Surface issues on 45 degree angled print, using Amidex PA6-66 on x1c

[bsteagall]

Need a little help narrowing down a problem I’m having printing with 3DXTech’s Amidex PA-6 66 while I wait for them to get back to me with an x1c profile.

Want to start off by saying that overall, I’m extremely happy and impressed with the results I’ve been having so far. Most of the parts I’ve printed for my HMC have come out superb, but these are all relatively simple (straps, clamps, gears, knobs, etc). The issue I’m having is surface problems on one particular part that is printed at a 45 degree angle, and all the tangs on the part are also 45 degree.

I’ve eliminated moisture already (dried 12 hrs at 70c in a Sunlu S2 then an additional 12 in the AMS at 65). I live in a very dry environment (desert southwest, USA) which normally is in the 7 -15% humidity, my AMS shows between 1-3% (the hygrometer is always stuck at 10).

Printing with their PA12 profile modified for the temperature’s recommended for this material (in this case, bed at 70, extruder at 265 and also tested at 270). Here are the images of what I’m getting

this is the part in the slicer for clarity from yesterday’s testing

In this image from yesterday, I did notice that the areas that are having the problem are where the slicer was slowing it down (I had left the overhang speeds default, here those areas are printed at around 37). The images above are from today’s test, where everything was set to 60, and frankly, no change (maybe even a little worse). Usually, my experience has been that surface issues like this are caused when speed is faster, not slower, so I’m scratching my head a little.

I’ve printed this same part in other materials, like PC, PLA and ASA, with no issues at all at default x1c speeds (at even steeper angles, like 37).

Is this just a matter of speed? I hesitate to slow it down even further (as the areas from yesterday’s test were slower) or do I need to look at something else?

Thanks as always for your insights,

Bryan

[EnoTheThracian]

I have not printed that particular material so only a few (maybe even useful ) observations.

It looks like the speed changes are caused by “slow down for overhangs”. So it may also be a case of excessive overhang angle for the filament.
You could consider increasing the angle at which supports are generated, try to slow down even more on overhangs (say 10mm/s) and/or decrease the layer height. The latter may be the most promising one if done deftly but carries the risk of nozzle clogging (especially if the material is fibre loaded).

The underside indicates that the support distance is a bit high. Always a tricky trade-off between quality and ability to remove. I am not sure what material would be suitable as a dissimilar material support interface but it would produce quite a bit of waste on an X1 a well.

While your drying is extensive, it may still not be enough. When I use high performance material and without a high temp drier, I usually leave them for up to 60h in 70°C.

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[bsteagall]

Hi @EnoTheThracian thanks for responding

I’m actually not using any supports (only a fin for stability) as the angle is such that it should be able to handle it. (should) I’m not worried about clogging as the material doesn’t have any fiber so I’ll give layer height a try although I think I tried adaptive layers at one point.

3dxtech states that it only needs 4 hrs at 90c for drying, so the little feedback I’ve had from them was that I should be safe there, but I guess it’s worth a try.

I’ll bring the speed down further and report back

Thanks Eno

[EnoTheThracian]

Hi @bsteagall ,

Before diving into the layer height solution, I’d look at using supports. There’s (quite) a bit of a nozzle clogging risk, in particular if the material is loaded and layer height is reduced significantly. However, the layer height approach will not help much if applied too timidly. So you’ll be operating in a coffin corner: Too low a layer height => Nozzle clog, Too high a layer height => Overhang failure.

There’s not much “should” in FDM as Physics usually tell us what “is” and “isn’t”. A quick overhang test does not need much material but can quickly show what is possible and what isn’t.
I have not had to do one myself in a decade but I found this little one quickly on MW which may be helpful if you enforce a brim.
Simple Overhang Test - Free 3D Print Model - MakerWorld

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[bsteagall]

@EnoTheThracian question, are some materials not able to print at a 45 angle without supports? Every angle on this part is designed to be within that threshold. Like I mentioned before, I’ve printed this same part at even steeper angles in other materials with no support without any issues whatsoever. I could see this being an issue with materials like TPU, but wouldn’t expect it with nylon

I haven’t been 3d printing for that long, but everything I’ve read and seen so far (and printed) suggests that I really shouldn’t (here’s that word again, lol) need them. I’ll give it a try and see what happens.

Could the printing temp be a factor? The specs from the manufacturer state nozzle temps from 255-270 with a bed temp of 70. I tried the generic PA profile from bambu at first, which has a much higher bed and nozzle temp (100 bed and 290), and this really caused the filament to be really soft and mushy. I tried the other end, at 255 and experienced layer adhesion issues (although I didn’t test it on this part, but on some of the others). So far these tests have been at 270 and 265

[EnoTheThracian]

Well, the max angle for adequate temp depends to some extend on the viscosity of the material as well as cooling properties.
If thermoplastics would be as liquid as water, we’d already find vertical walls challenging. Fortunately, printing thermoplastics is more akin to printing honey at room temp and then freezing it rapidly. But just like honey, there’s still a large range of not only temperature dependant viscosities. Moisture has a hughe effect but the real magic is in all of those additional ingredients in trace amounts that are kept a closely guarded secret by plastic manufacturers.

So do not take anything for granted regarding FDM. PLA is well explored but already with PETG, surprises can still happen. Nevermind engineering filaments.

I think you may also find an overview of Bambu filament properties interesting and helpful. That may give you an opportunity to review your material choice. I have a slightly dated dataset which I’ll post once back on the laptop. Sadly pics only atm. Some surprises in there…

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[EnoTheThracian]

Step 1: Raw data. Unfortunately, I can not upload pdf, xls, etc formats. Only png/jpg.

Note that the data is from last year, i.e. still the original PETG Basic.

Step 2: Comparison to PLA Basic.

Some interesting findings in there…

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[lkraus]

If you have not done so already, calibrate the filament yourself, especially pressure advance. Bad edges and corners are often caused when nozzle acceleration and flow are out of sync.

[bsteagall]

@lkraus Thank you Ikarus, I had done that in the beginning, but I think that on this part I resorted to something different. (what was in the PA12 profile)

I actually just got a profile from 3dxtech and in the process of printing it, and it had some interesting changes, so I’ll report back when done.

In this profile, they raised both the bed and nozzle temps (100 for bed, 280 for nozzle) and hardcoded pressure advance in the filament start g-code. @EnoTheThracian they also brought down the speeds in those areas down to 10, while keeping everything else standard and no supports

There are probably other settings, but I’ll investigate further and report back. They showed me pictures of a part similar to mine, and it looked great.. so fingers crossed!

[bsteagall]

I won’t be back home until this evening, but even now I can tell the difference, looks like this will work great