Graffiti Style Acrylic Pendants



Introduction: Graffiti Style Acrylic Pendants

About: I run Neal's CNC in Hayward, CA, an expert CNC cutting and fabrication service. Check out what we do at I'm a founding member of Noisebridge, a hackerspace in San Francisco, and Ace …

My friend DJ AGANA is a member of Few and Far, and she wanted to make some jewelry for her crew.  She had prepared images, I had access to a laser cutter, and this is the result!  She writes, "Few and Far is a movement that brings together dedicated, talented women all around the world. Skateboarding, graffiti and art, we consist of a team of open minded, creative every day females."  Check out their work at .

Step 1: Image Processing

I'm going to assume you have already made the artwork you want to cut from acrylic.  Due to the constraints of the laser and the strength of the material, there are some rules of thumb for best results.  Colors, obviously, will not show up!  The software does do an automatic greyscale dither if you have a raster image you want to engrave, although with testing you may find you prefer to do your own dither (dither is basically, replace smooth shades of grey with many tiny black dots, like in an old b&w newspaper photo; more dots, closely packed, for a darker area and fewer, spaced out more, for a lighter area).

We only made vector cuts on these particular pieces.  For best results with vectors, try to avoid having any very thin sections, especially thin sections supporting other areas, as they are prone to breakage.  Tiny holes are hard to pop out and may require a lot of tedious work with a toothpick or the point of a knife if you have many of them.  Holes with complex shapes may also be difficult to remove from the finished piece - consider breaking them up into smaller, less complex sections. Thin, wiggly areas make removal of the frisket (the paper coating on new acrylic sheet) difficult.  You can take the frisket off first and cut the acrylic "naked" but you may get smoke stains on it.  I prefer to leave the frisket on.

We used an Epilog laser cutter, and printed directly from Adobe Illustrator.  It is also possible to print from Corel Draw if you are more familiar with that.  In Illustrator, I first made a tiling of the images on a page the same size as the acrylic sheets we had bought (we had scraps in various sizes up to about one square foot).  Then I made sure that all the lines were set to a stroke width of 0.007 points.  We did some experimentation to come up with this number - 0.25pt, 0.5 pt, and 0pt, all did not make any cut at all.  If your print file does nothing at all when you press Go on the laser, check your line widths!  In Corel Draw, the correct stroke width is called "Hairline" and is in the pulldown menu, but in Illustrator you have to enter it by hand.

Step 2: Print Setup

I was printing a fair number of pendants, and wanted to use the acrylic efficiently.  I had pages in Illustrator the same size as the acrylic sheet I was printing on, but I also needed to make sure the print dialogs reflected this, or the prints would not start in the correct location.

Control-P, or File > Print, produces the dialog shown in the first image.  Several of the settings were incorrect - it came up with the default page size of 8.5 x 11, which was close but not good enough as the pendants went to 12 inches.  However the way to make these changes is a couple dialog boxes further on.  First you click Setup in the lower left, to get the dialog in the second image.  In that one, ensure the correct printer is selected, and click Preferences.

Finally you have achieved the Epilog setup dialog box.  Here is where to enter the size of the material, the speed, power, and frequency settings, and a choice for how the software will decide on its cut order.  See notes on the image for more detail.  I was cutting 1/8" acrylic, for which Epilog recommends 50% speed, 70% power, and 5000 Hz frequency for its 120 watt laser.  (Raster settings have different recommendations but I was not doing any engraving so did not enter those.)  This set of values worked for our blue acrylic, but the other colors for some reason would not cut quite through with those values.  I found that 45% speed, 78% power, and 5000 Hz (the maximum) worked well for our white, black, turquoise, orange, and clear frosted acrylic.  It is always a good idea to run some tests on the material you are cutting, as everything is slightly different - even the laser adjustments, from day to day.

In the final image, after you've OK'd your way back to the first dialog, you should see the correct values come up in the media size box.  Placement should be at 0 X and 0 Y if the media size and the print area size are the same; if you are printing on a larger media size than your document size, you can move it to different parts of your media by clicking on the TINY squares next to placement.  If either of those values is negative, however, you probably want to recheck your settings as that means part of your image is off the laser bed!

In many cases you're only cutting one copy and as long as the media size setting on the print dialog is bigger than your cut, you're good.  The sizes only have to match if you're filling your whole sheet up.

Step 3: Printing

The last Print button in the dialogs doesn't start the laser, unlike with paper printers which just go when you hit Print.  The laser cutter simply receives the file to print, and waits for you to press Go directly on the printer.  Once it has the file (or before you send the file), open the cover and place your media on the bed, in the upper left corner.  Focus the laser, either by hand (refer to owner's manual) or by using the autofocus.  Autofocus will move the laser head an inch or so into the material, and raise the print bed until a spring is compressed.  If your material has any holes in it, do NOT use autofocus or you risk breaking the print head should the spring go into a hole rather than onto the top of the material.

Any pieces of acrylic that are warped so a part is raised up more than about a mm or two above the bed should not be used, or the focus will be too far off and the part will not cut all the way through.  There is also the risk of running the laser head into a raised edge, if the warp is placed "smile up".  If you must use a warped piece, place it like an upside-down bowl, it will be more stable and less likely to damage the machine.

Once everything is set correctly, close the cover, press GO on the machine and watch it go!  Don't stare too long at it, of course... and don't leave the machine unattended in case of fire.  Once the cut is complete and the print head has returned to its home position in the upper left corner, open the cover and carefully remove your cut pieces.  If the settings are just right, and the acrylic is very flat, you may be able to take the sheet out with many of the cut pieces still in place held in only by a few scraps of the bottom frisket.  (If you must choose, however, between pieces that fall completely out and pieces that haven't been cut all the way through, go for the first!)

Step 4: Finishing

The pendants we cut had a fair amount of detail and needed a bit of finishing work.  Pushing out holes in A's and O's, peeling off frisket, and an occasional sandpaper or file where the laser had not QUITE cut through the acrylic and there was a sharp, broken edge.  That's it, though; if the frisket remained on and in good shape the resulting pieces will immediately be lovely, shiny, and ready to go.

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