameters: 1, 2, 3.

Laser Cutters in Fab Lab Oulu

Safety Rules in Fab Lab Oulu for Laser Cutting

During the Laser Cutting and Engraving Process the following safety rules should be applied:

  • First, ensure that the air input and output are open (see instruction on the wall near the machine).
  • Never cut unknown materials.
  • Always consult the list of allowed /not allowed materials.
  • Never leave the machine unattended.
  • At the end of the job, wait one minute before you open the lid. In this way you allow the toxic gases to be removed from the machine and not enter the room.
  • If you see any spark of fire:
    • FIRST, if you think it might catch fire by seeing the sparks, stop the operation.
    • SECOND, if it does not stop by pressing the stop button, open the lid.
    • THIRD, if the material is catching fire, if you can, bring it out and turn it off by using the fire blanket. If needed, use the fire extinguisher.
    • FOURTH, if you cannot bring it out, use the fire blanket inside the machine.
    • FIFTH, if the fire is too much and none of the above-mentioned steps are not possible, as the last solution, use the fire extinguisher directly inside the laser cutter and use the red emergency stop button. (Hopefully you will not have to do this because it might damage the machine but of course is better than burning the whole place!)!

VINYL CUTTING

  • Fab Lab Oulu’s Documentation for Vinyl Cutting!
  • The model that we have in Fab Lab Oulu: Roland CAMM-1 GS-24
  • GS-24 User Manual (also includes how to use CutStudio)
  • FabAcademy Tutorials
  • NOTE THAT: Your vinyl cutter files must contain only vectors. That is why you probably need trace bitmap operation!
  • Some Ideas for Vinyl Cutting:
  • Several Important Considerations for Vinyl Cutting:
    • The origin point is bottom left in the software. Anyways, after you finish your design, it is better and easier if you resize the document size to the object size in Inkscape. Of course, you should test a small design on a small piece that what happens if you do not do so (learning by doing)!
    • If you want to print on a fabric, you should use heat transfer vinyl, reverse your design, and you should load the material from the other way around (cut on the wrong side; The shiny side is usually the right side). Then you will use the heat press machine. Check the suitable temperature according to the material you use otherwise you might burn the cloth.
    • Normally rotating 90 degrees might happen only if the document width is bigger that the document height. But nowadays, when we send the print order from Inkscape, our vinyl cutter works well with the origin only if we choose 'rotate 90 degrees' in the printing panel, otherwise it might be a mess by starting to cut from anywhere! We will check this again in the local lecture when I am showing how to work with vinyl cutter.
    • You can also use CutStudio software for sending the print order to the vinyl cutter.
    • A good option would be preparing your design in Inkscape and then using the Inkscape's CutStudio extension to open the design in CutStudio and send the print order from CutStudio. You can do this by: Extensions >> Roland CutStudio >> Open in CutStudio
    • Do the test before cutting to make sure everything is OK. Because heat transfer sheets are expensive, and you need to be careful not to waste the material. So go for the bigger cut only when you know how to work with the machine.
    • Always in any process in the Fab Lab take into account how to do the job with the least waste of material'!

GROUP WORK

You need to experiment with:

  • Vector: speed, power, frequency
  • Raster: speed, power and DPI
  • Kerf for at least two materials
  • Joint Clearance
  • Laser Cutter’s Focus
  • Document your group work in group or individually?!

GROUP WORK FILES: CCC-Groupwork.zip

Please Note: There are color mapping and layer considerations in using the files.

ASSESSMENT

Check the Assessment Criteria!!

Individual Assignment.

Learning outcomes

  • Demonstrate and describe parametric 2D MODELING PROCESSES.
    • Tell what you are going to design. What is the purpose?
    • You should design the press-fit construction kit yourself. IT SHOULD BE YOUR OWN DESIGN.
    • Make screenshots from different stages of your design.
    • You can use free tools for capturing screenshots; For example, check this one.
    • Reduce the size of the screenshots or any other media and then upload to your page! You cannot upload big sizes even if you intend to change the size later! FIRST reduce the size and THEN upload.
    • Only screenshots are not enough! You should explain in text also. Always support your pictures and screenshots with text explanation.
    • For your design steps, you should tell which tools you used and from where you accessed those tools. E.g., I removed extra lines by using trim tool (Modify >> Trim).
    • Add captions for all your images.
    • Check copy right for anything that you use from internet.
    • Write references (Link to the pages) when you borrow ideas or words from others.
    • Don’t forget taking screenshot from your final view of your design. This will be your design hero shot.
  • Identify and explain processes involved in using the LASER CUTTER.
    • For your group work: You should explain what you did, as well as your observations and results of what you did. For example: it is not enough to say: We tested the power and speed and frequency for vector; You should say also, what was the effect of speed and power and frequency for vector based on the test that you did! The same logic goes for explaining the other parameters that you test.
    • You should explain how you used the laser cutter. What settings you did (e.g., origin, focus, print drive, etc.) before starting the task.
    • Take also pictures from the laser cutter for supporting your explanation.
  • Develop, evaluate, and construct the parametric construction kit
    • Take picture of the final product. This would be your hero shot.
    • Check the important considerations in the parametric design section explained above.
  • Identify and explain processes involved in using the VINYL CUTTER.
    • You don't have to design for vinyl cutting yourself. But, you should in any case explain how you prepared your design for vinyl cutting; for example, if you do trace bitmap operation, explain how you did it.
    • You should explain how you used the vinyl cutter: E.g., what mode you used and what happened when you used it (roll, edge, piece), how you loaded the material (leavers, pinch rollers, grit marks, etc.), print driver (get the measurement from the machine, etc.).
    • How you weeded the material. Which tools did you use?
    • How you transferred your design to the intended object (you use the transfer sheet).
    • Add pictures of different stages.
    • Add hero image when you have your result INSTALLED! For example, an image of a cut vinyl laptop sticker when you have removed the unwanted parts is not a hero image. A hero image for this task is an image that shows the sticker is pasted on your laptop or anywhere else. Have you
  • linked to the group assignment page
  • Explained how you parametrically designed your files
  • Documented how you made your press-fit kit
  • Documented how you made your vinyl cutting
  • Included your original design files
    • You need to upload 4 design files for this assignment:
      1. The .svg file of your vinyl cutting project.
      2. The local CAD file for your parametric design; for example, if you use Fusion 360, the local file is .f3d file.
      3. The .stl file of your parametric design.
      4. The .pdf file (check ** above in parametric design section).
    • Pay attention to upload the final version of your design files. We always check it and if the file does not match your results and content in your page, we ask you to upload the correct file again.
  • Included your hero shots
    • Three hero shots as explained above one by one.

Please note that IF YOU DON’T TAKE THESE CONSIDERATIONS INTO ACCOUNT, YOUR TASK WILL BE DOUBLED! Because after checking your documentation, if everything necessary is not there, you will be asked to again spend time and prepare those. SO, this guidance is useful not only for this week but also for other weeks and may take only 30 minutes of your time to read it through; but will save your time hugely in the future.

Please check for typos yourself or use spell check tools before pushing or asking an instructor to go through your documentations! Thanks for your understanding... I wish you success with this week's assignment and have fun :)