Hey all,
I've spent the last two or three months on an extended hiatus as I worked on a project with an immediate deadline, but that's neither here nor there. The point is that that just finished up and I'm getting back into the swing of things around here!
My current repstrapping plan is to CNC-retrofit this: [
www.harborfreight.com] cheap chinese import mill. If all goes according to plan I can use that as a cartesian robot for a RepStrap, slap an extruder on it and print off my Darwin, then convert it back to a conventional CNC milling machine and finish the day with both useful tools! (I'm looking forward to the day when we can print off metal filament/do easy casting more than anybody, but until then a milling machine is a practical addition to the workshop as well). This is similar to Nophead's strategy, except I'm not skilled enough to build my own mill from scratch.
Anyway, this is in the electronics forum because I have a specific question about stepper motors. I would prefer to use the same motors on my machine when switching between printing and milling, which means they have to be fairly beefy for milling work. So, I have several questions for those of you who understand this better than I do:
1. Does the arduino-driven stepper board have a preference between unipolar or bipolar steppers? I'm sure I've read this before, but it doesn't seem to be in the documentation (someone point me to where I should look!) [EDIT: I found it. Bipolar is preferred, and it looks like either motor is good for that]
2. The L298 can drive up to 2A/phase. There are two different motors I'm looking at using, one bipolar [
www.xylotex.com] and one that can be wired either way, as I understand it [
cgi.ebay.com]. However, either way, they both claim to draw between 2.8 and 3A per phase. My gut tells me that I would be fine driving either of these at 2A and not getting the full torque in their application as repstrap drivers, but my gut is not particularily well known for its acuity.
3. If (2.) won't work out, are there other stepper driver boards that are drop-in replacements for Zach's? I recall something about the step/direction protocol being an industry standard, but I could be completely off on that.
I'm still learning how this whole CNC thing works, I certainly know a lot more about RepRap. And the more I learn about CNC, the more confusing it gets... it makes me all the more excited for the coming personal fabrication revolution, where 99% of the population will get the benefit without having to think about this! Of course, me being who I am, I'll end up doing way too much thinking anyway, but that can't be a bad thing...
My back-up plan is still of course to get a set of cheaper steppers as well and just switch between them when I want to switch uses. But if I can get away with solely an electrical difference, not a physical one, it'll make things so much the easier.
Edited 1 time(s). Last edit at 03/04/2008 01:56AM by Kyle Corbitt.
