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Monthly Archives: June 2013

About five months have passed since you last read about HPRINT, and in terms of the story behind it you’re about nine months behind.  Time to catch up!

When I arrived at Tech in August, one of the first things I did was try out the new gantry components and was pleased to find that they worked fairly well, but I would need to seriously alter the extruder carriage and pulley layout to ensure smooth operation.  At around the time I was working on the CAD for that, the workload of classes hit and I was forced to put off further work on the machine until around late November.  Until that time, the printer – which some Undergraduate Lab Instructors had begun referring to as Gigantor due to its titanic frame – collected a fair bit of dust.

When I began to work on it again, I focused on one of the major issues everyone has to contend with building an H-gantry:  skew.  When an H-gantry carriage moves on any diagonal direction, unbalanced forces exist on the ends of the gantry itself, resulting in skew.  This is of course a very bad thing for precise applications like 3D Printing, as it ruins positional accuracy.  The only way around this is to have a structure that does not in any way permit skew, so I set about to design just that.

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Above is a picture of the updated gantry assembly as a CAD model, one of the gantry ends, and as it existed early on in the semester.  The increased length, a shift to brass bushings, and bracing using aluminum angle had a dramatic effect on overall rigidity.  Unfortunately, due to the level of inaccuracy present in the consumer machines used to create the parts they were effectively unusable: slight contraction of the plastic during printing had caused them to curve just enough to bind horribly on the linear rods.  It was at this stage where I decided to make the switch to a standard gantry setup, with one motor added to control the travelling X-Axis.

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After a few iterations and test prints, the result was a fairly robust and simple set of parts which would work as desired (and a lot of discarded and spare components lying on the conveniently-located build surface).  Though it is no longer uses an H-gantry, the balanced force from two motors on the Y-Axis can handle the now heavier gantry quite well.  A little bit more assembly and wiring later:

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And it was finally in a state where I could begin to really adjust firmware settings.  Though by that time, I was a bit busy with other things:

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The wait for the final part of – for lack of a better working name – Gigantor’s construction and setup will be considerably shorter than the wait for the second.  Until then, here’s a preview:

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-Jeff