As I described in an earlier post, really all a 3D printer is is a computer-controlled hot glue gun. Another big decision is what computer to use to control the printer. As always in the hobbyist 3D printing world there are lots of options.
First, let’s define what I mean by “computer”. In this case it’s not a tower or laptop that you might be familiar with (although those can and are often used in this manner!). It is a tiny board not more than a few inches long on a side with a special chip called a microcontroller at its heart. All a microcontroller does is keep doing a set of predefined tasks – in this case, it keeps checking for commands sent to it (or changes in input conditions), then does things based on the input.
For a 3D printer, for instance, let us say it receives the command ‘G1 X50 Y25.3 E22.4’. This tells the microcontroller it needs to turn the X-Axis and Y-Axis motors until the print head is 50mm away from the X home position, 25.3mm away from the Y home position and turn the extruder motor until 22.4mm of filament is extruded. The microcontroller then allows power to flow to the motors until the desired positions are reached.
Anything electrical is controlled by this device – the extruder heating element, the bed heater, fans, etc, so this is absolutely a critical piece. Since the hardware it controls is generally quite similar even for different models/manufacturers, most boards differ mostly in the number of inputs/outputs, how much memory they have, what flavor of computer control language they use, etc. This article from the Reprap.org wiki (a GREAT resource for 3D printing info, but since it is a wiki the usual cautions about crowd-sourced information applies) goes into great detail about the different electronics available.
For FrankenCore, rather than go for some specialized (and expensive) alternative, I’m going with what is really the workhorse of the 3D printing world – RAMPS. I’m using this for several reasons: 1) I’m already using it with FrankenPrusa and have never had an issue:
2) Whereas FrankenPrusa runs on 12V, FrankenCore will run on 24V and the modifications to the RAMPS to use 24v are trivial; and 3) I already have a spare RAMPS board in my possession from my failed attempt to get a Kossel (Delta) style printer running.
The X and Y axis assemblies have been printed and attached to the frame. Currently I still need to add the majority of the belt guides and run the belts before this segment is complete, but we have linear motion!
I hope the above video gives the idea of how this printer moves vs. FrankenPrusa. Notice how the printbed only moves up and down. This means that the bed ONLY moves when dropping a layer, at which time the x-y axes are still for that microsecond. This should reduce printing errors that result from mis-positioning of the print head due to the cross motion of the bed and head in the other design.
One of the disadvantages of a build like this where there are no “step-by-step” instructions and detailed pictures is that occasionally things are missed – like my math error that resulted in the frame re-cuts. In this case, rather than having a set of 3D files ready for printing like other designs, these parts had to be exported from a source file. Unfortunately, I didn’t realize that the spacers in these assemblies were not combined with the parts, so I have to print these spacers out. However, I think I will actually try to cut these spacers out of aluminum tube to add strength to these pieces.
Next time: The all important first layer and the belts go on, maybe some wiring completed too!