So close and yet so far away
…in Nevada, to be exact. That’s where my replacement Pololu stepper motor drivers are; unfortunately, two of the four I had turned out to be duds. So I have X and Y axes that work, and I can juggle the boards around to make the Z axis and extruder work, but I don’t have enough working drivers to run them all at once. I probably blew them out somehow, between my bad soldering and careless walking around on carpet with socks. Oh well, live and learn.
Everything is done except for these two remaining tiny little parts. And I do mean everything:
That bracket on the extruder motor is my own design. I found that the wires coming off the extruder had a tendency to get bounced and jostled around a lot as the carriage moved, so I designed a really quick-and-dirty strain relief bracket:
I’m repeating myself, but going from idea to printed part in ten minutes is really quite a pseudo-magical experience.
It all just kinda works. Truly, the last 10% of this project wound up being where 90% of the effort lay (especially since literally every wire needed to be spliced with a longer one) but it’s been so satisfying to see it all fall into place. This machine was pretty much built from hardware store components and extruded plastic. It’s basically a specialized light-duty CNC machine. The axes move with such precision… and in near-silence, too. The thrill of manipulating it is electrifying.
It’s not that I don’t already have a 3D printer, but building a RepRap literally from scratch was a very different experience compared to joining together the lasercut wood components of my Makerbot Thing-O-matic. Printing out the plastic pieces, doing it over again with better designs, selecting components one by one, waiting for the parts to trickle in, fitting everything together by hand, making mistakes and learning so much along the way—it felt less like assembling a product and more like building a mad scientist contraption. Total cost: $502, rising to $550 if you include the unnecessary purchases and broken parts that needed to be replaced. If I had to do it again, I’m positive I could shave $100-150 off the cost without breaking a sweat. For example, this Sanguinololu kit alone costs about $25 less than mine cost; this hot end is $10 cheaper, comes pre-assembled and even includes a funnier name, etc etc etc.
One more thing: there seems to be a lot of confusion out there about how to set the e_steps_per_mm variable in firmware. There’s actually a set of handy formulas that the RepRap community has come up with for setting the values on a per-motor basis. For example, here’s the formula for the extruder:
(motor steps x (1 / microstepping resolution) x (extruder gear ratio) ) / (pi x bolt diameter measured at the teeth)
Most bots will have motors with 200 steps per rotation and 1/16 microstepping resolution, and last time I checked pi hadn’t changed. The gear ratio of the herringbone gears I used in my extruder was 43/13, so I wound up with this:
(200 x (1 / (1/16)) x (43/13) ) / (3.1415927 x 5) = 673.83
You get the idea. There are more formulas for X, Y, and Z axes on the RepRap wiki.
note: the formulas on the wiki raise the micro stepping resolution to the power of -1; above, I expressed that in the form of (1 / the microstepping resolution) to aid clarity for the math-challenged.
Categorised as: 3D printing, Hardware