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Z-axis sensor not triggering when homing print bed

I pitched in with a number friends on a dual-extruder printer about 1.5-2 years ago.  The first unit we got had a shattered plate.  The replacement unit had a warped Z-axis screw (made things look like mummies).  I managed to cobble together a single working machine out of the two sets of parts and I think we successfully printed a gear before it was pretty much abandoned.

Today, I rescued the unit from a work closet and I'm trying to rehabilitate it.  I've gotten most of the setup issues sorted out, but one think I've noticed is that the Z-axis end stop sensor is active (sensor light is on), but when I send an M119 code via the Repetier Host software, it doesn't show that it's activated.  X and Y seem to be working fine.  First time I homed it, I thought it was going to shatter the base plate - fortunately I E-Stopped it before it did any damage.

23:54:13.998 : x_min:H x_max:H y_min:H y_max:H z_min:L z_max:L

Any ideas?  I can't really use it until I get this issue sorted out.



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I have a Creatr XL. 

Sending to home the Z axis it goes beyond the 0 position and collides with the print head.

Using the Repetier Host software the X and Y axis work well while the Z axis works well excluding the homing function. If I try to send the Z axis beyond the 0 position using the arrows it correctly stops when it reaches the 0. But if I press the Z Home button it goes crashing!

Since the machine goes home with X, Y and Z axis at the beginning of any work, it is impossible to begin working.

Any idea to solve the problem? 

Thanks. Carlo

Having already reached the position (0,0,0) I've sent the M119 command and I've received the answer (L,L,L).

I sent the X and Y axis to home. Not so for the Z axis to avoid collisions...

I've resent the M119 command and I've received the answer (H,H,L).

So, I'm sure that the printer now thinks to be at the home position for the X and Y axis while it is not at home with the Z axis - even if it is at the zero position...

How can I convince my printer that zero is home and it has not to go beyond zero?

Ok.. found that Slick3r has a Start / End G-code that send a G28 command to home all the axis.

So I think that erasing that command the printjob will begin without homing.... and I should do it manually before launching the printjob.

Remains the problem that probabily my Z end stop doesn't work... 

Any idea?

Does the Z end stop light up when you try and home it. Is the Z end stop close to the metal plate to activate it.

Yes, on mine, the Z end stop sensor does light up (see attached picture on original post) when the stage is sufficiently elevated.

I don't have a datasheet on that sensor or anything - is the sensor digital or analog?  If it's analog and the Arduino input is using ADC, maybe it's not passing some threshold?  I'm totally spit-balling here - I haven't taken it apart to see how things are hooked up on the controller board and it's corresponding shield.  But, if there were a way for me to diagnose the problem, I could probably do it.



I believe that it is digital .

In mine the sensor does not light up... 

Maybe the sensor is not working correctly?    ... I remember to have seen a red light coming from it at the very beginning... I started one job without using plastic - just to verify that the machine was ok - but I stopped it before the end... then I started some other jobs at the same manner, without any problem.

After that I moved the print head using the arrows of Repetier host and when I homed the Z axis the collision happened.

Now I do not find how to make the Z end stop function...

Ok, I've tried to send the bed downward to have some space at the side of the Z end stop.

Approaching the Z end stop with a tongs I see that it lights up.     ... but when I bring the bed near it it doesn't.

It cannot be a problem with the distance of the bed plate from the sensor because the tongs where slightly far from the sensor then the bed plate.

Maybe the sensor is not able to recognize the metal of the bed plate? I don't think so because it is the one that Leapfrog used to build the printer...


The structure of the printer is not enought rigid.

I found that it is not perfectly vertical (the base of the machine is not perfectly aligned with the top).

This causes the malfunction: the metal bed plate goes up along a non-vertical line and at the top it finds itself a bit too far from the Z end stop sensor.

Now I have to find the way to bring the whole machine to remain perfectly vertical... this way I'm sure it will solve the problem.

Advise to Leapfrog: You should revise the structure of the machine providing for triangular shapes which will grant its rigidity.

Good!! I solved the problem by simply adjusting the distance of the Z end stop sensor from the metallic flange that sustains the printing bed.

Another advise to Leapfrog: write in the user manual to check the correct functionality of the Z end stop sensor before trying to do anything with the printer - just to avoid collisions.

P.S. The bolts of the sensor where loosen! The printer was brand new...     these important bolts where loosen, and so where also the screw of the side panels... hopefully a better check on the machines before sending them to the customers!

Now I have to recalibrate the printing bed to keep it at the right distance from the printing head... but I need the plastic to do this job: it'll be done in the next days, as soon as I will have the filament at home.

Nice work, Carlo.  I'll try adjusting how close the sensor is on mine as well.  

Before you made any adjustments, did the light on the Z sensor go on when the printing bed was all the way up?  How far away was the sensor before?  On mine, the light goes on, but the M119 code still shows "L"ow for the Z end stop.  Does yours show "H"igh now?

Hi Casey,

before the adjustments the Z sensor did not light up even if the bed was all the way up.

I sent the bed down and I tried to aproach the Z sensor with a metallic object and I saw the Z sensor led lighting up. So I understood that the bed plate was a bit too far from it.

I brought the bed plate to the 0 position (in Z axis) - where it had to stop - and I saw that the Z sensor did not light up.   I tried to push towards the right the top of the machine (just pushed it with my hands) and I saw that the sensor had lighted up while pushing and switched off while not pushing the top of the printer.

I do not know exactly what is the distance because I do not have a measuring instrument to take the measure... it may be 1 or 2 mm.  But it is not so important because you have to find the distance proceeding how I described before: the sensor has to be loosen and aproached to the bed plate up to when it lights up (with the bed in home position). Then you have to block it at that distance.

If the sensor doesn't light up at any distance nor aproaching it with any metallic object may be you have to change that piece... ask leapfrog for details...

Hope you'll solve the problem.



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