1

i purchased an extra extruder to ease the pull on my main extruder.

I connected both stepper motors in parallel (I cut the 4 wires to the extruder and attached in parallel, the remote stepper motor. Both have the same gear size (12mm). To my surprise (I am new to this 3d printing as i got my first DIY printer just a couple of weeks ago) the new estruder was pushing the filament fast, but the old extruder with nozzle was pushing the filament slower than usual, as i saw the print that was having under extrusion in the result.

Can someone help me with how I can fix this issue? I would like to know if its ok to connect 2 steppers in parallel with the same driver or is that the reason i dont have enough power to energize 2 motors?

Thanks for all

1 Like
2

You can, but there are cautions to make them work right together. Same wire length to each. Each has to be the same stepper type/part number to insure they both will draw the same current. You have to adjust the current up on the driver circuit as now you have twice the load. If one is doing more work (most likely the one driving the plastic into the extruder because extruder pressures can be high) it is going to load down and require more current because it is doing more work. This will unbalance the system. It’s actually better to parallel the input signals to multiple drive chips and drive the steppers separately. This is easier if your chips are the plug in type.

3

I would agree with this reply as it’s more to the point, … Why two?

4

You shouldn’t be needing two extruders to push filament. The only time dual extruders is typically used is to push two filament types or colours into one hotend. Either one at a time or mixing like the diamond hotend or similar. I’m not understanding why you are needing to ease the one extruder?

5

If the motors are off and the hot end in on the good temperature you can easily push the filament tree the hot end if that is not the case you temperature is not good or you filament bumping to something… You can check if you have a clean hotel and the extruder above the hotel you must see from the extruder true the hot end And another thing you can not find and adjust two stepper for a 3d printer that 100% the same then you must have a stepper with encoder and a joined servo drive and that cost 1000s of euro

6

IMHO you shouldn’t (have to) use 2 motors to drive 1 piece of filament. There is something stuck in the hotend if it requires more force then 1 motor can deliver.

Z-axis motors are sometimes put in series, sometimes parallel. In series the current trough them is the same, so torque is the same. Parallel, voltage is the same, so theoreticaly RPM would be the same but these are steppers so there isnt realy a V/rpm thing… I’d put them in series. (And I did, for my Z-axis)

Try cleaning the hotend / checking if PTFE tube (if any) isn’t deformed or replace it, and try using a geared extruder with a single good motor (4+kg*cm).
Maybe play with the idler tension on the filament, to little causes slipping, to much causes breaking and blocking.

7

I was putting an extra extruder not to push the filament into the nozzle, but to pull the filament from the spool and not have the extruder have to work hard to pull from the filament roll. With a slack in between the two extruders, so that there is always the same slack between the two extruders. The PTFE tube seems clear and everything works perfectly without my added extruder whose purpose was only to pull from the filament hub and let a slack before the main filament.

Thank you for the information and I didnt realize there were different types of NEMA 17 motors, which I just found out and learning something new every day. Happy Holidays!

8

Joint servo drive seems very interesting, but the cost of it are a deterrent for my pocket. Thanks for the knowledge though, it is something new I learnt. Thanks!

9

Should not be necessary, I have 3 printers running, all direct feed and never had a problem with this in the last 6 years of running them.

10

Ah, interesting idea. I thought you had 2 motors pushing filament. Actually, I manually do what you second motor does, pull filament from the roll once in a while so there is slack and the extruder doesn’t pull itself upwards when the spool doesn’t want to uncoil.

With the 2 motors in series, that should work, just like a Z axis. If it doesn’t, feed the step/dir and enable signals to 2 motor drivers that each drive their own motor.

Hmmz… Some sort of motorized filament spool holder… (Meh, I’ll keep my current setup for now. But the idea is nice).

(NEMA17 is the physical size / separation of mounting holes. I also found out recently)

11

My filament sometimes gets/got tangled, then this might be useful. Manually untangling works too. A good spool holder helps a lot to prevent tangles too.

12

I agree that having 2 motors pushing filament isn’t the best idea. If they aren’t pushing filament in exactly the same amount, at some point the slack would either get tight or too much slack, both dangers with prints needing long filament. I did not know you needed same length cable and thank you for teaching me that. I still dont understand the lenght of cable requirement but I will do some research now and learn some more today.

I think my problem is best solved by making a smooth ball-bearing spool holder, which I want to design and print on my 3d printer so my worry and problem is resolved. btw i am also wanting to make a bigger 3d printer but my only concern is I don’t know how to calibrate the x,y and z axis. I heard of some way to change firmware, compile and upload but I never did that before and searching how to do it.

13

Hi

You will need to recalibrate your Extruder feed regardless of why it is different.

Using some software like Pronterface you can ask the printer to extruder 10mm of filament. Do this and then measure how much filament you actually get. Probably best if you cut the filament level with a face such as the end of your PTFE tubing first as it makes it easier to measure. Worth noting that you do this cold and with the filament removed from the nozzle.

After you have worked out the shortage or extra filament you then need to adjust the extruder steps by the same ratio. e.g. 8.5mm when asking for 10mm gives;

8.5/10 = 0.85

Then multiple your extruder steps by this amount and set the new value. The steps value will most likely be around ~80 to ~110 and you can set it in the menu system or by updating your firmware - sometime doing it by menu doesn’t get saved for later.

There are some good YouTube videos on calibration that are worth watching.

Cheers

Dave

14
15

I’m thinking a small loop of slack that can hit a switch when it gets tighter. The switch runs power to a DC motor (no stepper driver required).
spool_motor.png

16

You should check out the bunker smart filament storage system. Sounds like what you’re talking about with ‘feeding’ the filament from the spool . It keeps track of filament usage and other features… it’s on Kickstarter currently. Bunker - Your 3D Printer's Perfect Companion by 3D Printing Systems — Kickstarter Tho it looks like it didn’t get full funding.

17

There’s nothing fundamentally wrong with push-pull extruder setups, it’s a trick regularly used in the welding world to negate the friction in the bowden tube and allow less clamping pressure on soft wire/filament to prevent distortion causing issues elsewhere. Quad driven rollers are often used on single drive units too for wire over 1-1.2mm
However, your stepper driver should be current clamping, so wiring them in parrallel will give them only half the current each, if you have enough voltage overhead (steppers are usually a very low nominal voltage and your driver uses all the extra to maintain current draw when microstepping and similar), then wiring the two in series shouldn’t hurt performance anywhere near as much.
You should set your tension so the reel extruder always slips first. In fact ideally you should just run a pair of smooth driven wheels on them that are 1-2% larger than the nozzle one, and just set them soft enough to slip slightly, this way they’ll always be helping the nozzle extruder without causing any damage to the wire before the feed tubes.