Hey guys, I’m looking for a bit of help with my Prusa i3. I’m getting striations in the walls of all prints, and it’s happening in all directions. It is particularly visible on single walled prints.
A couple details about my printer:
It’s a Prusa i3 kit from Ooznest.
Bulldog Lite Extruder
Hexagon Hotend
RAMPS 1.4
Allegro driver step sticks
So far, i’'ve done the following to try and sort it:
Ensured all belts on all axes are perfectly aligned and musically tensioned.
Tuning the Pot on the stepper driver (I started by going all the way to the highest setting where is skipped, then backed off slightly, and very slowly decreased it during printing. At no point before is starting skipping at the low end did it look to improve the striations.
I’ve completely disassembled the extruder and hotend, cleaned them all out and reassembled.
I changed the Esteps during the print (it was calibrated to 104.8 but i tried changing down to 100 and up to 110)
Swapped the stepper driver out with another axis
Switched from Slic3r to Cura with the same test model for GCode
Despite all these changes, I cannot seem to resolve the issue. I have learned that its is almost certainly related to the extruder somehow, because the frequency of the striations changes with the Esteps, but they are still there.
Any help really is appreciated at this point, the only thing i haven’t tried is swapping out the RAMPS and Mega all together, but I don’t have one handy to do it with.
Its too even to be an over extrusion/pressure buildup. Are you missing any teeth on the extruder stepper? Watch it very carefully and see if any teeth are not grabbing onto the large gear at all. Missing a tooth or two every revolution could account for the apparent under extrusion at regular intervals.
Few questions, are you on a Wade’s geared extruder? Noticed all prints are single wall, spiral. Is this present in supported prints. Are you on imperial or metric pitch lead screws?
I think it’s microstepping errors in the extruder motor. I’ve encountered this before. The trimpot setting is too low. Set it by measuring Vref and setting the current near or at the current rating of the motor.
@mike_mackenzie-griev no, it doesn’t match the belt teeth and its along all axes l. Also, if i increase the esteps then it happens more regularly.
@Ryan_Hescock_Stanos its a direct drove Bulldog Lite extruder, so no teeth not to grab.
@Brandon_Satterfield it happens on all prints but is most obvious on single wall prints. My z height is m8 threads, but the z axis isn’t moving when this happens.
@Thomas_Sanladerer it has mech end stop auto levelling but I don’t use it, the imperfections in the mechanics are greater than the imperfections in my bed so prints come out worse when using it. So I don’t.
@Marcelino_Bernardo this was the original advice I had elsewhere and the first thing I tried to alter but it hasn’t worked. I can’t find the data sheet for the bulldog lite to set it with a meter so I tried by eye. I’ll do more digging to find the vref it should be at and grab a multimeter.
@Matt_Burnett it happens with multiplier of 1 and every setting after calibration (<1)
If anyone knows where to get the bulldog lite data sheet that would help!
@Christian_Bianchini I have done both. My calibrated ESteps is 104.8 but I’ve tried changing that both up and down and it made not difference.
Also made sure the bed is very level, its printing perfect objects in every way, except these imperfections.
I’m starting to think more and more its the VRef, but i just can’t find any actual details on the stepper used by RRD on this Bulldog or what the VRef should be. And i get the feeling that the sweet spot is so narrow, that doing it by eye is too difficult!
@James_Cadman the after sales support from reprapdiscount appears to be boo-boo.
Rearding specifications - when you have to search user forums to find specifications for a product there is something really wrong. And I only find recommended current for XL. Sorry.
How hard can it be to realise that pretty much every customer need to know the basic specifications and update the product page…
Edit: sorry for the rant. I’'ll go and get coffee now.
Hey @korpx at least it’s not just me then! I’ll have a crack at the current recommended for the XL, because I’m sure that the stepper itself is identical, its just got the extra gearbox attached to it.
Apologies I wasn’t clear enough. I have tried tweaking the Vref but because i couldn’t find a spec for the extruder to use a meter, I tried (on other advice) going it by eye.
I had a 40mmx100mm single shell model i started printing and every 5mm or so in Z height I changed tweaked the pot. Each time in very very small increments.
I couldn’t find any spot where it changed (either getting better or worse) and i took it right from being too low and skipping all the way up to too high and skipping.
Do you have any advice for a VRef i should try with my multimeter, and any advice on measuring it?
According to the wiki, Vref=1.6*A for the stepstick which limits the maximum setting to only 1A. It’s measured between the trimpot wiper and ground. For safety, I like to measure with the +12V supply off and the Arduino powered only from the USB. Most steppers used for 3D printers are rated for at least 1A. So, I’m not sure why it skipped when you turned the pot to maximum. I suggest repeating it and measuring the voltage this time around. I’ve also read that some stepper controllers from China use different sense resistors than what the boards normally come with. This is actually a bad practice unless they tell you that they changed it. You can also directly measure the current to the motors, but I haven’t done this myself.
Hey all - I’ve just whipped out the multi meter and set the VRef to 0.4 which is about the best starting point I could find without having any details of this extruder’s spec.
Just about the run a 40x10 calibration print and I’ll see how it goes!
@Moshe_Kashani I don’t think it’s this because it isn’t just in one direction and its consistent across all directions.
