Continuous vertical lines on shell
-
@nophead said in Continuous vertical lines on shell:
@diamondback How many teeth on your pulleys?
If it isn't related to belt pitch then perhaps motor steps.
Both idler and pulley have 20 teeth on both axis.
-
I have found the solution. You need to use teeth idlers instead of flat.
-
@petrzmax said in Continuous vertical lines on shell:
I have found the solution. You need to use teeth idlers instead of flat.
Glad this worked for you
I'm in the middle of switching my idler to a toothed one as well, need to fabricate a custom screw first though, the idler is 5mm ID and the attachment is an M4 screw.... -
@diamondback I'm in fabricating phase aswell. The research I made told me that it should make ghosting less visible and get rid of this lines. Unfortunatelly i have not standard derlin idlers so I will need to print idlers. I hope they will be good quality. If they will not I will need to buy metal ones and redesigns some parts which I'm trying to avoid.
-
@petrzmax This is how I first solved the problem: http://hydraraptor.blogspot.com/2011/06/half-belt-hack.html
For Mendel90 I just put a half twist in the return path of the belt because toothed idlers were not commonly available then.
-
@nophead Thanks for the idea! I will try to give it a go, but I'm on CoreXY and ther might be a problem with twisting them. Never tried twisting them before
-
@petrzmax Not sure it will work on core XY because the you can only put the twist in a stretch that doesn't contract to a short length, ideally constant length like above. I am working on an H-bot design and concluded I needed toothed idlers.
-
Ok, got my idler changed now to the correct toothed one, but that didn't do much I'm afraid...
So back to extrusion related issue I guess. Anything I can try to adjust software wise before taking the Titan apart?Maybe someone can take a look at my config.g in the first post and see if there are any obvious issues
-
If you print something with different outside dimensions do you ever get diagonal lines? I can't see how the extruder can create vertically aligned striations.
How many shells are you using. With single wall I sometimes see striations from the infill pattern through the wall.
-
I use F608 bearings for idlers in my corexy printer with the toothed side of the belts riding on them. I get no such vertical ridges. Maybe you need to use larger diameter pulleys. F608s are 22 mm in diameter.
-
@nophead said in Continuous vertical lines on shell:
If you print something with different outside dimensions do you ever get diagonal lines? I can't see how the extruder can create vertically aligned striations.
How many shells are you using. With single wall I sometimes see striations from the infill pattern through the wall.
I'm usually using 3 shells at .4mm, the lines are always perfectly vertical, sometimes there are diagonal lines on top of that, not sure where those comes from.
-
@diamondback What happens on diagonal sides?
If it was somehow a flow rate variability synchronised between layers I would expect it to look exactly the same.
If it is due to variations in linear speed due to motors or belts I would expect the pitch to increase on a diagonal because each axis is moving slower for the same linear speed.
-
@nophead said in Continuous vertical lines on shell:
@diamondback What happens on diagonal sides?
If it was somehow a flow rate variability synchronised between layers I would expect it to look exactly the same.
If it is due to variations in linear speed due to motors or belts I would expect the pitch to increase on a diagonal because each axis is moving slower for the same linear speed.
Just tested, straight vs diagonal do differ quite a lot. I'm currently test printing something without micro step interpolation.
-
@diamondback Let us know about the results!
-
Nope, no changes... Tried different micro stepping for both axis and the extruder, with and without interpolation, nothing...
Is it possible that my motors are just crap? (or not well selected for the task at hand)
I'm running these steppers on both axis and the E3D Pancake on the Titan.
(Used to be one of the ACT ones as well but I significantly reduced the X carriage weight a while ago and switched to that small stepper then) -
@diamondback said in Continuous vertical lines on shell:
Is it possible that my motors are just crap?
Sort of, yes. How tight are your belts? The reason I ask is that as a general rule, stepper motor bearings aren't realy designed to take the high lateral loading that we tend to apply. There is a real temptation to apply the highest belt tension that we think we can get away with, or that the belt manufacturer recommends. However, with this sort of loading, it is eminently possible that some degree of "stiction" (for want of a better word) of the shaft can occur. It may not be much but it could be enough that the requirement for higher torque, coupled with the lower torque available for partial full steps (due to micro-stepping) might mean that the motor will have a tendency to jump to the nearest full step. i.e. small (say single digit) micro steps might not necessary translate into any physical movement of the motor.
This is more a theory on part than any sort of scientific fact. Although, when I first built my printer, I was a bit too enthusiastic with the belt tension and had to use very high motor currents to get any sort of reasonable speed.
But it would be easy enough to slacken the belt tension a bit just to see if makes any difference. Worth a try I'd have thought.
-
@deckingman So do You think that it's worth trying higher motor current? Which should fix this problem on slower moves?
-
@deckingman said in Continuous vertical lines on shell:
@diamondback said in Continuous vertical lines on shell:
Is it possible that my motors are just crap?
Sort of, yes. How tight are your belts? The reason I ask is that as a general rule, stepper motor bearings aren't realy designed to take the high lateral loading that we tend to apply. There is a real temptation to apply the highest belt tension that we think we can get away with, or that the belt manufacturer recommends. However, with this sort of loading, it is eminently possible that some degree of "stiction" (for want of a better word) of the shaft can occur. It may not be much but it could be enough that the requirement for higher torque, coupled with the lower torque available for partial full steps (due to micro-stepping) might mean that the motor will have a tendency to jump to the nearest full step. i.e. small (say single digit) micro steps might not necessary translate into any physical movement of the motor.
This is more a theory on part than any sort of scientific fact. Although, when I first built my printer, I was a bit too enthusiastic with the belt tension and had to use very high motor currents to get any sort of reasonable speed.
But it would be easy enough to slacken the belt tension a bit just to see if makes any difference. Worth a try I'd have thought.
Just tested this, I made the belts as loose as possible while still not skipping teeth and while that added a bunch of ringing as expected, it didn't really affect the lines...
@petrzmax said in Continuous vertical lines on shell:
@deckingman So do You think that it's worth trying higher motor current? Which should fix this problem on slower moves?
I actually had them fairly high (housing got a bit too toasty probably) I lowered it a bit yesterday so that the housing is only handwarm...
I think I'll try different printing speeds next...
-
@diamondback said in Continuous vertical lines on shell:
.......................Just tested this, I made the belts as loose as possible while still not skipping teeth and while that added a bunch of ringing as expected, it didn't really affect the lines...
Oh well, it was worth a try..........(and bang goes that theory
). -
@deckingman said in Continuous vertical lines on shell:
coupled with the lower torque available for partial full steps (due to micro-stepping) might mean that the motor will have a tendency to jump to the nearest full step. i.e. small (say single digit) micro steps might not necessary translate into any physical movement of the motor.
This is a common fallacy / misconception that is all over the web. The torque available when microstepping is the same as full steps because the vector sum of the two coil currents is always the same. I.e. the peak current when only one coil is on is sqrt(2) times the current when both coils are on. So at any stop position the holding torque is the same. It isn't less at intermediate microstep positions.
It is true that the torque is always proportional to displacement from the rest position, so if you only move a very small step the torque applied is very low and may not overcome stiction. However that is only relevant at the start. If the the load does not move the displacement quickly increases and so does torque until it does move.
Once moving at constant speed the rotor lags the rest position by an amount that generates enough torque to overcome the dynamic friction. If that lag exceeds two full steps the motors stalls because the torque is sinusoidal so reaches a maximum. During acceleration it lags more and during deceleration it leads.
