Bulldog Lite Skipping when doing "micro steps?"

[sapient24]

I got a makerfarm 12 inch. With rumba board. Got it running with a bulldog lite. I had have extruder problems, and clogs and such. After breaking 2 heat breakers on my hexagon hot end, I switched to E3D v6 with bowden setup so I can by spare parts if I break again. And I did break another heat break.

To the point, I notice that at slow speeds, such as when placing raft, the exturder skips. Often retracting the filament by quite a bit. I suspect this caused my last clog with my bowden tube.
I did a test, on my graphics display connected to my rumba board, I move 1mm on the extruder to push out filiment, and pinch it with my fingers so it has to pull on the filament harder. All is well. Then if i move the filament by .1mm and pinch, is starts skipping and retracting filiment. It did this without pinching.

Could this have anything to do with the current in the step motor driver?

[sapient24]

I greatly loosened the screws that tighten the drive weal on the extruder. It skipped less. So I pushed the drive weal so it had 0 pressure on the gear that drives the filament, and it didn't skip at all. So I kept increasing the current on my stepper motor driver up to .7 "Mila Amps?" Its not perfect, skips less, but its definitely tocking. The Makerfarm instructions say to not go above .5 because it can make the motors get hot. I don't want to break another part.

Not to go above .5 was for the other nema motors, but I got the bulldog lite extruder. So I didn't use a nema motor for extrusion. I suspect it can drink more juice, but I really don't want to break another part. What do you guys think?

[sapient24]

Seems to go up to 1.5-2v before its too much. Going that high doesn't help. the slightest tightness on the drive gear causes a tock when moving the filament .1mm. The only thing that changed increasing the current was a louder tock sound. I also tried to manage the tightness in the extruder. If its tight enough to move the filament, it skips.

I would like to point out that I have set up proper steps for this motor in the firmware.

[sapient24]

Apparently, to a thread I found, this behavior is normal if your only doing 1/16 steps with your motor, and printing at low speeds. So I replaced my stepper driver with a DRV 8825 which luckily I had in hand. Now the extruder is set to 1/32 steps. Re calibrated the extruder, and then tested. The damn extruder still can't pull filament in micro steps.
Could my Bulldog Lite be bad? This is very frustrating.

[zx81]

I bought a bulldog xl to use as a Bowden for 3mm filament I got nothing but problems with it .. I ended up ditching the Bowden and going back to direct drive it works great now.

As for stepper current mine didn't come with instructions I just set it the same as my other stepper motors (1.4a) .. I recently found info on the stepper motor used apparently 1a is the Max and 0.6 is recommended.

[sapient24]

I bought a bulldog xl to use as a Bowden for 3mm filament I got nothing but problems with it .. I ended up ditching the Bowden and going back to direct drive it works great now.

As for stepper current mine didn't come with instructions I just set it the same as my other stepper motors (1.4a) .. I recently found info on the stepper motor used apparently 1a is the Max and 0.6 is recommended.

Hmm. I couldn't find info on recommended current on my bulldog.

Does your bulldog still tock on micro stepps?

You see, I have been doing all these test without the bowden. Just pulling filament through out in open air. It cant handle a few micro steps. It manifested when I first got my printer, feeding directly, but I figured I was too close to bed, or other general extruder problems. I print PLA at low speeds without a heat bed. And this give me problems placing the brim and rafts because the're very slow speed.

The problem with bowden as I understand, is retraction. If it pulls up gooey plastic up the bowded tube, it will quickly cool down and clog up between the bowden and heat break. As long as you calibrate your retraction it should be fine.

This slow speed micro stepping issue comes with a retraction issue. It tries to move a step 1/16 or 1/32, then retracts like 30 degrees at times, clogging. When I was feeding directly, my first layers were terrible.

[sapient24]

I went max out .75 on my DRV 8824, not 8825, that I had. .75a doesn't cut it. I put back the 4988 driver, and cranked it up. Once I get to .8a, the motor starts skipping doing a normal extrude for a few mm.

Are you really able to take yours up to 1.5a? If I go higher then .85, my bulldog lite has a seizure. lol

I'm surprised the community doesn't have much to say on this. Would any of you like me to upload a video?

[zx81]

just checked my configuration file for my Smoothieboard (i set current in my firmware) and all my steppers are set to 1a I think i turned them down a little. when it's higher they would constantly buzz, they were originally set to 1.68 (as per max rating on the datasheets for the stepper motors) then turned down to 1.4 then finally set to 1a where there is no noise and it still has plenty of holding torque. I always set the Bulldog extruder to the same settings.

the drivers on the board are the A9482, when I was using ramps I used the A9488's and later the DRV8825's all of them were set to 16 microsteps.

does it skip stepps when there is no filament in it ?

[printbus]

sapient24 - a bunch of considerations for you...

The Bulldog Lite has no gearing; available motor torque is going to be less than geared approaches like the Bulldog XL or Greg's Wade. This is why the Bulldog Lite is only available for 1.75mm filament. A direct drive motor doesn't have enough torque for 3mm. That's how close things are.

No mention has been made of acceleration settings. It could be that Marlin is trying to ramp up the extruder speed too fast, and this leads to skipping at the start. Try lowering the extruder acceleration way down and see if that makes a difference.

Have you tried a higher hot end temperature? It could be that the temperature you're using is on the low side, and the filament is simply hard to extrude.

Related to the temperature, it could be that the combination of your print speed, nozzle size, and layer height requires a higher extrusion volume rate than your hot end can keep up with. See what happens at a slower print speed on the rafts.

If the problem is mainly retraction, have you tried a slower retraction speed to see if that makes a difference?

Make sure your filament feed is as smooth as can be, including the filament spool being able to unwind easily. Any motor energy spent having to pull or tug filament off the spool is energy not available for pushing filament into the extruder.

You'll likely want to run the extruder stepper driver set to the highest current your set up can handle. The stepper driver adjustment is done in volts, set to a value that is the desired max motor current divided by 2.5. In other words, setting the voltage adjustment to 0.5v equates to a motor current limit of 0.5v x 2.5 or 1.25 amp. The bulldog extruder still uses a NEMA motor; it's just included as part of the bulldog. Things to consider here are the current limit of the motor used in the Bulldog (IDK what that is), the running temperature of the motor, and the operating temperature of your stepper motor driver.

The issue with retraction on a Bowden set up is that the filament in the Bowden tube has a hysteresis that acts somewhat like a spring. This can make it very hard to get retraction working properly, and often leads to print quality issues. I've heard many people say they don't even try to use retraction on a Bowden setup.

The amount of available torque goes down with microstepping. So, changing from 1/16 to 1/32 microstepping would have reduced the torque you had available. I can't speak for how substantial the difference is - I just know that the most torque is available with no microstepping, and it is reduced as microstepping goes up. It's a tradeoff - microstepping gives you more step resolution, but at a cost of less torque.

[sapient24]

zx81
No it's not skipping without filament.

printbus
Thanks for your consideration
I have all you have mentioned, except for acceleration settings. I will look into that.

Higher print speed and temperature will help yes. As I was using when I was feeding directly. As I calibrated my printer, I slowed down my speed and temperature, and ended up getting very nice pieces. No heat bed, 50mm/s default speed, .4mm nozel, .4mm layer width, .152mm layer hight, 195C on nozzle. Just problems places rafts where it was tocking and retracting, leaving gaps in between lines of filament placed. As soon as things got up to speed, it was all fine. Before bowden, It didn't give me problems clogging.

My test have been done with nothing going into a the hot end, just filament being pushed in open air. As soon as there is enough tightness in the extruder to actually move the filament, it can't handle moving it in increments of .1mm.

I now understand why geared extruder assemblies are used.

When I first read about microstepping in other forums, people said that increasing microstepping would help with this issue. Upon further reading, I find that its not necessarily true, that it make little difference, or even provides less torque as you have mentioned.

When I get home, I'm going to play with hotter temperatures and speed to gain some experience with my bowden set up.

At first I figured, if my Makerbot Replicator 2 can print at such low speeds, my i3v should be able to do as well. The Replicator 2 doesn't have a geared set up for extrusion. It has to be for other factors then.