Invert Inductive Sensor for different hotends

Anybody tried this before ?

Running a modified Prusa i3 and I sometimes swop from my e3dv6 hotend ( 0.4mm nozzle ) to my Volcano hotend ( 0.6 or 0.8mm nozzle )

Not wanting to keep adjusting the manual endstop on the Z axis each time I change, I thought about an inductive sensor.

However, the position of the nozzles, relative to the common mounting point for the hotends, is different, and could also differ when a nozzle is changed.

So this got me thinking. Why not position the sensor at the back of the bed, pointing upwards, and when I need to home the Z axis, move to the correct X and Y positions, and then home Z so that the sensor detects the nozzle itself, irrelevant of which hotend is on the printer at the time.


Please note that I do not want to use the sensor for auto bed levelling - I have a personal dislike for ABL for a number of reasons. My bed is already level so I only want to be able to get the nozzle to the correct height before printing starts.

Edited 1 time(s). Last edit at 12/22/2016 05:09PM by DaveOB.

Hmm, might work.
There might be some variation between the two, depending on the field of sensing. The heater block is different in size, that might influence the sensor.

But overall, yes that should work. The tips of the nozzles for the Volcano and V6 are shaped the same, so that would help keeping things consistent. I like the idea.

The next issue you will have would be leveling the sensor to the bed. I would suggest having 3 point levelling, but keeping the third point fixed. This is where the sensor would go as well. That way, your sensor will level the nozzle correctly to the bed and than you only have to level 2 points.

If inductive does not work, I'm sure something else would. Perhaps a mechanical endstop or IR sensor.

That's a neat idea. A simple mechanical switch should work fine in that config.

I considered a mechanical switch that the nozzle could push, but if there is any filament hanging below the nozzle from the previous print, then that would affect the function.

If you are not using the sensor for auto levelling and you are essentially using it as a z endstop, why not just use a regular z endstop? I gave up using ABL on my corexy as my bed was usually level and just fitted a good 'ol fashioned z endstop.

Edited 1 time(s). Last edit at 12/23/2016 01:32PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
DjDemonD
If you are not using the sensor for auto levelling and you are essentially using it as a z endstop, why not just use a regular z endstop?

Because depending on the type of part I am printing, I often swap between my e3dv6 ( 0.4 nozzle ) and my Volcano ( 0.6 or 0.8 nozzle ) hot ends. Sometimes up to 3 or 4 times a day.

Factors include quality required, time to print, etc.

The problem is that both hot ends fit in the same extruder, and the volcano is a longer / taller hotend than the e3dv6.

So each time I swap, I am having to adjust the Z end stop by around 10mm.

I am looking for the easiest solution where I do not need to keep changing the end stop.

Quote
DaveOB
I considered a mechanical switch that the nozzle could push, but if there is any filament hanging below the nozzle from the previous print, then that would affect the function.

Good point, but if you only need to re-establish Z when you switch hotends it might not be too bad to clean off any excess plastic at the same time.

Quote

The problem is that both hot ends fit in the same extruder, and the volcano is a longer / taller hotend than the e3dv6.
So each time I swap, I am having to adjust the Z end stop by around 10mm.
I am looking for the easiest solution where I do not need to keep changing the end stop.

I have a similar situation with quick change hotends, although the variation is only a couple of mm it still means I have to re-establish Z0 each time I swap a hotend. I've recently added a simple probe that clips onto the nozzle, so it's a manual setup needed, and it also requires the nozzle be clean to have a consistent Z offset, but it still works well enough to have made life much easier. I'd quite like to try your idea, but I'm also using the probe for ABL and distortion correction, and I don't think that would play well with an off-bed Z0 probe location.

Quote
DaveOB
I considered a mechanical switch that the nozzle could push, but if there is any filament hanging below the nozzle from the previous print, then that would affect the function.

Just make sure you only level with a hot nozzle. Than fit some tough bristles before the switch to clean the nozzle. This would actually than make for a great little pre-print script to level the nozzle and clean it before printing.