Laser Cutting Update

Given that the RoboSumo tournament is fast approaching, I expect that most teams who want parts laser cut have already submitted their drawings, but if you haven’t and you still intend to get parts cut, please be advised that the 3mm acrylic has now all been used up. There are still a few sheets of 6mm acrylic in stock (two colours: clear and white opaque) but the supply is limited, so to avoid disappointment please don’t leave it until the last minute. I’m doing my best to facilitate teams who submit drawings to me, but my own access to the laser cutter is restricted so it can take a few days. I’m not exactly sure when I will have access to the laser cutting machine and when I won’t, so please don’t send drawings at the very last minute and expect them to be cut immediately.

Laser Cutting guidelines

Here are some updated guidelines on submitting drawings for laser cutting.

File format for laser cutting

  1. If you’re drawing your pieces in Inkscape, the easiest file format for me to work with is the native SVG file format.
  2. If you’re drawing your pieces in AutoCAD, the easiest file format for me to work with is DXF.
  3. Please send me a single file (either SVG or DXF) containing all of the parts you want cut. Please don’t send a separate file containing each part, because that makes it very labour intensive for me.
  4. Please leave some space between the individual pieces in the drawing because I may need to select and group the lines for each piece into a single object so that I can move it around.
  5. Your drawing should contain only thin black lines. There should be no filled shapes – just thin lines on a blank background. The laser simply cuts every line in the drawing.
  6. Do not include dimension labels or other markings that you don’t want cut out because the laser will cut out these shapes also. If you wish to provide dimensions to confirm the desired size of the pieces, by all means attach a second file with dimensions included, but your actual laser cutting drawing must include nothing but cutting lines.
  7. The laser cutting machine is capable of engraving, but we aren’t currently offering that option because it takes a long time on the machine. However, if there is some special reason why you want a part engraved, it may be possible to make an exception.

Some useful tips:

  1. Your pieces will be cut from 3mm thick acrylic sheet. The colour will be whatever is in the machine when your pieces are cut.
  2. If you’re the person who has been given the job of drawing the laser cutting plans for your team’s robot, please ask your teammates to review the drawings with you before you get them cut out. Extra pairs of eyes make it easier to spot errors or oversights in advance.
  3. Another great way to verify that your pieces will fit together the way you expect is to print them out at their actual size on a normal sheet of A4 paper, then stick the printout onto an A4 piece of foam board. If you then cut it out very carefully using a craft knife and a metal ruler, you can produce an excellent working replica of each piece. Cutting out curves is tricky, but straight lines can be cut very accurately with care, which allows you to test interlocking pieces. This is exactly what I do myself when I’m planning a design at home. To emulate 6mm acrylic sheet, you’ll probably need to double up 3mm foam board.
  4. You can buy ten A4 pieces of 3mm foam board for €10 in Eason’s stationery shop on Nassau St (formerly Reads of Nassau St).
  5. Depending on the design of your robot, you may find that your foam board prototype is good enough to carry out some testing, or at a pinch even to compete in the tournament. (It wouldn’t be the first time.)
  6. If you need to laser cut gears for your robot, Inkscape has a really great tool for drawing them. Go to “Extensions menu -> Render -> Gear…”. There are a couple of good tutorials on YouTube for using this gear tool.
  7. If you want to make very precisely fitting parts, remember that the kerf (the width of the laser cut) is approximately 0.1mm when cutting 3mm acrylic. Roughly speaking, this means that the laser removes material 0.05mm either side of the line it follows. For most purposes, you don’t really need to worry about this, but in some instances it can be significant. I haven’t checked how big the kerf is when cutting 6mm acrylic, but I expect that it’s slightly bigger than for 3mm.
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