Itty Bitty Double Extruder

[RobH2]

Ok, you can eliminate a clogged bolt.

What about the amps you are driving your stepper with? Have you adjusted the pot on the board? Maybe it's too low and the stepper is not able to generate enough torque. Turn that pot up just a tiny bit clockwise and see if you notice a difference. Don't turn it too high or your stepper will run too hot. It probably should never need to be above 30-40% of its range starting from all the way counter-clockwise. Of course, each machine is a bit different.

What I do is turn it all the way down. I heat up the extruder and pull the filament out. Then I set a manual extrude of about 200mm at a slow rate, say 2mm/s. As the stepper is turning you'll be able to hold it still and overcome it. Very slowly turn it up until you can't hold it still and it feels really strong. Doing that I found that at a 25% increase clockwise from zero that my motors were strong. Also, having printed a lot since then, I've felt my motors and they do not get hot so I know I'm probably in a good place.

[adamfilip]

ive been turning my digi pots down, a bit as the extruder steppers have been kinda hot i have them set to 125 in Marlin
they are strong. i wasnt able to hold it

[RobH2]

From what I've read, they can run pretty darn hot, as high as 200C without damaging them. That's hard to believe and I wouldn't do it for long but what if you turned them back up temporarily, say to about 40% and see if the skipping goes away? If it does, then they are just too low. If not, then you can eliminate that too.

You say that you've been turning them down as they've run too hot. At the same time, you are getting skipping. On the surface it would appear that the turning down and led to the skipping. Maybe not, but I'd try to overdrive the steppers for a little bit and see what happens. Again, I've read that it won't hurt them to overdrive them for a short time. Verify that on your own though. I don't want to hear that I made you ruin your steppers. But, I really do think you'll be ok if you don't go higher than 50% on the pots.

[clough42]

i cleaned the hobbed bolt twice and it looks good.
when i pull out the filament and look at the teeth marks the pattern is obvious

Ahh...repeating defect. What's the period? Does it match the circumference of the bolt? That would indicate that it is related to the rotation of the bolt.

I wonder if that pulley is striking the head of the other hobbed bolt once per revolution.

If it isn't running straight on the bolt head, that could happen. If your belts are extremely tight, it could contribute as well. There's only about a mm of clearance. If your spacer is upside down or you got the 1mm and 2mm spacers swapped on either bolt, that could spell trouble.

[clough42]

From what I've read, they can run pretty darn hot, as high as 200C without damaging them. That's hard to believe and I wouldn't do it for long but what if you turned them back up temporarily, say to about 40% and see if the skipping goes away? If it does, then they are just too low. If not, then you can eliminate that too.

You say that you've been turning them down as they've run too hot. At the same time, you are getting skipping. On the surface it would appear that the turning down and led to the skipping. Maybe not, but I'd try to overdrive the steppers for a little bit and see what happens. Again, I've read that it won't hurt them to overdrive them for a short time. Verify that on your own though. I don't want to hear that I made you ruin your steppers. But, I really do think you'll be ok if you don't go higher than 50% on the pots.

Uhh...I think 200C is unrealistic. Most stepper motors are rated for "80C temperature rise" which I have understood to mean 100C. I personally wouldn't run them over 80C.

But in this application, you should be trying to keep them under 60C for sure and better under 50C or they will melt the extruder.

[adamfilip]

Im pretty sure its matching the hobbed bolt. once per rev
the bolt heads are not touching the other gears
no rubbing

once i get a few prints done on the working side i will take the hobbed bolt out for a better look.
BTW stepper is running at 52 degrees

[RobH2]

Uhh...I think 200C is unrealistic. Most stepper motors are rated for "80C temperature rise" which I have understood to mean 100C. I personally wouldn't run them over 80C.

But in this application, you should be trying to keep them under 60C for sure and better under 50C or they will melt the extruder.

That's just what I read in the specs for a stepper from a manufacturer. All I was saying was to drive them a little harder to see if the print succeeded and that if they got pretty hot for a few minutes that they'd likely be OK based on the manufacturers claim that they could run at 200C. I was not implying that was a smart thing to do. We've had many discussions here talking about trimming pots down to get cooler motors.

[clough42]

That's just what I read in the specs for a stepper from a manufacturer. All I was saying was to drive them a little harder to see if the print succeeded and that if they got pretty hot for a few minutes that they'd likely be OK based on the manufacturers claim that they could run at 200C. I was not implying that was a smart thing to do. We've had many discussions here talking about trimming pots down to get cooler motors.

No worries. I'm just thinking about people looking for help with Google who drop into the middle of threads like this and sometimes lack that additional context.

[rhonal89]

Can someone tell me. Am ordering http://www.reprapdiscount.com/hotend...otend-set.html and my current i3v 12 I have the 1.75mm and I would love to have the 3mm hexagon also. I would like to know if that combination will work well. Also will I'll be able to print right on top of the other like use 1.75mm filament and then 3mm filament for support or vise versa. Or should I stick with 1.75mm hexagon. One reason is I heard that 3mm filaments prints faster than the 1.75 filament. So I would love one side also for fast printing and the other side for better looking prints.

[sniffle]

Then answer is no, both have to be either 1.75 or 3mm.

There are only 1 set numbers in marlin to control the feed rate of both extruders. Until both extruders can be operated independently they must match