I found the gantry was dropping sometimes on poweroff.
I know the current recommendation is to park the head but in emergency-stop situations this was not idea.
Since they where cheap I decided to test buying some 2 start (2mm pitch, 4mm lead) lead screws (not referal link, and they came a little bent so wouldn’t recomend the seller) and I’m really, really happy with the results. I have not seen a need to slow down the z movements and the gantry stays put after the motors are turned off.
Is there a reason for having 4 start lead screws or is it just default because it worked before and “If it ain’t broke don’t fix it”?
4 starts are much more common. That makes them less of a headache to source and they can be found for less money/higher quality.
4 starts are the most common. 1 start is the next most common (which does have problems with speed). This is maybe the 2nd time I’ve seen someone use 2 starts, which seem like a good balance. We would need a reliable source.
I actually have a couple hundred 2 start screws here. I have not put them in the shop to avoid confusion. Seems some people would trade speed for the gantry staying up.
Yeah that makes sense, and I guess that explains my bent one, but quality-wise is not too far from other chinese leadscrews I’ve bought for 3D printers in the past.
I’m in europe so i just had to source them myself but maybe having them especifically labeled in the store or maybe just mention this as an alternative in the documentation could help some people as I’ve seen the gantry dropping mentioned more times with the lr3.
What speeds are you guys running in your Z axis anyway? As i said i tested it with the same config I was running before and it just worked flawlessly (can’t remember off the top of my head but it was a fairly normal speed for me, not particularly slow)
I could run tests with the drag race gcode and benchmark the z performance
There’s not that much distance to travel to begin with so maybe for some people it makes sense to lose a bit of potentiall speed.
You could also try running steppers with a higher detent torque, although that will slow down the z-hop as well. It’s a pretty heavy gantry compared to a 3d printer so it might be difficult to find a good balance between the speed and resistance.
The default firmware has 15mm/s max on the Z. That has been pretty reliable for 4 start and 12V.
It would be cool if they were a different color or something. We are all well trained to spot steel reinforced belts in build pics. (They are white and shouldn’t be used in these machines).
If you wanted more speed with a 2 or 1 start screw, the first change would be a 24V psu. What voltage do you have, @pastitas?
Oh yeah, i’m running 20v (quite non-standard, will probably go to 12 or 24 later) so that might be changing the result for me.
Also i’m using fluidnc so i did my own speed tests, can’t remember right now the accel and speed limit but that sounds close to what i have
Oh and i really don’t think one start is good, i already feel like i’m gonna have to be really on top of keeping the leadscrews lubricated so that friction is not too high