z axis problem

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z axis problem

Postby hopeluper » 2016-Jan-Tue-19-Jan

When we start a print, the threaded rods on the z axis turn nonstop lowering the print head all the way down to the bed and keeps turning to where the nuts go below where they are supposed to be. And it tries to print dragging the nozzle on the bed.

We are using a printrbot plus 2.1. We are also using the printrbot plus 1404 configuration if that's anything, we have also used two different programs (mattercontrol and repetier) and still having this problem in both.
Whenever we got the 3d printer it was working, so I changed the speed because the prints where horrible and it started doing this.
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z axis problem



Re: z axis problem

Postby RetireeJay » 2016-Jan-Tue-20-Jan

This is happening because your Z-axis "endstop" switch (or sensor) is not being triggered at the right place. Does your printer have a bed-sensing probe beside the printhead, as seen in this photo of the metal Plus http://printrbot.com/shop/assembled-metal-printrbot-plus/? It's the silvery, threaded cylinder to the right of the hot end.

I imagine not, if you have an older Plus. In that case, your Z zero position is sensed by a "microswitch" that's probably located in the back left corner of the printer. There's a long screw which is supposed to push on the lever of the microswitch when the carriage gets down to the correct height. It's critical to get this adjustment exactly right. If the screw doesn't touch the microswitch soon enough, then the head ends up resting on the bed (and your "down" movement may go on for a long, long time). If the screw touches it too soon, then the nozzle won't be close enough to the bed to get good adhesion. If the microswitch is not positioned correctly, then it doesn't get actuated when it should.

By the way, any time the Z nuts come out of their "sockets" you need to re-check the "level" of the carriage. I do NOT mean level with a spirit level, I actually mean that the nozzle needs to maintain a constant distance away from the bed whether it's at the left or the right end of its travel. So check this and if the carriage is not parallel to the bed then turn one of the threaded Z rods by hand and check again until you have it parallel. Only after ensuring that the carriage is parallel should you proceed with adjusting the Z zero point. There are actually lots of threads mentioning the bed clearance, as well as instructions on Printrbot.com and in other forums. Good luck

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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3, upgraded to MK3S
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