Saturday, May 15, 2010

O'Blue (Open3DP's Mendel)

This all started at the end of winter quarter 2010 in an advanced RP class where a group put together a MakerBot.  This started several conversations about building RepRaps and some different options for using the lab printers to make the RP parts.  These even included using the powder printers to make plaster parts.  There were two students who were very interested in exploring this during spring quarter (myself and Marcus Lew).

It was decided that the best approach was to build the lab a Mendel first and then procede to make two more using the lessons learned from the first one.  To that end, Professor Mark Ganter began printing parts for the labs Mendel using the labs Stratasys Dimension 768BST.  It was also decided that we should complete the first machine in time for the UW Engineering Discovery Days.

One of the first assemblies was the X carriage.

This has some odd features, due to printing constrants, such as the fact that the bolts sit at an angle and there is no recess to allow the head to sit flat.
The main frame was also started.
As the assembly progressed several other oddities were noted including spacers that are too short, but also not needed.

And the Z-axis tensioner sits higher than the rest of the belt path causing the belt to bind.  This was solved with additional washers.

z-axis tensioner is on the left

The biggest challenge was getting the electronics working properly.  We performed initial bench testing of the electronics before assembling them on the machine and everything seemed to be working. When the major assembly was complete we took the Mendel to Metrix Create: Space to get help with the final details.  Once these were complete we began testing the electronics and ran into intermittent issues with the stepper motors and could not get the extruder motor to turn.  At this point it was getting very late so we called it a night.

In the following days we were still unable to determine the problem ourselves so we asked our friends at Metrix for more help.  They spent some more time on it and determined that we had some bad solder joints and a bad extruder board, however they were able to get the machine working by the second day of the Discovery Days.  We had it printing parts and it got a lot of attention.

We then proceeded by figuring out exactly what changes we wanted to implement on our Mendels and what we needed to buy to get them going.  We were also able to get time on another commercial FDM printer to get some of our plastic parts printed.
 The first parts for the new Mendels

Next time I am planning to discuss the design changes we made.

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