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Week 3. Computer -controlled Cutting

Group Assignment for the week: Characterize your lasercutter’s focus, power, speed, rate, kerf, joint clearance and types

Laser Cutter

In our lab, we have two types of lasers: the Trotec Speedy 400 Laser Cutter and the Trotec Speedy 100 Laser Cutter.

Trotec Speedy 400 Laser Cutter Specification:

  • It has two laser sources in one system which allows the use of a wide variety of different materials in one Job.

  • Engraving speed of 4.2 m/sec.
  • CO~2~ laser power up to 250 watts.
  • Overall dimensions(W x D x H): 1428 x 952 x 1050 mm.
  • Max.height of workpiece 305 mm with CO~2~ and 283 mmwith fibre.
  • Laser power: CO~2~: 60-250 watts and Fiber: 20-50 watts

Trotec Speedy 100 Laser Cutter specification

  • CO~2~ laser which power up to 250 watts and can work with materials like acrylic, glass, fabric, papers, stones and woods.

  • Overall dimensions(W x D x H): 982 x 739 x 993 mm.
  • Max.height of workpiece 170mm.
  • Laser power: CO~2~:30-60 watts

What are the risks of using a laser cutter?

  • Beam exposure: When using Class 4 lasers like those in Trotec Speedy models, proper enclosure prevents harm, with the machine’s window absorbing reflected beams. Keep doors closed during operation and wear safety glasses when necessary.
  • Fire: Laser cutters can cause fires because they use intense heat to cut materials like acrylic, which can easily catch fire. Even a small flame, combined with the machine’s fume extraction fans pulling in air, can quickly lead to a big fire. It only takes a few minutes for a small flame to turn into a serious fire hazard.
  • Smoke and Fumes: Cutting materials produces smoke and fumes that must be removed. Some materials create harmful fumes that can damage the machine or harm you. -Avoid cutting PVC or anything with chlorine_ because it produces dangerous hydrochloric acid that can harm your lungs and eyes, and damage the machine. Always check MSDS (material safety data sheet) for new materials.
  • Electrical Hazards

Laser cutter safety measures:

  • Safety stop button for an emergency interrupt of the power to the entire machine.
  • Interlocking switch that prevents the laser from firing when doors are open.
  • Don’t cut PVC and other problematic materials.
  • Use air assist for cutting (airflow from air assist can put out small flames)
  • Keep fire extinguisher and fire blanket close to the laser.
  • Never leave laser running without supervision.
  • Don’t disable safety features and don’t operate the machine with laser doors open.
  • Keep machine clean.
  • Remove residue from honeycomb bed to prevent it from catching on fire.
  • Remove debris from the exhaust blower and duct system.
  • Use common sense and never leave laser running unattended.

For this week’s assignment, we chose to use the larger Speedy 400 laser cutter because it has a bigger working area, which is useful for larger projects. Additionally, the Speedy 400 can mark on aluminum, providing us with more versatility in the materials we can work with compared to the Speedy 100.

Characterization of lasercutter’s focus, Power, Speed & Rate

  • To ensure smooth and accurate results for laser characterization, we begin by thoroughly cleaning the laser’s working area, as well as we meticulously clean the lens to optimize its performance.

  • Steps to clean the lens using lens tissue:

    1. Laser cutter should be powered off.
    2. Loosen the screw on the lens cover to access the lens.
    3. Take a piece of lens tissue designed for optical cleaning. Avoid using regular tissue or cloth, as they may scratch the lens.
    4. If necessary, lightly moisten the lens tissue with lens cleaning solution or isopropyl alcohol.
    5. Using gentle circular motions, wipe the lens from the center outward. Avoid applying excessive pressure to prevent scratching the lens.
    6. After cleaning, carefully inspect the lens to ensure all debris and smudges have been removed.
    7. Once done with the cleanimg of the lens, tighten the screw on the lens cover.
    8. Power on the laser cutter and verify weather the lens is functioning properly.

  • In Inkscape, create circles and assign different colors to them.

  • The next crucial step involves calibrating the z-axis to ensure precise laser focusing. Using the focusing key, position the square side onto the ledge of the laser head. Gradually elevate the z-axis until the key gently slips off the laser head.

  • Once the z-axis is properly set, proceed to home the laser head and position the workpiece onto the workspace. It’s imperative to activate the exhaust vents before commencing work to maintain a clear and safe working environment.

  • Go to JobControl > settings > Material template settings. Here, assign different functions and parameters to each of the colors.

  • First Iteration - Power Variation: Keeping speed and pulses constant at 70 and 1000, respectively we assigned different colors to represent varying power levels, descending from high to low. This allows for an assessment of the laser’s performance at different power settings while maintaining constant speed and pulse parameters.

  • Second Iteration - Speed Variation: Keep power and pulses constant at 90 and 1000, respectively. Varying the speed parameter from high to low across different colors. By holding power and pulse settings steady, this iteration evaluates how changes in speed affect laser performance, enabling adjustments for optimal speed settings.
  • Third Iteration - Pulse Variation: Maintain power and speed constant at 90 and 70, respectively. Adjust the pulse parameter across different colors while keeping speed and power settings consistent. This iteration examines the impact of pulse variations on laser outcomes, providing insights into pulse frequency’s influence on cutting or engraving results.

  • Results & Conclusion:

    • After completing the job, we noticed how different velocities and powers affect the engraving. More power results in darker engravings, while higher velocities with the same power might not engrave as deeply. The power and speed settings are crucial for laser cutters and engravers.
    • High power is needed for dark wood or stamp engravings, while low values work for materials like paper. Speed controls how fast the laser head moves, affecting exposure time and the quality of the cut.
    • PPI (pulses per inch) determines the number of laser pulses per inch for engraving, higher values needed for smooth edges in materials like acrylic and lower values for bright cutting edges in wood.

  • Laser Engraving glossy Aluminum: For laser engraving aluminum, fiber laser machines can be used to engrave directly on the object, but if you want to use CO~2~ laser, a special pretreatment is needed.

Characterization of lasercutter’s kerf & joint clearances

  1. An innovative Kerf Check Parts Generator, created by Atsufumi Suzuki, a graduate of Fablab Kamakura, was employed. This tool helped in generating combs with varying gap sizes to determine the best fit for the material, which in this case was cardboard with a thickness of about 5mm.
  2. The gaps in the combs ranged from 4.4mm to 5.2mm, with increments of 0.2mm. This range allowed for a thorough assessment of the most suitable fit.
  3. Two combs were cut from the same material(C Flute Corrugated Cardboard) to study the kerf and joint clearances.
  4. After cutting and testing, it was found that the 4.8mm gap provided the best fit, ensuring optimal joint clearances.
  5. So, On 5mm cardboard, 4.8mm is perfect. Therefore, joint clearance = 4.8mm and kerf = 0.2

Fail of the Week:

Due to an oversight, the speed was inadvertently adjusted to 0.75 instead of the intended 70, and power setting was set to 90, this resulted in the cardboard being burnt.

File of the week

svg file