Make something big

This week I learned to use the waterjet and the ShopBot CNC.

Waterjet Autobot

I used inkscape to trace a JPEG of the Transformers logo. This was done by selecting Path | Trace Bitmap and playing around with the Edge Detection settings (I later found out PartWorks’s produced better results). I then exported the vector graphics as DXF so I could open it in AutoCAD. I made a few test cuts on the laser cutter, removing some extra lines and adding connectors to hold the exterior better. When done, I converted all measurements to inches and saved the result as an R12 DXF, the only format OMAX Layout was willing to accept.

In OMAX Layout I scaled and rotated the logo, setting the cut quality to 3 for all lines. I then ran clean quite a few times (dozens? hundreds?) until overlaps/duplicates/gaps were 0. I added the leads but still couldn’t generate the whole path, so I cleaned the drawing several more times after adding the leads, until everything was 0 again. For cutting, I used a tool offset of 0.15 and a thickness of 1/32" (=0.03125"). Since some of my cuts required an inside kerf and some an outside one, I wanted to choose the kerf side manually. Unfortunately, the software used such a high zoom during side selection that it was impossible to make informed decisions. I decided to stick with the default (left). The actual cutting went pretty smooth, though some edges came out a little rough because the cut was on the “wrong” side. I also had to manually remove a couple of parts that were hanging on a thread after the job was done, probably the result of gaps in my drawing, which were too small to be connected by the gap connector process. A tiny hole between the logo’s “eyes” stands as a testament to a barely noticeable line I didn’t remove from drawing in time.

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ShopBot Bookshelf

On my TA-monitored session I prepared an anatomically correct Red Ampelmann. Photo vs. the photo from berlin. I then experimented with pocketing, and learned that an OSB pocket is not deep enough to support the shelves in the bookshelf I had wanted to make.

I drew the shelf parts in SolidWorks then saved as DXF, adding some last-minute fillets using AutoCAD. After opening the DXF in PartWorks, I saved it as CRV then re-opened, to change the measurements to inches. I then created two profile toolpaths: inside for holes and outside for the plates. Setting used (for OSB): short 0.125” spindle, 18000rpm, feed 80 in/min and plunge 60/min. I had to pause the cutting several times to drill additional screws into the board: OSB is very light and moves quite a lot. All in all, the job took about 15 minutes to complete.

Unfortunately, it turned out the plates were too thick to fit in the slots prepared. Ozz and I tried sawing the slots a bit but that wasn’t enough. As I was struggling to make the necessary changes in SolidWorks, Ozz suggested I use the original drawing again, but calculate the toolpath as if I was using a 0.1” bit instead of 0.125”, thus making slightly wider cuts. This worked very nicely. A smaller value would have even been better and could spare me a few hammer blows.

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  1. Draw as clean and simple as possible. I originally planned to use a traced photo I had taken but couldn’t get a simple enough trace that also looked good.
  2. Test on the lasercutter.
  3. In OMAX Layout: clean, clean, and clean again!


  1. Measure very carefully and leave yourself some slack, especially when working with an uneven material such as OSB.
  2. Use inches in PartWorks!
  3. Learn from your buddy.
  4. Defining a bit size different than the real size is useful for creating slightly wider/narrower cuts than designed.

Thanks to Jen (RPL staff) for her help with the waterjet, to Yoav for his help with SolidWorks, and to Ozz for his pateince and illumination.