I picked up a big lot of filament that has a tendency to tangle and snag, which means that it stops feeding\extruding without triggering my runout sensor. So my printer (Bambu) just continues printing nothing in mid air.
Can anyone recommend a device that will simply cut the filament if it get’s stressed so that the runout will sense it and stop automatically?
For example, something that runs the filament over a spring loaded roller and when it’s pulled to tight it triggers a cutter that just chops the filament?
I’m a model maker rather than a device maker, so my experience is form rather than function, and I’d much rather support someone who’s already put in the effort to design one than re-invent the wheel.
My understanding is that some 3D printers have a mechanism which detects if filament is actually moving, rather than merely present — is that available as an option for your printer?
A brute force approach would be to simply turn a chair upside down on a table (think cleaning up at the end of the school day) and then put the problematic roll and an empty roll on different legs and re-spool from one to the other — doesn’t take that long.
Rather than that, my recommendation would be to make or purchase one of the mechanisms for re-spooling a roll using a drill for power.
I’m more looking for something that’s spring loaded rather than electical, or at least standalone. I’m using a Bambu so integrating anything into the main board will be difficult.
I hope the requirement you left out was by mistake. ie something to hold the filament after it is cut so that it doesn’t tangle. Personally, I’ve never run into a tangle which wasn’t human caused by failing to hold the end of the filament when swapping and feed it into one of the side slots on the roll.
But as others mentioned, filament movement sensors can be purchased off the shelf. Here is a video of one being added to an Elegoo Centauri Carbon 3DP. Reddit - The heart of the internet
I’m not knocking these devices, they seem to me like the kind of thing that should be coming as standard, so it’s great the somebody is making them.
The problem is that I’m looking for a standalone device. Something that runs completely independently of my printer rather than something that interfaces with the printer and pauses it.
I’m using a Bambu, and they’re locking down the ecosystem to prevent external apps from sending instructions to the hardware. You can monitor the hardware but not stop\start\pause it. Some people have found workarounds for some of it, but they could vanish with the next firmware upgrade.
What I’m ideally looking for is something with a bearing or wheel on a spring that the filament is looped over. If the filament gets too tight the spring squishes down and triggers a cutting mechanism. If the filament is cut the runout sensor will trigger and the printer will stop itself.
I’ve got a basic idea of the mechanism and could probably sketch it out, but I’m not engineering minded so I’d struggle to make one myself. I’m primarily a model maker, so it’s form over function most of the time.
I pointed that out not as instructions for you to follow but for an example of an existing device which could be used to do what you’d like. It has an electronic signal for each the end of filament action and the filament motion stoppage signal. Whatever cutting device you were thinking could be controlled by an Arduino and a servo or motor driver and operated as needed.
A mechanical system could work but it takes a good amount of force to cut filament and I’m not sure you’ll see that kind of force from the extruder motor/gears before the filament in the extruder gearing start stripping.
If you are the only one using your filament then the best way forward while this cutting machine/mechanism is flushed out is to stop letting your filament get tangled. It’s rolled onto the spool from the inside/bottom out and is not tangled originally. It only gets tangled by someone letting go of the filament end and letting it fall back to the spool and get under other loose loops. Also, try not to let any of the loops on the spool become loose because while you’re not looping/knotting anything, you might end up with a loop of filament under others and cause enough friction when pulled it doesn’t pull out during printing.
I work at a school and the first thing I go over and repeat over and over is not to let the filament end go during filament changes and repackaging.
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Whatever cutting device you were thinking could be controlled by an Arduino and a servo or motor driver and operated as needed.
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Unless someone is selling one as a kit, I’m afraid that I wouldn’t even know where to start with any of that.
to stop letting your filament get tangled. It’s rolled onto the spool from the inside/bottom out and is not tangled originally. It only gets tangled by someone letting go of the filament end and letting it fall back to the spool and get under other loose loops.
I’m have several roles from Reality (always white, for some reason) that have arrived with crossed over loops hidden in part way down the filament. They’ve run perfectly well for hours then suddenly I hear this tick tick tick sound and come in to find that the spool has a loop crossed over and it’s tight as a wire.
I’ve had this happen with a couple of different printers with different spool arrangements, including both direct drive and boden. Nothing that I’m doing, the loops were crossed over inside the spool.
You’d need a mechanism like a gun, where a relatively large force is held back by a small notch, and pressure from tension on the filament is like pulling the trigger and releases the force required to cut the filament. I’m not designing such a thing though!
You could overkill it with the pneumatic shears, 12v pneumatic solenoid and microswitch and make what you are interested in.
Run the filament over the microswitch so that the tension triggers the relay. The relay triggers the shears. You just need a 12vdc power supply and air compressor.
surly it would be easier just to have a spring loaded blade at a shallow angle so the stepper motor just drags the filament across it, like a potato peeler making a shallow slice till it cuts right through?
Put a loop at the end of the trigger where the cheese goes, put a razor blade (maybe a chisel blade may be better) on the ‘killzone’ of the arm and move the bail arm slightly to one side so it does not interfere with the filament or blade..
Then pass the filament under the arm and across the trigger. And then arrange it in-line with the filament path so that a hard knot in the spool tightens the filament and triggers the trap.
As a separate reply.. why focus on cutting the filament? If you already have a ‘filament present’ sensor that triggers a line (high or low) to signal a filament failure.
Why not have a simple microswitch with a roller bail arm that monitors tension on the filament and closes when it gets too great? Then you send a direct electrical signal to stop the print instead of cutting the filament. This might allow some problems to be resolved without having to re-feed the spool in again.
It would involve opening the Bambu, finding the filament sensor and tapping out the wires for it. But would be a better solution in many ways.
I’m looking for mechanical solution rather than an electrical one. I’m primarily a model maker, I understand mechanisms, electronic is all Greek to me.
Shipping is currently limited to the US and Canada.
If you’re hoping someone will make one for you that’s a big ask and then they would have to ship to where ever you are in the world… Now that you know the name of a commercial version of what you are asking for, have you tried finding any disassembly or design details which might allow you to take it to a local machinist or maker space and see if someone locally can make it for you?
Personally I still think an electronic version would be easier to make but it still requires a number of skill sets to pull off.
