Thursday, October 24, 2013

Assembling The Frame

The first step in building a Prusa Mendel is assembling the frame.  This is covered in videos 1 through 4.

Building the frame was easy and fun.  In these three videos, you simply follow along.  It was easy enough so that my five year old son helped.

The Prusa Mendel is built on a frame that is composed of threaded rods and printed parts.  It is held together by nuts that you position along the threaded rods.  The printed parts form the vertices/joints that attach one rod to another.  There are six vertices - two triangles linked to each other at each vertex.

Included in the kit are two wooden "measuring" rods that are to be used as guides to establish the correct distance between the vertices.  I found this to be awkward and tedious.  Instead I used my digital caliper.  I was fortunate to have purchased a 12" digital caliper instead of the 6" caliper that was suggested in the introduction video.  The 6" caliper is not large enough to be a substitute for the two wooden "measuring" rods because it's not long enough.

At the beginning of video #4, I am asked to mount the two z-motor mounts and attach two stepper motors them.  There is some confusion about the length of screw to use to attach the stepper motor to the mount - first it says M3 14mm, then M3 10mm and then I believe it says M3 14mm again.  I tried the 14mm screws and they were too long, but the 10mm seemed to work fine.  This sequence of steps requires me to hold the screwdriver upside down to screw in the eight screws that hold the two motors which is really awkward because I can't see the hole in the motor. 

After the end of video #4, I started to question why I'm asked to mount the z motor mounts since they don't appear to be a key component of the frame.  Even more mysterious is why it is necessary to mount the motors at this point.  It seems like this could be delayed until a later time.  The other suggestion I have is to attach the motors to the mounts *before* sliding the mounts onto the threaded rods.  This would have allowed me to place the mounts over the motors which would have left the holes visible and avoided the awkward upside down screwdriver step.

Here is how things look after video #3:

Here is what the Prusa Mendel looks like at the completion of video #4 and the z motors have been added:

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