3 is very capable.
I use a 3B+ on the v4 and on the MPCNC. v4 runs Klipper, CNC runs octoprint and that might change soon. Microcenter just after Christmas was sold out of all the good ones I wanted
(zero2’s and 5’s), so I bought a 3A+ (only 1 usb). It will run Klipper for a different system. Gave away all but one of the zeroe Ws. I was getting them for $5 each and using them for all sorts of things, but they are like the starter drug and so I distributed them.
Do the brakes work on the LR? I wonder how different rpms and torques would affect the stopping power.
So, we thought for a long time that we would just suggest no endstops to everyone and even after we got dual endstops working, we tried to convince people it wasn’t necessary. But at some point perception is worth more than being right. In this case, I bet you every user will have the bed fall at least once on them. At that point, they will really not like it. Especially if it knocks out an skr. It doesn’t really matter if there is a work around, people just want to have a good option to avoid the perceived failure. We had a similar thing with zip ties. If you did them right, they were fine. But people did them wrong or just thought they were janky. After a while it just didn’t make sense to try to convince the world.
That’s a really interesting question. What would the application be on a lowrider? Preventing Z drop at the end of a job just like on the repeat? I thought that happens on a LR because of the lack of mechanical advantage of the lead screw pitch and starts- would a brake stop it or just slow down the drop?
Tool changes leave X, Y, and Z powered on a LR, right? So there’s not a lot of benefit for tool changes?
Is there another use for the brake on an LR?
I missed this transition as I was still just lurking while all of you were going through that. But, it seems that ultimately the LR3 with dual endstops is a much better machine for the self-squaring capabilities that come with dual endstops. Maybe overkill for the vast majority of budget/hobby use.
When I first saw the zip tie being used that way, I had two thoughts more or leas a the same time-
“Damn, that’s really clever”
and
“Damn, that’s janky.”
But what I recall as an outsider looking in was lots of folks got them wrong, and the frustration is a huge turn-off.
I’m not sure the bed drop/blown driver is as much human error as it is an unexpected failure mode.
E.g. the way that newer boards like SKRs have a vulnerability that was perhaps not present in families like Rambo.
On this front, discovering that there’s an unexpected mode like resetting klipper after an update or accidentally using a slicer profile that doesn’t include the required end gcode is just such a bummer when it blows up your controller. That’ll put a lot of folks permanently off of the design. Rage quit type putting off.
The brake should have zero force at zero RPM, so in theory I don’t think it could completely stop something that couldn’t already be held stopped by the cogging/stiction torque of the stepper.
I’ve been looking for a stepper motor to play with to verify this stuff and, weirdly, I don’t have one that isn’t already attached to a machine of some kind.
Mostly, I am curious about the LR and the brake. It should still fall, but I bet it would be at a comically slow speed. The leadscrew has to turn fast for it to drop, so the brake should let it turn slowly and drop even slower.
But, people do want a way to keep it from dropping. It can be really bad when some gcode sender tries to save you a few cents and sends an M84 to disable the motors, and your router is still on. Dropping slower probably wouldn’t be a solution.
You, are an outside the box thinker. Just shows how I put blinders on to things I don’t feel are big issues but others do.
It is a very easy option. I would need to test it on the Jackpot to be sure the booting is not significantly faster or what happens if it does boot while still shorted.
I do hate to think about people just leaving their machine wherever it ended and coming back a few days later to a machine horribly tilted balancing on an end mill though.
Again, I guess this is just a case of ending your files properly or not. If you are worried, you can add it. This could help in the case of a power outage if your gantry drops fast.
Come to think of it, it must be fairly slow, as we have not lost a board to the LR dropping that I know of.
I know my gantry is real heavy with all the aluminum and an extra LED power supply plus the spindle and its a real graceful drop. Nothing crazy at all. I’ve seen lights flash on the board but never any smoke like with the V4 bed drop
The LR drop is what I use to see when its time to lube the screws/bearings LOL
Mounts parts are here - MP3DP v4 Tension springs mod by pavel569 - Thingiverse
Awesome!! Thank you!
Super easy to test. Raise the gantry, put some blocks under it, disconnect the steppers, short all the stepper wires together (could be just plug a pin header into them and wrap bare wire around the exposed pins), remove the block, see what happens!
Sadly, this won’t help when the TMC 2209s aren’t powered. But, firmware should make use of the passive braking feature of the driver, and if not that should be requested as an enhancement.
From the TMC2209 data sheet:
6.7 Freewheeling and Passive Braking
StealthChop provides different options for motor standstill. These options can be enabled by setting
the standstill current IHOLD to zero and choosing the desired option using the FREEWHEEL setting.
The desired option becomes enabled after a time period specified by TPOWERDOWN and
IHOLD_DELAY. Current regulation becomes frozen once the motor target current is at zero current in
order to ensure a quick startup. With the freewheeling options, both freewheeling and passive
braking can be realized. Passive braking is an effective eddy current motor braking, which consumes a
minimum of energy, because no active current is driven into the coils. However, passive braking will
allow slow turning of the motor when a continuous torque is applied.
That is a cool little hidden gem.
What about getting one of those power recovery boards (a few large caps), detect power outage, kill both heaters and only feed the power into the drivers and board. Tune it so it has enough juice to set the bed down slowly with the built-in freewheel settings.
Thinking about the bed drop on repeat and gantry drop on LR3 led me to go re-read the data sheet and find that pasive braking. I think passive braking will really help for the scenario where gcode disables the stepper enables. (“Use passive braking to avoid passive breaking.”)
For the power loss or board reset scenario, though- maybe this is where the addition of either a stacked protection module as discussed above, or perhaps your relay shorting devices come into play.
Power loss—> Firmware removes enable from the driver, then removes the DISABLE_BRAKE signal to the relay board.
Pre firmware reset —>. firmware removes enable from the driver, then removes DISABLE_BRAKE signal to the relay board, then performs a reset.
Power loss is now going to remove power from the system, but we won’t blow up the controller, and maybe even get either a nice slow set down of the flying parts of the machine, or perhaps on an LR3 the Z axis stays put or really really slowly lowers. If power is out, then the spindle/router is going to spin down as well, so the benefit would be you don’t drop a spinning router into the table before it spins down.
Any Klipper users already have something like a SHUTDOWN or BEFORE_SHUTDOWN macro that automatically executes to ensure Bed is moved to a safe location, before Klipper’s restart sequence deenergizes the steppers?
Curious if there’s some Klipper config startup/shutdown macros/setting option that can gracefully handle restarts caused by config changes?
Am already moving bed to safe location at end of print, or if idle_timeout triggers.
Just asked Klipper forum folks in this topic.
“You can write macros for save_config and restart using the rename_existing feature. That would allow you to move the bed before the restart is executed.”
Here we go!!
Have it home Z, then drive to Z max, then save config and reboot.
How is it you don’t even have Klipper yet and your already figuring shit out faster than any of us with it???
See this is why you will always be THE MAN!!!
That was from AZA’s question to the klipper group.
Well dang I thought I turned email notifications on for that post. Ill have to go check it out. I tried it real quick and apparently I still don’t know how to write a proper macro cause it threw up an error. I wanted to get back printing so Ill mess with it later.
I posted what I tried in there. Hopefully someone will let me know what it should say LOL. People always love to correct other so I’m hopeful ill get a good response soon
I don’t mess with my config much anymore. But I do restart the firmware. Most of the time. It has crashed or is unresponsive or it is an emergency stop situation. So a proper shutdown wouldn’t work there.