Setting Extruder to Bed Clearance on a Wilson II Printer


I had to replace the extruder nozzle on my WIlson II printer. The new nozzle
was a little longer than the original and there is 0 clearance between the nozzle
and the bed. I need to adjust this distance but don’t
know what the best process is to do this. Essentially I need to know how to
set the Z-axis home position on this printer. Running the “Auto Home” function
on the printer doesn’t seem to work…?? Any comments/suggestions would be
appreciated. My “slicer” is Simplify3D and setting the Z-axis offset doesn’t seem
to change or help??



so you gotta move your Z axis to the new “zero” (actually a little above the bed, how much of a little depends on your printer), then set zero using

G92 Z0

Then save that to firmware using … M500? Can’t remember that part dang it.

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I have a workaround to make the printer usable (physically lowered the bed).
G92 didn’t seem to work and in my troubleshooting, my bed stopped
heating! The gremlins are out…! Any way, now with the bed, I checked
the power to the bed (assume it should be 12V) and it reads 0. Checked
the printer power supply and there is 12V to the PICA board. It looks like
the BED HEATER is driven by a rather LARGE (physically) MOSFET.
Don’t know much about MOSFETs however measuring voltage at each
of the three legs find two at 0 and the third with a constantly changing
voltage between 4V and 6V. Seems odd, but perhaps this is normal.
In any case I would expect one of the three legs to be at a constant 12V
and none were.

I either have a bad BED or BAD PICA card. I would think if it were
a bad BED I would see 12V at the BED terminals - but I don’t. This leaves
the PICA as the culprit…

Your thoughts??



It’s Marty Rice’s PICA Shield board? That’s what I have on my Mendel90 (I have the 24v version).

Are you measuring the bed terminal voltage while it thinks it’s heating? Yeah should be 12v.

Try measuring the same on the hotend output terminals on the board while it’s heating and see what you get.

If it’s a bad board you may be out of luck, there was a recent thread … somewhere? maybe? where a user was saying Marty’s stuff was disappearing off the net. ETA: you could probably get some help from the Electronics folks here putting a new MOSFET on the board if you want to try to fix it.



The board is Marty’s RAMP. Its looking like the RAMP is bad since there is no power to the board when attempting to “PREHEAT FOR PLA”… Marty has taken down his forums which would have been a good source for parts and/or ideas. I have an OLD RAMP board… there was an issue with it but the issue
was NOT with the bed. I’m going to install it and if the BED heats, I’ll know its the board… then the
next hurdle, as you said, will be finding a replacement!! (BTW, the MOSFET appears to be surface
mounted and the back of the module is bare and I think soldered to the board - would be a bear to

There are several stand-alone MOSFET drivers on AMAZON that would probably work. Unfortunately I would prefer to have a schematic of the RAMPS card before introducing a module that may draw more current than the board is designed for.



Ah that’s too bad, the documentation was on the site where is forums are.



Post a pic of the board please.





I’ll be at the space tomorrow night if you want to bring that board up for me to look at.

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Sure… time and place??? On the MOSFET device shouldn’t I find 12v on one of the three leads?



I’ll be in the Vector area tonight around 6:30 and I’ll try to remember to wear my DMS instructor name tag.




Dumb question - is the fuse intact?



yep… good thought though…the hot end gets hot. Don’t think it draws the current the hot bed does… Steppers all work… Have found a source for the RAMPs card and have ordered one … but would sure like to know has gone bad…