Been having flowrate issues with my 2nd bot basically since day 1 of having it, but this is surprising as I’ve never seen it before. My prints on this Bukobot collapse in layer height occasional and sometimes consistently, but not due to compression of the nozzle (aka Z endstop being too low.)
The two robo hangers were printed one right after the other, with only a subtle change in filament diameter between them. What can cause this? I know my extrusion is thin in these (obviously shitty) prints just to get something out of the machine…
The Z motors make a beep sound when rising, instead of a clean spin of the motors. I was printing at .15 for the first time on this machine so it was harder to tell if rising on the Z was accurate, but made my issues more obvious (which is good.)
That one on the end obviously has issues with Z movement. You might want to put some zip ties around your Z couplers if you haven’t already, just to make sure they’re not slipping on the motor shaft when it turns.
I suggest making sure that your frame is nice and true all around and that you don’t have any slop that can contribute to binding, wihch then could cause missed steps (or slipping of the coupler) driving the Z-screw. I’ve seen this behavior – squashing – on a ThingOMatic where the Z was binding when I made heavy use of hop (the short stroke changes in Z was causing the binding as the bushings shifted around between the up and down strokes).
Making a “beeping” sound? It’s most likely not turning. Check you have no mechanical issues, then try turning up the Z current. Also, you should have heatsinks on the Stepper driver chips and a fan pointing at them (and the rest of your electronics).
@Joseph_Chiu My frame is pretty rigid as Bukobots are really solid from the get-go.
+Stuart Young I wasn’t too sure how to tell if its getting too little current. Too much current is a bit more obvious because the motor gets really hot…at least that’s my experience as the extruder 2 on this bit also jammed up so I throttled it down a bit. I don’t how to more accurately check current via the Panucatt stepper drivers you adjust with the screw. This particular machine isn’t behaving like my previous one with more noise (whirls, hums, 'n stuff) than I believe is normal. This is the V2 of the Bukobot when my BukoMini V1 is almost dead silent when not in motion.
To set the current correctly, send the axis, the z it sounds like, into long travels at a fast rate. I just send mine up and down in repeteir host or pronterface. If you hear the motor start clicking, you need to up the current. Try to use a non conductive screwdriver as apparently metal ones short the pot. I use metal, bit it does squeal a bit when I turn the pot which I’m assuming is not helping it’s lifetime. Once you dial just enough current, I just bump it up a tad higher for good measure.
In the configuration.h file, there’s a setting to keep the steppers on while not in use. I have my z set to off because my z motor will overheat, but I my current almost maxed out due to binding in my z… Due to cruddy design.
As for differing sound between bots, @Whosa_whatsis responded to some posts about different micro stepping multipliers and the sound difference. Also the motor step size will definitely make a difference (.9 or 1.8 deg) which he discussed as well. I don’t know how to link posts, so sorry I can’t be more specific.
The noise is normal. The new stepper drivers are smoother and more precise, but they do sometimes emit more noise in the audible range, especially if they idle on certain microsteps.
It doesn’t sound like Z binding to me just because that usually causes level issues on X bad enough for you to notice, since mechanical binding tends to favor one side over the other. Also, I don’t understand why your filament diameter would make a difference here. Maybe that’s a coincidence.
So it sounds more like skipped steps at the driver, or miscalculated steps.
Do you see any difference in the Z values in the gcode?
@Whosa_whatsis Yeah, but that wouldn’t cause the two prints to come out at significantly different heights, right? The short one looks about a cm low or so.
The one that is significantly smaller has way too much plastic on the edges (look at the second pic in full size on a large screen - that’s classic for missed Z steps), which is a sure sign that it’s redoing the layers without raising the Z height appropriately. Especially since @Ben_Van_Den_Broeck is using 0.15mm layers, the amount of plastic to be displaced by the previous layer isn’t huge. If the infill is also low (remember what infill you used Ben?), there should be ample room inside to avoid the rest of the layer causing too many problems.
Re: Missed steps. Temperature is everything. What temp difference was there in the room between the prints? Did you print one right after the other? Subtle temp changes can make all the difference, slightly changing values in the circuit enough so that issues that happen once in a blue moon start happening regularly. This is why the usual mantra with adjustments of the current is to get it working reliably and then give it an extra 1/8th of a turn (or whatever suits the drivers) - allowing a small amount of “buffer room” for variations.
@Phil_Hord I believe the Bukobot is a ganged z stepper configuration? In that case, it is possible for a overloaded motor to saddle power for both steppers that they both don’t step.
Good point. When I have a single z motor skip, the other one usually works more reliably. I chalked this up to physics, with my loss in one motor being passed on to its twin. When I used parallel wiring instead of the serial layout I have now, I would typically see my z loss on both sides. I completely forgot about that.
@Stuart_Young You are right, my infill is pretty low (12%), the prints were immediately after one another and room temp was probably around 68 degrees. So I’ll give upping the z motors current a try.
