Need to change the Bowden tube length in firmware
Ive recently made a few changes to my MK4S-MMU3 set up and deleted the Buffer chamber portion of the set up and added a new dry box that uses auto rewinding spool holder in the dry box, negating the need for a buffer chamber (Soooo much better!). This setup worked very good and was repeatable and reliable but loading it was a bit of a pain and cumber sum.
I wanted the MMU3 to be on top of the dry box for ease of loading and to clean the setup up a bit and make it more organized. So I soldered a length wire to the MMU3 control wire and added a new longer Bowden tube to the set up. see picture below. clean, easier to load but.......
Now the MMU3 will not load the filament far enough to reach the extruder. everything else works just fine on the MMU3. apparently there a hard coded length of 340 mm that the MMU3 will only go (because the buffer chamber would over flow, but i no longer have a buffer). Ive looked everywhere I can think of to make the load length longer in the Prusa slicer but I have had no luck with any of the changes, nothing makes the MMU3 load longer than 340 mm.
Ive tried changing the Start up G code using M708 A0x0b x 550 and Ive tried M708 A0x22 x550 but it doesn't change anything either. Am i skipping something when i change the start up g code? I'm saving the G code changes, re-slicing the part and loading it on the USB drive and then loading it into the printer.
I don't use Octoprint or any other software, Im only using the Prusa slicer software to make changes.
Can any one help me work this out, I really like the set up as it is and want to keep it this way.
Ive asked the factory for help and they state that this is an unsupported change and to look here in there Blog.
RE:
The printer is VERY picky about proper case and spacing. Instead of M708 A0x22 x550 try M708 A0x22 X550.
I hope this helps, but keep in mind that this will also have the effect of increasing the amount of material retracted into the buffer (or rewinder). Are you prepared to deal with that much more buffering?
RE: Need to change the Bowden tube length in firmware
P.S. The Bowden Length register (A0x22) is memory Persistent, so you only need to write to it once. After that, you don’t have to add the gcode any more.
RE: Need to change the Bowden tube length in firmware
But how do you change that value in the MMU and what do you use to change it?
RE:
Thanks for the reply!
All the research I've done shows a small case x IN front of the final number that's why I used a small case x. ill try a upper case x but I'm still not sure how to send it to the mmu. I've been putting it in the start up g code file and then re-slicing the part and loading it on to my usb drive, then i load that usb drive into the printer. but nothing seems to happen or change. what do I need to do the send that change to the mmu?
RE:
You can add the following in to the start of your GCode file just the once:
M708 A0x22 X####
where #### is the length in mm. There is information here: https://help.prusa3d.com/article/prusa-firmware-specific-g-code-commands_112173
Or you can send the command via octoprint or Pronterface
RE: Need to change the Bowden tube length in firmware
You were doing the right thing, sending it in your startup gcode. It just wasn’t successful because of the syntax.
RE: Need to change the Bowden tube length in firmware
Or you can simply create a file with one line.
M708 A0x22 X450
Make sure to put a Return at the end of the line. Save it as MMU_Change.gcode or whatever.
Print that file. Done.
RE: Need to change the Bowden tube length in firmware
That was it!! good grief all this head ache because I used a small x instead of a capitol X, I'm so embarrassed.
Thanks you guys for all your help!