Finally in CAD

Now that I've configured and tested the printer on the bench, its time to work on the frame.  At a basic level the frame can be quite simple as the only true requirement is holding the X, Y and Z axes orthogonal.  On the other hand, a well designed frame will hopefully fulfill many other roles as well.

The overall layout of the frame was driven by the components I am using, with the linear stages and extruder assembly having the most influence on the design.

The slower ATS stage must be used for Z, with the MX80L stages providing X and Y motion.  An ideal high speed printer would probably have a fixed or z-only bed to avoid shaking the part, but unfortunately the MX80L stages are not well suited to such an arrangement.  Stacking all three axes would require and awkward and heavy L bracket.

In the end I chose to move the bed in Y and the extruder in X and Z which is a fairly typical arrangement for hobby printers.

You might find this surprising, but the biggest design challenge of this printer was keeping its size in check.  The use of discrete linear stages and drives (along with two power supplies) means that the electronics for this build need a lot of space.  Furthermore, the printer is also running dual extruders plus a heated bed so there is even more wiring on top of what the linear stages require.

In the end I chose to design as compactly as possible by mixing the electronics into the structural components.  The final design is the result of several months of sporadic work in CAD.

This printer will be heavy.  The ATS125 linear stage I am using as a Z stage weighs 11.5lb on its own, more than many complete printers.  I estimate the final build will weigh somewhere in the range of 60-80lb.

	Footprint	Weight	Print Volume
Printrbot Simple	18.0x17.0"	10lb	6x6x6"
Prusa i3	16.5x16.5"	16lb	8x8x8"
LinearFDM	18.0x14.0"	80lb	6x6x8"

Despite its ridiculous weight, I succeeded in keeping the design compact and its footprint is roughly in-line with other hobby printers.

I completed full CAD for the entire printer before starting any fabrication.  This can feel really slow, but over time I've learned that it is generally smart in the long run.