Would it be possible for the printer to calculate the remaining filament on the spool by using the RFID tag in the bambu Spool? The closer to the end of the spool, the more the RFID chip passes the reader per extruded meter of filament.
Full spool: outerdiameter is approx. 1 meter of filament on the perimiter.
Almost empty spool; only 30 cm on the perimiter. So much more counts on the RFID scanner per extruded meter of filament!
That’s how it already does that. It’s not exact but is a good estimate of remaining filament. If you check the AMS filament display, the fill level of each color is an estimation of remaining filament.
I think RFID chip does not do any measurement or calculations. Ppl describing how to trick AMS using the same reusable spool RFID tag for different spools by disabling synchronization.
Also if you use BL filament on a non BL printer and put it back to BL printer it still shows the amount it recorded the last time you used it on a BL printer. Not the actual length left on the spool.
BL spools have a standard length. After every print, Printer sends the amount of meters filament it extruded + purged to BL. this will be substracted from starting length.
If I understand your suggestion correctly, you’re proposing that the current filament content be stored on the spool?
I think there’s some confusion about what an RFID tag on a spool actually is. It’s more like a license plate than a chalkboard—it’s typically a read-only device with a fixed, unchangeable identifier.
While rewritable RFID tags do exist, they cost 3–5 times more than single-ID tags. The same applies to the reader in the AMS: incorporating an RFID reader/writer would increase the cost of that component by 3–5 times compared to a read-only version.
We have to ask: does this use case justify increasing the cost of each spool by $0.50 and potentially adding $10–$25 to the printer’s price? It’s worth noting that Bambu’s filament is already 30–60% more expensive than competitors. For example, it’s speculated that Sunlu (or was it eSun—I always confuse the two) may be one of their foundries. Their filament is often available for $13 overnight with free shipping from Amazon, compared to Bambu’s $18 plus shipping unless bought in bulk.
While I like the idea, that function might be better suited for the Slicer to include a data management function that tracks spool contents by individual spool—or, even more beneficially, for those running a print farm. This feature has been suggested and requested many times before. Unfortunately, I suspect the market is still too small to support this kind of “print management” tool.
But hey, we can dream, can’t we? 
The process as I understand it is exactly like OP proposed. Remaining filament is calculated using the filament distance through the AMS odometer and using how often it sees the RFID tag to estimate spool remaining filament diameter.
It does that measurement every time the AMS sees a new spool whether it has seen the spool before or not. It doesn’t get confused if filament gets used in other printers because it tests the spool whenever it detects a change.
I have used tags from empty spools on 3rd party filament spools and the remaining filament is calculated just as it does for Bambu spools and tracks filament remaining just as it does with Bambu spools.
Try it yourself and you’ll see. It calculates remaining filament every time it sees you insert a new spool. Do it while power is off where it can’t detect it and then it won’t notice the new spool or color or filament remaining.
BL spools have a standard weight - not length. If you check the sales pages spools are listed by kg. They happen to be near the same length for the most part because their weights per unit length are pretty close.
The length comes from the odometer in the AMS that just monitors how much filament goes past it by how many times the filament turns an instrumented wheel.
I jump in, but with a slightly different question.
The fill level is really inaccurate:
I think there are only 5 display levels, 4 you can see on the screenshot and and of course a brand new role.
Theoretically, whereever this information is stored, I should be quite precise. Maybe it is already exact in the background, but I can’t see the detailed information somewhere, can I? This would be really helpful, especially with this “tape at the end of the spool”-issue. In future version of Bambu slicer there might be also a warning when sending to printer like “spool 2 does not have enough filament left and a refill will be required”.
Any plans to improve this in future?
Why not give a precise value for the remaining filament? It could be because they can’t give you a precise value. The odometer is only so accurate. The windings aren’t uniform so the circumference measure will only be so accurate.
If the tape on end of spool wasn’t an issue, it used to be possible to just let a spool run out and the printer would move to the next.
If you need that kind of accuracy, get a cheap scale and weight your spools. The tare weight on an empty spool will be within a gram or two of a uniform weight and that should be plenty good for knowing how much filament remains.
You can easily overengineer stuff to get you data you rarely use yet adds costs to building the machine.
Well, I was more thinking about the real value based on the gcode. Of course, there might be a tolerance of 1-2%, but it could be easily precise enough… or did I missed anything?
I think the G-code is how the filament required for a print is calculated already. For that to be of value you need to know how much filament is on the spool to compare and know if you have enough. You still need to know how much filament is on a spool.
If the odometer/circumference value isn’t good enough, you can always weigh the spool of filament and subtract the weight of the spool, hub, and RFID strip. That weight will be good to the quality of the scales and how uniform the spool, hub, and RFID weights are (which are probably pretty uniform).
Also, I think if you keep an eye on that filament display, it has lots of levels to display remaining filament and not just five.
Thank you, but it is not, that I need a way to determine the level of filament. I have some printed tools, which are fine for me. I am just wondering, why this can’t be displayed better in Bambu studio, as the data value must exist already.
I don’t trust that thing when I get close to the end. I have an empty spool. I put the empty on my kitchen scale, tare. Put the full spool on, that’s how much you have left. As long as the spools are the same its extremely accurate like ~5g, which I suspect could be the difference between the slice and reality.
I would very much like to see the weight of the empty spool added to the data sticker on the side.
I’ve weighed empty PPA-CF spools (195 grams) so I can more accurately determine how much filament is remaining.
It’d be quite handy to have for every type of filament though.
I believe the new ams units can calculate remaing filament on a spool (review)
using a calculation based around the amount of times the rfid tags revolve