garageFab.cc

Over the last couple of weeks I made some progress on the following things:

Adhesive printed labels as templates - it's kind of obvious idea I hadn't thought of before for some reason. Easy, fast, and very convenient when making different designs of something - such as the sliding elements. The accuracy is much better comparing to marking holes manually. With the labels, I quickly made several components for the construction set - mounts for the threaded rod, mounts for steppers, and several designs of the linear sliding element.

This PDF contains the current version of templates for the basic components of the set. There is a printed ruler - it's important to check first that the printer renders dimensions accurately - I found that my home inkjet adds an extra 1/32" to every 5 inches or so - which amounts to ~1% error. Pages 3-9 are meant to be printed on full sheet labels (Office Depot, Staples, ~$10 for 25 sheets), the templates should be cut out (the bend lines need very light cut - just barely scratching the surface). The templates are then adhered to the aluminium, bend lines to corners first. It's probably a good idea to mark the holes for drilling with an awl.

The linear sliding element evolved with small incremental changes. There is still plenty of room for improvement, but the current design seems to be good enough. The bearing pressure is now adjustable with 6-32 screws and although I couldn't get the element to roll freely on the rail (i.e. continue moving after being pushed), the bearings can be loosened to a point where the relatively modest force of the belt drive could actuate the element - which is good enough for me. I also thought about several mounting patterns of the sliding element. This led to the idea of separating it into two halves - each with a sliding and mounting section. So, now there are three configurations - full (sliding/mounting/sliding section), half (sliding/mounting section), and a long one (sliding/mounting/sliding/mounting section). When I make enough perforated angle, I'm planning to build a small PCB mill to see how well this works in practice. This will also be a good test for the aluminium angle stiffness (or lack thereof).

Finally, I built a new version of the drilling contraption with minimal flex between the workpiece and the drill frame. This was achieved by connecting the drill frame sliding elements directly to the workpiece sliding element. I did some tests and precision was pretty good. I made a Sketchup 3D model of the drilling contraptionl which is a bit more user friendly, and it has standard 23 size stepper motors to do all the work; I'm currently rebuilding the contraption according to this new design. For the computer control, I ordered open source Arduino USB controller board and open source stepper motor driver PCBs from RepRap foundation. Initially I wanted to buy the complete stepper control package from StepperWorld - and not having any experience with steppers, I probably should - but both of my PCs do not have a parallel port :( Now, of course the easy way would be to "borrow" a desktop PC from work, but that wouldn't be DIY would it?