Erroneous Extruder temperature changes during Manual filament change MMU printing on MK4
Problem: Recently upgraded from MK3S+ to MK4 and from PrusaSlicer 2.6.1 to 2.7.4. After changing the number of extruders on the MK4 from 1 -> 2 (and following the remainder of the process below), the 2nd extruder temp is used after the completion of layer 1/at beginning of layer 2. First filament change (M600) is not supposed to occur until layer 39.
Process: I used to do simple multi-material prints on my MK3S+ using Prusaslicer 2.6.1 with the following methodology:
- Change number of extruders from 1 to 2.
- Add M600 to the tool change G-code section inside "Custom G-code" section of Printer Settings.
- Leave "Single Extruder Multi Material" UNCHECKED.
- Associate the extruders accordingly.
- Disable wipe tower.
- Slice and verify correct colour change code placement within file.
- Export G-code.
- Open in wordpad and delete the first M600 colour change code that occurs after the purge line.
- Start print, change filaments when necessary.
- ????
- Profit.
I would normally use this process for either A) embedding a different colour text within the first 2 layers of the print, or B) utilizing a sacrificial support with a PLA support layer interface between 2 PETG parts. Method B is what I am attempting to use currently. Cross section of the model below for illustration purposes, PETG parts in blue, PLA part in red.
Background: I recently completed upgrading my MK3S+ (originaly purchased early 2019 as Mk3) to a Mk4 via the upgrade kit. I have had a few successful single material prints on the MK4 with Prusaslicer 2.7.4 but am running into a weird issue I did not have with my MK3S+ on Prusaslicer 2.6.1. I am currently attempting to print the Cap of a threaded container. I cannot invert the cap as the top is not flat. After following the process listed above, the resulting G-code has a listing of all the extruders (T0 and T1) as well as their associated hotend temperatures after the completion of the first layer. Since T1 is listed after T0 (the filament being printed for the first 7.8mm of the model) this ends up causing the hotend temp for T1 to be used while printing the material for T0. The resultant change from printing PETG at 260C to printing PETG at 230C is causing many issues.
Question: Is this erroneous extruder temperature change a result of migrating from 2.6.1 to 2.7.4? I have combed through the old G-codes from previous successful 3D prints and none of them had these additional listings. At the moment my only real solution is to convert the binary G-code back to ASCII G-code, remove the erroneous M104 values, manually verify the correct M104 values at the M600 spots, convert from ASCII G-code back to binary G-code, and then print. Any input or alternatives is greatly appreciated.
Entropy
Possible Solution
After spending a larger amount of time playing with settings than I would like to admit, I have figured out a possible solution to my initial problem. It seems now that you MUST check the "Single Extruder Multi Material" option now in order to avoid PS from listing all of the extruders and their associated temperatures. I have also done an excessive amount of reading about others' approach to a similar situation. These are the values within the Single Extruder Multi Material sub-menu I have found that work best for me:
I still have to convert from the Binary G-code to ASCII G-code and manually remove the first M600 command as I have not yet had a chance to try out some of the fancier custom G-codes to see whether they work appropriately or not in this situation. I have also taken to relocating the M104 and M107 commands to be located BEFORE the second M600 (where I am removing the PLA filament from the extruder and replacing it with PETG). The M104 directly preceding the M600 has the benefit of starting to heat up the nozzle while the M600 takes place. The M107 command before the M600 has the benefit of turning the fan off before the M600 takes place, so that way its not blowing full force for the entirety of the filament swap step. I print 99% of my PETG prints with 0 fan, and having the fan blowing the filament sideways whilst purging is very slightly annoying to me.
I initially tried using an M109 before the second M600. This worked, although in a fairly undesirable fashion as it parked the nozzle at the last position ON the print before initiating the M600. This resulted in a small melted area and a large blob of filament on top of it which ended up scrapping the print despite a later attempt at intervention. I may play around with this a little more and see if I can add a G1/G0 code before the M109->M600 combination to park the nozzle somewhere not directly on the print while it waits for the desired temp to be achieved.