The final chassis assembly brings together the four elements already constructed and adds the final two stepper motors.

I ran out of another bolt at this point - this time the 6-32 ¾inch UNC socket cap bolt. Fortunately, not only did I have some my extra ½inch bolts left over, these were also sufficiently long to do the job of the ¾inch screws - so I didn’t need any more extras. Clearly this slight mismatch between the Bill of Materials and the assembly instructions needs to be made right.

At  this point in the assembly I also had to make up the cables for the limit switches; this proved to be the trickiest assembly routine so far. As with the cables for the motors, each switch has a different length cable and these need labelling carefuly. The tricky bit is that each switch has a snap-in connector and the wires attach to these connectors by crimp-pins - and you have to attach the crimp-pins to the ends of the wires. There are full illustrated instructions for this on the Fab@Home site. This is not a desperately difficult process, but does require attention to detail if the pins are to slide nicely into the connector and snap securely into place. It is the first part of the whole assembly that I think might present some difficulties to at least some pupils - and the first one where I messed up… I ruined one of the crimp-pins and, of course, there are no spares. This time Maplin came to my rescue. Schools embarking on this process with pupils will either need to give them some initial practice, buy a proper crimping tool (probably the best bet) or, perhaps, have this one part of the assembly done by the teacher or technician.

Torben

This entry was posted on Friday, November 9th, 2007 at 2:05 pm and is filed under Fabber build notes. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.