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what causes this? not enough extrusion pressure? bad filament? flow rate? retraction speed to fast?

cambo3d wrote:what causes this? not enough extrusion pressure? bad filament? flow rate?

If it's coming from the hotend, it's either air bubbles in the filament or moisture in the filament, what sort of filament is it, PLA can absorb quite a lot of moisture.
Nylon is particularly bad at moisture absorption as is PVA and polycorbonate.
Try baking the filament for a couple of hours (on very low) below it's plastic transition temperature.

Polygonhell wrote:

cambo3d wrote:what causes this? not enough extrusion pressure? bad filament? flow rate?

If it's coming from the hotend, it's either air bubbles in the filament or moisture in the filament, what sort of filament is it, PLA can absorb quite a lot of moisture.
Nylon is particularly bad at moisture absorption as is PVA and polycorbonate.
Try baking the filament for a couple of hours (on very low) below it's plastic transition temperature.

its abs,

if it absorbs moisture. Should i be leaving it out? When seemecnc ships this they just wrap it in a little plastic. nothing to really keep the moisture out.

I also notice when this popping occurs that it leave gaps in the print path..

Also occurs when running too hot, any smoke with the sounds?

I always try to extrude about 10cm of filament into the air let it drop down and then feel it for bumps. It should be smooth as silk. Bumps generally mean too hot.

It's almost certainly water absorbed into the plastic, and yes, it can cause pitting. The pop is the sound of it vaporizing (it's above 100ºC after all) in contact with the hot end.

When not in use, store filament in airtight plastic tubs with desiccant packets. Your new filament may have included a small packet of desiccant, just like stereo equipment, but you can find it in larger packets at a sporting/hunting shop wherever they sell ammo and safes. You can bake a paper pouch of desiccant at 70~80ºC to "restore" it a few times.

this filament is less than three weeks old from when i received it from seemecnc. not sure how long they had it on there shelves. does filament absorb moisture that fast?

I think I may have accidentally gotten some ptfe lube on it when i was spraying down the extruder gears with lube and I think that's actually whats causing it.

I have had issues with popping from the beginning. I did reduce a lot of it by eliminating retraction. However, recently it seems my prints have been getting more popping. I am experimenting with slightly lower temps for extrusion which has helped some but has not eliminated all of the pops. I do store all my filament in a container with "closet dry" but it is not air tight. I am real close to baking my filament.

A posting on printrbottalk discusses baking at 80 to 85C for a couple of hours to remove moisture. Not sure how long the right time is but I would weight the spool before and after to see if there was any impact on weight after the water is cooked out.

Supposedly if you stay at the 80-85C range there is no out-gassing or detriment to the filament. I have not confirmed this at this time.

I've got filament over a year old, that I print with without issues, and I don't store it in an air tight container. ABS in particular is not very hygroscopic.
Usually if it's water in the filament you'll see steam escaping from the Hotend.

I was getting the same popping printing ABS at about 240 degrees. I turned down the heat (to 235) and "no more popping." I believe it's a hot end temperature thing.

Bill

EDIT: Let me add this. For about seven years I worked making "one-off" eyeglasses frames using Italian-made cellulose acetate (an "organic plastic). Cellulose acetate (CA) is made from a combination of organic materials (can be wood pulp, cotton seed lint, or other manufacturing/processing organic "waste", soaked in hydrochloric acid). Even after processing the cellulose acetate has a moisture content similar to that of kiln-dried lumber (in the neighborhood of 7%).

One of the steps in making these eyeglasses frames included inserting "core wires" into the temple pieces. To do this, the temple piece was inserted in a radio frequency induction heater for 2.5 seconds; this temporarily softened a "soda straw" down the length of the temple piece. Immediately after heating, the temple piece was transferred to a "core shooter" where a pneumatic ram pushed the core wire into the temple piece (the core wire was heated to 425 degrees F).

During the above process if the CA was heated too hot, too fast, or too long the moisture content in the "soda straw" area would come to a boil, causing microscopic bubbles in the plastic, and ruining the temple piece.

All plastics have some moisture in them, even ABS. If they are heated too hot the moisture in them can cause bubbles; IMHO it is the popping of these bubbles that is sometimes heard when the temperature of the hot end is too high and plastic is extruded through the nozzle.

I could be wrong about this.

Thanks guys popping filament solved, it wasn't the lube, it was the temperature. I found that my popping filament was caused my too high of a temperature setting as noted by you guys, I started off at 230 and kept lowering the temp by 5 degree increments till i found the sweet spot, no more popping filament and my print paths are coming out better

cambo3d wrote:Thanks guys popping filament solved, it wasn't the lube, it was the temperature. I found that my popping filament was caused my too high of a temperature setting as noted by you guys, I started off at 230 and kept lowering the temp by 5 degree increments till i found the sweet spot, no more popping filament and my print paths are coming out better

Wow, this is good information to have! Can't say I've ever really had this issue, though I might have encountered it once or twice when I first started playing with PLA on my Makerbot Replicator.

I've gotten some popping at normal temperatures.

The filament spool has been sealed within a gallon ziplock bag (10 cm spool just fits).

Hopefully adding some desiccant packets will pull out the moisture.

made a big difference in the print after making adjustment to temps. every time i hear a pop in the filament it would leave these gaps.

cambo3d wrote:Thanks guys popping filament solved, it wasn't the lube, it was the temperature. I found that my popping filament was caused my too high of a temperature setting as noted by you guys, I started off at 230 and kept lowering the temp by 5 degree increments till i found the sweet spot, no more popping filament and my print paths are coming out better

What temp did you settle at?

What temp did you end up with?

for the gray abs filament i was using, it was 215 degrees

( warning though, your temps will vary depending on how you have yours calibrated) just keep lowering your temps till that popping goes away. just dont lower it too much.

cambo3d wrote:for the gray abs filament i was using, it was 215 degrees

( warning though, your temps will vary depending on how you have yours calibrated) just keep lowering your temps till that popping goes away. just dont lower it too much.

Keep lowering but not too much? What is too much? I think a lot depends on how the thermo couple is seated.

I just opened a new package of the blue florescent ABS filament from Rainbot. I don't heat popping, but it's very bumpy, not smooth like the other filaments I've tried.

After sitting in the nozzle for a moment, when it first comes out, it is smooth for a couple inches and then everything else has these bumps. I imagine maybe it's moisture drying out in the nozzle? In the photo you can see smooth on the left and bumpy on the right. Click for hi res.

I'm baking now at 185F. Any other suggestions?

thanks!

barnett wrote:I just opened a new package of the blue florescent ABS filament from Rainbot. I don't heat popping, but it's very bumpy, not smooth like the other filaments I've tried.

After sitting in the nozzle for a moment, when it first comes out, it is smooth for a couple inches and then everything else has these bumps. I imagine maybe it's moisture drying out in the nozzle? In the photo you can see smooth on the left and bumpy on the right. Click for hi res.

I'm baking now at 185F. Any other suggestions?

thanks!

bluGlo.jpg

What temperature did you try at? The fact that if it sits in the nozzle for a while it extrudes fine implies to me that it needs a higher temperature.

After the first week experimenting with the printer, I decided 232C was working fine and I've used that for everything. With this blue problem, I tried 230, 240, 220 and 210 with basically no changes. Should I try 245C? The limit would be what, 255C?

Just be sure that as the temps climb you have some type of active cooling on the hotend tempurature barrier. A small fan for example. You can kiss you peek connector godbye otherwise.

barnett wrote:After the first week experimenting with the printer, I decided 232C was working fine and I've used that for everything. With this blue problem, I tried 230, 240, 220 and 210 with basically no changes. Should I try 245C? The limit would be what, 255C?

have you checked your filament diameter, seems like theres another problem here.

Thanks guys. I have the 25mm fan mhackney recommended, but I haven't wired it up yet.

Diameter is 1.70mm. The one thing I printed was the single wall calibration cube and it's kind of mealy... I suppose due to the bumpy filament. Walls came out wide even though I sliced w/filament diam at 1.75 and extrusion multiplier at 1. It's been in the oven about 2 hrs now. So I'll test again before bed.

barnett wrote:Thanks guys. I have the 25mm fan mhackney recommended, but I haven't wired it up yet.

Diameter is 1.70mm. The one thing I printed was the single wall calibration cube and it's kind of mealy... I suppose due to the bumpy filament. Walls came out wide even though I sliced w/filament diam at 1.75 and extrusion multiplier at 1. It's been in the oven about 2 hrs now. So I'll test again before bed.

ok why would you use a different diameter if the actual diameter is 1.70?

A reasonable question. I knew the print was going to be lame anyway because of the bumpy filament and I thought maybe the bumps would make the walls seem wider, so I tried to force them to be more narrow. It's dumb I know, but I wanted to print something before putting it in the oven.

Anyway good news is that the filament is coming out much smoother now. Not perfect, but much better. I have a new single wall box printing now (filament at 1.7mm and extrusion multiplier at 1) and it's practically glossy compared to the first one. Here's the new filament and the first (mealy) single wall box. The new one's almost done. I'll post in a few min.