Tools: Universal PLS6.75 Laser Cutter

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M360 Laser Cutter

The Universal PLS6.75 is a flexible tool for precise cutting and etching of flat materials like acrylic plastic and thin wood.

Use of the laser cutter requires the certification class.

If you are unsure about any aspect of laser cutter operation, cleaning, or maintenance, please ask for help in the #laser-engraver slack channel.

Tool Description

Universal Laser Cutter Model PLS6.75

  • 60 Watt CO2 laser.
  • 32" x 18" (813 x 457mm) cut bed.
  • Flat Cutting Table or removable Honeycomb Cutting Table.
  • High speed ventilation system for evacuation of fumes and particulates during cutting.
  • CorelDraw
  • Uses custom Windows print driver to specify laser intensities.
  • Raster and Vector modes.
  • 16 MB standard memory buffer.

Safety

Do not operate the laser cutter without taking the class. Do not allow others to use the laser cutter unsupervised without ensuring that they have taken the class.

Always wear safety glasses while watching the laser cutter operate. These are the laser-specific dark safety glasses near the laser cutter. Clear or dark-tinted safety glasses, sunglasses, etc. are not adequate protection. The laser used for cutting / etching is not visible to the human eye but can cause significant damage to the eye.

Always use the ventilation fan. This is turned on via a power strip on the table. Leave the ventilation fan running for some time after completing your work to draw smoke and other gases out of the space. Please turn off the ventilation fan when not in use to keep air conditioning costs down. Notify us immediately if the ventilation fan seems weaker than usual.

Always supervise the laser cutter while in operation. The risk of fire varies by material but is always there.

Be considerate of others using the space. If possible, please refrain from operating the laser cutter during or immediately before a class or other Meetup due to noise and smell.

Note: The person operating the laser cutter is responsible for ensuring the safety of others in the area. Visitors, guests, and even other members may not know proper safety procedures. Ensure that they do not watch the laser operate without safety glasses.

Be aware of the nearest fire extinguishers:

  • One just to the right of the laser-cutter
  • One just inside kitchen
  • One by front door

Materials (what to use, and not use, it on)

There are a wide variety of materials that are safe to cut and etch.

Unsafe Materials to Cut or Etch

Never cut or etch these materials. Most of these will produce toxic gases when heated.

Note that many manufactured items that seem like good candidates for etching are made of PVC.

Note that it can be quite difficult to tell the difference between polycarbonate and acrylic plastics. If nothing else, a small test etch or cut will help determine which plastic the item is made from.

Based on list from ATX HackerSpace.

  • PVC (Poly Vinyl Chloride)/vinyl/pleather/artificial leather
  • Thick ( >1mm ) Polycarbonate/Lexan
  • ABS
  • HDPE/milk bottle plastic
  • PolyStyrene Foam
  • PolyPropylene Foam
  • Fiberglass
  • Coated Carbon Fiber
  • Teflon (PTFE)
  • Chrome-tanned Leather

Safe Materials to Cut

Based on list from ATX HackerSpace.

  • Many woods (successfully used at THS)
  • Plywood/Composite woods (successfully used at THS)
  • MDF/Engineered woods
  • Paper, card stock (successfully used at THS)
  • Marshmallows (successfully used at THS)
  • Cardboard, carton (Thick cardboard will burn - the pockets are protected from the exhaust fan and air assist and will sustain a flame) (successfully used at THS)
  • Cork
  • Acrylic/Lucite/Plexiglas/PMMA (acrylic successfully used at THS)
  • Thin Polycarbonate Sheeting (<1mm)
  • Delrin (POM)
  • Kapton tape (Polyimide)
  • Mylar
  • Solid Styrene
  • Depron foam
  • Gator foam
  • EVA foam (according to ULS)
  • Cloth/felt/hemp/cotton
  • Leather/Suede (ONLY veg-tan leather. NEVER cut or etch chrome-tan leathers)
  • Magnetic Sheet
  • NON-CHLORINE-containing rubber
  • Neoprene rubber (according to ULS)
  • Carbon fiber mats/weave that has not had epoxy applied
  • Coroplast ('corrugated plastic')
  • Chocolate (successfully used at THS)
  • Worbla is reportedly safe to cut ( Worbla.com )

Safe Materials to Etch

Some materials can't be cut, but can be lightly etched.

Based on list from From ATX HackerSpace.

  • Most of the above "cut-safe" materials
  • Glass
  • Ceramic tile
  • Anodized aluminum (Read special instructions for this material)
  • Painted/coated metals (Read special instructions for this material)
  • Stone, Marble, Granite, Soapstone, Onyx. (Read special instructions for this material) (successfully used at THS)

Selecting Materials

  • Materials thicker than about 1/4 inch (6mm) may not cut cleanly through due to how/where the laser beam point focuses
  • Using the laser on chrome-tanned leather will produce cyanide gas. Veg-tanned leather is safe to use at THS. Refer to this video for more information on chrome vs. veg-tanned leather.

Materials Available at the Space

We do not currently resell materials for use with the laser cutter.

We keep a steady supply of scrap 1/4 inch plywood and acrylic sheet at the space for free use. Please donate any useful scraps and dispose of pieces that are too small to be used.

There are a number of donated pieces of other plastics, some tiles, etc. kept near the laser cutter for free use. Be aware that some of this plastic may be polycarbonate or other materials.

We have a good amount of donated matte board (scraps from framing art) that cuts well. It is kept in a lateral file below the office supplies.

Where to buy acrylic

Where to buy wood

Home Depot and Lowes sell 1/4" (and some other thicknesses) plywood as "project panel" / "luan" (cheap but often has knots in middle layers that may need multiple passes or a knife/saw to cut through)

Michaels, Joann's, Blick, and others carry Midwest Products birch plywood (not cheap but look for Joann's coupons)

Cards of Wood

Aircraft Plywood (recommended by Nervous Systems)

Also see: Where_to_Buy_Things#Wood

Tool Use

  • Videos: We have videos uploaded instructing on [1](removing/installing air assist cone) and [2](setting the z-height)
  • Check lens. If you have been trained in lens cleaning, Clean only if necessary (see Maintenance section below for procedures)
  • Create a new document in CorelDraw that is 24"Wx12"H
  • Load SVG or create design. Use only the 8 supported colors.
  • "Print" design
    • Before clicking "OK" to print, go to "Preferences" and set appropriate values for each color.
    • Review information from the class on how to do this.
    • Review Laser Cutter documentation and log book for what settings to use.
  • Turn on the exhaust fan.
  • Power on Laser Cutter.
  • If air assist nozzle is installed, turn on its air
  • Put masking on your material to reduce scorching. (We have a large roll of self-adhesive masking in the Laser Cutter work area.)
  • Place material on the cut bed.
  • Set the Z-axis height and return the focus alignment tool to it's storage location.
  • Close all Laser Cutter doors.
  • Press "Next ==>" on the laser cutter control panel to use the most recently printed file.
  • Double check your work.
  • Press "Start".
  • Never leave the Laser Cutter unattended!
  • When done, turn off exhaust fan, and air assist (if applicable)
  • Write a short entry about your print job in the Log Book about who, when, what you cut, what settings you used, and the cut duration.

Software

Corel Draw

Corel Draw 2021 (Academic and Non-Profit) is provided on the Laser Engraver workstation. The about page reports Version 23.1.0.389. It is used for job layout, as well as building vector (and other) images for cutting.

Inkscape

Inkscape is a free Open Source vector graphics editor that you can use to get used to the overall concept of vector based graphics design. However, be aware that there are certain issues you must face when transferring your design to the laser printer.

Inkscape uses 90 DPI and CorelDraw uses 96 DPI. If you are importing an SVG from Inkscape into CorelDraw using SVG format, you will need to rescale the image to 1.0666666666%. PDF and certain other formats do not suffer from this problem and are the preferred method of import.

Note: As of Inkscape 0.92 the default resolution has been changed to 96dpi to match the CSS standard and now matches that of CorelDraw. The information on scaling may be needed only if using an older version of Inkscape.

See this guide by the ATX Hackerspace for help.

Adobe Illustrator

Illustrator could be used, but specifics haven't been documented here.

Slicer for Fusion360

Slicer for Fusion 360 is a freeware/abandonware application that slices 3D models into 2D artifacts.

Installation

It can be downloaded from https://www.autodesk.com/support/technical/article/caas/tsarticles/ts/3yg7zznS94MHNDG7KMV8Qg.html, but there are some some caveats. "Slicer for Fusion 360 is no longer maintained on the Autodesk Fusion 360 App Store. The technology is deprecated and is no longer being maintained and supported by Autodesk. Provided below is the final release of Slicer for both Mac OS and Windows.

Unzip and install like any typical application.

Usage

Slicer for Fusion 360 can be run standalone. Ignore the 'Sign in' link at the top right. Typical workflow would consist of:

  • Import a 3d model in .stl or .obj format. Model does not rotate after import, so ensure “Change up-axis of the mesh to X/Y/Z”. It is odd that the Y axis is the default, Z would be used to stack layers from top to bottom, but sometimes things would be sideways. Later, the slice direction could be changed to account for the up-axis.
  • Manufacturing Settings is where you set stock size, material thickness, slot offset, and tool diameter. Tool diameter would be the router bit size on a CNC, but laser may be zero or 0.0001?
  • Construction Technique is either Stacked Slices, Interlocked Slices, Curve, Radial Slices, Folded Panels (think Pepakura), or 3D Slices.
  • Slice direction (except in Folded Panels), select the cone to rotate the angle the model is sliced.
  • Modify Form TBD
  • Assembly Steps TBD
  • Get Plans allows you to export as .eps, .pdf, or .dxf. Dxf allows you to set units in inches, feet, cm, or mm. Export to My Computer will save locally. Export to Fusion Team may work if logged in.

Other

There are others, see https://en.wikipedia.org/wiki/Comparison_of_vector_graphics_editors

Tips and Tricks

Since the terms are used repeatedly used in this document, here's the difference between Raster and Vector images.

Design tips from the first class

  • Set your page size to 24"W x 12"H.
  • Placing your image at the top left corner cuts it from the top left corner.
  • Keep a 1/8" margin in case the laser (or bed, or material) is slightly out of alignment.
  • Vector cuts should use line widths of 0.001" or hairline. Anything wider than 0.005" will be rasterized and not cut the way you expect. You can draw with wider lines and reset them before printing in CorelDraw using "Select All" then "Object" --> "Fill And Stroke" to reset all lines to 0.001".
  • Draw your "cut" lines in red, and "etch" lines in blue or green. Anything you want to rasterize should be in monochrome/greyscale. (Advanced users can use more colors for more things...but if you know enough to do this, then you don't need to be told how.)
  • Lines with colors not set to 255 for any RGB value or less than 100% opacity will be treated as black and rasterized or worse, ignored, by the print driver.[SIC] Don't use color models other than RGB.
  • Problem: I created an SVG in Inkscape but when I import it into CorelDraw it's the wrong size. --- Inkscape uses 90 DPI and CorelDraw uses 96 DPI. If you are importing an SVG from Inkscape into CorelDraw, you will need to rescale the image to 1.0666666666%

Other tips members have learned

  • CorelDraw lets you do math inside the size entry fields. For example, if you have a Width that is 4.228 in, you can append to that "+1.25" and CorelDraw will change the value to 5.478 in. Furthermore, you can enter values in either "standard" or metric units and CorelDraw will recalculate the value in the document's default units. For example: if the document is set to inches and you entered "65mm" CorelDraw will do the calculation and set the value to 2.5590 inches.
  • If you realize you forgot to turn on the vent, you should quickly turn on the vent! But it's better to not forget to turn it on in the first place.
  • It may be helpful to use the restroom/get a drink/stretch/etc before starting a particular long (complex) job. DO NOT leave laser cutter unattended while cutting or etching.
  • You can use scrap material (pieces that have already been cut) to test out a design, or for a finished piece if it is the right size. There is a bin of "scrap material" kept near the laser cutter.
  • Etching a large section of thin acrylic will cause warping.
  • If you are etching an oddly shaped and curved surface (for example a pumpkin), try setting the Z-height to the "median" (middle) height you are etching.
  • Refer to the following table for spot sizes (the width of the cut, or "kerf") and focal ranges of the lenses available. (Note: The Tampa Hackerspace only has the 2.0 lens, the others are presented for completeness.)
FOCAL LENGTH SPOT SIZE FOCAL RANGE
1.5 “ .003 “ + / - .075 “
2.0 “ .005 “ + / - .100 “
2.5 “ .007 “ + / - .125 “
4.0 “ .013 “ + / - .200 “
  • You can use the "pointer" mode to "proof" a design. If the any of the doors are open, the red light on the control panel will flash. If you press "Start" to run your job in this state, the job will begin and will trace out the entire design, HOWEVER, the standard invisible CO2 laser will be replaced with a red pointer dot (laser diode). This will let you test your layout and will calculate the job time. Be careful though, the red dot will be close, but not exactly where the laser will cut.
  • You can use the X-Y mode to find positions on the print bed. Press the "X-Y" button and use the arrow pad to move the red pointer. The LCD displays the current x,y coordinates under the pointer. These coordinates can be used to position a work piece, and the values entered into CorelDraw. Use the up-down arrows and "Select" to choose "Re-home pointer" when finished. (Check the manual, linked below, for a more through explanation.)
  • After the first time a job is run (including "pointer" test run mentioned above), during subsequent runs of the same job the control panel timer will change from a "count-up" timer to a "count-down" timer, telling you how much time remains on your job.
  • You can press the "Pause" button on the control panel to pause your job. The laser cutter will finish the current line, then return the head to home. If it's in the middle of a raster, this will happen almost immediately, BUT if it's in the middle of a long cut line, the line will finish first. This may take several seconds. Your job can be resumed where it left off by pressing the "Resume" button. There may be a slight offset when resuming a job, especially if the system was in the middle of a raster. "Wait for the motion system to stop and move to the home position before opening any door otherwise the laser beam will not resume from the position it stopped at."
  • Rastering an image on a full 24"x12" (width x height) piece of wood at the recommended settings of [Power 100, Speed 59, 500PPI ] will take 45-55 minutes. On a 24"x6" board, it will take about half that time. On a 12"x12" board, it will take about 10% less time than the full 24", so 40-50 minutes. For fastest raster time, orient your image so the longest dimension is aligned with the X axis.

Photo-quality raster images

Photo-quality raster images can be etched on material at high DPI(dots-per-inch)/PPI(pulses-per-inch). For example at 500 PPI on Acrylic.

  • Open your image in The GIMP or another program capable of editing photos. (CorelDraw doesn't support all the features we need.)

In GIMP:

  • Click on "Image" --> "Mode" --> "Grayscale" to convert color to greyscale.
  • Click on "Image" --> "Print Size" and set the X and Y Resolutions to the desired value (500 pixels/in).
  • If you want to invert the grays (change black to white and white to black), click on "Colors" --> "Invert". The black portions are what will be etched. I recommend etching less instead of more; etching a large section of acrylic black will cause warping.
  • If you need to adjust the gray levels, you can tweak the values using:
    • "Colors" --> "Levels" OR
    • "Colors" --> "Curves", You'll have to play around with these settings.
  • Save your image with a new name and as a JPG or PNG.

Cleaning Acrylic Cuts

  • For masking paper adhesive residue, some (untested) suggestions are Goo Gone, WD-40, mineral oil, naptha, or even cooking oil

Using X-Y Mode to Measure on the Laser Engraver

You can use the machine to directly measure on your material. See Using X-Y Mode to Measure on the Laser Engraver.

Common Problems

My job didn't cut

Problem: My design is in CorelDraw but all or a portion didn't cut. Some causes of this include:

  • The line thickness was not set to "hairline" or 0.001" inches and was ignored. (This color set to only "Vector" cut.)
  • The line color is not one of the basic colors supported and was ignored.
  • Driver setting for this chosen color set to "Skip".
  • Driver set incorrectly to "Raster" or incorrectly to "Vector".
  • Driver power level set to 0.
  • Design is outside the 24" by 12" cut area.
  • Design has transparency. This may manifest as vector lines rastering instead. Select the offending lines and set to "No Transparency" in the Object Properties.
  • If a CorelDraw document has multiple pages (see tabs at bottom of Corel window) and you print "Current Document" then each page will be sent to the laser engraver as a SEPARATE job. If a page is blank, it will STILL be sent, and will show up as a 0 power 0 speed job. Press the "Next >>" button to skip that blank job. NOTE: this may cause difficulty managing multiple jobs on the laser engraver, so avoid this situation by not printing blank pages.

My cut or etch isn't deep enough

Problem: My cut or etch isn't deep enough.

Without moving anything or changing any settings, you can press "Start" again and the exact same job will be run a second time, cutting in the exact same places if the work piece hasn't been moved. If your material is too thick, the laser may not be focused correctly to cut all the way through. You might be able to fix this by adjusting the Z-axis slightly lower.

Maintenance

Refer maintenance to qualified personnel. If no qualified personal are on-site, post in #broken and/or #laser-engraver slack channel.

Lens See Bryan Lee for training on lens cleaning procedure. Otherwise, follow this procedure.

Maintenance Schedule and Summary (From the manual)

Since the maintenance requirements of the laser system is dependent on the type of material being run, the quantity of material being removed, the hours of operation, and the quality of the exhaust blower, it must be user defined. As a starting point, we recommend the following schedule:

  • As necessary
    • Engraving table -- soap solution, or alcohol or acetone, and paper towels.
    • Main enclosure -- vacuum loose debris. Use soft cloth or paper towels and the soap solution to clean the enclosure.
    • Top door window -- cotton cloth and the soap solution. The top window is made out of acrylic. DO NOT use paper towels because they will scratch the acrylic. Also, DO NOT use window cleaner, alcohol, or acetone, as these chemicals will crack the acrylic. Only use cleaners compatible with acrylic.
  • Every 8 hours of engraving -- Turn off and unplug the laser system.
    • Clean X-axis and Y-axis rails and bearing tracks -- cotton swabs or paper towels, and alcohol or soap solution.
    • Clean X-axis and Y-axis bearings -- After the rails and tracks are cleaned, use a clean swab or paper towel, and alcohol to clean all of the bearings by holding the swab against each bearing and moving the motion system by hand to roll the bearings against the swab. There are seven bearings in the system, three (3) on the focus carriage, two (2) on the left side of the X-rail, and two (2) on the right side of the X-rail.
    • Clean X-axis belt.
    • Check beam window, #2 mirror, #3 mirror, and focus lens for debris. Clean ONLY if dirty. Do not clean immediately after use, optics will be hot. -- Refer this step to trained personal.
  • Every month
    • Clean cooling fan filters -- Wash the element in a soap and water solution, dry, and re-install. If scheduling prevents filters from being washed and dried, use a dust buster to carefully vacuum dust off the filters. Be certain to replace them with the same side out that they were removed.
    • Clean and re-lubricate Z-axis lead screws -- The only lubrication that may be required [on the entire laser system] is the screw threads for the table lifting mechanism. After some time, contaminants can adhere to the lubricant, which can cause the engraving table to bind up or sound squeaky. If this is the case, wipe off the contaminated grease with a soft cloth dampened with alcohol and apply fresh white lithium grease to the screw threads. NEVER SPRAY ANY DEGREASING SOLUTIONS DIRECTLY ONTO THE THREADS. Run the table up and down to work in the fresh grease. Repeat if necessary.
    • Check for X-axis and Y-axis belt wear – replace as necessary
    • Check and/or clean X-axis and Y-axis drive gears
    • Check for X-axis and Y-axis bearing wear – replace as necessary
    • Inspect system for loose screws and mechanical parts – tighten if necessary
  • Every 6 months
    • Exhaust plenum -- Remove it from the system. Using your soap and water solution, clean the inside of plenum as well as the inside rear wall of the Laser System.
    • Blower fan -- Check blower fan screen for loose cut material (cardboard) that may have been sucked through the exhaust system and be restricting air flow.
    • "Bucket" Filter Cleaning -- Cleaning is simply a matter of stabilizing the buckets so they don't twist, unscrew the top bucket's lid, remove the filter material, take it outside and clean, dry it, refold it (air must pass through 4 layers), reinsert it. The screen on the exhaust side can be removed, and cleaned. Soaking and/or brushing may be necessary. The other screen can not be removed. When done, and screw the top on.
      • The purpose of the exhaust filter is to reduce material passing through the exhaust blower "in the attic". The blowers were getting gunked up and needed to be exchanged every 6 months or so. We attempted to use a cyclonic system last year, but it did not allow enough airflow.
      • The current setup draws air from the enclosure, through a 4 inch flexible metal duct and into the bottom bucket. When air enters the bottom bucket, the volume expands, slowing the airflow (but not the total volume, cubic feet/minute). The flow impacts a baffle and some particles should stop moving and ultimately fall. The airflow changes direction several times, which should stop more particulates. The air enters the upper bucket and passes through the filter material, catching even more particulates. There's a perforated metal panel the air goes through, then up the stack into the blower, then up another stack out the vent in the roof.
      • Flow problems can happen if the hoses get kinked or excessively dirty inside.

Related Links

  • Boxes.py Generate SVGs for boxes. Includes boxes with FLEXIBLE, curved sides. Many output formats are available, use svg or pdf, and avoid dxf as it seems to add unnecessary vectors.
  • Youtube video of #sketchup plugin by Eneroth for #laser-engraver cutting and box-making. Brett Freeman writes: "Start sketchup and go to Extensions Warehouse. Search for Eneroth Laser tools. Click when you select it and then click Install."
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