stuttering steppers & 3mm filament

Hi,

I recently switched to a Bulldog Extruder as the hobbed bolt of my Wade always grooved my 3mm filament - my Bulldog worked fine for some time but the motor stutters now ALL the time.

I tried following:
# changed the resistance on the Pololu back and forth
# tried a brand-new Pololu
# checked if my temperature readings are ok (200°C PLA) + checked if my firmware settings of the sensor is correct
# different hot ends
# changed pressure of filament against filament screw of Bulldog
# wiring of cables is correct

Unfortunately I do have a LOT of 3mm filament laying around so I do not want so switch to 1,75mm - life would be much easyer with 1,75 as I think my problem is cased by a far to high pressure for extruding 3mm into 0,4mm.

...even when I extrude e.g. at 60mm/min (Repetier Host) the stepper of my Bulldog stutters...

Edited 2 time(s). Last edit at 07/02/2014 05:50PM by RepRapper_1987.

how much current are you putting into it? the stepper motor on the bulldog can take up to 1amp

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Quote
thejollygrimreaper
how much current are you putting into it? the stepper motor on the bulldog can take up to 1amp

I changed from far to low till too much Ampere by turning the resistor on the Pololu:
It ranges from no extrusion to extrusion with some stuttering till full stuttering

...I really think that 3mm filament is not the best choice I made- it causes so much pressure and force on the hobbed wheel and against the 0,4mm tip....

Anybody got an idea what could be wrong?
...would need to print very urgently but my printer won't let me do my work...

Edited 1 time(s). Last edit at 07/04/2014 08:29AM by RepRapper_1987.

I am not a expert with PLA but some of the new stuff as a very high temperature if it is this a fairly new role of filament I've heard of a manufacturer that suggests 235 c plus check to make sure it is PLA is what it says I've heard of some roles marked wrong and actually it was ABS. I probably would run new motor wires just to make sure that there is not a half broken wire inside insulation. When you changed extruders from the wades to the bulldog did you change your firmware steps per millimeter you definitely need to do this if you did not you are trying to push the filament way too fast. Check the firmware just to make sure that somehow it hasn't changed

Edited 2 time(s). Last edit at 07/04/2014 09:11AM by cnc dick.

Quote
cnc dick
I am not a expert with PLA but some of the new stuff as a very high temperature if it is this a fairly new role of filament I've heard of a manufacturer that suggests 235 c plus check to make sure it is PLA is what it says I've heard of some roles marked wrong and actually it was ABS. I probably would run new motor wires just to make sure that there is not a half broken wire inside insulation. When you changed extruders from the wades to the bulldog did you change your firmware steps per millimeter you definitely need to do this if you did not you are trying to push the filament way too fast. Check the firmware just to make sure that somehow it hasn't changed

I've done several successfull prints with my Bulldog: I changed the steps per mm and calibrated the extrusion width - therefore definitely not on the side of the firmware.

It's definitely PLA as it is much "stiffer" than ABS and extrudes pretty good - except the fact that the stepper motor is hopping/stuttering...

Edited 1 time(s). Last edit at 07/04/2014 10:07AM by RepRapper_1987.

Do you remember if the problem started when you changed filament like I said there's a lot of different filaments out there and some are quite different with temperature. When at a problem like that arises I always look to what I've changed first. And depending on the filament I've heard some people print up to 235 C for certain types of PLA try to think back is it when you put a new spool on or a different spool. Do you have something that wipes the filament as it comes off the spool to protect against dust and debris getting into the hot end you might have the clean your hot end

Edited 2 time(s). Last edit at 07/04/2014 02:10PM by cnc dick.

What about speed? How fast do you print? I don't know exactly, what torque this motor has, but usualy Nema17 has 1, 5-4, 4 kg*cm. And (in my experience) for direct extruders it isn't enough for extrude 3mm filament faster 20-30mm/min.

Edited 3 time(s). Last edit at 07/04/2014 05:06PM by Eugie_A_Deef.

Quote
Eugie_A_Deef
What about speed? How fast do you print? I don't know exactly, what torque this motor has, but usualy Nema17 has 1, 5-4, 4 kg*cm. And (in my experience) for direct extruders it isn't enough for extrude 3mm filament faster 20-30mm/min.

On the Bulldog there's a smaller version of the Nema as we usually use for our XYZ axis.
I usually print at max. 65mm/s for infill and sometimes go down to 20mm/s at the outer perimeter -BUT it also occures at that very low speed!
The PLA spool I printed several successful (and good quality) prints was not changed in the meantime: also no dimensional error on the spool could be found - I also have a sponge to prevent dust coming into the extruder.

What I'll try today:
# Try to extrude PLA with a much higher temperature (235 instead of 210) even if the extrusion looks pretty well at 210.
# clean and inspect the hobbed wheel again
# If this does not help I'll change the standard Nema which came with the Bulldog (short version) and try the Nema I had on my Wade extruder before ("standard Nema")

Additional to that I decided to use 1,75mm filament in the future (I ordered a 1,75mm extruder) as I guess that all my problems are caused by far to much pressure on the tip of the hotend: the 3mm material has nearly 3 times more area than the 1,75mm (7,07mm2 vs. 2,4mm2 = 2,93).


######
EDIT:
# changing the stepper was not possible: the gear is directy attached/milled onto the shaft of the stepper
# hobbed bolt was clean and in perfect condition
# first the extruder worked well but after some time when extruding at e.g. 260°C the stepper started stuttering again

Edited 4 time(s). Last edit at 07/05/2014 02:31PM by RepRapper_1987.

It seems I was wrong in my previous post. Ok, let's think. I know four causes for extruder motor stuttering (black magic is not counted).
1) Torque is too low. (Unlikely: if you use common Bulldog's model with gearbox then you have gear ratio 6:1, and it should be more than enough, even with relatively weak motor. It's more probably that hobbed bolt would start to groove filament than to stutter).
2) Nozzle obstruction. (Unlikely: you tried different hot ends, didn't you?)
3) Temperature is incorrect, too low (Unlikely: see below. Besides, PLA doesn't have a glass transition stage and either flows or not flows. You would immediately notice problem with temperature control.)
4) Polulu overheat. This needs more explanations
Polulu module's chip has an overheat protection and it's very difficult to cool it well. Without special cooling systems you reach the overheat temperature when amperage is ~1am. It sounds VERY-VERY like а motor stutter, but realy it isn't а stutter - just overheat protection is working.
So I think you need to check Рolulu cooling. Maybe you need also to turn the amperage potentiometer down a bit.

P.S. Pardon for my bad English, it isn't my mother language.

Edited 4 time(s). Last edit at 07/05/2014 05:05PM by Eugie_A_Deef.

Quote
Eugie_A_Deef
P.S. Pardon for my bad English, it isn't my mother language.

Mine is German, so I wouldn't be able to see a mistake

I tried different Pololus and also different stepper motors - I'm currently on the way to install a brand new Ramps board which I had purchased about a month ago (because of the attached display which the Sanguinololu doesn't have).

...will be able to test the RepRap in about an hour and let you know - currently I guess I destroyed something on the (Sanguninololu) electronic board as EVERY stepper in combination with EVERY Polulu stuttered.

Quote
RepRapper_1987
...will be able to test the RepRap in about an hour and let you know - currently I guess I destroyed something on the (Sanguninololu) electronic board as EVERY stepper in combination with EVERY Polulu stuttered.

I don't think so. If you broke controllers output pin, step motor wouldn't work at all. There isn't analog electronic parts on Sanguinolulu between controller and Polulu module for demonstrate such symptoms. I'm pretty sure that this is a Polulu problem. I've seen this.
In my opinion, using Polulu in RepRap projects is a forced decision. Unfortunately, Polulu has several bad problem when you use it with Nema17 motors

Edited 6 time(s). Last edit at 07/05/2014 05:54PM by Eugie_A_Deef.

Quote
Eugie_A_Deef
I don't think so. If you broke controllers output leg, step motor wouldn't work at all. There isn't analog electronic parts on Sanguinolulu for demonstrate such vague symptoms. I'm pretty sure that it's Polulu problem. I've seen similar. (

...and you're right: it's not a Sanguinololu/Ramps problem as I do have the stuttering also with the new board.
But it's also not a Pololu problem: I've tested the 4th Pololu now and it's not getting better...

Edited 1 time(s). Last edit at 07/05/2014 05:54PM by RepRapper_1987.

Ok! Turn Polulu potentiometer down to the bitter end, and then turn it backward to quarter of a full turn and try again.
Do you have a multimeter? Can you check resistance in a motor winding?

Quote
Eugie_A_Deef
Ok! Turn Polulu potentiometer down to the bitter end, and then turn it backward to quarter of a full turn and try again.
Do you have a multimeter? Can you check resistance in a motor winding?

Here the resistances (see attached picture)!

So, If I'm thinking right, operating amperage is ~1amps. This corresponds to the specs. So, don't turn Polulu potentiometer more than half-turn from mininum.
Do you have a fan on your board for Polulu cooling? If not just do a simple test - take any fan, start extrusion and direct the airflow to Polulu. If you will see changes, then my version is right. If you will see no changes then we will think more.

#######
EDIT
# If it isn't a Polulu problem, I'm afraid that it's a mechanical failure of the motor or gear box.

Edited 6 time(s). Last edit at 07/05/2014 07:44PM by Eugie_A_Deef.

Quote
Eugie_A_Deef
So, If I'm thinking right, operating amperage is ~1amps. This corresponds to the specs. So, don't turn Polulu potentiometer more than half-turn from mininum.
Do you have a fan on your board for Polulu cooling? If not just do a simple test - take any fan, start extrusion and direct the airflow to Polulu. If you will see changes, then my version is right. If you will see no changes then we will think more.

#######
EDIT
# If it isn't a Polulu problem, I'm afraid that it's a mechanical failure of the motor or gear box.

Had a fan (60mm) which was orientated directly on the Pololus BUT with the new Ramps board laying open under the printer I did the following:

Blew onto the E Pololu and everything printed fine - stopped and the stepper begun to stutter.
As far as I can say now is that i need a huge fan just for my E Pololu + a much bigger heatsink and I should be able to print again - many thanks Eugie_A_Deef and others who helped me.

Up to now I have microstepping enabled also on my E axis (that's why I have 495 steps in the firmware) - would it be better if reducing microstepping from 1/32 to 1/16 to let my Pololu stay cooler?

Edited 1 time(s). Last edit at 07/05/2014 07:55PM by RepRapper_1987.

Keep on a max microstep. In my experience, Polulu willn't stay cooler if you reduce the microstep. It seems that his chip's temerature significantly depends from amperage only. If the motor will stutter again, just reduce amperage a bit.
Good luck

Edited 8 time(s). Last edit at 07/05/2014 09:33PM by Eugie_A_Deef.

Quote
Eugie_A_Deef
Keep on a max microstep. In my experience, Polulu willn't stay cooler if you reduce the microstep. It seems that his chip's temerature significantly depends from amperage only. If the motor will stutter again, just reduce amperage a bit.
Good luck

Was able to print for about half an hour (50% of the parts I would need urgently) without any problem- unfortunately the print failed too even if I point a 60mm fan directy onto the Pololu heatsink as the Pololu gets too hot again.

I assume everthing is caused on the fact that a "standard" Nema 17 has 3,8 Ohm resistance and the one on the Bulldog has 2,8 Ohm.
Not sure about that but as P = U*U/R there is a slight difference in power from old to the new Nema stepper which leads to the heat probem on the Pololu. (?)

I usually use step motors with resistanсe of winding 1.68Ohm. So I don't think that 2.8Ohm is a great problem to Polulu. The spec says, that Buldog's motor recommended amperage is ~0.6Amph and 1Amph is max amperage.
Try to search a right amperage. Turn off a fan, turn on power on motor. Just power on... m-m-m... I don't know how this mode called in English... "hold mode", maybe... when you keep the coils powered but do not turn the motor. After a while you will hear a distinctive rhithmic tapping - it's working a termal protection, and it's your "stutters" . Take a dieleictic screwdriver (I use a flat sharpened toothpick for this ) and carefully turn amperage potentiometer. If the frequency of tapping become more, then amperage is increasing, if less - amperage is decreasing. Achieve for no tapping, or very infrequent. It will a right amperage for your stepmotor. You still need a fan for protect Polulu from environment temperature fluctuation, but it must work well.

Edited 9 time(s). Last edit at 07/08/2014 10:06AM by Eugie_A_Deef.

Quote
Eugie_A_Deef
Try to search a right amperage. Turn off a fan, turn on power on motor. Just power on... m-m-m... I don't know how this mode called in English... "hold mode", maybe... when you keep the coils powered but do not turn the motor. After a while you will hear a distinctive rhithmic tapping - it's working a termal protection, and it's your "stutters" . Take a dieleictic screwdriver (I use a flat sharpened toothpick for this ) and carefully turn amperage potentiometer. If the frequency of tapping become more, then amperage is increasing, if less - amperage is decreasing. Achieve for no tapping, or very infrequent. It will a right amperage for your stepmotor. You still need a fan for protect Polulu from environment temperature fluctuation, but it must work well.

I did this several times with all my Pololus I have here at home - extruded about 300mm of material without a problem just 15 minutes ago but when it comes to print the stepper starts stuttering on the first layer. I point a 60mm fan directly onto the heatsink and tried different settings in mid print but with no success: the heatsink is hot as hell no matter which setting I go for and my stepper always stutters

...will have a beer (or a dozen) to keep me calm today

#####
EDIT:
As I have a stepper motor with a 14:1 gearbox (Bulldog: 5:1) at home and I tried to move it instead: the Pololo keeps cool even at much higher speeds I could ever turn on the stepper of the Bulldog!!

Edited 2 time(s). Last edit at 07/08/2014 04:22PM by RepRapper_1987.

Hm... I'm afraid, I haven't more thinks now. I'm sorry :-( If I will have an idea, will wright about. What the motor model Buldog has? Exactly, if it possible. If I will can find specs, maybe, I will get ideas...

Edited 2 time(s). Last edit at 07/09/2014 05:39AM by Eugie_A_Deef.

Quote
Eugie_A_Deef
Hm... I'm afraid, I haven't more thinks now. I'm sorry :-( If I will have an idea, will wright about. What the motor model Buldog has? Exactly, if it possible. If I will can find specs, maybe, I will get ideas...

Unfortunately there was no label on the stepper of the Bulldog.

As you can see on the picture I replaced the 5:1 geared stepper motor with a 14:1 I had in stock at home: now the Pololu does not even reach 50 degrees and everything works perfect again! *yeah*
Could not switch the stepper motor without the gearbox as the main gear is directly attached to the stepper shaft.
Already ordered some gearbox steppers (5:1 and 19:1) from china as I need my 14:1 stepper for my DLP printer...

Edited 1 time(s). Last edit at 07/09/2014 02:56PM by RepRapper_1987.

It's strange. Maybe, native Bulldog's stepmotor realy just failured. Resistance on winding is normal for Polulu, but maybe when stepmotor is heating, resistance increase. Once I saw something like this. Suddenly, stepmotor started behave like Polulu is broke, and suddenly started to work normally. I couldn't find a cause, although disassembled the motor and board to one screw All wires and contacts and Polululu module was well. It is that I called "black magic".

Edited 2 time(s). Last edit at 07/10/2014 06:48AM by Eugie_A_Deef.