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Z axis Reversing

Posted by Dennis Mc 
Z axis Reversing
February 23, 2016 11:52AM

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.
Re: Z axis Reversing
February 23, 2016 07:05PM
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.
Re: Z axis Reversing
February 24, 2016 08:52AM
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
Re: Z axis Reversing
February 24, 2016 08:54AM
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.
Re: Z axis Reversing
February 25, 2016 12:39AM
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.
Re: Z axis Reversing
February 25, 2016 12:40AM
Likely the problem. Thx. D.
Re: Z axis Reversing
February 25, 2016 12:41AM
Thx guys. I'll check connections.
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