Printer and printhead settings to be modified for third party printhead on UM2

[3DSkip 2]

Hello,
I am trying to get an alternative printhead which allows high temperature printing to work in my UM2.
Since my new printhead has other dimensions and is a bit larger compared with the original UM2 head, I have set the printhead settings in Cura according to the new printhead dimensions. So far everything ist fine.
But I have two issues:
1.) What is not clear to me is the question if I have to tick the box "origin at center" in the printer settings and what this really does when ticking this box (the original UM2 has neither a tick in this box, nor an extruder offset in both directions). When looking at the original print head, the nozzle is not below the crossing points of the axes - so what is this setting about?
2.) However, my main problem now is that when trying to calibrate the build plate, the head hits the right printer wall, which is no wonder because the printer firmware does not know about the changes done in the Cura print head settings (I guess the changes in the print head settings in Cura are just considered in the new gcodes generated with these settings, but of course not at all in the UM2 firmware). Or do I only have to reload the UM2 firmware with the new renamed printer with the new print head settings activated in Cura?

 

So I would be happy to learn, how to do a proper build plate calibration avoiding a collision of the head with the printer wall or how to consider the different printhead dimension in the UM2 firmware to avoid the collision of the head with the printer wall.
Any help would be highly appreciated.

[gr5 2,234]

1) That is only for delta printers.  Do not check "origin at center".  If you don't know what a delta printer is then look that up using google images.

 

2) So UM2 has "software limits" for the "high side" of each axis X,Y,Z.  So there is only one limit switch for each axis.  The position can only be changed by changing the firmware.  There are several positions in the firmware: purge position, the 3 leveling points, width of bed (software limit), nominal Z height and so on.  So you can either 2A fix those and rebuild the firmware or 2B move the limit switch more to the left.  Or possibly 2C, tinkerMarlin might let you set those.  I'm 90% sure it doesn't.  @tinkergnome?

 

2A) so I think you need to edit the firmware.  I hope you know how to use good search tools.  I don't know where those values are stored.  Also for sure those values are also stored in the eeprom so even when you fix the defaults you will have to do a FACTORY RESET function on the UM2 control panel before it will switch to the new values.  I suspect at least.  Anyway first step is to find where those are stored.  Probably in an ".h" file like Configuration.h or similar (Configuration_adv.h??).  The best source code to start with for sure is tinkerGnome's version of Marlin (not Ultimakers):

https://github.com/TinkerGnome/Ultimaker2Marlin

 

how to build UM2 marlin

 

 

[3DSkip 2]

Thanks a lot for the quick response! I will check it out and will share what I have learned (which will take some time...).

[3DSkip 2]

Hello again, I managed to get marlin running on my UM2 with the new printhead. The head is now not any longer hitting anything. Thank you!
Marlin is a great software, in particular the PID temperature auto tuning is very useful for my new printhead and was a positive surprize.
I am only facing one more issue: the two fans for the print cooling are not working.
When I directly feed them with power they are working. But not when they are connected to the board. In cura I have set the fans "on 100%" from 0.4mm layer thickness - but they stay off even above 0.4mm (though marlin is showing 100% on at the display).

Any hints would be welcome.

[gr5 2,234]

So the fans are strange: 24V is sent to the two side fans but the fans are in series.  Meaning each gets half the voltage (if they are identical loads).  So they are supposed to be 12V fans but if one has a lower load then one is getting more voltage than the other.  Which could in theory destroy one fan.  Over cooking a fan usually results in an open but sometimes a short - and if you get a short then suddenly the other fan has 24V across it.

 

This arrangement is not standard and not to spec for 12V fans.  I doubt any fan has a specification saying "you can put two of these in series and double the voltage" yet the UM2 does it.

 

Anyway my point is not just any fan will work in that configuration.  These fans tend to have computers in them these days (I know - crazy, right?).  The computer may detect overvoltage and shut down in some way or something.

 

More likely you bought 24V fans but you need 12V fans?  Or you bought 5V fans and you are lucky they haven't burst into flames yet.

[3DSkip 2]

Everything solved now - thank you for the support!
Here is what I did to make the new printhead work properly:

 

1.) I kept the limits witches at place and just changed the X_MAX_POS from 230 to 206 and Y_MAX_POS from 225 to 210. I am working with the alternative software recommended above (tinkerGnome's version of Marlin). In addition I changed the printhead and extruder settings as attached - now the center is exactly in the middle of the glass plate.

2.) I figured out what the problems with the fans are about and I found the answer here: https://drucktipps3d.de/lueftermotoren/
The alternative printhead head was equipped with two 12V fans which do not allow a serial connection. So I bought 24V fans and put them in parallel. Now it works.
One thing to remark: the serial connection of the fan (12V) works as long as one fan is the original UM2 fan. With the two fans (12V) delivered with the alternative head it did not work. The alternative fans are electronically switching the power on/off which does not allow serial arrangement. Anyhow I consider a parallel arrangement as the better solution.

Finally I am very happy with the new solution - thanks!

[gr5 2,234]

On 2/1/2022 at 3:24 PM, 3DSkip said:

1.) I kept the limits witches at place and just changed the X_MAX_POS from 230 to 206 and Y_MAX_POS from 225 to 210. I am working with the alternative software recommended above (tinkerGnome's version of Marlin). In addition I changed the printhead and extruder settings as attached - now the center is exactly in the middle of the glass plate.

Good job!  You make it sound easy but I know that rebuilding Marlin is a pretty big deal.  I'm glad you were able to follow my (long!) instructions and then get it installed onto your printer.