22MIL2DAY
Posts: 53
Joined: Thu May 30, 2013 9:51 am
Location: SARASOTA FLORIDA

drops and blobs

Sun Oct 06, 2013 5:12 pm

Why do some prints have drips and blobs? Is this a dirty heat tip? or a programming error?

dalew8abz
Posts: 120
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Location: Cleveland Heights, Ohio USA (4 mi. from MakerGear HQ!)
Contact: Website

Re: drops and blobs

Sun Oct 06, 2013 6:18 pm

22MIL,

It probably depends on a lot of things, like:

* type, brand, color of filament
* temperature settings (different filaments soften, melt, expand, and stick at different temperatures)
* cleanliness of hot end
* I.D. of hot end barrel vs O.D. of filament (too much room to expand means taking longer to build up pressure, etc.)
* distance from extruder drive gear to nozzle tip (especially a big deal for those whatsitsname extruders where the filament motor/drive gear is stationary and the extruder tip moves on the rails and there's a long tube between them)
* settings in Creator for:
+ coast (how far before the end of axis motion to stop feeding filament)
+ retraction (how far to back out the filament before doing a rapid move to another area of the print)
+ return from retraction (how far to push the filament back in after a rapid move before starting X/Y moving with extrusion)
+ speed of rapids (without extrusion) vs speed of X/Y moves with extrusion
+ speed/extrusion rate when bridging (extruding in open air with nothing under a section of filament)
+ axis acceleration and deceleration (for X/Y/extruder in tandem) for when you, say, get to a corner and change direction
+ and probably a few others

These are the things you have to play with to get nice (what I will call) "transitions" -- places where you go from extruding along at constant motion and extrusion speeds to not extruding, changing direction, going to the next layer, etc., etc., etc.

Example: there was an incorrect sequence in earlier versions of Creator, where retraction and Z-lift (when both were enabled) were happening "out of order". When doing rapids, the G-code that was generated did this:
* Retract filament
* Lift Z
* Return Z
* Return filament
* Do the rapid move

All this did was (usually) leave a blob at the point where the retract/lift occurred. Plus it did the rapid with the Z height right at the layer height, potentially knocking stuff over. This got fixed, and in 1.1.5, the retraction/lift sequence is correct:
* Retract filament (so you don't leave a blob)
* Lift Z (so you don't knock stuff over
* Do the rapid move
* Return Z (so you're back at the right layer height)
* Return filament (so the nozzle is back under pressure and your extrusion will push filament)
* start the extrusion move

So the Z-lift, retraction, coast, and other stuff on that same tab in Creator is what you need to dink around with (preferably one variable at a time) with test prints to find the "sweet spot" for your printer and filament.

Hope this helps....
Dale

22MIL2DAY
Posts: 53
Joined: Thu May 30, 2013 9:51 am
Location: SARASOTA FLORIDA

Re: drops and blobs

Mon Oct 07, 2013 12:45 pm

Dale, thank you very much for the info. Might you know the default (PLA) settings for these:

+ coast (how far before the end of axis motion to stop feeding filament)
+ retraction (how far to back out the filament before doing a rapid move to another area of the print)
+ return from retraction (how far to push the filament back in after a rapid move before starting X/Y moving with extrusion)
+ speed of rapids (without extrusion) vs speed of X/Y moves with extrusion
+ speed/extrusion rate when bridging (extruding in open air with nothing under a section of filament)
+ axis acceleration and deceleration (for X/Y/extruder in tandem) for when you, say, get to a corner and change direction
+ and probably a few others
Also is there a guide that describes functionality of each of these settings other than the popup on screen? something a bit more explanitory and helpful with regard to complex, large, long running prints?

dalew8abz
Posts: 120
Joined: Sun Mar 24, 2013 11:14 pm
Location: Cleveland Heights, Ohio USA (4 mi. from MakerGear HQ!)
Contact: Website

Re: drops and blobs

Mon Oct 07, 2013 2:01 pm

22MIL,

I think I read another post where a user said that you can go back to defaults by selecting another material or quality, and then going back. So write down all your settings first ( :shock: ), then make a couple of those major changes (material, quality), then go back and see if the settings got set to defaults for that profile.

As for what each of the settings actually does, I think we're all waiting with great anticipation for a "reference manual" or other documentation. Right now, you pretty much have to go with:
* the descriptions that are there on the screen
* the tooltips that come up when you hover the mouse over one of the settings
* the quick-start guide
* what people have typed here in the forum

My machine has had so many dinks from the defaults I can't keep track any more, and I have NOT been writing things down -- just saving my Process each time. IIRC, here's a function to export your process, so you can get it back.

I'm one of those who can't/won't /don't do, so we TEACH!

Hoping you develop better habits than I have, I remain:
Dale

22MIL2DAY
Posts: 53
Joined: Thu May 30, 2013 9:51 am
Location: SARASOTA FLORIDA

Re: drops and blobs

Sat Oct 12, 2013 12:28 pm

I am still having terrible results with regard to blobs. I can not print anything. Each and every print is loaded with blobs (see photo). I was having so much success early and now the programs seem to be doing very odd things without any input or programming on my part. The blobs happen at the start of each extrude movement. It will retract, move, and create a big blob at the start and then the filament extrudes noramal. The blobs are so big that the tip hits them when traveling to other "X" -"Y" locations. I do have another post explaining odd movemants off the printbed that make no sense to me. Also on this print it lowered the "Z" all the way down and then back up for reason, never did it before and I did not program that. What is going on?
Attachments
blobs.JPG

22MIL2DAY
Posts: 53
Joined: Thu May 30, 2013 9:51 am
Location: SARASOTA FLORIDA

Re: drops and blobs

Sat Oct 12, 2013 12:31 pm

Forgot to mention that large collection of filament was due to the printer running off the printbed and extruding fillament off the glass for no apparent reason and I still don't know why that is happening

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jimc
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Re: drops and blobs

Sat Oct 12, 2013 3:27 pm

22mil, ok i responded in the other thread as well. i see your using pla. the priming at the beginning is normal. that is supposed to do that and its always done it before starting any print. the print you are showing a pic of is just starting. does the printer continue to leave blobs like that through the whole print or just in the beginning like your showing? do you have the skirt setting on? i cant really tell from the pic but it looks like the printer does the wipe and goes right into the print. it should go and do maybe a 2 line wide skirt around before going into the print. this gets the pressures right in the tip and get everything going right before it start on the real item. mine leaves a blob like that as soon as it starts to put the skirt down but then its fine when moving to the print. if you could post up an fff file for us it would really be helpful and save some time.

22MIL2DAY
Posts: 53
Joined: Thu May 30, 2013 9:51 am
Location: SARASOTA FLORIDA

Re: drops and blobs

Sun Oct 13, 2013 3:01 pm

jimc, thanks for your input about "coast" & "retract". I had the "coast" feature off so I turned that on and ran the start of the print. It was better then I set a -.2 for retract and it is real nice, no blobs. Thanks again.

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