Yikes! Z-axis gone wild

I just got my printer and finished the 9 calibration steps. Thought I was ready to go but holy smokes when I try to print the little cube, the z-axis went down to the plate and tried to go well below the plate. The the z-axis screws continued to turn in the down direction and the little nuts started spinning. They wound the connecting wires tight and then the motors started chattering. Fortunately nothing broke.

Now I CAREFULLY restarted the calibration procedure and CAREFULLY followed the steps. What I see now is in the home position X and Y look okay, but z is touching the plate. Not only that, but if I manually turn the left and right x-axis screws, they go a little more than one full turn before the head lifts off the plate.

Any help would be appreciated.

 

you need to adjust your z end stop screw so it doesn't throw your nuts.

 

I don't see an end stop adjustment screw. Different model?

 

Do you have the new version with the auto bed leveling? (two switches below the z axis?)

 

You probably need to calibrate your z offset

 

This same thing happened to mine. Had to power down to get it to stop. The whole carriage rests on 2 switches which move with the carriage. The extruder got down to the plate and rested there while the switches and nuts on both sides continued down. They should have stopped as the switches would have no load from the carriage at that point, but didn't. This only happened to me once while using the version of MatterControl that shipped with the unit.

 

Seshan, yes, I believe I have the auto leveling system because the z-axis screws have nuts below the bed and there is a black box around the nuts with two wires connected to it.

Mike, the calibration process (9-step) adjusts the z-axis in 3 different locations, yet after I do that, the Home Z function puts the head down on the plate and the screws continue down a full turn after the head bottoms out. Are you suggesting there is a different way to adjust the Z-axis without using the calibration tool? If so, what is the procedure?

 

Home the printer so the head rests on the build plate. Using your control software raise the z height by .1mm until the nozzle barely comes off the build plate. Enter this value into the z offset. I believe a slip of paper was included in your printer that describes what to do with this value.

 

Mike, it might also be beneficial to have him get the version of Repetier you sent to me. Sounds like he is having the same problems w/ MC that I was having, which are eliminated by Repetier & Cura.

Ultimately, it would be nice to have it solved for MC, but in order to get started up at least. . .

 

I don't understand why the calibrator adjusts the z-axis to a paper thickness above the plate, yet right after that, homing the z-axis drives the head too low. Isn't the calibrator's entire purpose to level the plate ie: adjust the z-axis?

 

One would think, but mine didn't work right either. Its like it's not accepting the z offset properly.

Or, as Mike has suggested previously, there is a problem with their logic behind the switches that creates some sort of fault when combined with Matter Control.

 

Here's how it works. The Paper calibration is meant to adjust the levelness of your x axis. It does not affect Z height. You are simply verifying that the x moves parallel to the bed surface so one side is not higher than the other.

The Z height is being auto-calibrated by the probing. When the nozzle rests on the plate the couplings begin to unseat from their housings. This movement off the housing is detected by the switch. However there's a certain amount of travel that occurs from the moment the bed touches the surface to when the switch disengages. This is the Z-height offset.

What happens now is the nozzle stops at actually 0 but the switch activates on say -.7mm. You then need to tell the printer that 0 is actually .7 off from what the system thinks zero is. When you try and home after homing once it will try to go to 0 but actually will stop at .7mm and then continues to try and go down till the couplings unseat completely from the housing

 

I just upgraded the MC from 1.04 to the website's 1.05. No help.
Here's what I think is wrong... In MC, I set the Z home offset to 1.2 and click make settings activate and save to default. When I reload MC, the z offset is back a 0.00. The z offset value isn't "sticking" across MC loads.

 

OHhhhhh... I don't think I did the make active thing in MC. I missed that when I was doing it and Jerry didn't show me that in the shop.

When you say "save to default" there is likely a profile called "Default". Do you have any other profiles saved? PLA heated bed, PLA no heated bed?

If you have a choice you want to choose the option you actually use as Default likely applies to a specific profile not all profiles.

I'll look in to this more when I get home.

 

Thanks Mike, that is what I thought the z-offset was for. In my testing, 1.2 appears to be the correct offset number. Unfortunately, when I set that, it has ZERO effect. I can set the z offset to 50 - (Five Zero) and it still does not home above the plate.

 

When you tell it to home it should stay on he build plate. The z height compensation should only come into play when you print.

If you home twice there's still a good chance it'll throw the z nuts. It's a bug between marlin and MatterControl it seems.

 

Picky: When you start a print and it gets to the portion of the print where it attempts to test the 9 points for bed leveling, does that part work for you or does your carriage just continue to travel up from point to point without going down to the bed?

 

It might also be the case this value needs to be added into the firmware once you calculate it. That should override matter control's values.

Unfortunately I don't use matter control so I'm not very familiar with it's nuances

 

Okay Mike, got that. BTW: throwing the Z nuts is pretty tough on the wires connecting the switch. I'm afraid that if they get thrown again, one or more of them wil break and I'll be in wire repair mode.

How about this for a plan. I will set the z offset to 50 and then try to print the calibration square. If what you say here is correct that should result in the printing the item way above the plate. That will give me time to shut the thing down if it still tries to get to low. (I am pretty gun shy about this after the first time it threw the nuts and wrapped the wires).

Is that a good plan or is there something else I could try?

 

If you mean that I should set the offset in the eeprom, that is what I am doing, but as I said, the offset does not "stick" across MC loads.