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Making centered, evenly spaced perforations in the aluminium angle stock turned out to be bigger challenge than I expected. Measuring and marking every perforation takes a lot of time, so I made a foot-long template out of 1" aluminium strip, with 12 perforations. I also made an angle template to mark the first hole in the other leg of the angle stock. These kind of worked, but the resulting perforations were still a bit off center and/or not exactly 1" apart. This resulted in alignment problems when I tried to build simple structures like boxes, specifically some holes did not match up by as much as 1/16" or even more, and/or some angles were not 90 degrees.

In addition, the holes in the templates started getting loose after a while, increasing the errors. When I used newly made perforated angle as a template, the errors compounded. I thought of using steel for the templates, but figured it would last only so much longer.. And perhaps most importantly, drilling with the templates was *still* pretty labor intensive and time consuming. At some point I thought I needed a robot which would make accurate perforated angle. Initially I scoffed at the idea of making A to make B to make C, but hey, it's a Cartesian robot construction set, why not use it to make a drilling robot?

With already made linear slides, I put together a drilling contraption, something of a drill press movable along one axis - all from aluminium angle. On the upside, I tested in action some ideas for the construction set - specifically, linear sliding element actuated by a threaded rod, and threaded rod mounts. Both work well, and I made about 3 feet of the perforated angle pretty quickly.

On the downside, the precision of the contraption is poor. I guess that's due to a) flex in the aluminium angle. There is also b) a bit of play in the drill spindle, and I wonder how much it contributes to the errors. The picture shows the best result I got - by reducing, um.. perimeter of the structure which connects the drill to the workpiece. The markings are 1/8" apart, but it can be seen that many are off by maybe 1/64"-1/32".

Now I'm planning to radically reduce the flex by leaving out everything except for the drill frame, with its sliding elements directly connected to a single sliding element for the workpiece itself. Bonus - it would use a lot less angle stock than the above contraption.

Also, the design of the sliding element is evolving. I think I found an arrangement that allows (more or less) to adjust the degree of friction with the slide. More on this later.