Making better use of Flush-into object in Bambu Studio

Thanks - Yes - will release it - once I have refined it a bit and have at least a small version printed - progress has slowed a bit because I am not doing a lot of multi coloured printing at the moment.

I am hoping it works out that once you have created the basic parts and produced a fairly small table (or potentially other shapes) you can then just expand the dimensions as more flush-into parts became available as a byproduct of other prints.

Think I will have a go at doing a smaller scale single test print tomorrow - using low value filament in order to try and make a bit more progress on this initiative.

Update. 28/11. - print now ready to go with most of the essential parts to create a corner of the purge-table - one 1g of flush.

Also trying it with prime tower removed by post processing GCODE
10046 G0 and G1 commands commented out
2.5 M prime saved


Update - purge-table starting to take shape - all individual parts now tested.
Just need to build up a few more top parts and legs - big incentive to get on with some nice big multi colour prints


Not strictly related to the subject of purge reduction - but I have just seen this interesting post on Facebook about problems with prime towers in ‘multi material’ support interface prints - Redirecting...

Interesting issue. My thoughts are

  1. Priming is probably even more essential than normal for multi material support interface layer prints - as you need a really clean flow of both of the materials when they are overlapping each other - so turning off the prime tower is probably not a good idea.

  2. In the prime tower the initial inconsistent flow in combination with poor inter layer adhesion between different materials does mean that it is more likely to fail than a single material prime tower.

The solution I think has to involve separate prime towers per material. This then leads to the issue of creating masses of extra material swaps to in this case keep the PETG tower the correct height.

The solution to this issue I think is introducing a variation of the ‘no sparse layer’ prime tower logic in Prusa slicer - which allows the prime tower to have less layers in it than the actual print.

This method though would suffer from the same height restrictions as you get when ‘printing by object’.

I think however that you could work around this issue by keeping the PETG prime tower not too far behind the PLA tower by adding just the occasional extra PETG colour change - which is used to add a few layers to the PETG prime tower - so that it doesn’t get too far behind.

Whilst ideally this should all be done in the slicer - I think it would be possible to write a gcode post processor to

A) split out the materials into separate prime towers

B ). Add ‘no sparse layer’ type functionality

C) enhance ‘no sparse layer’ to stop towers from getting too far behind the main level

Any extra colour changes required for this would have to be created by manually adding them into the model at the correct heights.

Sounds like an interesting technical challenge - for waste reduction purposes I was already considering having a go at creating a GCODE post processor to
a) alter the shape of the prime tower to make it into a more useful shape (such as a section of ‘purge-table’) rather than waste
b) adding in a ‘no sparse layer’ capability -
so might have a look at the splitting the tower into materials too at some point.


Your discoveries are impressive.
This started as a forum thread but feels like a complete research paper when I read it.

In the past few days I began to do the same as you, only I was using the Hive model as purge into object.
I had satisfactory results but I was interpreting the numbers in the BL final table quite bad. Your thread makes it clear.

My question is: do you keep in BL flush volumes auto-calculated with fixed multiplier?

I had good results with my colors that I mostly use with multiplier 0.6 even with prime tower only and poop out the chute.
Increasing the number of sacrificial objects that does not matter the color composition will decrease the wasted plastic with flush.

I am no near able to automate a script to remove prime tower but I am interested in that if you want to share.

I’ll keep a close eye on your thread
Thanks in advance


Thanks, yes I use auto calculate and usually 0.5 multiplier. Using flush-to objects mostly slightly increases the effective flush a tiny bit. Removing the prime tower reduces it a little bit - so I guess it may end up resulting in having to push the multiplier up a little.

Will share the post processor once I have tested it out a few more times, plus worked out the best way of sharing python3 code in such a way that it is easy for others to install.

I have tried out some of the flush checking methods like the AMT_MW test models - bit I think it is probably going to be too complicated for to keep track of all of the different flush volumes for different colour combinations - so will probably just stick with auto calculate for now - because as long as you are flushing into useful objects an extra little bit of flushing isn’t necessarily a bad thing.


This is amazing. Just got the AMS added to my P1S and coloured my first print (turned Barry Bear into a panda) and I was disappointed to see my 90g print was going to make 180g of waste. I figured someone must have found a way to reduce that. I knew about flush-to-object so I had a couple of functional pieces I had waited to print for this reason but they only reduced the waste by 20 g or because they were either too thin or too short. Your experiment (which is how this read like Cmaneaonline said) was extremely helpful and got my waste down to 23g and 330g of functional. So although my filament usage increased to 22% my waste was reduced by 89%. And this was without using your table pieces or your python code (since I felt too inexperience to try it). I hope your research here becomes part of the Bambu Wiki as I think everyone could benefit from it.

Decided to have a go at individual colour swap purge lengths based on the AMT_MW models on maker world. Initial results showed definite benefits over auto calculate for some colour combinations - without a clear pattern.

As am currently away from printers - have used the time to create some automations on top of Bambu Studio using the Mac only ‘Keyboard Maestro’ app.

  1. First macro is an easy one to automate the setting of all flush lengths to 50.

  2. Next set of macros can then be used to store any newly calculated optimal lengths against the associated filament types and colours - so that they can then be easily re-applied whenever required.

It should also be possible to enhance these macros to do more generic enhancements to the build in auto calculate.

Initial ‘set lengths to 50’ macro shared below - if there is any interest in the others let me know.


Brief update -

I’ve got quite a few ideas for ‘flush into as colour doesn’t matter’ objects - such as

  1. Large multi part functional items - designed with ‘flush-into’ specifically in mind, that can be built up over time - such as:
    A flexible size table - made out of multi colour flush - that I am calling the ‘purge-table’.
    Plus other big multi part things like shelving etc.
  2. Xmas decorations - such as multi coloured balls etc -
  3. Printer add ons - like AMS risers / AMS helpers / Scrapers etc
  4. Storage - like Gridfinity etc.
  5. Decorative things like Vases and 3DPB string art etc that are actually enhanced by the ‘random’ multi colouring
  6. Big strong functional things - like the parts for the MPCNC for example
  7. Custom packaging for fragile designs
  8. Internal components of decorative items

Additionally I have a couple more ideas

Have made a start on a collection here to try and illustrate the sort of thing I am talking about. Flush-into colour doesn’t matter | Collection - MakerWorld

Finally got round to doing another multi colour print too tomorrow - this time of a BS hand coloured (my first using BS) Star Wars Corvette (from Thingiverse AirTeuteu Star Wars CR-90 Tantive IV split by AirTeuteu - Thingiverse) - flush will go down from 34g (30%) to about 1.25% (1%) using the ‘prime-table’ parts. It does push print time up by about 45 mins though.

Update 19/12 - First attempt at print failed - due to not spotting that top rows of engines needed support added - pretty happy with reprint though - and fairly small amount of flush waste.

Support removal quite tricky

But came out ok I think

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Bit controversial I know - but I was wondering if I could be a bit more creative with the ‘purge-table’ legs as I am not doing enough multi colour prints at the moment to make much progress - so I was thinking about maybe incorporating some other ‘waste’ material in them in addition to the multi colour flush.

So printed with first ever Bambu Lab built in Benchy - have tried and failed a couple of times before - but it seemed to work very well on the cool plate on an X1C with the latest firmware ok. Quite noisy though I guess due to the high speed.

Not exactly sure how the structure the part - to make best use of the pretty strong structure of a benchy into the table structure - my first attempt is going to be something like this…

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Looking at ‘The Real Sam Prentice’ seagull video with masses of Purge Waste -

Thought I would have a go and see if I could do better with purge-table components.

With the model as downloaded from makerworld Bambu Seagull by marksolly - MakerWorld - total print time 25 hrs on a X1C - with 236g of flush vs 95g for the model - so about 250% flush.

If I change the flushing to auto calculate and reduce the multiplier to 0.5 (as per Teaching Tech YouTube) - then this brings the flush down to 132g. and print time down to 22.5 hrs

If I add in quite a few purge-table leg components for flush-into - I can get the flush total down to 5.7g - which is only a little over 5% - vs the original 250%. However doing this will increase the total print time quite a bit up to about 32hrs.

The next challenge after this is seeing what can be done with those massive supports - could most of the support also be replaced with useful objects too I wonder?

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Interesting. But if the intent is to minimize plastic waste, aren’t you increasing total plastic being used?

Model without edits: 391g
with 50% reduction: 287g
With purge-table legs: 558g

While there is less poop, you’ve used 160g more filament to get the same outcome no?

Is there a way to have total filament kept at 287g, and reduce poop?

Correct - I am almost always increasing total plastic used - but using the saved waste plus additional plastic for something useful and that I was potentially going to print anyway.

In theory it would be possible to get the total additional plastic down lower with some additional different sized shapes or shapes that are wider or more complex at just the right heights where the big amounts of flush are needed.

Another way of getting the total amount used lower is by varying the amount of infill - so that there is more at the heights where flush is needed, rather than increasing the number of shapes. I guess I am sort of doing this by selecting shapes with top surfaces at different heights - so that they match where the most flush is.

I guess rather than building the top surface of the prime-table out of simple rectangles I could try and create it out of more complex interlocking shapes - that will therefore if printed in the right orientation may end up being more efficient in terms of less extra plastic used.


Slightly strange set of numbers for this print.

Original model 0.92g, with flush waste 13.19g - so over 1400% total filament 18.37g at 0.12 layer height
Decided to print a couple of ‘flush-into’ shoe horns with it - which normally take 26.22g at 0.2mm layer height.
New flush waste 0.8g, new total filament 50.64g - which is less than the total weight of the two ‘flush-into’ objects - bizarre must be to different layer heights or infill percentages or something.

Original model - which are tiny cruise ship propellors and motors (AZIPODS)

Flush-into object on its own - which is a shoe horn (tool for making it easier to get shoes on without undoing the laces) that I will put on makerworld.

Original model plus two copies of flush-into object.

Main print failed, and one of the shoe horns lifted off at one end due to bed adhesion problems - need to get some more Gold Textured plates as whilst I like the black ones - they are not great for long narrow or tiny models.

Made go use of the recently added ‘stop failed objects’ feature.

Anyway one of the shoe horns still worked ok and I am pretty please with it. Now on Makerworld. Colour doesn’t matter shoe horn

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Did some stock taking of filament over the last few days - and decided that some of the older brittle PLA (some of it over 6 years old) and the short lengths really needs to be used up. So decided to use them to try and getting the first small version of the prime table built.

Took two approaches, purposely coloured one of the prime table segments to force colour swaps, then flushed-into all of the rest.
The biggest issue with this approach is that when each filament change happens for a spool that is almost run out and where the end has gone past the first stage feeder - then the only way for the printer to colour switch is to purge out all of the filament in the PTFE tube, which is quite time consuming and wasteful.

The 2nd issue is for brittle filament it occasionally snaps in the AMS or tubes so things have to be taken apart.

The 2nd approach I took was to just colour the Purge-Table parts all white, and set all of the colours in the AMS channels white, then just place loads of small lengths of filament or odd rolls in, and occasionally swap them around and cut the filament etc. This approach was more reliable, but the colour swaps don’t look as good as they are more widely spaced.

Also tried sport mode for the first time for both options and it worked pretty well.

All that remains now is for some joiners to be printed tomorrow, plus possibly a few misc size sections.

Then once I have a small prime table I can then just extend the size by adding extra sections as I start doing more multi colour printing.

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First small complete version of purge table done.
AMS included for scale (plus proof that it is strong enough to be useful.
Design needs a few refinements - but overall I think it looks great.


Decided to see if there was any way I could incorporate the many old prime towers I have kept into the prime/waste table design.

Decided to take advantage of brim to hold the prime tower firmly at the bottom.

Bigger prime towers will be able support themselves, but smaller ones will need some help - (out of flush-into or waste filament objects).

Finally added hat to the top - with dovetail type joint to fit to other sections.

May not end up being practical - but thought it was worth a try.

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Taking things a bit too far maybe - but those benchy’s are quite strong

Should probably have positioned them slightly back - but though it would be nice if a bit of the top showed through.

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Purge Table Version 1 now on Makerworld Purge Waste Table V1 by Ukdavewood - MakerWorld
& Facebook Redirecting...

Plus quit a few more ‘prime tower’ leg sections made - not yet fixed properly - and probably too many now for the table with this size top.

Unfortunately I think prime towers etc. will be more useful for leg sections than table top sections due to the Brims.


Some better Prime Tower and Benchy holder component parts.

Test Prime tower holder hand modelled - but automated creation of a prime tower holder should be possible from analysing GCODE, or perhaps better still an STL of the prime tower that can then be used in Bambu Studio as a boolean object to make space for the prime tower to be incorporate into any ‘flush-into’ object.

The surrounding parts can probably be quite thin - as most of the strength should come from the prime tower or Benchy.

Also heat press purchased so that I can try out creating some of the Flat sheets out of melted 3d printer waste demonstrated by ‘Teaching Tech’ YouTube a few weeks ago. Those flat sheets if they work could make up a good deal of the middle of a table top for example.

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