3. Computer - Controlled Cutting

The first machine week, in this week we’re learning how to handle with laser cutting and vinyl cutting.

Assignments

Our tasks for this week are:

Group assignment:

• do your lab’s safety training
• characterize your lasercutter’s focus, power, speed, rate, kerf, joint clearance and types

Individual assignment:

• cut something on the vinylcutter
• design, lasercut, and document a parametric construction kit, accounting for the lasercutter kerf, which can be assembled in multiple ways, and for extra credit include elements that aren’t flat

Group Assignment

Click here to group work.

For Individual assignment, I use Laserbox Rotary in ISA Innovation Centre (Science City).

For Group Assignment, I did some experiments with annother machine in another lab— ISA Innovation Centre (Liwan), the machine is 大族粤铭. I learnt this:
The parameters of each machine are different.
Take this machine as an example. The following issues occurred when cutting at the beginning:
Issue 1: The focal length of the laser beam is not aligned, and there is no specific tool to help record the focus length position;
Issue 2: The edge of the cut object is not smooth and has obvious jagged edges;

I use ‘spot shoothing’method to find the optimize focus, it’s hard to find since you need to adjust the length between the beam and paper manually!And there are no auxiliary tools!
Once the hand shakes, the error is very large! This machine is not scientific, it should be equipped with auxiliary measurement tools!

To solve problem 1, I used the “spot shooting method”. The spot shooting button can be found on the operation panel of the machine. After manually adjusting the position of the laser head each time, press the “spot shooting” button until the smallest dot appears on the paper. This is the best focal length. Because there are no auxiliary tools (such as a triangle ruler), in order to record the distance between the laser head and the paper at the best focal length, I used materials of different thicknesses. When I used a 3mm (if the spot is too large, it may be 4mm/5mm. I forgot a little when documenting this. If you see this, you can use 3mm to test it first) thick wooden board, gently stuff it between the laser head and the cutting board, and the wooden board can just fill this distance.

To solve problem 2, it is mainly to control the light intensity and speed during cutting. Note that the thicker the material being processed, the slower the speed may need to be adjusted. Under this laser machine, after my test, its ideal processing parameters are:
Power: 70% Speed: 10mm/s
In order to distinguish the processing parameters during cutting, you need to set different layers for different objects and use different colors to distinguish the processing parameters.

External factors affecting the accuracy of laser cutting machine:

1. Cutting materials: Under the same circumstances, the cutting accuracy of different materials is slightly different. Even if it is the same material, if the composition of the material is different, the cutting accuracy will also be different. Generally speaking, under the same other conditions, the smoother the material, the higher the cutting accuracy;
2. Auxiliary gas and nozzle: During the laser cutting process, the auxiliary gas and nozzle play a role in cleaning and controlling the cutting speed to a certain extent. If there is uneven pressure and temperature in the airflow, it will cause changes in the density of the airflow field. Such a density gradient causes the refractive index in the field to change, thereby interfering with the focusing of the beam energy, causing refocusing or beam divergence.
   One thing that needs to be recognized is that the accuracy of the laser cutting machine is not only related to the equipment itself, but also to external factors. When we use the laser cutting machine, we need to set and adjust the relevant parameters of the equipment according to the specific processing materials and the user’s quality requirements, such as power, focus position, cutting speed, auxiliary gas, etc., in order to achieve the product precision requirements required by the user.

My Laser Cut

Laserbox Rotary

I use Laserbox Rotary in ISA Innovation Centre (Science City).

Safety Instruction of Laserbox Rotary

For Safety Instruction, see here.

For more usage guide, check this below:
For Help Hub: Explore the knowledge base of Laserbox Rotary.
For Lessons: Laser cutting lesson plans for educators to bring Laserbox Rotary into classrooms.
For Teaching Resources.

For Features, one can easily learn how to cut/engrave using this machine. It’s very intelligentized.

Laserbox features a high-definition camera with an ultra-wide-angle lens enabling it to automatically measure the thickness of the material. Based on the measurements, Laserbox automatically adjusts the focus before it starts laser cutting or engraving. No manual measurement or manual focus is required.

For Chinese version Operating Manual, check this.

Technical Specifications

Technical Specifications Product Laserbox Rotary
Dimensions (L × W × D） 958 × 528 × 268 mm
Net Weight 43.5kg
Laser Source CO₂ Glass Laser Tube
Laser Power 40W
Lifespans 8000~10000h
Safety Class I ( FDA Certified)
Work Table Area 500 x 300 mm
Work Table Surface Black (Special surface finishing technique helps reduce burn marks or discoloration)
Max. Workpiece Height 22mm (with Honeycomb Tray)
Max. Workpiece Dimensions 500 × 300 × 52 mm (without Honeycomb Tray)
Camera High-resolution Ultra-wide Camera
Number of Pixels (Effective) 5MP
Visible Area 490 x 290 mm
Positioning Precision 0.025mm
Autofocus Accuracy 0.1mm
Image Resolution 1000DPI
Noise Rating ≤70dB
Onboard Memory 4G
Operation Panel Push Button + Circular LED Indicator Light
Frame Materials V0 Flame Retardant ABS / PC
Connecting Interfaces USB cable / Ethernet cable / Power cable / Aviation Connector Outlet Diameter 63.5mm
Positioning AI Visual Positioning（Error range≤5mm)
Cooling Closed-loop self-contained internal liquid cooling system
Air Assist Internal air assist with no external compressor hookup required
Connection / Transmission Wi-Fi, USB, Ethernet
Focus Mode AI Visual AF / Material Recognition AF / Material Set-up AF
Power 220/110VAC
Work Consumption 600W（Smoke Purifier included）
Nonoperating Temperature 0~45°C
Relative Humidity 5-90°C
Operating Ambient Temperature 0~35°C
Operating Systems 64-bit Windows 7 or macOS Mojave10.13
Processor Core i3 or AMD A6 2.4Ghz
Memory Space 4GB RAM
Storage Space 5GB available space
Operating Systems Windows、macOS
Design Software AutoCAD, Solidworks, Inkscape, CorelDRAW, PowerPoint, Illustrator, Photoshop, Google AutoDraw, etc.
File Type(s) SVG, DXF, JPG, JPEG, PNG, BMP, PDF, TIF, CR2, etc.
Max. Cutting Depth ≤15mm (Paulownia)
Material Capability Paper, Corrugated Paper, Wood, Acrylic, Cloth, Denim, Leather, Base Plate, ABS-based Color Board, PET, Rubber, Veneer, Cork, Sandpaper, Food, Glass Fiber, Plastic, Delrin, etc.

Lasercutter kerf of Laserbox Rotary

To achieve optimal fits for press fit, chamfer, and finger joints, it is crucial to determine the right clearances.This can be facilitated through the use of a parametric comb, featuring slots with varying widths based on the kerf of the laser cutter and the thickness of the material.

I used Fusion 360 to draw this parametric comb (in fact, for this machine, setting the range of 2.5~3.4 is basically enough), and the test object was 3MM plywood.

Fusion 360 to add Text / to save as DXF

>

Laser Cut with Xtool

Issue & Solution - Sketches designed in Fusion 360 become mirrored after importing into the laser cutting software

To import Sketche

I don’t know why every time I import an image from Fusion 360 it is mirrored. To solve this problem, you just need to find the “Flip Vertically” option on the laser cutter software.

Introduction to drawing for the laser cutter using Inkscape
A Quick Look at Kerf

Ungroup the text and the body

Processing type for Text:

Processsing type for the body:

For Material: Select 3mm Pine Plywood

Settings of Power and Speed

Notice: if material can’t be cut through, try slow down the speed.

• Power: 95%
• Speed: 13mm/s
• Pass: 1
  

Measure each slot:

Kerf & Clearance :

Results vary from different machines and material, the following result are for current case refference only.
Kerf : Amount of material removed by the cut of the blade.
Fit and Assembly Clearance: The intentional gap designed into the parts to ensure that they fit together properly without being too tight. This clearance accounts for variations in material thickness, laser kerf, and potential warping or thermal expansion of materials.
When working with plywood, I found that a fit of thickness - 0.2mm Kerf provided the best results. And Clearance between 2.78 ~2.88 mm is good.Further tests revealed that the optimal clearance was 2.80 for 3mm of plywood.

Press-fit Construction Kit

• A Press-fit must fit together without using glue, nails, screws or other fasteners,we need to adjust the joints to fit together in a precise way.

• A “parametric construction kit” in the context of laser cutting refers to a set of components designed with parametric modeling techniques, allowing for easy customization and adaptation of the parts’ dimensions and features. This approach leverages the power of parametric design to create flexible and scalable kits that can be easily modified to fit different requirements or constraints.

To add parametric 2D modelling:

When you design a pattern and need parametric for future modification, go to ‘Modify’ in Fusion 360, select ‘Change Parameters’, click + sign and add User Parameter, notice that if you don’t need units, select ‘No Units’.

My Construction kit Unit

I designed 2 construction kit unit by Fusion 360, for dupilication, I use the Laser Cutter Tool - xtool , to make Rectangular Pattern.

• Round Unit:
• Square Unit:
• To Duplicate these pattern - using Grid Array
• Let’s Cut:
  (test demo:)
  

My Construction Kit Gallery

Let’s Vinyl Cut

We are using Cricut machine for Vinyl Cut Assignment. To operate this machine, you need to download its software.

After download, setup the machine first:

For model type : Cricut - Explore Family.

Connected:

Section 1 :To test the machine, follow these instructions : Place a small cardstock piece on the mat and press the move button, so that the machine holds the paper in place.

The test was successful! (Though I put the cardstock front and back wrong.)

Let’s vinyl cutter!
Press ‘make’ in the top right corner:

Try to vinyl cut my name:

It looks really cool !

Issue & Solution — Fusion 360 Data file is offline and cannot be opened:

This is because of Working Offline, click here Working Online;

Image Compression

Click here for more details.

Convert all PNGs to JPGs

magick mogrify -format jpg *.png

Compress All JPGs TO QUALITY 30%

magick mogrify -quality 30% *.jpg

Video Compression

See commands here

Download FFmpeg:

• Go to the FFmpeg download page.
• Windows: click here

Extract FFmpeg:

• Extract the contents of the zip file to a folder of your choice (e.g., C:\ffmpeg). You can do this by right-clicking the zip file and selecting “Extract All…”, then choosing the destination folder.

Locate FFmpeg Executables:

• Open the extracted folder (C:\ffmpeg).
• Look for the folder containing the FFmpeg executables. If there is no bin folder, the executables (e.g., ffmpeg.exe, ffplay.exe, ffprobe.exe) might be directly in the root of the extracted folder or in a subfolder named something like bin.

Add FFmpeg to System PATH:

• Open the Start menu, search for “Environment Variables”, and select “Edit the system environment variables”.
• In the System Properties window, click on the “Environment Variables” button.
• In the Environment Variables window, find the “Path” variable in the “System variables” section, and click “Edit”.
• Click “New” and add the path to the folder containing ffmpeg.exe (e.g., C:\ffmpeg\bin if it exists, otherwise the path where you found ffmpeg.exe).

Verify Installation:

• Open a new Command Prompt window (press Win + R, type cmd, and press Enter). Type ffmpeg -version and press Enter.

• You should see output similar to this, indicating the version of FFmpeg and various configuration details:

python
ffmpeg version 4.3.1-2020-10-01 Full ffmpeg build from Zeranoe

• High Compression (smaller file size, lower quality):

ffmpeg -i input_video.mp4 -vcodec libx264 -crf 28 -preset faster -acodec aac -b:a 96k output_video.mp4

Breakdown of the Command:

ffmpeg: This is the command to run the FFmpeg tool, a powerful multimedia processing tool.

-i input_video.mp4: Specifies the input file, which is input_video.mp4.

-vcodec libx264: Sets the video codec to libx264, which is an encoder for H.264 video, a widely used video compression format.

-crf 28: This stands for “Constant Rate Factor.” It controls the quality of the output video. The range is typically from 0 to 51:

Lower values mean higher quality and larger file size. Higher values mean lower quality and smaller file size.

A value of 28 is considered a relatively low quality/high compression setting.
-preset faster: Specifies the speed of the encoding process:

Presets range from ultrafast (lowest compression, highest speed) to placebo (highest compression, lowest speed).

faster is a mid-range preset, offering a good balance between speed and compression efficiency.
-acodec aac: Sets the audio codec to AAC (Advanced Audio Coding), a common audio format.

-b:a 96k: Sets the audio bitrate to 96 kbps. Lower bitrates result in lower audio quality and smaller file size, while higher bitrates result in higher audio quality and larger file size.

output_video.mp4: Specifies the output file, which will be named output_video.mp4.

Adjusting for Lower Compression (Higher Quality):

To achieve lower compression (higher quality), you can adjust the -crf value to a lower number and choose a slower preset. Here is an example with lower compression:

ffmpeg -i input_video.mp4 -vcodec libx264 -crf 18 -preset medium -acodec aac -b:a 128k output_video.mp4
Explanation of Adjusted Parameters:
-crf 18: Lower CRF value for higher quality. A value of 18 is considered visually lossless or very high quality.
-preset medium: This preset offers a balance between encoding speed and compression. You can use slow or veryslow for better compression efficiency at the cost of encoding time.
-b:a 128k: Increased audio bitrate for better audio quality.

Summary:

Higher Compression (Lower Quality, Smaller File Size):

ffmpeg -i input_video.mp4 -vcodec libx264 -crf 28 -preset faster -acodec aac -b:a 96k output_video.mp4

Lower Compression (Higher Quality, Larger File Size):

ffmpeg -i input_video.mp4 -vcodec libx264 -crf 18 -preset medium -acodec aac -b:a 128k output_video.mp4

Feel free to adjust the -crf, -preset, and -b:a values according to your quality and file size requirements.

Original Design files included

Click here to download my design files. Notice: the Congrats Card Badge file (from Xtool )is not my original design, included them for future use.