Print nozzle hitting bed with PINDA all the way down.
 
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Print nozzle hitting bed with PINDA all the way down.  

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david.m17
(@david-m17)
Active Member
Print nozzle hitting bed with PINDA all the way down.

When I do the XYZ calibration (Selftest OK, Firmware current) the print nozzle keeps hitting the bed. The bed is heated and the PINDA is down at the bed level and cannot be lowered any more or it will be lower than the nozzle. Ideas??

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Posted : 26/01/2017 5:14 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

I forgot to mention - yes the bed is heated.

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Posted : 26/01/2017 5:23 pm
JeffJordan
(@jeffjordan)
Moderator
Re: Print nozzle hitting bed with PINDA all the way down.

first: ❗
are you sure, that your y-axis assembly sits completely down inside the notches at the z-frame ?

then: ❓
did you check the connector of the pinda probe at the rambo board ?
the probe should be approx. 0.7 - 1mm higher than the tip of the nozzle.
this should allow a correct detection of the printbed inlays at the reference points, no need to align it down to the nozzles level.

furthermore: ➡
the pinda is an inductive sensor, so it might detect other magnetic fields.
so if there are sources of strong magnetic fields at your environment (strong radio transmitter, old tube based tv near the printer, mrt 😆 ), they may interfere with the probe and block it's function.

dem inscheniör is' nix zu schwör......
Posted : 26/01/2017 7:58 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

Thank you.

I have verified that the Y axis is completely down in frame.

PINDA was above the nozzle and still is by a very small amount, When the nozzle catches the paper, the PINDA is just barely above the paper providing trivial resistance.

The PINDA wires are in the correct location on the RAMBO board and there is a light on the PINDA.

No equipment in the area.

Could the PINDA be bad?? What is it sensing?

David

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Posted : 26/01/2017 9:12 pm
jason.s6
(@jason-s6)
Trusted Member
Re: Print nozzle hitting bed with PINDA all the way down.

If the nozzle is catching the paper when it starts the first steps of calibration ( 1 of 4 etc ) then you need to lower the Pinda. The nozzle shouldn't have any friction on the paper

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Posted : 26/01/2017 9:54 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

I understand that, however, the PINDA cannot go any lower without being the thing that hits the bed first.

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Posted : 26/01/2017 10:12 pm
JeffJordan
(@jeffjordan)
Moderator
Re: Print nozzle hitting bed with PINDA all the way down.

....and there is a light on the PINDA.
did i miss something ? never saw light on the pinda.

dem inscheniör is' nix zu schwör......
Posted : 26/01/2017 10:18 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

The base of mine is illuminated where it connects to the cable. I took it as an indicator that it had juice.

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Posted : 26/01/2017 10:22 pm
JeffJordan
(@jeffjordan)
Moderator
Re: Print nozzle hitting bed with PINDA all the way down.

cool, never noticed that... can see it here only if i switch off every surrounding light source :mrgreen: .

dem inscheniör is' nix zu schwör......
Posted : 26/01/2017 11:37 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

Anyone with additional ideas?

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Posted : 27/01/2017 4:01 am
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

"this should allow a correct detection of the printbed inlays at the reference points, no need to align it down to the nozzles level."

If this is what is being detected, and all else is in order, is it possible that there is a problem with the printed inlay that is supposed to be detected? Is there any way for me to diagnose this problem? All of the items that have been referenced have been checked multiple times.

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Posted : 27/01/2017 2:48 pm
david.b14
(@david-b14)
Honorable Member
Re: Print nozzle hitting bed with PINDA all the way down.

As a test, get a coin or small piece of metal that a magnet will stick to. Tape the coin to one of the points to see if it triggers the pinda.

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Posted : 27/01/2017 2:53 pm
william.w3
(@william-w3)
Active Member
Re: Print nozzle hitting bed with PINDA all the way down.

Hi, Y'all,
Just thought I would add my two cents worth.

When you do the calibration, you first take the Z all the way to the top. The routine depends on this having been done so that it will know how far to travel down before it starts looking for activation on the PINDA. If you start lower, it will hit the bed. I am assuming you did this correctly.

Remember, The procedure is calibrating the PINDA, not the nozzle. It knows nothing about the nozzle. If you are trying to protect the PINDA by not lowering it you are actually endangering the nozzle. If the PINDA is working the only way it can hit the bed during calibration is if it starts too low (as mentioned above). You should be able to extend the PINDA beyond the nozzle for the purpose of testing. Once you determine that it does detect the bed, then move it back up to about a mm above the nozzle.

How did the test with the metal taped to bed work. I guess you know that US coins are not magnetic. They do have an inductive reluctance, however, so they may work.

Thanks
William

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Posted : 27/01/2017 8:30 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

Ferrous metal attached to the bed did nothing to change the outcome.

Since the problem was occurring with the first calibration point on XYZ, I switched over to Z Calibration and the nozzle hits the bed at every calibration point. In all cases, the Z-travel is topped out on the frame prior to calibration.

The PINDA probe is wired correctly at the RAMBO box and has a glowing base, which I presume means it is getting power.

Any reason to not conclude that the PINDA probe is bad? Is there some other way to check it?

David

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Posted : 28/01/2017 4:09 pm
william.w3
(@william-w3)
Active Member
Re: Print nozzle hitting bed with PINDA all the way down.

I am afraid you re correct, David. I had sent a lengthy reply but then I found that my WiFi was down. Lucky you.

I am no expert on Prusa. I have only had my MK2 since November. I would assume that the PINDA is an inductive proximity that is fed a high frequency oscillation which is then measured for frequency shift, similar to the way the vehicle detectors at red lights work. I believe the probe only has two conductors leading to it so if it s illuminated that should mean it is getting its signal.

I have not tried this but I would assume that if you have a pickup loop on an oscilloscope you should be able to see the signal. I suppose it is possible that the leads are connected to the LED but separated from the coil.

Let me know what you find out.

Thanks.
William

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Posted : 31/01/2017 7:30 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

Thanks for that idea, but that is not something I have laying around. My main activities are in the healing arts and application programming. Have never had need for an oscilloscope, but thanks for the response. My diagnosis is that the probe or the main board is bad. Still waiting to hear back from support on what their conclusion is. I appreciate the time you gave it!

David

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Posted : 01/02/2017 4:51 am
MrMik
(@mrmik)
Honorable Member
Re: Print nozzle hitting bed with PINDA all the way down.

The light on the PINDA probe should be blinking when it senses proximity to the calibration points.

Holding a steel screwdriver or similar object underneath it should trigger the LED light to show you that it is sensing the metal.

It sounds to me like you have a broken PINDA probe, but maybe you have broken PINDA cables.

Check if you can get the light to blink with a metal object. Don't stick it to the bed, just hold it under the PINDA wherever it is at the time, as long as it's powered up.

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Posted : 01/02/2017 2:12 pm
david.m17
(@david-m17)
Active Member
Topic starter answered:
Re: Print nozzle hitting bed with PINDA all the way down.

Interesting. I can get the PINDA probe to flash by putting a screwdriver under it (almost has to touch). However, it does not flash during calibration even when the nozzle contacts the bed. It hits on the first calibration point for XYZ (then I stop it) and all 9 on Z calibration. The PINDA cannot go any lower without hitting first.

I made this video of the calibration process. https://drive.google.com/open?id=0Bzk76NJWKrjGMmdWdnhJRlkzZkk

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Posted : 01/02/2017 11:36 pm
ryan.c4
(@ryan-c4)
Active Member
Re: Print nozzle hitting bed with PINDA all the way down.

It looks like your Y endstop has something activating it way before its supposed to be activated. That is a lot of space for it to be off.

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Posted : 02/02/2017 6:29 am
richard.l
(@richard-l)
Moderator
Re: Print nozzle hitting bed with PINDA all the way down.

You don't have probe problem, you have something else wrong in your build. During calibration it isn't even getting close to the first row of calibration dots.

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Posted : 02/02/2017 7:57 pm
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