Jump to content
Ultimaker Community of 3D Printing Experts
Sign in to follow this  
closedcircuit

Lots of stringing

Recommended Posts

Over the past three weeks, I started having a lot of stringing on every piece I print (see picture) and I don't seem to be able to find a solution.

Stringing

Here is what I've tried so far:

  • [*]Lowering the Temp. from 230° to 220° but then, the filament stops coming out after about 10-15min and the print fails[*]Speeding up the print to 75mm/s but then I get underextrusion, or the filament stops coming out after a little while[*]Applying the atomic method (several times)[*]Re-leveling the bed[*]Changing the filament (all my filaments come from UM)

I've used the following settings for the print in the picture shown above, :

  • [*]Printer: UM2[*]Filament: Pearl White from UM[*]Temp. 230°C[*]Bed 60°[*]Speed 50mm/s x 75% = 37.5mm/s[*]Layer height 0.06[*]Shell thickness 2[*]Fill density 100 (they are small pieces and need to be strong)[*]Brim on[*]Cooling fan enabled[*]Combing enabled

The other settings are the same as "Factory Default".

I'm not sure where to go from there and any suggestion would be very much appreciated.

Thanks

Phil

Share this post


Link to post
Share on other sites

I didn't see a mention of retraction being enabled or not, that would be the first thing to check. It's a checkbox under the "Basic" tab in full settings mode. Also check the expert settings for retraction and see that "Minimum travel" hasn't been set to something weird.

After slicing the object, switch to layer view and look for little blue lines going straight up from the print, these indicate retractions.

 

Share this post


Link to post
Share on other sites

Hi Robert - Thanks for your help. Retraction is enabled and I have the following settings in the Expert menu:

Minimum travel: 1.5

Enable combing: Ticked

Minimal extrusion before retracting: 0.02

z hop when retracting: 0.0

I can see the little blue lines going up after slicing.

 

Share this post


Link to post
Share on other sites

On my brand new UM2, 4.5mm (the default) wasn't enough. It needed more like 5.5 or 6mm. 5.5mm was enough for me. After I secured the bowden better (a month or two later) I was able to reduce that to 4.5mm. Try increasing your retraction a bit.

Also for some filaments I have to lower the temp to 190C to eliminate stringing but that may mean printing even slower. Although usually 210C is plenty cool enough. Also make sure your travel speed is fast - 150mm/sec minimum - try 250mm/sec. This helps break the thread/string. Moving at 250mm/sec is not a problem for pretty much any 3d printer out there - it's the acceleration where the UM is so impressive.

 

Share this post


Link to post
Share on other sites

Thank you all for your help.

Things are getting worse as I don't seem to be able to print at 210°C anymore. Nothing comes out despite numerous atomic cleanups and ensuring that the outside of the head is clean.

Is it possible that these problems are caused by some debris is stuck in the Nozzle? If so, what should I do if the Atomic method doesn't help?

I have a ultrasonic bath at home. Is it worth a try, and if so, is there a tutorial somewhere that shows how to dismantle the Nozzle?

Cheers

 

Share this post


Link to post
Share on other sites

Things are getting worse as I don't seem to be able to print at 210°C anymore

 

This is a common problem on the UM2. I suggest you go over to this thread and print this test piece at 230C which will test out your thermostat, extruder path, feeder, bowden, filament, everything at once. It is *critical* you test at 230C even if your problems are at 210C.

http://umforum.ultimaker.com/index.php?/topic/4586-can-your-um2-printer-achieve-10mm3s-test-it-here/

 

Share this post


Link to post
Share on other sites

No, it's unlikely to be related to nozzle problems. You've got too much filament coming out, rather than not enough. You need to make sure it's really retracting; that the plastic you have laid down has space to fit, and time to cool; keep the head pressure as low as possible (i.e., print thin layers and/or slowly) and make the moves as quickly as possible.

1) Make sure retraction is actually happening. Do you hear the double chirp of the retractions, and if you hold the filament lightly between your fingers can you feel it moving out and back in, each time? I'd turn off 'enable combing', and set the minimum extrusion amount to zero, to make sure retraction really happens.

2) On the printer, set retraction to 5.5mm at 35mm/s.

3) Set the travel speed as high as possible - you should be able to do at least 250mm/s. This will reduce the time spent moving, and so the time for oozing.

4) It looks like the columns are printing solely out of concentric passes, due to the thick shell? Try reducing the flow a little bit so that there's no chance of excess plastic building up in a limited space. If it does, it will get on the outside of the nozzle.

5) Make sure all your fans are running properly, and be sure to set a minimum layer time of at least 7 seconds or more, so that the plastic has time to cool.

 

Share this post


Link to post
Share on other sites

Re-reading the thread that gr5 pointed me to, I un-thightened the four screws at the top of the head and ran the cylinder test. It looks alright, but I'm not sure that I understand why I've got holes at around 5mm3/s and not after?

As the cylinder looked quite good, I re-launched the print that was causing me troubles to see if the untightening of the screws solved the problem. I'll let you know how it goes.

@illuminarti: Thanks so much for taking the time to highlight all these points. I'll retry the print with the heavy stringing using your suggestions once the current print is done (probably tomorrow).

Cylinder 1

Gaps at 5mm3 / s

 

Share this post


Link to post
Share on other sites

The problem at 5mm³/s was probably just a random skip due to something about the filament... maybe it got caught up on the spool, or had a slight irregularity in it or something. The fact that it recovered ok, and compelted the test shows that there's nothing to worry about.

 

Share this post


Link to post
Share on other sites

I don't understand about loosening screws. Did I say to loosen screws? The 4 thumbscrews should be tight. The bowden itself can be locked down better if you want but isn't mandatory. I think I suggested a longer retraction distance (more than 4.5mm - maybe 6mm is right for you).

 

Share this post


Link to post
Share on other sites

Several people mentioned loosening the four thumbscrews in the thread which you kindly provided above. This really worked for me in terms of solving my second issue (being unable to print at 210 and hence not being able to implement your suggestion of lowering temperature). In fact I'm about 12hours into a fairly long print at 210 and it hasn't failed yet.

The stringing issue is still there and I will be implementing your and illumination other recommendations over the weekend.

Thanks again!

Share this post


Link to post
Share on other sites

The thumbscrews need to be snug, but not overtight. Depending on what position the Bowden and collet are in before you tighten the screws, you can end up putting too much stress on the end of the Bowden and causing more problems that way.

Also, I've seen a printer where the thumbscrews were tightened so much during assembly that the linear bearings in the head deformed and started making some very weird noises as the head moved.

 

Share this post


Link to post
Share on other sites

I've made several more tests and stringing is getting better (although it still there), but I now have a new issue. The layers don't seem to be aligned anymore the final result looks "wobbly" (see pictures).

All the settings are the same as in my first post, except:

 

  • Retraction is now 5.5mm and 35mm/s
  • Travel speed = 250mm/s
  • Speed = 75mm/s

PAL 6870

PAL 6869

 

Share this post


Link to post
Share on other sites

Just from a very outside view (as I do not have an UM2), you may try to make a mark with a pen on each pulley and an according mark on the rod, print something and check if the marks still correspond after the print has been shifted (just abort the print).

 

Share this post


Link to post
Share on other sites

The higher speeds moves are causing skipped steps, it looks like. It might be a physical slipping of a pulley... most likely on the short belts. Or perhaps some extra frictions somewhere, such as a belt or pulley rubbing on the frame, or not sitting quite straight in the pulley.

Power the printer off, and try moving the head by hand - pushing on both sliding blocks on an axis at the same time is best. Feel for any resistance; both axes should be equally easy to move. Have you lubricated the printer lately? A few drops of sewing machine oil on the axes and cross rods may help.

 

Share this post


Link to post
Share on other sites

You might only need to tighten all the pulleys. Tighten the heck out of them. The hex screw should twist a bit. There are 5 per axis on the UM2 (6 on the UM Original). The most important 2 are the one on the motor and the other one on the short belt.

 

Share this post


Link to post
Share on other sites

Technically there are 5 on one axis, 6 on the other, on an Ultimaker². At the top, the y short belt goes around a double-sided pulley with a single screw in it, that also functions as one of the 4 long belt pulleys. The x short belt has its own pulleys, separate from the 4 for the long belts.

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!