Z axis Reversing

Greetings.

Built a Prussa I2 last year. Works great. Recently added heated bed which also works as expected. But, occasionally & now more frequently, the Z axis misbehaves. I'll start the machine up, demand & the Z axis will "home" UP. It will go up ~1mm & stop. Subsequent "home" demands will do the same thing. The end stop (mechanical) is working fine. Hardware includes Arduino Mega, RAMPS 1.4 & 14V, 20A regulated power supply. Software includes "Sprinter" on board the Arduino driven by "Pronterface". Sprinter has been reloaded twice now.

Any suggestions would be appreciated.

Thx, Dennis.

Is your home behavior configured to home quickly, back off the endstop, and home again more slowly? If, as is typical, you are using normally-closed endstops, I would expect one of the connections between your board and your Z endstop is becoming intermittent and, when you have no continuity, the board sees that endstop as always being triggered, so it stops immediately, backs off, and stops immediately again.

Just happened to me last night, looked more closely and somehow one of the wires from my end stop came off, the printer thought it was being activated and tried to back off the end stop, when there was no change, it stopped the axis

If you look in a command interface with the printer, when you send a raise z axis or lower z axis command it will be responding with z axis ends top active and do a whole lot of nothing

Or you may have a different problem

Edited 1 time(s). Last edit at 02/24/2016 08:55AM by DaGameFace.

Sounds reasonable. Nodrmally it approaches the end stop then backs up & closes slowly. but when wonky,It just backs "up" & stops. I'll check connections. Thx.D.

Likely the problem. Thx. D.

Thx guys. I'll check connections.
D.