parts for future gel boxes!

Today I hauled about 10 pounds of assorted acrylic 15 miles into the city of Cambridge and back to where I live.  The journey took about about 7 hours, and about four hours were spent laser cutting!  Of course, that is operator time, not tool time.  Since I am cutting, the big factors to control are material usage and tool time.  I cut the boxes at danger awesome, which charges $2/laser minute, meaning if you cut for 5 minutes, you are charged $10.

This makes part packing really, really important.  Part packing is the positioning of each part on the sheet that it will be made of.  Like many spatial challenges (routing PCBs, putting linkages on different planes, etc.) in engineering, there are probably tools for this, but there is certainly a sense of satisfaction in using your very own brain to solve the problem.  While the box was designed with fabrication in mind, I hit some speed bumps during cutting and learned a lot.

Black edge- 12 x 12 rectangle
Red edge- actual sheet
Green edge- parts I made

The first problem was that the parts I wanted to cut were 6×5 inches and would barely barley fit on a 12×12 sheet (as seen on the right).  I am pretty careful, and given a few thou over 12″, I was pretty sure I could cut out parts per sheet, like on the right- but the sheet was smaller by 1/8-1/4″ on each side!  So I went ahead and re-arranged the cusheet in coreldraw into a pinwheel shape (strangely, corel is much better than solidworks for this), and I ended up with excellent results, as seen below!

The nice thing about packing parts like this is you get to share edges, which is basically 50% off the cut time for that edge, plus you save on material between parts and have a lower chance of melting or warping parts with nearby cuts.

One of the nice things about the gel box is that most of the parts have similar-sized notches cut in them for mortise joints.  By keeping these the same throughout the box, the parts are easier to arrange, and they can share cuts!  A tip here is to make groupings of parts, and arrange them (sharing edges) into mega-parts that have edges that are easy to share with other mega-parts.  That is how i ended up with these cutouts being so clean.  You can see on the bottom two cutouts that the parts were mirrored across a horizontal line, and on the top the parts were pinwheeled again.

This might be it for the notes on making the gel system- I could write about boxing it all up, but I haven’t discovered a good way to do that except to do it while drinking a hot beverage or while watching a movie.