there seems to be quite a few people using linuxcnc for rep-raps.. Like https://www.youtube.com/watch?v=R_Q0mGSz4ag
maybe contact some of these users and see what gotchas there are... sam On 01/11/2013 08:25 PM, Ed Nisley wrote: > TL;DR summary: advice needed on a LinuxCNC-based 3D printer project. > > The background... > > About a year ago, high-end DIY 3D printers outstripped the capabilities > of Arduino-based controllers: the gymnastics required to stuff > acceleration control into 8 bit microcontrollers appears to be a dead > end. There's a notion of re-re-writing the Arduino firmware in 32 bit > style for [ARM | Beagle | RPi | whatever] running on another generation > of custom microcontroller boards. > > Rather than waiting for more of the same, I want to explore what > LinuxCNC can enable for an advanced (albeit Cartesian) DIY 3D printer, > starting with a solid motion-control foundation plus all the other > features LinuxCNC provides, the ones that would require serious firmware > development for Arduino-based code. > > For example... > > Hard real time motion control, rather than interrupt-based motor > handlers that go awry when userland code inadvertently disables > interrupts to bit-bang an I2C peripheral. > > Userland scripting, extensible language features, a G-Code dialect with > loops / branching / subroutines, stuff like that. > > Probing the build platform to correct for for height variation and > misalignment: probekins. > > I think a HAL-based extruder model that could include second- and > third-order effects should provide better control than a simple > linear/angular axis, particularly for a printer with multiple extruders. > The plasma torch controller modules seem like good starting points. > > Similarly, ladder logic offers interesting possibilities for an extruder > "tool changer". > > LinuxCNC offers a *much* better UI, with devices that aren't teleported > from 1990. I want to get a Touchy interface running early, just to show > it off, plus the usual gamepad jogging and suchlike. > > Network-aware capabilities right out of the box, a real operating > system, and enough compute power & storage to make everything work. > > Plus all the topics I can barely pronounce when you folks discuss using > them on your industrial machinery. > > The hardware plan... > > I'll start with a stock Makergear M2, which seems to be the most solid > and well-designed DIY printer currently available. I'd prefer an > enclosure to stabilize the ambient temperature, but that's basically a > big box. > > Once the stock M2 works well enough, replace its RAMBo controller with > Mesa 5i25 + 7i76. > > The 7i76 has enough robust digital outputs to drive SSRs for heaters and > whatnot, with HAL components closing the temperature loops. The thermal > time constants seem long enough to not require high-frequency PWM > proportional control, which should simplify things. > > It also has sufficient digital inputs for home switches, probe contacts, > and stuff like that. > > However, the printer controller also needs multi-channel thermocouple > inputs, because thermistors seem underqualified for long-term > measurements at 200+ C. I'd like to use a Mesa 7i87 for analog input, > but it appears unsupported by the HostMot2 driver: > http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Mesa_Cards > > An alternative might be some Arduino love with this shield, although > four channels seems limiting: > http://www.mlgp-llc.com/arduino/public/arduino-pcb.html > > The Mesa 7i32 stepper driver board doesn't connect to the 5i25 at all. I > don't know whether a Gecko G540 4 channel board (which is one axis shy > of what I want) would make more sense than a quintet of M542H boards hot > from the usual eBay vendor, but, for sure, blowing a single-channel > board would be much less painful than taking out the Gecko. > > Although I have some of those tiny Pololu drivers, I think they're > underqualified for this job. I'd love to be proven wrong. > > The goal is to produce a 3D printer with a contemporary control system > that's easily extensible and isn't constrained by the quirks of DIY 3D > history. Eventually, I want to tinker with better printer mechanics, in > particular extruders, but the M2 should suffice for much of the > proof-of-concept work. > > I have the attention of a guy who knows his way around the innards of > the latest accelerated-motion-control Arduino firmware. I'll get my M2 > running to show it's possible, then poke around at system improvements, > after which he can build a similar setup and begin doing wonderful things. > > What I need... > > Guidance around my blind spots! > > F'r instance, I'm sure I've missed a hardware gotcha. Are there more > practical ways to drive five stepper axes, get a bunch of digital I/O, > and read thermocouples? > > Although I'm generally a big fan of lashing up surplus parts in my shop, > I want to do this with reasonably standard hardware, so as to simplify > building the next one. It's coming out of my pocket, however: the sky is > *not* the budgetary limit. > > I'll surely have a bunch more questions as I make progress over the next > few months (the M2 will likely take several months to arrive), but I'd > appreciate any advice in the interim. > > Thanks... > > ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. ON SALE this month only -- learn more at: http://p.sf.net/sfu/learnmore_123012 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
