• Marking metal with a laser cutter

    Peter Walsh • 12/01/2022 at 19:52 • 0 comments

    Summary:

    Dry Moly lubricant can be used with a laser cutter to mark metal. This is widely available at auto parts stores, and much cheaper than Cermark.

    You can use this process to, for example, put your logo or printed text on metal enclosures or milled pieces. The markings are permanent, and won't come off short of scratching the metal.

    Overview

    I wanted a metal Christmas gift tag, and decided to mark it using the laser cutter at the local makerspace.
    (The metal tag is an in-joke, having to do with preventing woodpeckers from damaging my house. No, really: woodpeckers. The recipient will get the joke.)

    It's well known that Cermark can be used with a laser cutter to mark metal.

    What's less well-known is that dry moly lubricant can be used for the same purpose. When marked by a laser cutter, the laser sinters the molybdenum into the metal (so I'm told), making a permanent mark on the metal.

    The mark is fairly robust, and won't come off short of scratching the metal.

    Dry moly lubricant is available at most auto parts stores, and is much cheaper than Cermark.

    Step 1: Clean the metal

    Clean the metal piece using alcohol and let dry.

    Step 2: Spray coat the piece with Dry Moly

    Moly sprays on like paint, but it's not liquid or sticky so it doesn't get everywhere.

    Step 3: Allow the lubricant to dry

    Despite appearances, it takes some 20 minutes for the lubricant to dry. It's ready when the coating doesn't smear (like paint) when handled.

    Step 4: Etch the pattern, using a laser

    You want the metal to heat up at the focus point of the laser, so use high power and slow speeds.

    For our 80 watt laser, I used 100% power and 10 mm/s for the bitmap (etch), and 100% power and 1 mm/s for the line etching. The lines probably came out too heavy for this application, next time I'll back off on the power or increase the speed.

    The border decoration (ornaments and curly lines in the corner) looks really nice on the final tag, but doesn't photograph too well due to the tag's mirror finish.

    Step 5: Clean off the unsintered moly

    The dry moly comes off easily with alcohol and a paper towel.

    The shiny tag doesn't photograph well, but the intricate ornament work in the corner looks really nice.

    Notes for future jobs:

    The excess heat from the laser caused 2 bits of the anodized surface to come off, notably in the "r" character of "Christmas" below.

    I don't care about that for this project, and it's only a problem with anodized surfaces anyway... but if I had to do it over, I'd reduce the line power and maybe split the job into segments to give the metal a chance to cool down in between.

  • Fixing a vehicle floor mat, redux

    Peter Walsh • 12/01/2022 at 18:33 • 0 comments

    Summary

    Fix the hole in your car floor mat.

    This is not really a hack, just an odd use for a laser cutter.

    This is the 2nd time I've had to fix this mat. The first time was seven years ago, and since then the repaired section has itself worn out and needs replacing.

    The problem

    The floor mat in my truck has a hole, right under the gas pedal.

    The solution

    I noticed someone on Craigslist had brand new toyota floor mats on the "free" list. Apparently the new mats came with a used vehicle they purchased, and they didn't need the mats. So for the price of driving 10 miles I got some "new carpet" stock for repairing my own vehicle carpets.

    The new hole in my mat was on the edge of the original hole (the newly worn section was on the border of the original mat and the repair carpet), so in retrospect the original repair was off center a little.

    To compensate, the new repair will use a larger cutout.

    Step 1: Debriding

    Center the laser on the carpet pad, and cut out a 150mm circle.


    Step 2: Make a replacement

    Cut a similar hole in fresh carpet


    Step 3: Apply carpet tape

    Using carpet tape, fix the newly cut replacement to the original pad.

    Step 4: Final results


    I don't really care that the color doesn't match my original pads exactly, it's just nice to have a fresh piece of carpet under my foot. Seven more years of use on that carpet!

  • Free stock for your laser!

    Peter Walsh • 11/01/2020 at 16:23 • 2 comments

    Political signs make great cutting stock for CO2 lasers, and starting Wednesday you can get a boatload of them for free!

    The official term for the stiff material is "corrogated plastic"(*), and it's basically corrugated cardbord using polypropylene instead of paper. It's light, stiff, strong, and waterproof.

    Here's a desk organizer made from it. The pieces were lasercut and then hot-glued together. (Then glued to a wooden base.)


    Here's a closeup showing the corrugation style of the board.



    Some older types might be PVC, and you shouldn't cut these on the laser, so be sure to perform a flame test on anything you find before you start cutting. Modern signs should be polypropylene, which is fine to cut.

    (*) Some trade names:  Cartonplast®, Polyflute, Coroplast, FlutePlast, IntePro, Proplex, Correx, Twinplast, Corriflute or Corflute

  • Connecting USB lasers to linux

    Peter Walsh • 10/16/2020 at 16:01 • 0 comments

    Overview

    This post explains how to troubleshoot and fix USB laser cutter connection problems on linux.

    More specifically, if:

    • You have a laser cutter
    • Your cutter communicates via USB
    • You are trying to communicate with linux
    • Your software cannot talk to the laser

    ...this post will take you through the steps needed to troubleshoot the problem.

    Step 1: The Quick Fix

    If you are reading this post for the first time, see if this fixes your problem.

    In a command window, type:

    > sudo usermod -a -G dialout $USER

    Enter your password when prompted, and if no error is shown reboot your system.

    If your software now works with your laser, you're done: It was a permissions problem, you fixed it, you can stop reading.

    (Note: enter the command literally as shown, including the $USER field. $USER is a variable set by the command prompt containing your login name.)

    If this does not fix the problem, the next steps will help you identify where the problem is, and give some suggestions on how to fix it.

    Step 2: Hardware/Electrical

    The first step is to check the physical USB connection to your laser.

    With the laser disconnected from your computer, in a terminal window enter "lsusb" to list the USB devices. (Note: "lsusb" is one word, no spaces.)

    Without rebooting, connect the laser to your computer and enter "lsusb" a second time.

    Look for an extra device in the USB listing, one that appears after you connect your laser.

    For example, on my system I see the following:


    Before:

> lsusb
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

    Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    
After:

> lsusb
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

    Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 002: ID 0403:6001 Future Technology Devices International, Ltd FT232 USB-Serial (UART) IC
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

    When I connect my laser to my linux system, a new device of type "Future Technologies USB-Serial" is seen by the system, and all is good.

    If you do *not* see a new device line (of any type) when connecting your laser, you have an electrical or physical problem with the USB connection.

    Some things to try:

    • Check that your laser is turned on (doh!)
    • Verify the USB cable is seated properly: jiggle the connectiors, swap the cable end-for-end
    • Be sure the USB connector at the laser is connected to the USB port and not the UDisk port
    • Try a different USB port on your computer (sometimes they burn out)
    • Try a different USB cable
    • Try a different computer/laptop
    • Be sure your laser is configured to communicate by USB and not, for example, by network with USB communications turned off
    • Be sure your computer and laser are plugged into the same outlet, or same outlet strip (grounding issues)
    • Ask your laser vendor for help

    Step 3: Device drivers

    If your laser is shown on the USB listing, the next step is to see if the system is using the correct device driver.

    With the laser disconnected from your computer, in a terminal window enter "ls /dev" to list the available system devices. (Note: "ls /dev" is two words, with space between.)

    Without rebooting, connect the laser to your computer and enter "ls /dev" a second time.

    Look for an extra file that appears when you connect the laser.

    For example, on my system I see the following:

    Before:

> ls /dev
bsg dvdrw i2c-4 loop6 ppp snapshot ttyS14 ttyS26 uhid vcs5 vhci

After:

> ls /dev
bsg dvdrw i2c-4 loop6 ppp snapshot ttyS14 ttyS26...
    Read more »

  • Etching anodized aluminum

    Peter Walsh • 12/24/2016 at 02:38 • 0 comments

    Laser etching anodized aluminum

    One thing we teach in the laser authorization course at my hackerspace is that the laser will remove the anodization from aluminum.

    The laser won't touch the aluminum metal, or any metal in general(*), but etching away the anodization is sometimes useful when you want to put your logo on a finished project, or for front panel markings.

    The process does not remove *all* of the anodized layer, so the end result is a slightly tinted aluminum against the anodized background. In other words, the process does not result in perfect contrast of the image against the anodized background.

    Still, it's something you can do with the laser that will give your project a professional, polished look.

    You can purchase anodized aluminum plate (and many other forms) on eBay.

    (*) This is not strictly true, but it's against house rules to try, so we tell people that the laser won't do it.

    Christmas for Frankie

    So when my grand-niece had her water bottle stolen and her mom suggested I get her a new one for Christmas, I made personalized versions. The results are shown up top.

    She's studying genetics doing research on viruses and fruit flies, so one bottle has a virus capsid, one bottle has fruit flies (which doesn't photograph very well), and one bottle has Alice and the caterpillar.

    Each has her name engraved along the bottom, so they're less likely to be stolen.

    [HA! I just now figured out how to make Hackaday.io break paragraphs at the image boundary. Take *that*, Hackaday!]

    Speed and Power

    Scan speed is 350mm/s, scangap is 0.15mm which is about 3 scans per line with our laser's 0.5mm line width.

    Remember to turn OFF bi-directional scanning to avoid any backlash in scan positioning. Turn ON bi-directional, and the left scans will be offset from the right scans by backlash in the mechanical system, making edges look like saw teeth. Probably not what you want.

    The power reading of 50% for our aging 80-watt laser probably translates to about 25 watts(*), convert as needed for your system.

    (*) Our unit mins out at about 25% due to the age of the tube.


    Positive and Negative

    Be careful with the positive- and negative-ness of the image. The "Alice in Wonderland" image is originally black on a white background, but the etching removes the darker anodization to reveal the brighter aluminum.

    The Alice scene thus became a sort of "X-ray" version - I should probably invert the image and make another one, but I ran out of bottles.

    Engraved Closups

    The accuracy of engraving is pretty good, considering the spot size of our laser is .02" to begin with. The line on the right is freehand from the image; ie - it's not a computer-drawn straight line.

    The aluminum metal has a slight bluish (left) or greenish (right) tinge from leftover anodization, because the engrave process doesn't remove everything.

    It would be interesting to see how the anodized/etched sections respond to chemical etching. Chemical etching might be an interesting hobbyist way to make complex thin aluminum pieces using a laser cutter.