E3D v6 thermistor

[Chris A, PhD]

I've been bequeathed a BfB rapman, with PCB marking "www.BITSfromBYTES.COM Version3.3", and Firmware BfB-BSV4.2.1t/02 . The printer, with heavily modified hw and sw by my late friend, has been working well for 2 years, but the hotends are now failing with Error 12 or 14. One failure due to nichrome wire, another from thermistor GT. It appears that the E3D v6 head (12V, direct, 2.85mm) is an almost suitable replacement, albeit for the V6 thermistor being a 104GT in cartridge vs the existing BfB 204GT embedded in Aluminum antiseize and fire cement. I don't have access to the modified firmware source nor config.g, so will the gcode in the print file will be equivalent? TIA for anyone still out there!

M308 S1 P"temp1" Y"thermistor" A"Nozzle" T100000 B4390 C7.06e-8     ; configure sensor #1 104GTA2 from mouser thermistor, maybe

[Dries Verbruggen]

I’m curious what modifications were done to hardware and software Chris? The firmware was closed source (except maybe some of the first versions) so not sure what could have been modified there. It is not a version of Marlin or anything else and couldn’t be customised via config file or USB access. In some ways it was way ahead of its time as it was already a 32 bit chip as far as I remember.  When we converted them to clay printers we bypassed the thermistor by installing a fixed value resistor that would always report room temperature or something else. The firmware has no cold extrusion prevention so it doesn’t care.

M308 will not work. Reprap.org still has a nice overview of which codes are supported by which firmwares, including BFB. M308 is only supported by RRF: https://reprap.org/wiki/G-code#M308:_Set_or_report_sensor_parameters

I remember there was something implemented to define different types of toolheads. Like a CNC head etc. This was done using a specific value resistor on one of the extruder pins, a different resistance would define a different extruder. 

I found this back in the old wiki (local backup). If you are interested, here’s my entire archive of WIKI, manuals and all firmwares: https://www.dropbox.com/scl/fi/ysqb5077xa3wps1jbq7o9/BFB-ARCHIVE.zip?rlkey=5iav4xbu5lra8lb62am9ifmvw&dl=1

You can also try browsing the forum on the Internet Archive: https://web.archive.org/web/20130127101109/http://www.bitsfrombytes.com:80/forum

Tool Header

The RapMan identifies the type of tool fitted by checking the voltage dropped across a reference resistor, values as follows:

Description Resistor A/D

976 Ohm resistor for PEN 1K (90)
4.7K Ohm resistor for Extruder 4K7 (320)
9.9K Ohm resistor for Extruder2 10K (500)
22K Ohm resistor for Not Defined 22K (700)
47K to 100K Ohm resistor for Router 47K to 100K (840 to 920)
1M Ohm resistor for No Tool 1M to open circuit(1010 to 1024)

At Ver1.0.5 the Extruder, Pen and Router have been defined in firmware.

I’m not sure if it would be feasible to build a hardware thingy (using Arduino) that remaps the values from the new thermistor to the old one? 

I converted a bunch of Rapmans to clay printers back in the days so still have some unused extruder and hotted parts. Happy to send some over if you want. 

Another route would be to replace the electronics altogether, I did that on a BFB3000.

Ps. What slicer are you using?

All the best,

Dries

Op 21 apr 2025, om 16:08 heeft Chris A, PhD <ccat...@gmail.com> het volgende geschreven:

I've been bequeathed a BfB rapman, with PCB marking "www.BITSfromBYTES.COM Version3.3", and Firmware BfB-BSV4.2.1t/02 . The printer, with heavily modified hw and sw by my late friend, has been working well for 2 years, but the hotends are now failing with Error 12 or 14. One failure due to nichrome wire, another from thermistor GT. It appears that the E3D v6 head (12V, direct, 2.85mm) is an almost suitable replacement, albeit for the V6 thermistor being a 104GT in cartridge vs the existing BfB 204GT embedded in Aluminum antiseize and fire cement. I don't have access to the modified firmware source nor config.g, so will the gcode in the print file will be equivalent? TIA for anyone still out there!

M308 S1 P"temp1" Y"thermistor" A"Nozzle" T100000 B4390 C7.06e-8     ; configure sensor #1 104GTA2 from mouser thermistor, maybe

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[Chris A, PhD]

Thanks for the good info, Dries!  Here are some pics of the modded rapman: https://photos.app.goo.gl/ZszzVz4i355c6EkJ9 . It's now mostly metal (my buddy had a metal milling hobby too), and uses a worm gear-like drive mechanism. Also, note the pics of the failed hotends, with autopsy exposing the nichrome wire and thermistor. I think I will try using a variable potentiometer with the e3d v6 potted thermistor, since I'm unable to source a potted 204GT equivalent, nor the stainless (?) sleeve enclosure to pot my own. I need a long-term mechanism for replacing heater and thermistor, and it appears time-consuming to rebuild failed rapman hotends. I'm using KISSlicer ATM, since there are pre/postfix commands that may be specific to the modded rapman -- I've used Cura for other (not-mine) printers, but have been too lazy to switch as yet. 

[Chris A, PhD]

Rather than a potentiometer, possibly setting gcode head temperature to ~212⁰C will be close enough to the true target head of 250, the former being the 104NT vs the latter 204GT thermistor. LMK if I'm about to release magic smoke please! 

[Dries Verbruggen]

Wow, that is a seriously modified Rapman!! Reminds me of early day bootstrap RepRap :)

One solution would indeed be to manually remap the temperatures and corresponding resistance values of the 204GT to the values of a 104NT. I was thinking of it but it’s also risky maybe? You would need to be very precise in converting the tables but doable as they are not too far apart. Attached is the one for the original 204GT that is also in the shared dropbox download.

I remember using Kissslicer at some point indeed, it supports the Rapman. Cura has a profile too but I never tried, not sure when it was introduced, there’s an old discussion dating back to 2015: https://community.ultimaker.com/topic/11210-cura-for-bfb-rapman/.  Prusa has no means to setup a BFB and it is not very trivial. BFB machines still use the old ‘3d’ Gcode instead of the newer ‘5d/FiveD’ flavour where the extruder is controlled as an axis: https://reprap.org/wiki/3D-to-5D-Gcode-php.

It's eons ago that I sliced for my BFB’s and that was usually with Skeinforge on Mac or Axon on PC. I only have some operational in museum installations and they usually print the same old set of files.

After I send my original reply I tried running the question through ChatGPT, I’ve recently had some good experiences using Deep Research for topics like this and I’m quite intrigued by the response. Looks like ChatGPT is very good at referencing old posts on the now defunct fora that still live (but barely!) at http://elco.crsndoo.com. Here’s a link to the output, you can ignore the first response that didn’t use Deep Research.

Looks like it is quite complete and mostly correct, although the section on flashing alternative firmware on BFB board is wrongly sourced and I believe close to impossible. Some other small mistakes here & there but the approaches align with what is already discussed here. Funny that it references this mailinglist and states that it is mostly inactive ;)

I would still suggest thinking about swapping the controller for a RAMPS or maybe DUET clone if you want a lot of flexibility and still keep this monster alive.

To view this discussion visit https://groups.google.com/d/msgid/openbfb/d693ce0a-ac77-4390-8122-3a1c242e5670n%40googlegroups.com.

[Chris A, PhD]

Impressive result from LLM/chatGPT -- thanks to your good prompts. At some point, I'll likely swap the board out if I want another project, or take the easy(er) way out and buy a new printer. I did get an extra e3d-v6 thermistor to see if I can bodge a 204GT thermistor into the cartridge/cylinderWithEndCap. Will post joy||sad update, hopefully within a month.

[Chris A, PhD]

It's Alive! Printed adapter for e3d-v6 with the last bespoke manually wound nichrome hotend. Using (an incorrect) temp setting in KISSslicer to match the resistance at the actual temperature at the nozzle appears to work for at least a few prints.