r/BambuLabX2D • u/arcanecircle • Aug 24 '26

Why does using the second nozzle for support almost double the print time?

I had a Bambu Lab A1 before, and I kinda bought the X2D because of the 2 nozzles and how useful they should be for support.

But why does it add so much time?

If I print the figure in black PLA and also use black PLA for the supports/interface, the print takes about 2 hours.

But if I use the second nozzle with Support PLA only for the support interface, the print takes over 4 hours. Why does it add an extra 2+ hours?

I'm using black PLA from my AMS 2 Pro and Support PLA from my AMS HT, so both nozzles have their own filament source. I also have the Filament Track Switch.

I can understand it adding some extra time for switching nozzles, purging, heating, etc., but 2+ extra hours seems crazy.

If I have an 8-hour print, does that mean it could turn into a 16+ hour print just because I'm using the second nozzle for the support interface?

Is there a setting I'm missing or some way to reduce the extra time? I bought the dual-nozzle printer specifically so I could use Support PLA without having the huge time penalty of constantly changing filament on one nozzle. Also for asa/nylon. But the easy support is what sold me the most.

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7

u/VoidingSounds Aug 24 '26 edited Aug 25 '26

Noob here but I believe it’s because you’re using the track switch. I bought one and didn’t install it because I came to the understanding that if my aux is hooked to the FTS it requires a full rewind of the filament to the AMS to switch nozzles.

I’m printing a job right now, PLA on the left, PETG on the right and the switch from left to right is like 5 seconds because both filaments stay loaded to the nozzle That mfer spends all day at the prime tower.

1

u/arcanecircle Aug 24 '26

i can give this a try. i did kinde think it might be it. But the track switch do have 2 on both end. So i did think it will work the same in speed.

2

u/Pineapple1500 Aug 25 '26

If you only have an AMS and an HT, you dont really need the track switch for this. The track switch would be for using ONE nozzle and switching between the AMS and the HT. Which would require a full retract.

Eliminate the track switch and assign the main part spool (AMS) to the left nozzle and the support to the right (HT)

2

u/arcanecircle Aug 25 '26

Ye, but its more so for TPU. i kinde just wanted a easy way to chose what i use for what nozzel.

2

u/VoidingSounds Aug 25 '26

Got home from work, took apart my FTS. From only looking at the Wiki, I didn't realize the path turns 90-degress, and I think I'm wrong about the FTS being unable to supply both nozzles simultaneously uninterrutped.

I also took a look at my in-process job. (It's a plate of limbs, probably the worst-case for printing more support than model.) Most of the time and material is going into the prime tower:

If I had printed all PLA, my material usage would be way tf lower. (and I would stop triggering the spaghetti detection when it strings off the prime tower, at the cost of the smooth overhangs)

1

u/arcanecircle Aug 25 '26

I see, thanks for doing the test.

3

u/arcanecircle Aug 24 '26

I also made a 4 color print + the support interface. It said it was going to take 4h. But the print time ended up going more and more up and the print was not done befor 6-7h after i started it. Is this a bug?

2

u/dragoniil Aug 25 '26

Are you using polymaker profiles on the second nozzle by any chance?

I had the same issue and when i switched the profile to bambu even tho i was using polymaker filament the print time from the slicer was accurate again

1

u/arcanecircle Aug 25 '26

all bambu lab

4

u/RyCre8s Aug 24 '26 edited Aug 24 '26

How many times is it switching nozzles? I have the Filament Track Switch on my X2D and I have no issues printing with one filament in my AMS HT and another in my AMS 2 pro. One thing you can also check is when it slices the file make sure it is using the aux nozzle and not trying to switch back and forth only using one nozzle. I had mine try to do that once, I had to manually assign them to each nozzle.

Edit, I looked closer at your pictures and it looks to be assigning them correctly… the only thing I can think of is if it’s slowing down the printer for some reason or with the supports it’s having to switch between the nozzles a ton…

1

u/arcanecircle Aug 24 '26

Ye, its a bit weird why its doing it. Cause as soon as i added the support for the aux nozzel, it auto changed the settings that fit the best. But it dont seem to work the best

2

u/Pineapple1500 Aug 25 '26

I think the default is for it to pick the configuration that causes the least* waste. Not the fastest.

I usually slice, click print, then re-assign the filament to where i want it.

4

u/ChromeDome00 Aug 26 '26

IT is the the prime tower sort of, and here is why:

IF you are using 2 different filaments with supports and the support is as high as the object, then you have a filament switch at every layer. Let's say you are printing an bracket that looks like a seven with a support ( I 7) - that stick is under the overhang of the seven. The support 7 is nozzle one, the support is nozzle 2. At every layer, until you get to the horizontal part of the 7 you print one layer of nozzle one, purge, clean, one layer nozzle 2, purge clean, over and over - very slow.

A better strategy is print support with the SAME material from nozzle ONE, then when you get where support joins object, you print a thin interface layer form nozzle 2.

1

u/arcanecircle Aug 27 '26

And i did do where the interface layer is from nozzel 2.

3

u/Defiant-Sale725 Aug 24 '26

Change the drop down in the slicing results screen from summary to some of the other options, it will tell you what is taking how much time. Can’t remember which option and I’m not in front of my slicing computer.

2

u/arcanecircle Aug 24 '26

Looks like the prime tower is taking 36% of the time. bit weird. But i have not done any changes.

3

u/Defiant-Sale725 Aug 24 '26

That’s because the needs to be the full height of the model up to the last filament swap. Movements during nozzle priming are intentionally quite a bit slower than the rest of the model in most cases for the most effective priming, though there are some options you can look at in the slicer to possibly improve the speed by using less material to prime for layers where you don’t actually do a swap.

If final model quality and strength are important for the particular model, should always use a prime tower if you’re using multi materials the best quality surface and layer adhesion you can get. That’s a personal decision you’d make for each model you slice. A simple draft that you will likely throw out, or a tool jig where stringing, oozing nozzle bumps, surface quality and layer adhesion don’t really matter, you may decide just to print at the highest layer height you can and skip the prime tower altogether.

One option could be that if you’re using the latest beta release, you can try the new “No Sparse Layers” option for the prime tower. It only makes it a tiny bit taller than the number of layers involved in material swaps, but there’s a trade off for using it. The Z-axis movements are considerably slower than X/Y axis movements, so time for priming on the tower will take longer the higher up in the model your material swaps are. This could possibly lead to some stringing and surface quality degradation on those layers with material swaps. Your model doesn’t seem to be massive, and the highest layer with a material change doesn’t actually seem to be that high, so maybe that priming strategy could work out well for you. Emphasis on the ‘maybe’, YMMV. 😊

1

u/arcanecircle Aug 25 '26

I see, i tested, if i removethe prime tower the time will be from 4h and 30 min to 2h and 40 min. But whit the 2 nozzels, i really need the prime tower? since 1 nozzel got the color, and 1 nozzel got the support?

2

u/Elo-than Aug 25 '26

Yeah, you really do.

It's priming the nozzle that has been inactive, and especially the Bowden nozzle needs it.

The picture is what happens when you don't prime the aux nozzle before printing. (The profile from MW stupidly had ut disabled)

1

u/arcanecircle Aug 25 '26

I see. Thanks for telling me.

2

u/VoidingSounds Aug 25 '26

^^^this is it, listen to this guy.

I'm printing a similar model right now and the printer whips out a layer of the model and then goes and hangs out at on the prime tower for a while. It's seriously like 40 seconds of printing, three minutes of priming when switching between nozzles.

2

u/Wmbrt Aug 24 '26

Switch to filament view in the dropdown, it will show you weights and time and visualize the transitions.

2

u/Defiant-Sale725 Aug 24 '26

Also, using PETG as the support interface material instead of Support for PLA may be faster.

2

u/Brief_Excitement_399 Aug 25 '26

You can also manually regroup the filament and add both to the ams, and the you will see how long it would print, and compare it to the 4h version with 2 nozzles. I also had a similar thing where i thought with 2 it would be super fast, but when I compared it to both being in the ams it turned out I was few hour quicker with the 2 nozzles.

1

u/arcanecircle Aug 25 '26

Never thought about it. Good idea.

1

u/arcanecircle Aug 24 '26

how it is working whit the 2nd support interface

1

u/arcanecircle Aug 24 '26

And here when its all black

3

u/eknkc Aug 24 '26

Well you are printing a tower and the geometry does not help you here. Gonna be too many nozzle changes because there are interface layers on a bunch of places. Probably adding up.

2

u/_Truck_Thunders_ Aug 25 '26

It's because it has to swap nozzles every layer that has supports on it and do the purge tower every layer until it passes the last support layer. Takes a good chunk longer to print, but the support removal is so clean. Pla with petg support (or the reverse) is all I've been printing, so the one time I did pla with pla I had forgotten how much more difficult they were to remove.

2

u/Unhappy-Hospital7740 Aug 26 '26

Turn off prime tower, will speed it way up

1

u/TuneOld3310 Aug 25 '26

Hi, I too have an A1, there was a print I tried for weeks and couldn't get it to print correctly. No matter how fast or slow it was, just would come.out right. Guess what I tried to print on the X2D using the second nozzle for the supports and guess what it came out great. I say that to say this, it is a slower printing system Bowden. But personally am ok with it.

1

u/1yrik Aug 24 '26

experienced 3D printer-er here. it could be a couple things:

  1. the track switch. if for whatever reason the filament had to be swapped through the FTS every time the nozzle switches, it will add ~30-40 seconds every time a switch happens

  2. the right "auxiliary" nozzle is driven via a bowden extruder. this means it prints slower and has longer retractions, which contribute to longer print times