Z-Probe Offset Question

Can someone explain the best or appropriate way to raise my nozzle a little further away from the bed during printing? The Marlin setup that I have is:
#define Z_PROBE_OFFSET_FROM_EXTRUDER 0.35 // Z offset: -below +above [the nozzle]

Should I change it here or with an offset command and save to Eeprom?

I am running an inductance probe and it it positioned slightly closer to the bed than the nozzle. The terminology in some of the Marlin FW is a little confusing and ambiguous.
Thanks for any explanation.

For an inductive probe, the Z_PROBE_OFFSET_FROM_EXTRUDER number will be positive. It says when the nozzle is at .35mm, the probe will trigger. The nozzle will need to be lowered by .35mm to just touch the bed.

If you want a little more clearance... lower the Z_PROBE_OFFSET_FROM_EXTRUDER number. For example... You could set it to .25mm to get .1mm more clearance.

Makes no sense to me but I will try it.
Thanks.

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Roxy
For an inductive probe, the Z_PROBE_OFFSET_FROM_EXTRUDER number will be positive. It says when the nozzle is at .35mm, the probe will trigger. The nozzle will need to be lowered by .35mm to just touch the bed.

If the nozzle is at .35mm above the bed when the probe triggers, that means that Z_PROBE_OFFSET_FROM_EXTRUDER needs to be -0.35. In general, only probes that use the actual nozzle (like piezo sensors) will need a positive Z_PROBE_OFFSET_FROM_EXTRUDER.

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nkuck
I am running an inductance probe and it it positioned slightly closer to the bed than the nozzle.

Do you mean that the actual physical bottom of the probe is closer to the bed than the tip of the nozzle? Or do you mean that it triggers lower than the nozzle? If it's the former, unless you have a mechanism to extend/retract it I don't see how you could print without the sensor dragging across the bed.

I believe that I need to get a more sensitive inductive probe in order for the nozzle the be physically below the sensor probe. Currently, I have the orange tipped probe that I have seen commonly on printers. It’s sensitivity has forced me to put it too close to the bed, I think. But I will look at it again. Then your comments would make sense. Thanks.

Can you recommend an appropriate probe? It is a Chinese reprap clone. Thanks.

The one I use is M18 8mm DC 5V NPN NO LJ18A3-8-Z/BX-5V Inductive Proximity Sensor Switch. It's designed to run off 5V so you don't have to worry about level conversion and has a quite long sensing distance (4-5mm against a 3mm aluminum bed). The disadvantage is that it's relatively large and heavy compared to sensors with closer sensing distances.

Free advice is worth what you pay for it. But I'm not a big fan of inductive (or capacitive) probes. They are too hard to get working right. A servo that kicks down a probe leg with a micro switch on it works very well and has a high degree of repeatability.

I don't expect anybody to actually take this advice, but my experience says inductive probes are more trouble than they are worth.

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Roxy
I'm not a big fan of inductive (or capacitive) probes. They are too hard to get working right.

Not a big fan of core math although I can achieve a passing grade.

Remade the original Z-Axis solidly mounted proximity sensor. The design left absolutely no way to accurately calibrate the distance between the nozzle and the Sensor.



In the 3D Printing innovation we have many different printing surfaces, we should have a quick way to be able the swap and calibrate for these surfaces.
I have had inductive probes for two years, they are mounted on an adjustable 3D Printed thumb screw calibrated mount.
I have never had any problems getting the bed level or the nozzle in the correct printable position in a short period of time.

Red Mount from thingiverse, White remodeled to work with the smaller Flat Omeron TL-W Proximity sensors.
Nothing wrong with the proximity sensors just needed an adjustable mount to achieve the desired calibration.

^{Old and New thumb screw adjustable mount}


Their are so many different styles of 3D Printers and even more ways of calibrating them, our minds do not work the same nor do our solutions.
Unlike School where the teacher or professor says solve it this way or fail (show your work or fail, the correct answer is solving the equation).
We have many ways of accomplishing tasks today, we are creative individuals that all have a different perspective.

I replaced the SN04 because of its size and distance from the nozzle, it would hit the frame and making it out of alignment.
Then the TL-W3M became my proximity sensor, it was smaller and could be placed within 20mm of the nozzle and does not hit the frame.

Edited 5 time(s). Last edit at 05/10/2018 10:43AM by Roberts_Clif.

I find my inductive probe reliable and accurate, and since I got the 5V NPN version of the probe it was plug-and-play into the Z-min connector. If you're using the 6V-36V or PNP probes you need to worry more about setup and play around with voltage dividers, diodes or optoisolators, but there are easy to use inductive sensors. My only complaints are that you have to make sure that it doesn't probe too near the edge of the bed, and the fact that it's pretty heavy.

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MMcLure
If you're using the 6V-36V or PNP probes you need to worry more about setup and play around with voltage dividers, diodes or optoisolators.

After testing in circuit and determining the sensor functions purchased a box of 5. Installing the TL-M3W Flat Omeron proximity sensor on all 3D Printers.
Using the TL-M3W Flat Omeron proximity sensor on 5vdc on multiple controllers for over 2 years with no noticeable sensor degradation.

Recently noticed the voltage requirements of 12-24vdc with a working voltage at 10vdc for the TL-M3W Flat Omeron sensor.
Have Purchased optical coupler isolator's to correct for the voltage discrepancy, have not seen the urgency to change what works though wanted parts just in case

Motto!
(IF IT AIN'T BROKE, DON"T FIX IT)

Thanks for all of the experience lessons. I appreciare everyone’s responses.