Hello guys! I’m starting to test/run my pellet 3D printer, it uses a extrusion screw (external big driver) as others but a secondary screw to feed the shredded plastic (I’ve tried different methods but since the recicled pla starts getting stuck on the funel that’s the best option was to have a controlled auxilixar feeder). Once that’s clearefied…
I need to send paralel signals to the adicional motor but… I need to be able to adjust the rotation distance of each one of them.
Cannot help with klipper advise since I am new to klipper but I have experience with screw extruders from a while back, and what those machines do is they have a series of sensors that measure the level in the feed funnel. If it drops below a certain low level the secondary screw starts to feed pellets till the level reaches the high level.
If you do not use sensors to tell the main control unit the level in the first stage, you risk over feeding it when you are not extruding so much. Vice versa if you are extruding at a high rate you risk starving the extruder of new material which is fatal for the screw. The screw has to be surrounded with molten plastic at all times, this is what keeps the screw central and stops it from scraping the extruder inner walls.
So what you are looking at is some way to know the level in the feed funnel and convert this to a signal that klipper might use to start and stop the secondary stepper.
Basically the process of feeding is related to the extruder screw but it is a separate process which is not linked to the instructions that klipper gives to the screw stepper. It is a process that is a result of the level sensors in the funnel.
I hope this helps some klipper specialists with giving you some hints as to how to hook this up and what types of macros you need to write for this to work.
I suppose it will have a short piece of code with functions in it but as I said I am not a klipper expert yet.
If I were to hard-wire this I would simply use a small dc motor and power supply. Two level sensors and wire it so that the motor kicks in when the bottom sensor looses signal and it stops when the top sensor gives a signal. This way the level would always stay between the two sensors but you do not control the feed rate, it is simply on and off. This has a potential problem that the feed-rate of the funnel screw could be lower then what the extruder screw is consuming.
Thank for the idea, I’ve thought in something like this, my biggest problem is that the end of the feeding screw is very close to the start of the extruder screw, maybe a fiber optical industrial sensor will work (have used in other machines), but I’m not sure…
I brought this screw extruder kit (vertical one) in china and tried many funel designs, but since the opening is not very big and the triturated material is very bad at sliding it didn’t work. Then i got the ideia of using another screw for feeding the main screw. It worked well but now i need a way to control them separately. Since I don’t have much time, I need a way to send signals to two motors but with different rotation distances. I known its not the best option but is what I need now
Immediate thought I have is that the raw material is too varied in size and shape. For good effective feeding it is of utmost importance that the pellets, or granules, are of even shape and size. Especially those long fibrous strands will easily form a blockage that nothing will get past. A feed-screw will just pile more and more material into the blockage but not clear it I think.
I have seen feed systems use a vibration needle to agitate the granules, but those were real granules like the kind of raw plastics you buy from the big chemical suppliers. Those are rounded off (squarish) pellets of 2.5 mm across and between 2.5 to 3 mm long. Since they are rounded off due to the way they make them, they slide more easily then your shards from the grinder.
I would think your could try to grind them more, even use an office shredder with a slightly bigger motor on it, and try to get these pieces more uniform.
I like the idea though, it looks a bit bigger then what I am trying but in principle the same.
Second thought is that since you experienced the feeding problem, you now restricted the opening even more by adding a screw which no doubt has a jacket inside that feed funnel to stabilize the system and give a support mount to the screw motor. I think if you take the screw feed off, look at widening and smoothing the feed funnel, and at the same time control the pellet size better, you might get away with a gravity feed using a vibration needle or even some vibration device on the outside of the funnel itself. A vibration device would not need any input signals and could run at a constant speed or with a timer going on and off.
Very interesting project, makes me want to drop everything else I do at the moment and kick start my own again
Let us know what you are thinking of these suggestions?
Kind regards
Kees
So you have 2 motors that you want to spin in parallel, but you want one to turn more than the other?
If it’s a fixed ratio, like 1:2, you can just lie in the stepper config that one stepper has a shorter rotation distance than the other. Then if you command both steppers to move that axis they will move in that ratio. You can do this directly with the gear_ratio setting.
How are you configuring the two steppers now? Are they [extruder_stepper]s synced to the extruder?
Hello Sineos, thaks for the info. I’m just in doubt about how and whre to write the extruder I want to sync
[extruder_stepper my_extra_stepper]
extruder: # The extruder this stepper is synchronized to. If this is set to an # empty string then the stepper will not be synchronized to an # extruder. This parameter must be provided. #step_pin: #dir_pin: #enable_pin: #microsteps: #rotation_distance:
See the “stepper” section for the definition of the above
parameters.
can you show me how it should be written?
do I need to use SYNC_EXTRUDER_MOTION if this function above already have a sync option?
So you have 2 motors that you want to spin in parallel, but you want one to turn more than the other?
Yes!
How are you configuring the two steppers now? Are they [extruder_stepper] s synced to the extruder?
Today one is running on a external driver and the other on a A4988 in the board.
If it’s a fixed ratio, like 1:2, you can just lie in the stepper config that one stepper has a shorter rotation distance than the other. Then if you command both steppers to move that axis they will move in that ratio. You can do this directly with the gear_ratio setting.
I’m not sure what is missing.
Just fill out the [extruder_stepper] as per the documentation and provide the main extruder as the stepper to be synced to, e.g.
[extruder_stepper my_extra_stepper]
extruder: extruder
step_pin: # enter the respective value
dir_pin: # enter the respective value
enable_pin: # enter the respective value
microsteps: # enter the respective value
rotation_distance: # enter the respective value
You can also leave extruder: extruder empty and use the commands given above to dynamically turn on/off the synchronization
Thank you Sineos! it was so symple that I can’t belive it hehe
Another question… is there a way to adjust rotation distance with a multiplier ? (so I can ajust in percentage… something like send a macro with ROTATION_DISTANCE_MULTIPLIER= 0.9 ?
