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Printing with PP

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Posted · Printing with PP

Hello dear Ultimaker Community,

 

I come in need of your help, a customer of mine chose polypropylene as material to print his prototypes, and we have been having trouble printing with it, we are getting very inconsistent results these past weeks, we work mainly with treed and smartfil polypropylene, we gave ultimaker pp a shot too but it didn't give us the results we need.

 

My client has been printing polypropylene with consistent results on a Ultimaker 3 Extended, it was all good, then he ordered an ultimaker S5 for the need to print bigger models, and an Ultimaker 3 Extended for the need of more production capacity, but in the past few weeks all hell broke lose when the S5 have not been able to give us one single good result, while the Ultimaker 3 has been giving us what seems almost like random results.

 

The main reason of failure is under extrusion like en the picture attached below.

 

Another problem is some kind of shininess to the print that is present from time to time, aesthetically it is not really a problem, but most of the time when the print is shiny like that the print itself isn't strong enough and breaks, the most bizarre part of the phenomena is the fact that it can happen many times in a single print, alternating between portions where the print is mate and not shiny, and parts where it is shiny, i am unable to take a proper photo right now to show the anomaly, temperature does not seem to be the culprit, i will try to get some better photos tomorrow and post em.

 

What we tried so far to solve the problem:

 

1- Adjust the lever screw to adjust tension on the filament: the results were not satisfying, either the filament got too shewed or slipped, so we followed this guide https://ultimaker.com/en/resources/36111-material-is-ground-down-by-the-feeder, we did not see much of a change

 

2- Play with temperature: 

 

3-Adjust retraction prime from 35 to 10, and even lower retraction speed, no noticeable effect.

 

4- try with different material:

   a- we tried different providers for polypropylene, we didn't have any better success with other providers material, we usually go for Smartfill, we tried Treed and didn't get any better results, we tried Ultimaker's pp which gave us a very different result, it was way softer and it had a shiny look to it, shiny in a different way, other filaments when showed the shiny aspect were totally shiny all arround on the portions where it would show, ultimaker's was like spots here and there, we also tried a material called Fortis, a kind of propylene with white pigments, somehow it prints better, but from time to time we experience the under extrusion problem.

   b- we tried also printing with a variety with other materials, we tried Carbon, Nylon, Cpe, and a few other materials, and they print from the first try, the only other material we had problems with is TPU, is it because of the flexibility of the material?

 

Right now, i did so many tests, but i am willing to retake all those tests to find the reason, i will try to get a better camera to take new pictures and show the problems.

 

 

IMG_20190603_152231.jpg

IMG_20190603_152153.jpg

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Posted · Printing with PP

I feel it usually takes 100 prints in a particular material to get good at it and I've only done about 7 PP prints.  But I've done many high temp materials.

 

Firstly it's usually good to enclose the top and front of the printer for high temp materials like PP.  without doing this you will get weak layer adhesion and prints will break easily along layer lines.  Also for the same reason lower the fan speed a lot - to about 1/3 the power (which may be 1% or may be 40% fan speed depending).  Play with the fan speed until you figure out where the power starts to drop.  On my UM3 it starts to drop around 10%.  In other words 10% and 100% are identical but 9% is around 90% power and 3% is about right for high temp materials.  On my S5 30% and 100% are the same speed and 10% is good for high temp materials.  You should figure out what's a good reduced fan setting for each of your printers individually.

 

Now the more serious problem - underextrusion so severe it sometimes stops printing (last photo above).

 

Some materials clog easily especially if you print "too slow".  So sometimes thicker layers (like say 0.2mm height) is less likely to clog than 0.1 because you get more plastic flowing so the plastic stays hot for less time.

 

Check your feeder - with the material in question (PP this time) insert the filament half way down the bowden, then energize the stepper with "move material", then pull and fight that feeder.  The feeder on a UM3 or S5 should be able to pull with about 15 pounds (8kg) force.  Anything less than 10 pounds is a defective feeder and needs to be fixed right away.

 

If the feeder is fine, in addition to trying thicker layers, try a different core.  The nozzle may have some kind of issue.

 

I probably wouldn't mess with nozzle temperature as UM is somewhat reasonable at making profiles with the right temperature (but I wouldn't trust them 100%).

 

Here's a list of causes of underextrusion for UM3.

CAUSES FOR UNDEREXTRUSION ON UM3 AND HOW TO TEST FOR THEM AND REMEDY THEM

As far as underextrusion causes - there's just so damn many.  none of the issues seem to cause more than 20% of problems so you need to know the top 5 issues to cover 75% of the possibilities and 1/4 people still won't have the right issue.  Some of the top issues:
1) Print slower and hotter!  Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers) and .4mm nozzle:
20mm/sec at 200C
30mm/sec at 210C
40mm/sec at 225C
50mm/sec at 240C
The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion.  Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp.  But don't go over 240C with PLA.

Note that your "print speed" may be 40mm/sec but it may be printing infill at 80mm/sec so CHECK ALL SPEEDS.

2) Line Width larger than nozzle.  In cura 3.X search in settings for all line widths.  If any of them are larger than the nozzle diameter this can cause underextrusion.  There are 8 of these in cura 3.2.1.

3) Curved filament at end of spool - if you are past half way on spool, try a fresh spool as a test.

4) curved angle feeding into feeder - put the filament on the floor -makes a MASSIVE difference.

5) Bad core.  Try a different core.  It could be clogged, or something more complex like the temp sensor in the core.

5a) clogged nozzle - the number one most suspected problem of course.  Sometimes a grain of sand gets in there but that's more obvious (it just won't print).  Atomic method (cold pull) is the cure - from the menu do a few cold pulls.  The result should be filament that is the exact shape of the interior of the nozzle including the tiny passage to the tip of the nozzle.  If it doesn't look like that you need to pull at a colder temperature.  You can do it manually instead of through the menu if it's not working right but learn through the menu initially.  95C is roughly the correct "cold" temperature for PLA.  Higher temps for other filaments. Simpler cold pull (3dsolex cores only - doesn't work on ultimaker cores because you can't remove the nozzle): https://www.youtube.com/watch?v=u07m3HTNyEg


5b) Temp Sensor bad - even the good ones vary by +/- 5C and bad ones can be any amount off - they usually read high and a working sensor can (rarely) fail high slowly over time.  Meaning the sensor thinks you are at 220C but actually you are at 170C.  At 170C the plastic is so viscous it can barely get out of the nozzle.  You can verify your temp sensor using this simple video at youtube - on you tube search for this: mrZbX-SfftU


6) feeder spring issues - too tight, too loose.  You want the tension such that you can clearly see the diamond pattern biting into the filament.  You want to see at least 2 columns of diamonds.  4 columns is too much.  You usually want the tension in the center.

7) Other feeder issues, one of the nuts holding UM2 and UM3 together often interferes with the feeder motor tilting it enough so that it still works but not very well.  Other things that tilt the feeder motor, sleeve misaligned so it doesn't get a good grip.  Gunk clogging the mechanism in there.

😎 Filament diameter too big - 3mm is too much.  3mm filament is usually 2.85mm nominal or sometimes 2.9mm +/- .05.  But some manufacturers (especially in china) make true 3.0mm filament with a tolerance of .1mm which is useless in an Ultimaker.  It will print for a few meters and then clog so tight in the bowden you will have to remove the bowden from both ends to get the filament out.  Throw that filament in the trash!  It will save you weeks of pain

8b) Something wedged in with the filament.  I was setting up 5 printers at once and ran filament change on all of them.  One was slowly moving the filament through the tube and was almost to the head when I pushed the button and it sped up and ground the filament badly.  I didn't think it was a problem and went ahead and printed something but there was a ground up spot followed by a flap of filament that  got jammed in the bowden tube.  Having the wedgebot (link below) helps you feel this with your hand by sliding the filament through the bowden a bit to see if it is stuck.

https://www.youmagine.com/designs/wedgebot-for-ultimaker2

9) Extruder mis calibrated.  Maybe you changed equipment or a wire fell off.  Try commanding the filament to move exactly 100mm and then measureing with a ruler that it moved 100mm within 10% accuracy.  If not adjust the steps/mm (this is done by editing a json file on the UM3).

10) Z axis steps/mm.  it's easier than you might think to double or half the Z axis movement as there is a jumper on the circuit board that can be added or removed.  If the Z axis is moving 2X you will get 50% underextrusion.  Your parts will also be 2X as tall.

11) Crimped bowden.  At least one person had an issue where the bowden was crimped a bit too much at the feeder end although the printer worked fine when new it eventually got worse and had underextrusion on random layers.  it's easy to pull the bowden out of the feeder end and examine it.  Similar to 8b above - use the wedgebot to feel how much friction there is in the bowden.

12) Worn Bowden.  After a lot of printing (or a little printing with abrasive filaments) the bowden resistance can be significant. It's easy to test by removing it completely from the machine and inserting some filament through it while one person holds it in the U shape.  Preferably insert filament that has the pattern from the feeder and fight the movement by applying 2kg force on both ends at the same time and then seeing how much harder you have to push it on top of 1kg force.  UM2 feeders can push with 5kg force.  UM3 can push quite a bit more.  5kg is plenty.

13) Small nozzle.  Rumor has it some of the .4mm nozzles are closer to .35mm.  Not sure if this is actually true.  I'm a bit skeptical but try a .6mm nozzle maybe.  This shouldn't be a problem on the UM3 which has very good quality control but try a different core.

14) CF filament.  The knurled sleeve in the extruder can get ground down smooth - particularly from carbon fill.  4 spools of CF will destroy not just nozzles but the knurled sleeve also.  Look at it visually where the filament touches the "pyramids".  Make sure the pyramids are sharp.

15) Hot feeder driver.  I've seen a more recent problem in the forums (>=2015) where people's stepper drivers get too hot - this is mostly a problem with the Z axis but also with the feeder.  The high temps means the driver appears to shut down for a well under a second - there is a temp sensor built into the driver chip.  The solution from Ultimaker for the um2 is that they lowered all the currents to their stepper drivers in the newer firmware.  Another solution is to remove the cover and use desk fan to get a tiny bit of air movement under there.  This doesn't seem to be a problem on UM3 even though it's the exact same circuitry but they lowered the current in the firmware.  But it's worth considering if air temp is 30C or hotter.  It would probably happen only after printing for a while (air heats up slowly under the printer).


16) third fan broken.  This tends to cause complete non-extrusion part way through a print.  In the door of the head.  You can hear it come on when cores get above 40C.  Without this fan several things can go wrong.  It can take a while as usually you also need several retractions to carry the heat upwards.  There are a few failure mechanisms and I don't understand them all.  One of them is probably that the molten PLA spreads out above the teflon and sticks to the metal in a core or fills the gap at the base of the bowden in UM2.  Later it cools enough to keep the filament from moving up or down.

17) Spiralize/vase mode.  This is a rarely used feature of Cura but you might have left it on by accident?  In this mode the wall of your part is printed in a single pass.  So if you have a .4mm core and the wall is .8mm thick it will try to over extrude by 2X.  This is difficult to do and may instead lead to underextrusion.

18) too many retractions (this causes complete failure) - if you have too many retractions on the same piece of filament you can grind it to dust.  10 is usually safe.  20 is in the danger zone.  50 should guarantee failure.  You can tell cura to limit retractions to 10 per a given spot of filament.  Do this by setting "maximum retration count" to 10 and "minimum extrusion distance" to your retraction distance (4.5mm for UM2 and 6.5 for UM3).

19) Brittle filament.  Espciallty with older PLA but even brand new pla can do this.  If you unspool some (for example if it's in the bowden) for many hours (e.g. 10 hours) it can get extremely brittle and it can snap off into multiple pieces in the bowden.  It's not obvious if you don't look for this.  Then it starts printing just fine and at some point one of those pieces reaches the print head and gets hung up somewhere and the printer suddenly stops extruding for now apparent reason.  This usually happens within the first meter of filament - once you get to printing the filament that was recently on the spool it should be fine from then on.

20) The "plus" feeder can have an issue where the filament doesn't sit properly for one print and it permanently damages the arm inside the feeder as shown by this photo - the hole is ground down asymetrically: http://gr5.org/plus_feeder_issue.jpg

=======
 

 

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Posted · Printing with PP

Hello gr5,

 

I appreciate the time you took to write such a thorough response.

 

The first part on your answer revolving about the force the feeder should be able to push was an eye opener, we chose 5 materials and tried em all with a rig and the results gave us the confirmation that the feeder is not the problem, nor the material in itself, the combination of the two is the problem, given that we already had some suspicion that retraction is the problem we worked from there trying very low retractions at very low speeds and going up, trying to get better results, today we have reached a milestone, we have our first print that is not plagued by under-extrusion nor by stringing.

 

For future reference, we were at 7mm retraction at 35mm/s, we now are at 5mm at 20mm/s speed with a prime of 10mm/s.

 

Thank you very much for your help.

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