Poor quality when printing Polymax PC-FR

Bambu Lab P1 Series Troubleshooting
1

I’m a new owner of a P1S, and I’ve been able to print PLA without any trouble. I’ve also had success printing TPU, and it seems that I’ve got the printer pretty well dialed in.
I’m trying to print some items that need to be tolerant of high heat, so I’m using PC-FR filament.
I’m using the Bambu Labs .4 nozzle, with the Bambu Labs engineering plate, setup with the “hot side” up.
I’ve created a small disk, 30 mm diameter, with a 4 mm thickness. I’ve applied some hair spray to the hot plate, and run a couple of tests. The prints adhere to the bed really well, and the first couple of layers are clean, but by the time that it reaches the 5mm mark (25 layers), the filament seems to be melted and deformed. It seems that most folks have trouble extruding the filament, or getting it to adhere to the bed, but I’m having a problem at the halfway point of the print. Any suggestions?

Disk_1
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The picture above shows how the print fails, at about layer 20.

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My first thought is that you may have uneven cooling which may be contributing to the fact the layers may be cooling at incorect rates.

The setting can be found here.

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But before you go spinning your wheels messing around with temps, there may be a less complicated solution.

The following example was done with Bambu brand Silk PLA. Unfortunately I did not hold onto similar failed prints for TPU but these examples will serve just as well.

Notice the left and center models have near perfect form at 5mm. Then everything turns to garbage.

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The answer:

Dry your filament thoroughly!

My so-called ‘out of the box’ factory-fresh Bambu brand PLA, allegedly the best-tuned filament for Bambu printers, and not to mention that PLA is allegedly not prone to being hygroscopic. Well, guess what? The item on the left was the out of box print, in the middle is when I dried the filament in my kitchen oven for 2 hours at 140°F. The after weight was 5g less, which equates to 5ml. Better than the one on the left but still far from acceptable. So, I placed it in the kitchen oven overnight for 8 hours at 140°F, and the example on the right was the result.

I reproduced this result a few months later with Gizmo Dorks Black TPU. Unfortunately I did not keep those photos but it produced results similar to what I am showing with silk. In that case, drying helped quite a bit but printing in silent mode which is 50% speed is really what solved the problem.

In the end, this is one of those rare cases where I would say try another brand first.

I gave up on Gizmo Dorks TPU as their brand didn’t perform and given that I only needed a small amount I wasn’t going to pay for a full spool and given the experiences of Bambu filament I knew that their filament was random quality. So I purchased on price and “Before” I printed… guess what? I dried it thoroughly and got a PLA-Class print quality with no stringing or problems of any kind.

The filament I chose comes on small reels which puts them at a reasonable price. I’ve never heard of this brand before but then again I was looking for cheap and this brand performed perfectly the first time.
https://a.co/d/9pnQ4v2

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The moral of the story

Including me, do NOT believe anything you read until you have personally tested it out yourself. There is always some small detail overlooked which is why I mentioned my experience in manner I did. All and I mean “all” of the advice I got pushed me into the wrong direction except one small voice who recommended drying. In the Bambu filament chart, it states that TPU should be dried but Silk? It says it’s optional. I’m saying don’t trust that.

Good luck🍀 and let us know how you make out so that others can share in your experience.

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3

Olias,
Thanks for the thorough response.
I tried printing with this PC a couple of weeks ago, and it was a disaster. I could not get the filament to stick to the plate at all. Well, fast forward 5 weeks, and I’ve learned a lot. My new configuration for printing with PC filament includes using the Hot Plate from BBL, spraying hair spray onto the plate, and drying the filament using a Sunlu S2 dryer.
When I put the PC filament into the drier it showed about 40% humidity. After about 5 hours of drying, the relative humidity was now down to about 22%, which I thought would be low enough in order to get the filament to work for me.
Given that my prints are now sticking to the build plate, and the first 20 layers are printing pretty well, its clear that I’ve solved some, but not all of my issues.
Thinking about your thoughts that it’s the humidity that is the crux of the problem, I’m wondering if you’ve tried to use a dryer, such as the Sunlu S2, and whether you had any way of knowing what the relative humidity was, when you were able to successfully print, using PC.
And lastly, you brought up a point that I was afraid of. The point is that we cannot treat any and all brands of filament the same. So, it might be a good idea to try another brand. I’ll see about doing that ASAP, and get back to you.
Thanks for all the great suggestions,
Cliff

4

Have I looked at Sunlu S2, yes, here is a recent post on that topic that may provide some insights and methodologies to overcome some of the shortcomings in dryer technology.

The one hint I will share with you that my writeup only touches upon. Humidity sensors are practically worthless. My findings were that there just isn’t a consumer level product that can be trusted. Weight is the only truly reliable way of measuring moisture reduction. But as was recently point out to me by a fellow forum member, if you have a cardboard spool, even weight is thrown off substantially due to the spool itself becoming a source of moisture. This is yet another reason I prefer plastic spools. That said, I am taking the plunge and will be constructing a respooler precisely so that I can respool cardboard onto plastic and therefor eliminate cardboard as a factor in drying.

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5

I have a Sunlu S2 and have printed Nylon and PC at 20% RH on the dryer’s reading and had no issues. IMO, 22% for a PC based filament should be fine. Personally, I only dry my filament to 20% and never have issues. That goes for hygroscopic filaments like Nylon and TPU, as well as Bambu PC which all ran through the S2 with no issues. Its plenty strong. Granted, I’m in So Cal, and the humidity levels never get higher than 50% when it’s not raining. That said, I did print a little lid prop to help evacuate moisture out of the S2 and that helps shorten drying time a lot, but that’s the only mod.

As far as your problem, which profile are you using to print the PC-FR? Generic PC? Or a modified profile.

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As @just4memike says, “As far as your problem, which profile are you using to print the PC-FR? Generic PC? Or a modified profile.”

That’s the rub. PC-FR is nothing like PLA or TPU. Did you set up a filament according to the PolyMax settings? Hot Bed, Hot Chamber, Hot Melt AND NO FAN? Check the settings for retraction and print speed as well.

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I would suggest starting out with the basic “Generic PC” profile in Bambu Studio. You might have to enable it. I’d bet that gets you in the ball park, if not perfect. From the Polymaker TDS and SDS, its basically a PC with fire retardant in it. Not sure how much the fire retardant affects the printability, but I’d start off with a PC profile.

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I was drying some PLA and got it down to 1252 grams. I then forgot about it for a few days after the heater stopped and it went up 4 grams to 1256.

Most new filament, Bambu included, lose between 2 and 6 grams of water, and I have had some that lost 9 grams.

I have never bothered looking at the humidity meter, I just weigh it periodically until it stops losing weight.

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9

No need to ballpark it or guess. They give the important settings.

Printing, Drying and Annealing Settings

Printing Temperature: 250˚C - 270˚C
Bed Temperature: 90˚C - 105˚C
Chamber Temperature: 90˚C - 100˚C
Printing Speed: 30mm/s - 50mm/s
Fan: OFF

Direct Drive:
Retraction Distance: 1mm
Retraction Speed: 20mm/s
Indirect Drive:
Retraction Distance: 3mm
Retraction Speed: 40mm/s

Drying Settings: 75˚C for 6h
(Only if the material has absorbed moisture)

Annealing Settings: 90˚ for 2h <<<<<<< Take Note

10

Thanks to you all for your suggestions.
I’ve been able to get the RH down to about 16% (According to Sunlu S2) and have also looked into all of the settings that you’ve recommended. Preliminary results are looking very good so far.
With each print, I seem to improve the result, and am then confronted with the next issue.
Now, with all of this said, it seems that the direction that I need to go in is to use the settings which are recommended by Polymaker, even though they are quite different from the “Generic PC” profile. Those settings, combined with having a very dry filament seems to be improving the results.
I’ll do some more testing today, and see if I can get a clean print.
It is somewhat shocking that the print speed needs to be as low as 30 in order to get the filament to lay properly on the previous layer.
More to come

11

Being a PC, 30mm/sec is very low, but the Bambu 200+mm/sec is possibly too much. Run a simple Max Flow Rate test with Orca slicer and measure what the Volumetric flow should be. I almost guarantee you 30mm/sec is way too conservative.

Its quick and pretty simple to do if you download Orca slicer, with is effectively Bambu Studio with a few add ons. Calibration · SoftFever/OrcaSlicer Wiki · GitHub

12

OK, I’ve been testing all morning. Here are the results…
First of all, I’m trying to print part of a control knob for a Samsung Cooktop. This plastic insert fits into a Stainless Steel outer shell, but it is this plastic piece that sits on the control spline, which is one of the 5 knobs that control the burners.
Looking at the two pix below, you can see how this piece printed when I used a simple Black PLA.

PLA-1
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PLA-2
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Notice on the first picture, the cone prints great, but more important, the shaft prints perfectly. The shaft is printed from layers 70 to 207, and during this printing, the hot-end remains in tight quarters, quickly laying layer after layer on this relatively small area. With the piece printed with PLA, there were no issues. But, looking at the next two pictures, you can see that the base of the part prints perfectly, but as soon as the hot-end starts to print layers 70 - 207, the print fails.
PC-1
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PC-2
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The main part of the piece has printed successfully at 265 C, but I’ve tried temperatures from 280 down to 260. I even tried printing at 250, and the print was the cleanest that I had been able to generate. However, when we reached layer 70, none of the new PC filament adhered to the previous layers, and I watched a birds nest grow right before my eyes. Generally, the range of 260 - 265 C seems to deliver the best results.
But, I thought that perhaps the temperature of 250 was too low, so I increased the hot-end to 265 again, and gave it a try. I had no luck, and the result was similar to what you see in the last two pictures.
In one of the recent responses, Ken-N-Texas suggested the settings promoted by Polymaker. I’ve faithfully used these settings, and that is where I noticed that the recommended speed is 30-50.
I was not able to find the setting for Retraction distance in Bambu Studio. Can someone shed some light on this?
I had an idea that if I could slow the head down even more, but only during layers 70-207, I might be able to get better results, but it does not seem that the slicer can be directed to alter speeds, based on the layer that is printing. Any suggestions?
Some folks have suggested a flow test, but I can’t see how this will tell me anything. The flow seems to be perfect for the first 70 layers, then we start to see problems.
PS, all of the prints this morning have been done with PC-FR filament that has been drying for at least a day, and is sitting inside the Sunlu S2, which shows a RH of 12-13%.

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What’s your minimum time for a layer set to? Looks way too short for the material. The base Generic PC profile has 2 seconds, but judging by that, should probably be 8. I bet that’s the fire proof blend coming in.

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You cand find everything here.

15

I think his problem is more about what’s on this page, Auto Cooling in Filament Settings | Bambu Lab Wiki

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More precisely, this brand of PC is probably sensitive to the fast layer printing without any time to cool. It fits the problem. The larger section (that takes longer to print) has plenty of time to cool before the next layer goes down. But the thin cross section layer doesn’t have the appropriate time to cool. So, it just becomes a hot mess of filament.

I think he’s going to want to change the following settings.

“Max Fan Speed Threshold - Layer Time” - 8 Seconds
"Slowing printing down for better layer cooling " - Enabled
“Min print speed” - 5 mm/sec or possibly lower

Below is what the Generic Profile has as a default for PC. I think the 2 Second minimum layer time is too low for this fire-retardant filament.

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For a single part, I’d just reduce the speed as much as necessary for the whole part and be patient.

If many copies are being made, I think this is a case for a modifier. A primitive cylinder slightly larger than the shaft, positioned to cover it. Then adjust the speed settings in Object mode to reduce speed only for the parts of the model inside the modifier.

17

Sorry for the delay in responding.
Here are the results of my attempts.
As stated, the part prints perfectly until we get to layer 72. At that point, the work to build the lower cone is done, and the printer sets out to build the tower portion of the part. This portion has a key-shaped hole in it’s center, and is only about 10mm in diameter.
Here are the major settings
All printing speeds set to 30
Retraction set to 5mm, spiral
Bed Temp set to 90
Hot-End Temp set to 260 (1-3), 265 all else
Cooling Min/Max 10/60
Cool off for 3 layers
Aux Part cooling fan set to zero

The part prints the entire cone region perfectly, but as I said, at layer 72, the layer time and print pattern is now very short, very small. Instead of printing the cone, which takes about 40 seconds/layer, the cylinder portion takes only about 8-10 seconds to print.
The first 3-5 layers of the cylinder print, and look very clean. However, by the time we lay down the 5th or 6th layer, on the cylinder, it looks like the filament simply melts, and collapses. When it collapses, all of the layers that had looked good moments before, have now collapsed, and fallen towards the center of the cylinder.
So, to me, it looks like the filament is able to cool, settle and harden enough, when the layer print times are longer. However, when the layer times are shorter, and the new filament is in close proximity to previous extrusions, the residual heat builds, until the last few layers have simply softened, and melted.
I would like to find a way to command the slicer to slow down even more, once it reaches a point in the process, or to get the slicer to pause after each layer, allowing it to cool adequately.
Or, perhaps there is a way to turn on cooling more aggressively, once I reach layer 72.
This morning, I created a new part to test. I’ve created a tower, made of 5 concentric circles, each smaller than the previous, with a hole in the middle. Each layer is extruded about 10 mm, and I’ll examine the results, to try to determine at what point the system melts.
The test part is parameterized, so i’ll vary circle diameter sizes, and heights, to try to get the best information, but any insight on how to better manipulate the slicer would be helpful.

18

You can do exactly that with a modifier.

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