Initial Testing of Stepper Switch Codes Not Working

Are you sure it's not just going back to the first extruder (the grinding noise indicate that it's trying to rehome.) It sounds like your 3.5 seconds is a littler short. Try for 4 seconds and then try for 6 seconds. You should see it rotate one way or the other depending on the time.

I was able to get it to work on a few of them with increased counting. I am assuming I'm just counting off. So going to just try to get it going since the gcode will be better than my counting abilities. Now I am trying to figure out the Prusa mounting setup, there is really no documentation on what the trigger is supposed to mount to on the board to make the limit switch work. It kind of looks like there is a spot for maybe a tie wrap, but kind of at a loss. Does anyone have a picture of what their Prusa MK3S+ look like under the printer to see how this goes?

Here's a picture of it.

Assuming there is a lot of variables here, possibly how the bottom of the bed frame is, but looks like mine is activating at 182 with the mount flush with the edge of the printer. I did notice that the youtube video on limit switch mounting had a number more in the 200s. Is there something that I may have missed?

Yes, the flag is on the back "X brace" of the Y axis, not the front one and the switch is about 4" from the front of the printer.

That makes a whole lot more sense now that I think about it, especially why the trigger mechanism is in place as well. I'm hoping once I am done with setting this up that I can document it and do some lessons learned/tips.

These should help clear it up.

I've added these images to the 3D Chameleon Switch Mount page on Thingiverse: https://www.thingiverse.com/thing:4663605

I'm still working on this, got it mounted and looking like its doing the switching okay. I have had to reduce my tension on the extruder, was scarring the filament too much to be fed back and forth. I have now had a couple layer changes between two filaments, just doing a simple test for now. Main thing I'm noticing is the start of extruding has a blob with the first extruder filament in the middle and the other in a bigger blob circle. The second layer change just has another blob. I haven't seen a ton or almost no blob volume in subsequent filament changes. I am assuming the filament has to be up to the little black spot just past the coupler, otherwise the filament kind of pulls back out. Is this correct? Just trying to see if there is something I need to modify or change. Also to note, I was initially running into problems in PrusaSlicer 2.4 as well, which slowed down my progress a lot yesterday until I found your post with the python script. It does fix the issue you detailed.

Blobs at the start of each layer indicate that you're loading the filament too far... reduce the distance between the extruder drive gears and the hotend so it doesn't push it in so far.

I even set the E part to zero and still getting blobs, though a lot less (first extruder almost none, but I get blobs of the previous filament after it switches out and loads the new filament). This is the line I'm assuming I am supposed to use to set this: G0 E0 F2000 ; <<<<<----------- EDIT THIS DISTANCE TO FINE TUNE THE FILAMENT LOADING TO STOP BLOBBING OR UNDEREXTRUSION

For large moves, don't edit the tool change gcode directly, edit the parameter in the gcode generator, that way it will flow through the entire system. By only editing that line (especially down to 0) you're only editing the very last move, but not the entire sum of all the moves. (This parameter is really a fine tuning element, for that last mm of accuracy.) Course adjustment should always be done with the gcode generator parameter so that it both loads and unloads the correct distance.

Looking in the gcode, I see, makes since, will give it another shot. Might just be my end, but the button location appears to be hard coded to Y209 in the generator. I have just been modifying it manually myself.

The button location is calculated based on the position you enter into the gcode generator. It always subtracts 3mm from it... so if you enter 212, it will put in 209. But if you put in 215, it'll put in 212.

Bill

Any reason why it removes 3 from it? The prusa location has it as 212 when I dial to it and the gcode works when it is set to 212.

That's correct... but the holding position is always 3mm less (than pushing the button) on both the X and Y axis... when it wants to press the button, it always moves 3mm and engages the button... but then backs back off.

Thanks for your help, I have gotten further along. I'm struggling with jamming, but it seems like it may be a matter of temps impacting too long of strings when it retracts. It either drops pieces in the extrusion or still has bits out when another color comes out and gets stuck. I had to set the extruder offset to zero to remove blobs. For now I ran out of time to mess with it further. I don't know when I'll have time to try again. Seems I'm close though.

I have gotten pretty far with just two color changes as tests. On my third filament change, I have been getting a notch around 195 mm or so without fail. If I don't pull the filament out and cut and put it in before the next change, it wont pull it due to the friction. If I cut that piece off and reput it in the tube, it will complete. I have loosened a lot of the tension on the extruder gear, so not sure if that would be causing this, seems to be at about the same point each time. Not sure if the angle of the green switching mechanism and the tubes could be doing it too. It's a fairly glossy filament, using jessie pla at 215 C.

When you say you're getting a notch around 195mm... what do you mean by that? (BTW... I print Jessie PLA at 230 on my Ender 3... prints much better for me.)

I might try 230, I usually have good success at 225, but it makes such a long string that it blocks the other filament when it retracts. It's kind of a notch in part of the filament, I think it gets caught just before it can go to the hot end on that notch.