Hello, just build a workbee! After having done many test Cuts and holes and been pretty happy with the results for now, I’ve run into a problem. I did a more complex job and it suddenly missed about 15-20mm of steps on x axis. The result wasn’t exactly joy... as the pic shows. I’m running it off a mks 2.0 cnc board with tmc2209 in chopcycle mode at 16th step resolution. when jogging and doing tests the drivers run completely cool. however when I did the bigger job they start to get warm. Not too hot to touch, but noticeably warm. I’m running Grbl1.1h and controlling it via usb, which hasn’t given any problems so far. the machine has some occasional resonance when jogging over 1700mm/sec, which seem slow to me. But I decided to ignore it for now and stay under 1000mm/sec where it runs super smooth. Any suggestions on where to start hunting down the failing parts would be very welcome.
1.7A peak drivers are more suited to NEMA17s and 3D printers Consider the OpenBuilds Blackbox with 4A peak, 3.2A RMS as more suited to the typical CNC application
Hm. That’s fair input. What’s the black box based on? I was wondering if I should go for dedicated drivers with closed loop steppers if I need to upgrade anyway?
Grbl as well, so you don't need to re-learn everything you know While closed loop is awesome, consider that we have many many happy customers without issue - its simple, self-contained, warrantied, and you know we only supply stuff we believe in and that we spent many many days obsessing over it to make sure it fits the rest of our ecosystem, and had been designed to be a perfect match to all our other components See https://docs.openbuilds.com/blackbox and https://www.youtube.com/user/OpenBuilds/search?query=blackbox
Thanks for the link. It’s very nicely documented, but i didnt find any place stating what stepperdrivers are actually Used? also i’m planning on adding limit switches on all axes (i.e 6 switches). However i only found three limit switches on the Black box - is That because you expect to be able to catch it running off the end of an axis in software and therefore don’t need the hardware for it? Cheers Kristoffer
yes. I was considering closed loop steppers. Can you drive them with the std. grbl/arduino board just by using the four pins (en,step, dir, gnd) by the stepsticks. or do you need a different kind of feedback from the drivers? And just a newbie question, how does the drivers compensate for a missed step? Do the just keep the signal until the motor responds? Or how does that actually work? I like the idea of running closedloop steppers. It would definitely be a good upgrade.
Arduino only has three limit inputs, that's normal: gnea/grbl Yup! Same as all stepper drivers. Same thing is happening internally in the BlackBox, but you can't just buy a "Muscle" (drivers) board without a "Brains" (basically an Arduino Uno) board, though I suspect a lot of people- who are sufficiently advanced enough in their journey not to necessarily be advantaged by a full-aftermarket-service integrated solution and also understand the downsides of integrated solutions- would buy one. This is part of the reason why they run cooler- the driver increases the current upon resistance, to try and power through it, but if it doesn't work, it cuts power to the motor entirely until you power-cycle it. This is a very fast process, and may in certain circumstances help stop you damaging your machine. It's not a replacement for limit switches though! I explain them further in the thread I quoted from, actually. Explanation post here: ARC issues with grbl What I can do/have done before which doesn't quite fit with my understanding of them just yet is when you have a hex wrench on the motor shaft coupler/pulley/whatever, you can just pull the motor around with it, but then it'll return to its previous position. It's a neat party trick, and really exemplifies the servo nature of the system, but I'm not 100% sure how it doesn't error out the driver- that's a LOT of unanticipated encoder steps. I like them a lot. Like I say in the other thread, I don't think they're necessary for NEMA 17 projects, but I doubt I'd use anything else for NEMA 23/24/34 projects at this point.
Wire them in parallel. Sig on controller, to sig on first switch, to sig on second switch. Same for V+ and gnd
Mr. Van Der Walt - I have been perusing the forums looking for confirmation regarding a build concept using OpenBuild components & a BlackBox motion controller. We only need 3 axis ( X / Y / Z ) movement but, with a twist - apologies for the pun… The concept uses an C-beam XY table driven by 2 stepper motors connected to the BlackBox. The XY table rests under another device. That device is stationary relative to XY table motion & has a “dispensing” head that rotates ( Z ) by means of a third stepper motor connected to the BlackBox. Application concept — the XY table motion creates a path or relative to the fixed Z axis. Imagine that the Z axis controls “headlights” such that the headlights always point along the path that the motion of the XY table creates. So, when the path is straight, e.g. an Y axis only move, then the Z axis is fixed. When the path traces out a radius (XY move) then the Z axis rotates in order to keep the “headlights” pointed “down the road”. The XY path is pretty simple so I will write the g-code by hand. At appropriate points in the path I will code in the requisite rotation commands ( Fxx Axx ) to rotate the Z axis in order to achieve the orientation result described above. Looking through the forums I don’t think the BlackBox motion controller using gbrl is capable of being used for the application described above. It’s more likely that I would have to go down the LinuxCNC route. Mr. Van Der Walt - I’m reaching out to you specifically because I seem to see your responses to technical applications more often in the forums. I truly appreciate any time you take in response. Thank you!
Finally got my new closed loop steppers. And voila, it cuts like a champ! I can push it quite hard, and no problems with lost steps or anything. The weakpoint on that account is my 500w china spindle - but so far it's really not an issue. so, great thanks, Rob, for suggesting closed loop steppers. Next up is getting the rs232 cable to actually configure the drivers just a few snaps:
Well... Felicitaciones! Yeah some drivers allow tuning, some don't for some reason, so it's definitely a possibility depending on what you got. I think some allow you to tune the PID loop and tweak following error, all that stuff.
thanks. And the drivers does allow tuning. Especially I want to tune when they go in alarm state. Currently they only do in case of massive errors. Like when you try to run the spindle into the table (which of course never happens because one forgot to set the correct tool length. Erhm) then I need to wire the alarm state to the controller so it immediately stops the job. Next up is some aluminium cutting.
