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Cold bootup, nozzle pushes into bed
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Description

I moved a powered off Quiver from one location to another. In the process of moving, the toolhead slid all the way down onto the bed. When powered on, the nozzles did their routine where each tool head cycles up and down. In this routine, it pushes the nozzle into the bed, raising the entire toolhead up. What is the purpose of this cycling? Seems it would be best if both nozzles retracted to a safe position on power-on.

To reproduce:

Power off printer
Move toolhead all the way down on Z
Power on

Event Timeline

jebba created this task.Jan 11 2019, 5:30 PM
jebba created this object with edit policy "LulzBot Hardware Products (Project)".
karrad added a subscriber: karrad.Jan 15 2019, 8:57 AM

Testing on marlin .72 I do not see any movement in the tool heads when powering on. E1 remains in the lowered position, while E2 is in the upper position. This was the position of the tool head on start up.

Testing with E2 down and E1 up on power up, E1 lowers on start up and E2 raises.

@marcio Is it possible to have both extruders in the upper position at the same time, and then lower the tool head when T0/T1 is fed to it?

marcio added a comment.EditedJan 15 2019, 9:02 AM

@karrad: Not really. Because Marlin has no knowledge of a state for "both nozzles up", so basically the nozzles need to be in one state or the other. At startup, I have to force the nozzles into a known state.

jebba added a comment.Jan 15 2019, 9:14 AM

Maybe home Z before moving the nozzles? Or up in Z?

Up in Z a tiny bit sounds like a good solution, as long as the tool head would stop at the top of the Z axis, in case it was resting at the top when it was turned off.

We could home Z, but at some earlier point where this discussion came up there was a concerns about unexpected moves injuring the user. It seems to me like less movement is better.

It sounds like the axis falling and putting pressure on the nozzles is the real problem here. That should be an issue that is resolved some other way. Perhaps we need an electrical break board in the TAZ just like the Mini?

Up in Z a tiny bit sounds like a good solution, as long as the tool head would stop at the top of the Z axis, in case it was resting at the top when it was turned off.

@lansky: It would only stop if it was a homing move, which would mean moving all the way to the top.

I guess if there is a brake board on Mini2, why wouldn't one also be needed on Quiver? TBH, I'm not sure how it operates.

@jebba Quiver uses geared Z motors which hold the axis in place in most conditions. The Mini 2 is using standard motors which would drop axis more quickly without the break board. The shipping packaging would hold up the axis in shipping so the issue would largely be if the printer is transported after already assembled.

@marcio I think we are too far along with electrical testing to throw in an additional board and I don't think is the only answer to this issue. I think we should do some testing of the pinch point in consideration of homing Z at start up. This would also work in conjunction with T5206 which would level the X axis in the Z home at every start up.

It's not hard to put a "G28 Z" at startup, if that's what we want.

tutley added a subscriber: tutley.Thu, Jan 17, 10:39 AM

i dont think that we should fully home the z at start up, i think maybe raise the z axis 10-20mm or so on start up would be a better option

@tutley: This would be tricky to do, plus homing at startup helps level the X-axis, so there is a reason to do it.
@jebba: If you are satisfied with the behavior in .78 or .79, please close this ticket.

Running .79

Seems fine to me. I powered off, moved the toolhead to different positions, then powered on. Each time the toolhead just moved up to the top most position.

jebba closed this task as Resolved.Tue, Jan 29, 1:21 PM