Y Adapter filament switching

[Yonkiman]

Thanks for the continuing updates!

I'll probably also try some smaller steppers in between the monsters I have now, and the small ones David mentioned. Can never have too many spare steppers.

True…but 24V could come in pretty handy, too. I just ordered one of these http://www.mouser.com/search/ProductDetail.aspx?r=709%2dLRS200%2d24 to replace the noisy 24V supply I've been using. The Duet's drivers are so quiet that I couldn't take the PSU's obnoxious fan noise. I'm using these https://www.aliexpress.com/item/3A-Adjustable-LM2596S-DC-DC-Step-Down-Buck-Power-Supply-Module-Adapter-3-2-40V-to/32594772519.html for all my 12V fans.

[Yonkiman]

However, that means if I want to change filaments outside of the script[print], I need an extra step, so I added a T0.g / T1.g macro:
M83 ; relative extrusion
G1 E-5 F3600 ; Retract 5mm - adjust this to your standard retraction
G4 S2 ; pause 2 seconds
G1 E-4.9 F1200 ; unretract 4.9mm
T0 ; switch to T0

I don't understand the purpose of this - the last line switches the tool but the first 3 appear to just move the filament back 0.1mm. Wouldn't you want to retract the filament from the old tool ~100mm, select the new tool, then extrude that filament ~100mm?

I'm probably missing something obvious…

[kraegar]

You must retract, pause a bit, unretract. This is the "trick" I found with the v6, to get around needing a "ramming" swap. The goal is to get a clean break on the filament by having as little melted filament in the nozzle as possible, for as short of a time as possible.

The other option would be to ram 5mm of filament out by doing something like:
G1 E5 F1200

Then immediately do a single long (150mm) retraction @ 100mm/s. But that leaves a lot of filament mess, where the above process achieves almost the same thing.

[Yonkiman]

Ah…my problem was thinking that "change filaments" meant switch between extruders, not swap out spools of filament.

So you're saying that before pulling all of the filament out of the extruder/bowden tube, etc., this code [retract, wait, and unretract] makes the filament come out cleaner and with less mess than not doing it. What I still don't get is it seems like after the unretract, the filament is now just minus 0.1mm away from where it started. It seems to me like it would just melt again and leave you basically where you started.

I'm not saying you're wrong or anything - I'm just trying to understand what's happening.

[kraegar]

Yes, this is to switch two filaments with one hotend (two extruders). The goal is to have the filament look like this:
http://imgur.com/msU4hia

There are a couple ways I've found to accomplish that, depending on what your extruder is capable of. If you just pull the filament back, you get long tails, and it doesn't look like that at all. The tails WILL jam an e3d v6. In quite spectacular fashion (I had to take mine apart to clear one)

The first effort was around ramming / purging. The idea was to push out filament as fast as possible, then yank it back. This generated an awesome break, very clean. But left a ton of filament mess. It was basically:
G1 E5 F1200
G1 E-150 F3600

Simple. But messy, and requires a very fast retract.

Step two, I figured out how to get rid of that purge. The trick was to mimic what it's doing. So you unretract, then PAUSE. 2 seconds or so of pause is enough to actually cool the retracted filament down. Then you push it forward, and pull immediately. Clean break, if you can retract at 100mm/s. So, basically this:
G1 E-3 F3600 <- whatever a "normal" retract is for your setup
G4 S2 <- pause two seconds, to cool the retracted filament
G1 E2.9 F3600 <- whatever a "normal" unretract is for your setup
G1 E-150 F6000 <- yank the filament back

Then I hit a new issue, I put on titans (for more torque, so I could lower my temps some). But 100mm/s retractions don't work, so I played around (lots of jams) until I could generate a clean-ish break. This involves "packing" the filament.

G1 E-3 F3600 <- whatever a "normal" retract is for your setup
G4 S2 <- pause two seconds, to cool the retracted filament
G1 E2.9 F3600 <- whatever a "normal" unretract is for your setup
G1 E-20 F3600 <-Retract enough to pull it into the heatbreak
G1 E20 F3600 <- Pack the filament in, this will get rid of most of the stringing
G1 E-150 F3600 <- Pull the filament out past the Y adapter.

There may be simpler ways to do this with an e3d v6, I've just been playing with it until I find something that works. If you can retract at 100mm/s, the 2nd method above has worked for me for over 2500 filament swaps in a row, with no jams. If you can only retract at ~60mm/s, I've just started with the third method, but it's worked around 500 times now, with no jams.

My testing method is to just swap filament in air, extruding 20mm between each swap using a macro. It looks something like this:
http://imgur.com/DXYp6nT

Once I can complete 50 in a row, I try a print.

[Yonkiman]

Thanks - I understand all that (and am fortunate enough to be able to retract at 100mm/s).

OK, I just realized what my confusion was. Your T0.g script was:

G1 E-5 F3600 ; Retract 5mm - adjust this to your standard retraction
G4 S2 ; pause 2 seconds
G1 E**-**4.9 F1200 ; unretract 4.9mm

When I saw the "unretract 4.9mm", I thought that was a fancy way to say you were pushing the filament back into the hot end. (4.9mm seemed so precise I assumed this was some sort of filament shaping trick.) I didn't look at the command itself which clearly shows you are actually retracting 4.9mm farther (my bad).

I totally understand now - thanks for your patience!!!

[kraegar]

Doh, no, that was a typo, you are pushing it back (extruding it). It is a filament shaping trick

I'll edit.

The goal is to have your nozzle filled with melted filament, but for as little time as possible. That's what gets it to break, rather than string. It seems pointless, but with the E3d v6, if you don't do it, you will get constant jams.

[DjDemonD]

I cant wait to try it sounds like fun, and we will be so far into it thanks kraegar for all the hard work you've done here. Now just finding time to install the Y adaptor and second extruder.

[kraegar]

I'm not entirely convinced on my newer packing method for slower extruders. I'd much prefer to get the kind of break I was getting with 100mm/s retractions. Maybe once more of us are doing it, we'll find a better method.

Also, I really don't like that my retractions are currently at 5mm, so we need more people using the Y adapter with the v6, to see if we can find retraction settings that don't string, and aren't so long!

[Yonkiman]

@kraegar:

Doh, no, that was a typo, you are pushing it back (extruding it). It is a filament shaping trick

Ok, now you're just f-ing with me.

So back to a rephrasing of my original question: what happens immediately after the 4.9mm extrusion/unretraction? Something has to happen next, right?

[kraegar]

@Yonkiman:

@kraegar:

Doh, no, that was a typo, you are pushing it back (extruding it). It is a filament shaping trick

Ok, now you're just f-ing with me.

So back to a rephrasing of my original question: what happens immediately after the 4.9mm extrusion/unretraction? Something has to happen next, right?

If must seem like I am just screwing with you!

Ignore the "some happens in the slicer, some happens in the firmware" aspects of this, and let's take the simplest case, where we can do 100mm/s retraction, ok?

So, here would be the "during a print" steps.

Retract (G1 E-5 F3600) and zhop to clear your print
Move to your purge area (G90; G1 X0 Y130)
Pause two seconds to let the filament cool (G4 S2)
Extrude all or nearly all; aka, unretract (G1 E4.9 F1200)
Retract 150mm of filament (G1 E-150 F6000)
<new tool="" becomes="" active,="" same="" hotend,="" second="" extruder="">Feed in new filament (G1 E142 F6000; G1 E3 F1200 )
Unzhop and get back to printing.

That's it. You can't just remove the filament to switch. You have to pull a bit back, cool it, extrude it, then yank it back again. Or, that's what I've found works for me anyway.</new>

[Yonkiman]

I totally get the basic principles. It's just that your T0.g script seems incomplete:

You have to pull a bit back, cool it, extrude it, then yank it back again.

Where is the "yank it back again" part in the T0.g procedure? Does another macro start that yanks it back? Does control go back to the object's gcode file where the Tool Change script yanks it back?

Maybe I just don't understand when/how T0.g and T1.g are supposed to be used. To me they look like scripts that retract the filament, then shove it back in (minus 1/10 of a mm), and then things go idle, almost as if Tx.g had never been run.

Thanks again for bearing with me!

[kraegar]

Ok, now we're on the same page. T0.g does the "prep" work of priming the filament, so to speak, then at the end of it is the command "T0"

So, if your current extruder is T1, and you run my "T0.g" it will do the following:

Run T0.g
Run tpre1.g
Run tfree1.g
Run tpost0.g

Those last 3 are called when the T0 command is interpreted by RRF.

[Yonkiman]

That's it! Should have realized that a tool change will call those three .g files regardless of where it comes from. Thanks!

[Yonkiman]

I got it (mostly) working! Can swap filaments with T0.g and T1.g doing your packing trick. Dealing with some bed-leveling issues (the two Bowden tubes are causing some flexing of my printhead) and working on the same trade-off between putting the code in S3D vs in the Duet's .g files. I also think the swapping might be easier with my Lite6 (bowden tube all the way down to the nozzle) than with an original V6. Before I got your packing working reliably, I saw some pretty ugly, long filament trails, but it never jammed. Also, I didn't appreciate how useful it is to have a transparent Y adapter! Was originally going to try this with a printed Y, but the ability to see what's happening is alone worth the $20.

I also had an entertaining accident: S3D writes the extruder commands in absolute mode, but somewhere an M83 was accidentally inserted (or an M82 was missing), so my extruder was interpreting absolute commands as relative, and my 4:1 geared extruder sounded like a jet's turbine engine as it started spinning up with no end in sight. Apparently the right commands in the right order is sorta important.

Thanks again for your help, kraegar. Will post my best config once I dial things in a little more. Please let me know where you settle on the S3D/macro split.

[kraegar]

Awesome, glad it's working. I suspect the lite6 will indeed do better - it should suffer from heat creep less. Depending on what extruder you're running, if you can retract at 100mm/s you might want to try that method, as it was by far the cleanest.

Playing with the pause and such can make a big difference, too.

[DjDemonD]

This seems very relevant to the latest edge firmware:

Known issues

If you enable tool mixing, you should use relative extrusion only. If you use absolute extrusion, then if you pause and resume the print, the extruder is likely to extrude the wrong amount of filament in the first move after resuming.

[kraegar]

I only use relative extrusion during my prints, anyway, but I've wondered what would happen if you were switching from absolute to relative & back within your free/post scripts. I was guessing it probably wouldn't go so well.

[Yonkiman]

Ah…didn't know there was an S3D option for relative extrusion. That should make things a lot safer!

Here's my current setup/scripts:

S3D Tool Change Script (at this point I'm doing it all in tpost and tfree):

T[new_tool]		; Change tool

tfree:

; tfree0.g
; called when tool 0 is freed
 
M83			; Make sure extruder is in relative mode (prob not needed anymore)
G1 E-5.0 F3600		; Retract filament as soon as possible...
G91			; Relative
G1 Z2 F6000		; ...Then lower the bed...
G90			; Absolute
G1 X115 Y232 F18000	; ...Then get the hell away from the print
G4 S2			; Pause two seconds to cool the retracted filament
G1 E4.9    F3600	; Pack the filament to eliminate the tail
G1 E-150.1 F6000	; Yank the filament past the Y adapter and into its Bowden tube

tpost:

; tpost0.g
; called after tool 0 has been selected
 
G1 E145 F6000		; Extrude 145mm @ 100mm/s
G1 E5   F1500		; Extrude   5mm @  25mm/s
G91			; Relative
G1 Z-2  F6000		; Raise bed
G90			; Absolute

The retracted filament end doesn't look perfect (needs to be optimized for PLA with an E3D Lite6):

But it was working well enough that I could print this:

It's pretty ugly because I just built this printer and have a lot of single-filament fine-tuning to do, but it's a solid piece of plastic in two colors! Thanks for all your help, kraegar!

Now back to the fine-tuning…

[kraegar]

Off to a good start!

To test my switching, I just made a macro to retract a single extruder, and ran it over and over, slightly changing things until I got the cleanest break I could. I literally ran hundreds of tests. That break isn't bad, but for the lite6, I'd guess you can improve it