Feeder skipping?

[ignace-de-keyser 0]

Hello,

I am having some trouble with printing at normal and higher speeds. When printing at these speeds ( >50mm/s), my feeder will often skip backwards, causing parts of the print to be underextruded. I am using an Ultimaker 2 and using PLA, printing at 230°, the layerheight does not seem to make a difference.

If I print at slow speeds, I don't experience any skips.

Most of the time I print Jorisstyle, I don't know if it has any influence.

I would appreciate your feedback,

with kind regards

Ignace De Keyser

 

[cleven 4]

When did you acquire your printer?

Most likely the PTFE is worn. remove and inspect the ptfe spacer for wear.

acquire a new one if possible. Also possibly upgrade or change your feeder system.

many topics regarding this issue:

http://umforum.ultimaker.com/index.php?/topic/7024-teflon-spacer-replacement/

 

[gr5 1,075]

What is your shell thickness? In "spiralize" (joris mode) if you ask for a .8mm (for example) shell it overextrudes 2X so that you get a .8mm wall with a .4mm nozzle. This is difficult to do so you have to print slower. Also what is your layer height. .2mm is double the flow as .1mm.

Anyway I would try raising the temp to 240C if you are skipping steps. Or lowering the sped of course.

Here is a test you can do to see if your printer is "normal" or defective. You must do the test at 230C for the test to have meaning. Anything below 6mm^3/sec I would consider failing. 8^3mm/sec and faster is a pass:

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

 

[ignace-de-keyser 0]

Did the test, feeder starts skipping at 4mm³/s.

 

[ignace-de-keyser 0]

I did the test again at 240° and now it only started skipping somewhere between 7 and 8mm³/s

 

[gr5 1,075]

1) You never answered the question about what your shell thickness was. Also what was layer height and print speed?

2) Please update your profile settings to indicate your country - it matters for support issues - under "location". Please also indicate in profile settings that you have a "UM2".

3) You can calculate mm^3/sec by multiplying 3 numbers together: layer height, print speed, nozzle width (.4mm) although in spiralize mode use shell thickness instead.

4) 4mm^3/s at 230C is indeed a somewhat faulty machine. It means you have to print at about half the speed that a good working machine is capable of. There are about 10 well known possible causes. Also recently there have been several faulty temperature probes so I would start there - these probes read 20 to 30C hotter (at 220C) than reality so you may be printing much cooler than you think. Try setting the nozzle temp to 110C. Wait a full minute then put a drop of water on the tip of the nozzle with your finger. It should quietly sizzle. If you look at it closely you should see tiny bubbles furiously boiling inside. Faulty machines won't do this until around 140C.

 

[ignace-de-keyser 0]

My apologies for not answering your question.

1)I was printing at layerheight of 0.1mm at 80mm/s with a shellthickness of 0.8mm.

2)I will update this soon™.

3) Would using a nozzle with a higher width allow to print faster with a shellthickness >0.4mm?

4) I will attempt this test as soon as my current prints finish.

Thank you for responding to my questions.

with kind regards,

Ignace De Keyser

EDIT:1mm changed to 0.1mm

 

[eldrick 58]

3) Would using a nozzle with a higher width allow to print faster with a shell thickness >0.4mm?

Yes, in principle. The ideal extrusion width should be in the range of 1.1-1.5x the nozzle size. This assumes that the rest of the machine is up to the job and well adjusted for the material.

Also, you should not have to extrude PLA at temps near 240C. If really you need to run that hot, something probably is obstructing extrusion or your temp sensor is off.

 

[gr5 1,075]

1mm at 80mm/s with a shellthickness of 0.8mm.

 

1mm? I hope you mean .1mm!

Did you do the math? All you have to do is multiply those 3 numbers together. Why do people have so much trouble with simple math?

Okay so .1 * 80 * .8 is 6.4mm^3/sec. That's faster than any print I've ever done. Except test prints. And you already demonstrated that you can't print over 4mm^3/sec at 230C so there's your problem.

I recommend you do 40mm/sec and you should be fine. 6mm^3/sec is kind of fast for anything you want to be "okay" quality. Much too fast for high quality prints.

EldRick has had problems printing at 220C and hotter but I have been fine. 220C is my most common printing temp and I commonly go up to 240C. I think that the temperatures for different printers vary more than I initially assumed.

 

[eldrick 58]

I think that the temperatures for different printers vary more than I initially assumed.

 

I suspect that also, but the lower temps that seem to work for me are in agreement with another printer. Last night I printed some complex gear/pulley parts for a belt-driven feeder at 218C / 20mm/s (DiamondAge PLA) - hotter temps caused stringing and globbing.

 

[ignace-de-keyser 0]

Thanks for the responses.

 

I didn't do the math :oops: .

looks like I will keep it at 40mm/s and/or tweak my temperature.

I'll do some research about using a nozzle with more width for spiralized mode.

 

[gr5 1,075]

I have a second UM2 nozzle. I had someone drill it out to .7mm for me. Joris himself has a larger nozzle diameter - I forget but I think .8mm maybe.